SYNTHESIS AND CHARACTERIZATION OF PHENYL FUNCTIONALIZED MAGNETIC
NANOPARTICLES AS SORBENT IN MICRO-SOLID PHASE EXTRACTION OF POLYCYCLIC AROMATIC
HYROCARBONS AND ORGANOPHOSPHORUS PESTICIDES
FARAH WAHIDAH BINTI MOHD HASSAN
UNIVERSITI SAINS MALAYSIA
2018
SYNTHESIS AND CHARACTERIZATION OF PHENYL FUNCTIONALIZED MAGNETIC NANOPARTICLES AS SORBENT IN MICRO- SOLID PHASE EXTRACTION OF POLYCYCLIC
AROMATIC HYROCARBONS AND ORGANOPHOSPHORUS PESTICIDES
by
FARAH WAHIDAH BINTI MOHD HASSAN
Thesis submitted in fulfillment of the requirements for the degree of
Master of Science
February 2018
ii
ACKNOWLEDGEMENT
In the name of Allah, the Most Gracious and the Most Merciful,
Alhamdulillah, all praises to Allah SWT, the Almighty for His mercy and blessing, has given me the strength and patience to complete this study.
I would like to express my appreciation and deepest gratitude to my main supervisor, Dr. Noorfatimah binti Yahaya for her guidance and endless supports throughout the study. I am thankful for her advices, inspiration, kindness and unwavering patience that enabled me to approach master study positively. I would also want to extend my gratitude to my co-supervisor, Dr. Muggundha Raoov s/o Ramachandran for his assistance, insights and critical comments regarding my research,
Special thanks to my beloved family for their endless love, prayers and encouragement has given me the strength to complete my research and thesis writing.
My special acknowledgement also goes to my lab mates and all the staff in Integrative Medicine Cluster and Oncology Lab of Advanced Medicine and Dental Institute, USM, for their support, ideas, and guidance.
Finally, I am gratefully acknowledged Ministry of Education Malaysia (MOHE) for the financial support through the MyBrain scholarship and USM for the facilities and accommodation provided. I would also like to extend my appreciation to everyone who has directly or indirectly influenced in the completion of this study and made this thesis possible.
iii
TABLES OF CONTENTS
ACKNOWLEDGEMENT ii
TABLE OF CONTENTS iii
LIST OF TABLES vii
LIST OF FIGURES viii
LIST OF ABBREVIATIONS xiii
LIST OF SYMBOLS xviii
ABSTRAK xix
ABSTRACT xxi
CHAPTER 1: INTRODUCTION
1.1 Background of study 1
1.2 Problem statement 4
1.3 Objectives of study 6
1.4 Scope of study 6
1.5 Significance of study 7
1.6 Outline of the thesis 8
CHAPTER 2: LITERATURE REVIEW
2.1 Overview 10
2.2 Organic pollutants 10
2.2.1 Polycyclic aromatic hydrocarbons 11
2.2.2 Organophosphorus pesticides 15
2.3 Extraction methods for chemical analysis 18
2.3.1 Liquid-liquid extraction 18
2.3.2 Solid phase extraction 19
2.3.3 Supercritical fluid extraction 20
2.3.4 Microwave assisted extraction 21
2.4 Development of microextraction methods for chemical analysis 21
2.4.1 Sorbent based microextraction methods 22
2.4.1(a) Solid phase microextraction 22
2.4.1(b) Dispersive micro-solid phase extraction 23 2.4.1(c) Magnetic dispersive micro-solid phase extraction 24
2.4.1(d) Micro-solid phase extraction 25
iv
2.4.1(e) Microextraction by packed syringe 26
2.4.2 Liquid phase microextraction 27
2.4.2(a) Hollow fiber liquid phase microextraction 28 2.4.2(b) Single drop liquid phase microextraction 29 2.4.2(c) Dispersive liquid-liquid microextraction 30 2.4.2(d) Ultrasound-assisted dispersive liquid-liquid
microextraction
32 2.4.2(e) Vortex-assisted liquid-liquid microextraction 34 2.4.2(f) Biosorption based microextraction 35
2.5 Magnetic nanoparticles as sorbent 36
2.5.1 Functionalized magnetic sorbent 38
2.5.2 Application of functionalized magnetic sorbent in sample preparation
39
2.5.3 Extraction of PAHs 41
2.5.4 Extraction of OPPs 46
CHAPTER 3: METHODOLOGY
3.1 Overview 49
3.2 Reagents and materials 49
3.3 Part I: Methodology for synthesis and characterization of phenyl- functionalized magnetic sorbent (PMS)
50 3.4 Part II: Methodology for a facile vortex-assisted emulsification
combined with salt-induced demulsification phenyl-functionalized magnetic dispersive micro-solid phase extraction prior to GC-MS for the determination of PAHs in aqueous matrices
51
3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 3.4.6 3.4.7 3.4.8 3.4.9 3.4.10
Preparation of PAHs standard 52
GC-MS condition 52
Samples collection and pretreatment 53
Optimization of VAE-SID-MDMSPE 54
VAE-SID-MDMSPE procedure 54
Solid phase extraction procedure 56
Enrichment factors of PAHs 56
Reusability of PMS in VAE-SID-MDMSPE 56
Method validation of VAE-SID-MDMSPE 57
Application to real samples 57
3.5 Part III: Methodology for a biosorption based dispersive liquid-liquid 58
v
microextraction combined with magnetic dispersive micro-solid phase extraction prior to GC-FID for the determination of OPPs in cabbage samples
3.5.1 3.5.2 3.5.3 3.5.4 3.5.5 3.5.6 3.5.7 3.5.8 3.5.9 3.5.10
Preparation of OPPs standard 58
GC-FID condition 58
Sample collection and pretreatment 59
Optimization of Bio-DLLME-MDMSPE 60
Bio-DLLME-MDMSPE procedure 60
Solid phase extraction procedure 62
Enrichment factors of OPPs 62
Reusability of PMS in Bio-DLLME-MDMSPE 62
Method validation of Bio-DLLME-MDMSPE 62
Application to real samples 63
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Part I: Synthesis and characterization of phenyl-functionalized magnetic sorbent
64 4.1.1
4.1.2 4.1.3 4.1.4 4.1.5 4.1.6
FTIR 65
BET analysis 67
XRD analysis 68
FESEM 69
TEM 70
VSM 72
4.2 Part II: A facile vortex-assisted emulsification combined with salt- induced demulsification phenyl-functionalized magnetic dispersive micro-solid phase extraction prior to GC-MS for the determination of PAHs in aqueous matrices
73
4.2.1 Optimization of VAE-SID-MDMSPE 74
4.2.1(a) 4.2.1(b) 4.2.1(c) 4.2.1(d) 4.2.1(e) 4.2.1(f) 4.2.1(g) 4.2.1(h)
Effect of sorbent mass 77
Effect of type emulsification solvent 78 Effect of volume emulsification solvent 80
Effect of extraction time 81
Effect of type desorption solvent 82
Effect of desorption time 83
Effect of type salt-induced demulsification 84 Effect on amount of salt-induced demulsification 86
vi
4.2.1(i) Effect of sample volume 87
4.2.2 4.2.3 4.2.4 4.2.5 4.2.6
Reusability of PMS 88
Validation of VAE-SID-MDMSPE 88
Real sample analysis 93
Comparison with other published methods 95
Conclusion 98
4.3 Part III: A biosorption based dispersive liquid-liquid microextraction combined with magnetic dispersive micro-solid phase extraction prior to GC-FID for the determination of OPPs in cabbage samples
98
4.3.1 Optimization of Bio-DLLME-MDMSPE 100
4.3.1(a) 4.3.1(b) 4.3.1(c) 4.3.1(d) 4.3.1(e) 4.3.1(f) 4.3.1(g) 4.3.1(h) 4.3.1(i) 4.3.1(j)
Effect of amount biosurfactant 103
Effect of sorbent mass 105
Effect of type disperser solvent 106 Effect of volume disperser solvent 107
Effect of extraction time 108
Effect of type desorption solvent 109
Effect of desorption time 110
Effect of volume desorption 111
Effect of salt addition 112
Effect of sample volume 113
4.3.2 Reusability of PMS 114
4.3.3 Validation of Bio-DLLME-MDMSPE 115
4.3.4 Real sample analysis 120
4.3.5 Comparison with other published methods 121
4.3.6 Conclusion 124
CHAPTER 5: CONCLUSIONS AND FUTURE DIRECTIONS
5.1 Conclusions 125
5.2 Future directions 127
REFERENCES 129
APPENDICES
vii
LIST OF TABLES
Page Table 2.1 Chemical structures and characteristics of selected PAHs
compound.
