Development of a Comprehensive GCMS Method for Simultaneous Analysis of three major groups of components in Drinking water

Introduction

A simple, fast GCMSMS method has been established for simultaneous estimation of 16 Polycyclic aromatic hydrocarbons (PAHs), 19 Polychlorinated biphenyls (PCBs) and 29 Pesticides including Organochlorine and Organophosphates (OCP and OPs) in drinking water. 

PAH’s are a class of organic compounds, characterised by two or more fused aromatic rings. Occurring in the environment, they give cause for concern because of toxic, mutagenic and carcinogenic activity. 

PCB’sare manmade organochlorine chemicals that have been recognized worldwide as highly and ubiquitous environmental pollutants. Industrially, PCBs are synthesized via catalytic chlorination of biphenyl giving up to 209 different congeners, all with the formula (C12H102xClx; x 1 –10).

Pesticides including both OC’s and OP’s have the potential to contaminate drinking water supplies.  They are applied to farmlands, gardens and lawns and can make their way into ground water or surface water systems that feed drinking water supplies poses eco-toxicological risk. 

These three group of compounds are highly familiar and important to routine environmental analysis in testing laboratories for their stringent regulatory requirements. In conventional method the whole analysis is completed in following three steps i)Extraction of water sample with solvent, evaporation and reconstitution for instrumental analysis ii) Analysis of prepared sample in GC ECD for identification and estimation of individual OCP and total PCBs. iii) Analysis of prepared sample in GCMS MS for identification of PAH and organophosphate pesticides individually.

The literature search revealed that, although simultaneous estimation of all the three components was primarily done in sediment samples though estimation of 16Polycyclic aromatic hydrocarbons (PAHs), 12 Polychlorinated biphenyls (PCBs) and 9 Organochlorine pesticides (OCPs) are only reported (Fidaet.al.) In addition, Abdelkaderet.al reported simultaneous estimation of only PCBs and OCPs in water. USEPA 525.23 method is there for estimation of semi volatile components in water but does not include naphthalene and OP’s. 

Henceforth, we have developed and validated a simple and fast single GC-MS method to quantify all the three multi residues in water by employing simple solid phase extraction technology. The advantages of the method include the simultaneous measurement of 64 analytes with simplicity, low cost and high sensitivity. 

Experimental

Apparatus

Agilent SPE apparatus used for extraction and sample preparation.

Thermo Scientific TRACE™ 1310 Gas Chromatograph and the TSQ 8000 DUO Mass Spectrometer were used for GCMS analysis.

Reagents, materials and standards

Bond Elute Plexa SPE cartridge, Methylene chloride, Ethyl acetate, Methanol

PAH, PCB and Pesticide Standards containing compounds are listed in Table 1.

Method validation

The developed method was validated for the following parameters.

Linearity, Limit of detection and limit of quantification, Recovery and Precision

Results and Discussion

Method Productivity & Performance

Entire list of compounds was analyzed effectively by GCMSMS, in the multiple reaction monitoring mode (MRM). For each analytes, precursor ion and 2 product ions were determined. One product ion used for quantification and one for qualification. 

Total ion chromatogram is given in Fig 1.

Linearity:

The calibration curve was prepared using reference standards at five calibration levels. The calibration curve of PAHs was obtained