14 Table 2.2 Chemical structures and characteristics of selected OPPs
compound.
16 Table 2.3 Summary of some existing functionalized magnetic sorbent
for detection of PAHs and OPPs compound.
40 Table 2.4 Summary of some previous extraction methods for detection
of PAHs compound.
44 Table 2.5 Summary of some previous extraction methods for detection
of OPPs compound.
47 Table 4.1 FTIR characteristics of native MS and PMS. 67
Table 4.2 BET analysis of native MS and PMS. 68
Table 4.3 Analytical performances of the VAE-SID-MDMSPE and SPE of PAHs spiked in water samples (n = 3).
89 Table 4.4 Percentage of relative recoveries (RR), reproducibility in
RSD (n = 5) of VAE-SID-MDMSPE.
92
Table 4.5 PAHs contents in real samples. 94
Table 4.6 Comparison of VAE-SID-MDMSPE to other published methods for the determination of PAHs.
97 Table 4.7 Analytical performances of the Bio-DLLME-MDMSPE and
SPE of OPPs spiked in cabbage samples (n = 3).
118 Table 4.8 Percentage of relative recoveries (RR), reproducibility in
RSD (n = 5) of Bio-DLLME-MDMSPE.
119
Table 4.9 OPPs contents in cabbage samples. 121
Table 5.0 Comparison of Bio-DLLME-MDMSPE to other published methods for the determination of OPPs.
123
viii
LIST OF FIGURES
Page Figure 2.1 Schematic of liquid-liquid extraction (LLE). 19 Figure 2.2 Schematic of solid phase extraction (SPE). 20 Figure 2.3 Schematic of solid phase microextraction (SPME). 23 Figure 2.4 Schematic of dispersive micro-solid phase extraction (D-µ-
SPE).
24 Figure 2.5 Schematic of magnetic dispersive micro-solid phase
extraction (MDMSPE).
25 Figure 2.6 Schematic of micro-solid phase extraction (µ-SPE). 26 Figure 2.7 Schematic of microextraction in packed syringe (MEPS). 27 Figure 2.8 Schematic of liquid phase microextraction (LPME). 28 Figure 2.9 Schematic of hollow fiber liquid phase microextraction
(HF-LPME).
29 Figure 2.10 Schematic of single drop liquid phase microextraction (SD-
LPME).
30 Figure 2.11 Schematic of dispersive liquid- liquid microextraction
(DLLME).
32 Figure 2.12 Schematic of ultrasound-assisted dispersive liquid- liquid
microextraction (UADLLME).
33 Figure 2.13 Schematic of vortex-assisted liquid- liquid microextraction
(VALLME).
35
Figure 3.1 Schematic of VAE-SID-MSPE procedure. 55
Figure 3.2 Schematic of Bio-DLLME-MDMSPE procedure. 61 Figure 4.1 Schematic of the matrix structure in functionalization
process.
65 Figure 4.2 FTIR spectra of native MS (a) and PMS (b). 66 Figure 4.3 XRD pattern of native MS (a) and PMS (b). 69 Figure 4.4 FESEM image of native MS (a) and PMS (b). 70 Figure 4.5 TEM image of native MS (a) and PMS (b); particle size
distribution histograms of native MS (c) and PMS (d).
71
ix
Figure 4.6 Magnetization curve of native MS (a) and PMS (b) and (c) photograph of the separation of PMS under an external magnetic field.
73
Figure 4.7 Effect of type of sorbent on extraction efficiency of PAHs.
Extraction conditions: 100 µg L-1 of spiked solution;
amount of sorbent, 15 mg; extraction time, 80 s; desorption solvent, 200 µL acetone; desorption time, 3 min; sample volume, 35 mL. Peak areas calculated based on average values of peak area of PAHs, n = 3. Error bars represent standard deviation of results, n = 3.
75
Figure 4.8 Possible mechanism of interaction between PMS and PAHs. 76 Figure 4.9 Effect of microextraction modes on efficiency of PAHs.
Extraction conditions: 100 µg L-1 of spiked solution;
amount of sorbent, 15 mg of PMS; extraction time, 80 s;
desorption solvent, 200 µL of acetone; desorption time, 3 min; sample volume, 35 mL: emulsification solvent, 20 µL of 1-octanol; salt-induced demulsifier, 2% of Na2SO4. Peak areas calculated based on average values of peak area of PAHs, n = 3. Error bars represent standard deviation of results, n = 3.
77
Figure 4.10 Effect of mass of sorbent on VAE-SID-MDMSPE efficiency of PAHs. Extraction conditions: 100 µg L-1 of spiked solution; emulsification solvent, 20 µL of 1-octanol;
salt-induced demulsifier, 2% of Na2SO4; extraction time, 80 s; desorption solvent, 200 µL of acetone; desorption time, 3 min; sample volume, 35 mL. Peak areas calculated based on average values of peak area of PAHs, n = 3. Error bars represent standard deviation of results, n = 3.
78
Figure 4.11 Effect of emulsification solvent on VAE-SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 15 mg of PMS.
79
Figure 4.12 Effect of volume of emulsification solvent on VAE-SID- MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 1-octanol as emulsification solvent.
80
Figure 4.13 Effect of extraction time on VAE-SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 20 µL of 1-octanol as emulsification solvent.
82
Figure 4.14 Effect of desorption solvent on VAE-SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 80 s extraction time.
83
x
Figure 4.15 Effect of desorption time on VAE-SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with acetone as desorption solvent.
84
Figure 4.16 Effect of type salt-induced demulsification on VAE-SID- MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 3 min desorption time.
85
Figure 4.17 Effect of amount of salt-induced demulsification on VAE- SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with Na2SO4 as salt-induced demulsifier.
86
Figure 4.18 Effect of sample volume on VAE-SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 2% Na2SO4 as salt-induced demulsifier.
87
Figure 4.19 Reusability of PMS material on VAE-SID-MDMSPE efficiency of PAHs. Microextraction conditions are as Figure 4.10 with 35 mL of sample volume.
88
Figure 4.20 Figure 4.20 Typical GC-MS chromatograms of PAHs in (a) water sample before (PAHs, 1000 μg L-1) and (b) after VAE-SID-MDMSPE (PAHs, 1000 ng L-1) (c) real river water (FLA, 0.018 µg L-1; PYR, 2.04 µg L-1) and (d) paddy field water samples (FLA, 0.01 µg L-1; PYR, 0.015 µg L-1).
Peak identities: (1) fluorene, FLU; (2) anthracene, ANT; (3) fluoranthene, FLA; and (4) pyrene, PYR.
95
Figure 4.21 Effect of type of sorbent on extraction efficiency of OPPs.
Extraction conditions: 500 µg L-1 of spiked solution; mass of sorbent, 15 mg; salt addition 5% of NaCl; extraction time, 1 min; desorption solvent, 150 µL of acetonitrile;
desorption time, 4 min; sample volume, 30 mL. Peak areas calculated based on average values of peak area of OPPs, n
= 3. Error bars represent standard deviation of results, n = 3.
101
Figure 4.22 Possible mechanism of interaction between PMS and OPPs. 101 Figure 4.23 Effect of microextraction mode on the extraction efficiency
of OPPs. Extraction conditions: 500 µg L-1 of spiked solution; mass of sorbent, 15 mg; salt addition 5% of NaCl;
extraction time, 1 min; desorption solvent, 150 µL of acetonitrile; desorption time, 4 min; sample volume, 30 mL.
Peak areas calculated based on average values of peak area of OPPs, n = 3. Error bars represent standard deviation of results, n = 3.
103
xi
Figure 4.24 Effect of amount of biosurfactant on Bio-DLLME- MDMSPE efficiency of OPPs. Extraction conditions: 500 µg L-1 of spiked solution; mass of sorbent, 15 mg; salt addition 5% of NaCl; extraction time, 1 min; desorption solvent, 150 µL of acetonitrile; desorption time, 4 min;
sample volume, 30 mL. Peak areas calculated based on average values of peak area of OPPs, n = 3. Error bars represent standard deviation of results, n = 3.
104
Figure 4.25 Effect of mass of sorbent on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with 40 mg trehalose lipid as optimum biosurfactant.
105
Figure 4.26 Effect of disperser solvent on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with 15 mg as mass of sorbent.
106
Figure 4.27 Effect of volume disperser solvent on Bio-DLLME- MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with tetrahydrofuran as disperser solvent.
107
Figure 4.28 Effect of extraction time on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with 500 µL tetrahydrofuran as disperser solvent.
109
Figure 4.29 Effect of type desorption solvent on Bio-DLLME- MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with 60 s extraction time.
110
Figure 4.30 Effect of desorption time on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with acetonitrile as desorption solvent.
111
Figure 4.31 Effect of volume desorption on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with 4 min desorption time.
112
Figure 4.32 Effect of salt addition on Bio-DLLME-MDMSPE of OPPs.
Microextraction conditions are as Figure 4.24 with 150 µL acetonitrile as desorption solvent
113
Figure 4.33 Effect of sample volume on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.24 with 5 % NaCl salt addition.
114
Figure 4.34 Reusability of PMS material on Bio-DLLME-MDMSPE efficiency of OPPs. Microextraction conditions are as Figure 4.22 with 30 mL sample volume.
115
xii
Figure 4.35 Figure 4.35 Typical GC-FID chromatograms of OPPs (a) in cabbage sample after Bio-DLLME-MDMSPE treatment (OPPs, 500µg L-1) (b) blank cabbage sample and (c) OPPs detected in cabbage sample (SLP, 1.38 µg L-1; TCM, 6.54 µg L-1; CLP, 0.33 µg L-1; ISP,0.74µg L-1 and ETN, 1.83 µg L-1) and (d) mix standard OPPs (5000 µg L-1). Peak identities: (1) sulfotep, SLP; (2) diazinon, DZN; (3) tolclofos-methyl, TCM; (4) chlorpyrifos, CLP; (5) isofenphos, ISP; and (6) ethion, ETN.
121
xiii
LIST OF ABBREVIATIONS
ACE Acenaphthene
ACY Acenaphthylene
AFME Agarose film microextraction
ANT Anthracene
APTES 3-aminopropyltriethoxysilane
AZM Azinphos-methyl
BaA Benzo[a]anthracene
BaP Benzo[a]pyrene
BbF Benzo[b]fluoranthene BET Brunauer–Emmett–Teller BghiP Benzo[ghi]perylene
Bio Biosorption
BkF Benzo[k]fluoranthene C18 Octadecasilyl-bonded silica CE Capillary electrophoresis
CHR Chrysene
CLP Chlorpyrifos
CLT Chlorothalonil
CRL Co-ral
DahA Dibenz[a,h]anthracene
DI Direct immersion
DLLME Dispersive liquid–liquid microextraction
DSF Disolfonate
xiv DSPE Dispersive solid phase extraction
DSM Demeton-s-methyl
DSME Dispersive micro solid phase extraction
DZN Diazinon
ECD Electron captured detector
EDS Endosulfan
EFs Enrichment factors
EPA Environmental Protection Agency
EU European Union
ETN Ethion
FESEM Field emission scanning electron microscope
FID Flame ion detector
FLA Fluoranthene
FLD Fluorescence detector
FLU Fluorene
FNF Fonofos
FNN Fenthion
FNP Fenamiphos
FNT Fenitrohion
FPD Flame photometric detector
FTN Fenitrohion
GC Gas chromatography
HF Hollow-fiber
HPLC High performance liquid chromatography-
HS Headspace
xv IcdP Indeno[1,2,3-cd] pyrene
ICP Iscocarbonphenphos
I.D. Internal diameter
IL Ionic liquid
ISP Isofenphos
LC Liquid chromatography
LDS Low-density solvent LLE Liquid–liquid extraction LOD Limit of detection LOQ Limit of quantification LPME Liquid-phase microextraction MAE Microwave assisted extraction mCNTs Magnetic carbon nanotubes
MDMSPE Micro-dispersive magnetic solid phase extraction MEPS Microextraction in packed syringe
MgSO4 Magnesium sulphate
MLN Malathion
MNPs Magnetic nanoparticles
MPT Methyl-parathion
MRLs Maximum residue limits
MSPE Magnetic solid phase extraction
MTN Methidathion
MWCNTs Multiwalled carbon nanotubes
NAP Naphthalene
NaCl Sodium chloride
xvi Na2SO4 Sodium sulphate
OPPs Organophosphorus pesticides PAHs Polycyclic aromatic hydrocarbons
PFP Profenphose
PMS Phenyl-functionalized magnetic sorbent POP Persistent organic pollutant
PSL Phosalone
PSM Phsomet
PNP Phenamiphos
PRE Phorate
PXM Phoxim
PYR Pyrene
QNP Quinalphos
RSD Relative standard deviation SBSE Stir bar sorptive extraction SDME Single drop microextraction SID Salt induced demulsification SIM Selective ion monitoring
SLP Sulfotep
SMT Sumithion
SPE Solid phase extraction SPME Solid phase microextraction
STP Sulfotep
TCM Tolclofos-methyl
TEM Transmission electron microscopy
xvii TEOS Tetraethyl orthosilicate TEPS Triethoxphenylsilane
THF Tetrahydrofuran
UAE Ultrasound-assisted extraction
UADLLME Ultrasound-assisted dispersive liquid-liquid microextraction VA-d-µ-SPE Vortex-assisted dispersive micro solid phase extraction VAE Vortex-assisted emulsification
VALLME Vortex-assisted liquid-liquid phase microextraction VSM Vibrating sample magnetometer
XRD X-Ray diffraction
xviii
LIST OF SYMBOLS eV Electronvolt
Kow 1-octanol/water partitioning coefficients Log P Partition coefficient
m/z Mass-to-charge ratio mL min-1 Milliliter per minute
MΩ Mega ohms
n Number of observations or replicates ng L-1 Nanogram per liter
OH Hydroxyl
r2 Coefficient of determination rpm Revolution per minute w/v Weight per volume
xix
SINTESIS DAN PENCIRIAN NANOZARAH MAGNET BERFUNGSIKAN FENIL SEBAGAI PENGERAP DALAM PENGEKSTRAKAN MIKRO FASA
PEPEJAL BAGI SEBATIAN HIDROKARBON AROMATIK POLISIKLIK DAN RACUN PEROSAK ORGANOFOSFORUS
ABSTRAK
Suatu pengerap magnet berfungsikan fenil (PMS) telah disediakan dan digunakan dalam kaedah pengekstrakan mikro yang dicadangkan bagi analisis sebatian hidrokarbon aromatik polisiklik (PAHs) dan racun perosak organofosforus (OPPs) yang terpilih. Satu teknik pengemulsian dibantu vortex bergabung dengan penyahemulsian garam teraruh dan pengekstrakan mikro fasa pepejal serakan magnet (VAE-SID-MDMSPE) berasaskan PMS telah dibangunkan bagi penentuan sebatian PAHs yang terpilih iaitu, fluorena (FLU), anthacena (ANT), fluoranthena (FLA) dan pirena (PYR) di dalam sampel air sekitaran, jus tebu dan teh. Di bawah keadaan VAE-SID-MDMSPE dan GC-MS optimum, kaedah ini menunjukkan kelinearan yang baik (R2 ≥ 0.9931) bagi semua sebatian PAHs bagi julat kepekatan 0.01-100 μg L-1 dengan had pengesanan rendah dan had kuantitif, masing-masing adalah 0.003- 0.016 µg L-1 dan 0.01-0.054 µg L-1. VAE-SID-MDMSPE menunjukkan kelebihan daripada segi keringkasan, cepat (5 min proses pengekstrakan), faktor pengkayaan yang tinggi (EFs, 61-239) dan penggunaan pelarut organik yang sedikit (200 µL), keperluan pengerapan yang sedikit (15 mg) dan membuktikan kejayaan kaedah pengekstrakan dengan pengembalian relatif yang tinggi dalam julat 85.3-109.1%
dengan sisihan piawai relatif (RSDs) dari 1.0-8.5 % (n=5). PMS juga digunakan sebagai pengerap dalam erapanbio berdasarkan pengekstrakan mikro serakan cecair- cecair serakan bergabung dengan pengekstrakan mikro-fasa pepejal serakan magnet (Bio-DLLME-MDMSPE) bagi pengekstrakan sebatian OPPs terpilih iaitu, sulfotep (STP), diazinon (DZN), tolklofos-metil (TCM), chlorpirifos (CLP), isofenfos (ISP)
xx
and etion (ETN) dalam sampel kubis. Di bawah keadaan optimum, Bio-DLLME- MDMSPE menunjukkan kelinearan yang baik (R2 ≥ 0.9953) dengan had pengesanan yang baik dan had kuantitatif, masing-masing adalah 0.075-0.15 μg L-1 dan 0.25-0.5 μg L-1 kesemua analit OPPs. Kaedah ini memberikan faktor pengkayaan yang tinggi (EFs, 46-516) dengan pengembalian relatif yang cemerlang dalam julat 85.8-107.9 % bagi semua analit OPPs di dalam sampel kubis. Kaedah pengekstrakan mikro bergabung dengan bahan PMS yang digabungkan menunjukkan sebagai ringkas, cepat dan cekap dengan cirian yang lebih baik berbanding teknik pengekstrakan yang selalunya digunakan dan sesuai digunakan bagi pengesanan PAHs di dalam sampel air, jus tebu dan teh serta OPPs di dalam sampel kubis.
xxi
SYNTHESIS AND CHARACTERIZATION OF PHENYL
FUNCTIONALIZED MAGNETIC NANOPARTICLES AS SORBENT IN MICRO-SOLID PHASE EXTRACTION OF POLYCYCLIC AROMATIC
HYDROCARBONS AND ORGANOPHOSPHORUS PESTICIDES
ABSTRACT
A phenyl-functionalized magnetic sorbent (PMS) was prepared and employed in the proposed microextraction methods for the analysis of selected polycyclic aromatic hydrocarbons (PAHs) and organophosphorus pesticides (OPPs) compounds. A vortex-assisted emulsification combined with salt-induced demulsification and magnetic dispersive micro-solid phase extraction (VAE-SID- MDMSPE) based on PMS was developed for the determination of selected PAHs compound namely, fluorene (FLU), anthracene (ANT), fluoranthene (FLA) and pyrene (PYR) in environmental water, sugarcane juice and tea samples. Under optimized VAE-SID-MDMSPE and GC-MS conditions, the method revealed good linearity (R2 ≥ 0.9931) for all PAHs compounds over a range of 0.01-100 µg L-1 with low limits of detection and limits of quantification, 0.003-0.016 µg L-1 and 0.01- 0.054 µg L-1, respectively. VAE-SID-MDMSPE exhibited superior advantages in terms of simplicity, rapid (5 min extraction process), high enrichment factors (EFs, 61-239), and low usage of organic solvent (200 µL), low sorbent consumption (15 mg) and proved a successful extraction method with high relative recoveries in the range of 85.3-109.1% with relative standard deviations (RSDs) of peak area varied from 1.0-8.5 % (n=5). PMS was also employed as sorbent in a biosorption based dispersive liquid-liquid microextraction combined with magnetic dispersive micro- solid phase extraction (Bio-DLLME-MDMSPE) for the extraction and preconcentration of selected OPPs compounds namely, sulfotep (STP), diazinon
xxii
(DZN), tolclofos-methyl (TCM), chlorpyrifos (CLP), isofenphos (ISP) and ethion (ETN) in cabbage samples. Under the optimized conditions, Bio-DLLME-MDMSPE showed good linearity range (R2≥ 0.9953) with good limits of detection and limits of quantification in the range of 0.075-0.15 μg L-1 and 0.25-0.5 μg L-1, respectively for all OPPs analyte. The method provided high enrichment factors (EFs, 46-516) with excellent relative recoveries in the range of 85.8-107.9 % for all OPPs analytes in cabbage samples. The developed microextraction methods incorporated with PMS material have demonstrated to be simple, rapid and efficient with characteristics that are superior over the commonly used extraction methods and suitable for the detection of PAHs in water, sugarcane juice and tea samples as well as OPPs in cabbage samples.
1 CHAPTER 1
INTRODUCTION
1.1 Background of study
Throughout the past few decades, abundance of different organic chemicals has been synthesized for numerous applications to be utilized as pesticides, herbicides, detergents, insulating materials, etc. Polycyclic aromatic hydrocarbons (PAHs) and organophosphorus pesticides (OPPs) are examples of persistent organic pollutants (POPs) which may cause long-term effects on humans and wildlife even at trace levels (Arslan-Alaton and Olmez-Hanci, 2013). Hence, more studies regarding the effect of organic pollutants and pesticides have been carried out by various researchers.
PAHs is a large class of persistent organic compounds which are particularly composed from incomplete combustion of natural materials throughout industrial process and other anthropogenic activities including automobile traffic, cooking, processing of coal and tobacco smoking (Goda et al., 2014). The stability of PAHs in the environment are influenced by their chemical structures, chemical configuration and physical-chemical properties. Most PAHs compounds are capable to be transported over long range before they come back to the earth with rainfall (Goda et al., 2014). Thus, PAHs causes a serious problem to human health through different routes of exposure such as food, air, water and soil (Wu et al., 2012). Nevertheless, contamination of PAHs in food is the main sources of their exposure to human.
2
Formerly reported work stated that PAHs compounds cause the boom of cancer cell in human (Arslan-Alaton and Olmez-Hanci, 2013).
The growing numbers of utility of pesticides in agricultural industry have prompted severe hazard to human health and the environment. Pesticide may be described as any substance or mixture of materials supposed for mitigating, repelling, destroying, or stopping any pest. It is a poison design specifically to kill unwanted plants and insects. Pesticides are labeled according to their capabilities such as fungicides to kill mold or fungus, herbicides to kill weeds and insecticides to kill bugs (Fenik et al., 2011). Besides that, they are also categorized based on their physical state, target organisms, chemical structure and chemical families such organophosphorus pesticides, organochlorines pesticides and carbamates pesticides.
Pesticides are used extensively during cultivation, harvesting and storage in order to protect the crops from pest, bacteria and to provide food quality assurance (Nan et al., 2015). Furthermore, they are used to avoid many dreadful diseases. In order to increase the production yield of crops; pesticides were applied in many stages of cultivation to provide protection against pest-eating crops. Nevertheless, improper use of pesticides can be dreadful to human health. Therefore, a good agricultural practice is very important to minimize the possible risk to human health and the environment.
Due to adverse effect of POPs to the ecology and human health, stringent constitutional controls are enforced to monitor the manufacture, utilization and emission of POPs. It is necessary to determine and monitor POPs contamination
3
level in environmental matrices to ensure that they are within the safe limits.
Therefore, in order to identify and determine POPs in complex matrices, a selection of an appropriate analytical technique and a robust sampling design is very crucial.
There has been a great challenge face by the scientist to identify and determine POPs as they are usually found at a trace level amount and due to matrix interferences (Arslan-Alaton and Olmez-Hanci, 2013). Hence, sample preparation procedure is required to reduce or eliminate complex matric interferences, pre-concentrate the targeted analytes and to improve sensitivity of the developed analytical methods (Ali et al., 2015).
Over the past decades, numerous procedures have been developed for the extraction and preconcentration of organic compounds. The most commonly procedures used are liquid-liquid extraction (LLE) (Taylor et al., 1995), solid-phase extraction (SPE) (Kayali-Sayadi et al., 1998), solid-phase microextraction (SPME) (Fisichella et al., 2015) and stir bar sorptive extraction (SBSE) (Blasco et al., 2004;
Bourdat-Deschamps et al., 2007; Gomes et al., 2011; Hu et al., 2013; Xiao et al., 2016). Although, LLE has been an effective sample preparation technique, it is exhaustive, labor-intensive and utilize huge amount of hazardous organic solvents (Farajzadeh and Feriduni, 2016). Even though SPE has minimized the limitations of LLE, in term of simplicity, high selectivity and recovery, low consumption of organic solvents (Fotouhi et al., 2017), it also suffer from limitations such as large secondary wastes, a lengthy step, solvent loss and a need for complex gear.
Nowadays, modern trend in analytical chemistry are heading to the simplicity and minimality of sample pretreatment as well as reducing the consumption of hazardous organic solvent (Blasco et al., 2004).
4
In this study, a phenyl-functionalized magnetic sorbent (PMS) was synthesized using a simple method and used as a sorbent material for the extraction and preconcentration of PAHs and OPPs. The previously successful reported works on functionalization of magnetic nanoparticles with thiol and urea, have led for further study on the functionalization of magnetic nanoparticle with triethoxyphenylsilane to form PMS for the extraction of PAHs and OPPs (Salehi et al., 2015). To the extent of our knowledge, this is the first employment of PMS in proposed microextraction systems for PAHs and OPPs determination. Factors affecting the extraction performance based on PMS on the developed microextraction methods were comprehensively studied and evaluated.
1.2 Problem statement
Regardless of the advances in highly efficient analytical instrumentations, some compounds are still beyond from the detection thresholds of these instrumentation. Desired analytes are usually subjected to hindrance by the profoundly complex matrices (e.g., food, environmental and biological). Besides that, most of the analytical tools cannot deal with the sample matrices directly. Thus, sample pretreatment is crucial in the overall chemical analyses. It is essential to concentrate and isolate the targeted analyte of interest from the matrices to ensure the suitability of the analyte for a separation and detection system.
In order to overcome the limitations of conventional methods, a magnetic solid phase extraction (MSPE) is introduced as a refined type of SPE. MSPE is an extraction technique that utilized magnetic materials as sorbents. An alternative of
5
MSPE termed magnetic dispersive micro-solid phase extraction (MDMSPE) has been reported (Cheng et al., 2014). The selection of adsorbent material is very critical as it largely determine the selectivity and sensitivity of the method (Han et al., 2012). Compared to the traditional SPE sorbents (florisil, C18, silica, etc.) which usually co-extract compounds that interfere with analysis due to non-particular interface interactions (Cheng et al., 2014), magnetic materials had simplify and improve the SPE extraction technique. The magnetic materials are directly dispersed in sample solutions, which can enhance the extraction efficiency by broadening the proximity between analytes and the sorbents (Bai et al., 2010). They can be easily recovered with the help of external magnet force and eliminates the tedious filtration or centrifugation procedure (Cheng et al., 2014). Despite their superior characteristic, bare magnetic materials are easily agglomerated and oxidized when exposed to air (Al-rashdi, 2016). Therefore, it is necessary to modify the surface of magnetic materials to achieve selective and sensitive extraction system.
In this present study, a phenyl silane-coupling agent has been selected to be functionalized to the surface of the magnetic sorbent due to its unique structure which is benzene ring and Si-O. The presence of benzene rings in the functionalized magnetic sorbent is most likely will form a hydrophobic and π-π interaction with the targeted analytes (Guo et al., 2015; Stevenson et al., 2017). PMS material with high affinity, high selectivity, and high stability were synthesized and developed as extraction sorbent for PAHs and OPPs. PMS offers many benefits such as high selectivity towards analytes of interest and compatibility for complex matrices, high extraction efficiency, rapid separation after extraction, simple preparation and surface modification of the material, exceptional dispersibility in water sample and
6
good reusability. The application of PMS in vortex-assisted emulsification combined with salt-induced demulsification (VAE-SID-MDMSPE) and biosorption based dispersive liquid-liquid microextraction combined with magnetic dispersive micro- solid phase extraction (Bio-DLLME-MDMSPE) methods are expected to enhance the feasibility and capability of microextraction systems for the detection of PAHs and OPPs.
1.3 Objectives of study
The aim of the study is to develop microextraction methods based on PMS material. The particular objectives of this work are to: -
i. synthesize and characterize phenyl functionalized magnetic sorbent (PMS).
ii. develop a vortex-assisted emulsification combined with salt-induced demulsification (VAE-SID-MDMSPE) for the analysis of PAHs in aqueous matrices.
iii. develop a biosorption based dispersive liquid-liquid microextraction combined with magnetic dispersive micro-solid phase extraction (Bio- DLLME-MDMSPE) for the extraction of OPPs in cabbage samples.
1.4 Scope of Study
This study focuses on the development of new microextraction methods based on PMS, namely VAE-SID-MDMSPE and Bio-DLLME-MDMSPE for the determination of PAHs and OPPs in water, juice and vegetable matrices. Four
7
selected PAHs compound namely fluorene (FLU), anthracene (ANT), fluoranthene (FLA) and pyrene (PYR) were used in this study. The selected OPPs are sulfotep (STP), diazinon (DZN), tolclofos-methyl (TCM), chlorpyrifos (CLP), isofenphos (ISP) and ethion (ETN). The extraction capability of the developed microextraction methods was determined using gas chromatography mass-spectrometry (GC-MS) system and gas chromatography flame ionization detector (GC-FID) for PAHs and OPPs, respectively. Factors influencing the extraction efficiency were optimized thoroughly prior to method validation and application to real samples. The capability of the developed microextraction methods were tested on real samples such as lake water, pond water, river water, paddy field water, sugarcane juices, tea and cabbage samples.
1.5 Significance of study
In order to overcome major limitations in the conventional LLE and SPE methods such as high consumption of solvent and sorbent material, time consuming and tedious operation, new microextraction methods that are efficient, rapid, environmentally friendly and cost-effective are desirable. Magnetic based microextraction system has been introduced to shorten the extraction time and simplify the conventional SPE by hastening the mass transfer of analytes from sample matrices to the magnetic sorbent. The developed VAE-SID-MDMSPE and Bio-DLLME-MDMSPE operation in extraction providing attractive and creative way of combining different microscale sample preparation method. The developed microextraction systems have ‘green chemistry’ nature due to its microscale format (mg amount of sorbent and µL of solvent required for the extraction). More
8
importantly, the procedure for conducting VAE-SID-MDMSPE and Bio-DLLME- MDMSPE is simple and involved unsophisticated devices (vortex and ultrasonication system), generally found in a typical analytical laboratory.
1.6 Outline of the thesis
This thesis composes of five chapters. Chapter 1 provides in detail the research background, problem statement, objectives, scope as well as significance of the study. Chapter 2 compiles the fundamentals of the selected organic contaminants studied and their properties, introduction to conventional and microextraction methods and potential microextraction methods of PAHs and OPPs and finally the applications of magnetic sorbents in sample preparation. Chapter 3 elaborates the research methodology of each objective independently while Chapters 4 describes in specific the study associated to the objective of the study as mentioned in Section 1.3.
Chapter 4 is divided into three parts, corresponding to each specific objective.
The first part describes the results for synthesis and characterization of PMS material. The second part reports the results and discussion on optimization study, method validation and application of in VAE-SID-MDMSPE towards the determination of selected PAHs in aqueous matrices. The third part investigates the application of PMS materials in Bio-DLLME-MSDMSPE for determination of selected OPPs in cabbage samples.
9
The performance of VAE-SID-MDMSPE was verified for the analysis of four target PAHs analyte namely, fluorene (FLU), anthracene (ANT), fluoranthene (FLA), and pyrene (PYR) in environmental water, sugarcane juice and tea samples.
Several significant VAE-SID-MDMSPE parameters such as, type and volume of emulsification solvent, extraction time, type of desorption solvent, desorption time, type and amount of salt-induced demulsified and sample volume were investigated.
The performance of Bio-DLLME-MDMSPE was optimized and validated for the determination of selected six OPPs analytes, namely, sulfotep (STP), diazinon (DZN), tolclofos-methyl (TCM), chlorpyrifos (CLP), isofenphos (ISP) and ethion (ETN) in cabbage samples. Important Bio-DLLME-MDMSPE parameters such as addition of biosurfactant, amount of biosurfactant, type and volume of disperser solvent, mass of sorbent, extraction time, type and volume of desorption solvent, desorption time, salt addition and sample volume were thoroughly investigated.
Lastly, Chapter 5 summarizes the major findings of the study and directions for future studies. This chapter covers the overall results obtained including the optimization study, validation data and analytical characteristics of the developed microextraction methods. Future directions are discussed for potential further studies.
10 CHAPTER 2
LITERATURE REVIEW
2.1 Overview
This chapter compiles and discusses the fundamentals of the selected polycyclic aromatic hydrocarbons (PAHs) and organophosphorus pesticides (OPPs) with its analytical determination, development of conventional and microextraction methods and applications of magnetic sorbent in sample preparation.
2.2 Organic pollutants
Over decades, variety of organic chemicals has been manufactured for different purposes such use as insecticides, herbicides, detergents and insulating materials. However, many of them are persistent in the environment which they stay pristine for long spans as they withstand chemical, photolytic and biological degradation (Wong et al., 2005). Polycyclic aromatic hydrocarbons (PAHs) and organophosphorus pesticides (OPPs) are classified as persistent organic pollutants (POPs) due to their physical and chemical characteristics such as highly toxic even at low levels, ability to transport at a long range through air and water, hydrophobicity and lipophilicity which enable them to bio-accumulate in fatty tissue of an organism, especially on a species at the top of the food cycle (Jacob and Cherian, 2013; Tang, 2013; Xu et al., 2013).
11
Nowadays, POPs contamination had been a public concern due to their adverse effects to the environment and human health. POPs are spread globallyand they may act as hormone disruptors and causing neurologic disorders, suppressing the immune system and increasing the risk of cancer (El-shahawi et al., 2010; Xu et al., 2013). Therefore, there is a concern of special environmental relevance in regard to the investigation and monitoring of these compounds. However, direct analysis of organic compounds by analytical instrumentation is mostly difficult due to the existence of matrix hindrances and traces amount of the analytes. Hence, sample pretreatment process is crucial to separate the analyte from the sample and to preconcentrate the targeted analyte, to enhance the sensitivity and capability of the detection systems.
2.2.1 Polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are a set of chemical mixture that are constitute of two or more fused aromatic rings. There are abundant of PAH compounds, each distinct in the orientation of substituents on the general ring system and the number and position of aromatic rings (Eisler, 1987). PAHs are classified into light PAHs and heavy PAHs based on the number of fused aromatic ring in their structures (Goda et al., 2014). PAHs that contain four or less fused aromatic aromatic rings are categorized as light PAHs whereas heavy PAHs are those with more than four fused rings (Farhadian et al., 2010). Unsubstituted lower molecular weight PAHs made up of 2 or 3 rings, display significant severe toxicity and other deleterious effects to some organisms, but are noncarcinogenic; the higher molecular weight PAHs, consists 4 to 7 rings, are significantly less toxic, but some of the
12
compounds are teratogenic, mutagenic or carcinogenic to the diversity of organisms such as mammals, aquatic life, amphibians and birds (Eisler, 1987).
PAHs are mainly generated during incomplete combustion or pyrolysis of carbon-containing organic substances, fossil fuels, domestic burning, industrial operations and other human activities (Food Safety Authority of Ireland, 2015; Guo and Lee, 2011). Other than that, PAHs are formed by natural processes such as volcano eruptions and forest fires (Srogi, 2007). They are ubiquitous in the environmental compartments such as atmosphere, water and soil. The production of PAHs leads to food contamination causing dangerous effects to human health. PAHs are possibly formed in foods during domestic food preparation and industrial processing and such as frying, smoking, roasting, barbecuing, drying, baking or grilling (Food Safety Authority of Ireland, 2015).
PAHs are generally have relatively low water solubility but highly lipophilic, low vapour pressure and high melting and boiling points (Srogi, 2007). These compounds tend to move through the food cycle and can be transmit over long ranges (Katsoyiannis and Breivik, 2014; Ting et al., 2017). Regardless of PAHs high lipid solubility, they exhibit low tendency to bio-magnify in food cycles, probably due to their rapid metabolism (Bansal and Kim, 2015). Although they exist in minute concentrations in the environment and food samples, many studies have shown that it could lead to cancer (Menezes et al., 2013; Shi et al., 2016).
The US Environmental Protection Agency (US EPA), Agency of Toxic substance and Disease register (ATS-DR), International Agency for Research on
13
Cancer (IARC), and European Union have named 16 unsubstituted PAHs as priority pollutants and they are commonly used to characterize the PAH content (Bansal and Kim, 2015; Singh et al., 2016). Benzo(a)pyrene (BaP) is frequently used as a marker for total PAHs exposure in industry, food as well as in the environment due to its highest volatility and lowest boiling point (Srogi, 2007). However, in 2008, the European Food Safety Authority (EFSA) has governed that there was unreliability in BaP as a dependable marker for the occurrence of PAHs in food (Bansal and Kim, 2015; Purcaro et al., 2013). Nevertheless, up until now, the administrative regulation for PAH levels have been lacking due to the complexity of the matrices (Bansal and Kim, 2015). Even though, lighter PAHs have weaker mutagenic and carcinogenic properties, they are the most abundant in the urban atmosphere and reactive toward other pollutants to form more toxic derivatives (Srogi, 2007). Besides that, there is only few info regarding the study of lighter PAHs compared to heavier PAHs. Thus, in this study, four PAHs were selected as model analytes, such as fluorene (FLU), anthracene (ANT), fluoranthene (FLA) and pyrene (PYR). Chemical structures and characteristics of selected PAHs are described in Table 2.1.
14
Table 2.1: Chemical structures and characteristics of selected PAHs compound.
Common name Empirical formula
Molecular mass
(g mol-1) Log Kow Water solubility (mg L-1)
Boiling point
(°C) Chemical structure
Fluorene (FLU) C13H10 166.22 4.12 1.992 295
Anthracene (ANT) C14H10 178.23 4.56 0.022 340
Fluoranthene (FLA) C13H10 202.25 5.64 0.265 375
Pyrene (PYR) C13H10 202.25 5.58 0.135 404
15 2.2.2 Organophosphorus pesticides
Pesticides are widely utilized to restrain pests and obviate infections in harvest like vegetables, cereals and fruits. Organophosphorus pesticides (OPPs) are widely employed for agricultural processes due to their high efficiency in increasing agricultural productivity by controlling pests and diseases. However, due to the extensive consumption of OPPs, they have become the most common and persistent contaminants of products of agriculture. Moreover, the slow deterioration and improper utilization of OPPs causes in excess of these compound in the environment which lead to soil contamination. Majority of OPPs are persist in the environment and may enter the food chains through various ways resulted in potential risk to human health (Eleršek and Filipi, 2006). They alter the enzyme acetyl-cholinesterase used to control the nerve function for animals and humans as well as insects (Sogorb and Vilanova, 2002). The European Union had established the maximum residue levels in vegetables and fruits ranging from 0.01 to 3 mg kg-1 (Xu et al., 2014). The detection of OPPs in agricultural products is necessary to eliminate and reduced the potential risks to human health. Thus, it is critical to establish an effective analytical method which is high in sensitivity, selectivity and simplicity for the analysis of trace OPPs in variety of samples to guarantee public welfare and international trade. In this current study, six OPPs were chosen namely sulfotep (SLP), diazinon (DZN), tolclofos-methyl (TCM), chlorpyrifos (CLP), isofenphos (ISP) and ethion (ETN).
The chemical structures and characteristics of selected OPPs are shown in Table 2.2.
From the table, these OPPs composed of similar general structure but indifferent in terms of their chemical and physical properties.
16
Table 2.2 Chemical structures and characteristics of selected OPPs compound.
Common name Empirical formula
Molecular mass (g mol -1)
log P
Water solubility (mg
L-1)
Boiling point
(°C) Chemical structures
Sulfotep
(SLP) C8H20O5P2S2 322.3 3.99 10 136 to 139
Diazinon
(DZN) C12H21N2O3PS 304.3 3.69 60 315.9
Tolclofos -
methyl (TCM) C9H11Cl2O3PS 301.1 4.56 0.708 338.5
17
Table 2.3 Chemical structures and characteristics of selected OPPs. (Continued) Common
name Empirical formula
Molecular mass (g mol -1)
log P
Water solubility
(mg L-1)
Boiling point
(°C)
Chemical structures
Chlopyrifos
(CLP) C9H11C13NO3PS 350.62 4.70 1.05 349
Isofenphos
(ISP) C15H24NO4PS 345.3 4.04 24 345
Ethion (ETN) C9H22O4P2S4 384.4 5.07 2 384
18
2.3 Extraction methods for chemical analysis
Analysis process consists of five steps namely, sampling, sample preparation, separation, detection as well as data analysis which are extremely important to achieve reliable data. The main aspects in achieving a successful analysis from complex matrices are the quality of sampling and sample preparation as they covered more than 80% of analysis time (Vas and Vékey, 2004). Hence, the preferred sample preparation technique has huge impacts towards the accuracy of the analysis. This chapter gives some insight on the extraction techniques, i.e. from conventional to microextraction techniques
2.3.1 Liquid-liquid extraction
Liquid–liquid extraction (LLE) in Figure 2.1 is a classical separation technique in analytical chemistry which take advantages of the dissimilar solubility of the analyte in the sample solution and in immiscible organic phase, to selectively extract the analyte into one solvent leaving the rest of the matrix in the other. LLE has been broadly utilized as sample pretreatment for metal cations (Khoutoul et al., 2016), biological (Jouyban et. al., 2016), beeswax (Yáñez et al., 2013) and aqueous samples (Farajzadeh and Feriduni, 2016). Nevertheless, there are major limitations of conventional LLE; it needs huge amounts of organic solvent that is costly and hazardous to the environment and it is tedious due to evaporating step of large volume of organic solvent.
19
Figure 2.1 Schematic of liquid-liquid extraction (LLE).
2.3.2 Solid phase extraction
Solid phase extraction (SPE) in Figure 2.2 apply the affinity of analytes dissolved in a sample solution for a solid sorbent. The sorbent is the heart of SPE which regulate the effectiveness and the selectivity of the extraction (Pichon, 2000).
Therefore, the selection of sorbents depends on the analytes characteristic and interactions between analyte and sorbents. SPE is an alternative method of LLE to pretreatment and preconcentration analytes, and it is successfully applied for the detection of pollutants in environment (Blackwell et al., 2004; Heuett et al., 2015; Li et al., 2007) and biological samples (Mei et al., 2011). However, most of conventional SPE methods need to utilize organic solvents to elute the analytes after all the samples was completely pass through the cartridges filled with sorbents. Thus,
20
SPE method is exhaustive, relatively expensive, especially for large volumes of samples, time-consuming and labor intensive.
Figure 2.2 Schematic of solid phase extraction (SPE).
2.3.3 Supercritical fluid extraction
Supercritical fluid extraction (SFE) needs a supercritical fluid as extracting solvent to extract the desired analytes from the sample. Carbon dioxide (CO2) is commonly employed as critical fluid due to its critical pressure of 72.8 atm and critical temperature of 31.2 °C (Rissato et al., 2005). Moreover, CO2 is nonflammable, odorless, non-toxic, tasteless, inert and cost effective. SFE has shorten the extraction time and it is environmentally friendly with high precision and selectivity compared to the conventional extraction techniques (Han et al., 2015).
21
Nonetheless, this method is inappropriate for routine analysis due to the need for special gear which is costly.
2.3.4 Microwave assisted extraction
Microwave assisted extraction (MAE) is considered as a new sample pretreatment of liquid, semi-solid and solid matrices. MAE depend on the dielectric susceptibility of both solvent and matrices result from the rapid heating processes that happen when a microwave field is employed to a sample. MAE is beneficial due to its flexibility to cover variety types of sample and the selectivity can be maneuver by changing the solvent polarities. MAE has been widely used in food (Bouaid et al., 2000; Z. Wang et al., 2013) and biological analysis (Kumar et al., 2014).
2.4 Development of microextraction methods for chemical analysis
In order to overcome the problems in the classical extraction techniques such as large solvent consumption, labour-intensive operations, and high cost, new microextraction method based on minituarized methods were developed. They have received a tremendous attention from the researchers as they are more simple, efficient, economic and environmental friendly due to minimum usage of hazardous chemicals. In order to minimize the environmental pollution and towards the green analytical chemistry process, a miniaturization in the development of sample preparation methods is critical.
22 2.4.1 Sorbent based microextraction methods
2.4.1(a) Solid phase microextraction
Solid phase microextraction (SPME) device in Figure 2.3, consists of a syringe assembly which act as a holder for the fiber assembly and a fiber assembly which comprised of a needle that protects the polymeric fiber (Magdic et al., 1996).
SPME is an extraction method of volatile and semi-volatile analyte from sample to the adsorptive polymeric fiber of SPME (extracting phase) (Menezes et al., 2015).
The amount of adsorption on the extracting phase mostly relies on the thickness of the coating which decide the volume and surface area of the extracting phase. SPME is simple, fast and solventless alternative the classical extraction methods. However, SPME has some drawbacks which the process for preparation of the film for commercial devices is costly, suffer from carry-over effect and fragility of the fiber which it can break easily during sampling and injection (Merkle et al., 2015).
23
Figure 2.3 Schematic of solid phase microextraction (SPME).
2.4.1(b) Dispersive micro-solid phase extraction
Dispersive micro-solid phase extraction (D-μ-SPE) in Figure 2.4 is a diversion of dispersive solid phase extraction (DSPE) which utilized solid sorbent in the range of µg or mg to be dispersed in a sample solution for rapid interaction between the sorbent and targeted compound as well as reducing the time taken for sample pretreatment (Kocot et al., 2013). This microextraction technique had simplify and subdue the limitation of conventional solid phase extraction (SPE) method, which is tedious, produce large of secondary wastes, and need for special equipment. D-μ-SPE have been successfully employed for the analysis of semi volatile compounds from plant tea (Cao et al., 2014), cadmium and lead from water samples (Krawczyk et al., 2016) and triazines from water samples (Jiménez-Soto et al., 2012).
24
Figure 2.4 Schematic of dispersive micro-solid phase extraction (D-µ-SPE).
2.4.1(c) Magnetic dispersive micro-solid phase extraction
Magnetic dispersive micro-solid phase extraction (MDMSPE) in Figure 2.5, is variation of magnetic solid phase extraction (MSPE) method. MDMSPE utilized just a small amounts of solvent and milligrams of sorbent in the extraction compare to the common MSPE (Es’haghi et al., 2016). MSPE and MDMSPE have been applied for the extraction of organic compounds and heavy metal (Es’haghi et al., 2016) in different types of aqueous and food matrices (Bai et al., 2010; Galán-Cano et al., 2013; Rocío-bautista et al., 2016; Zhao et al., 2011; Zhou et al., 2017).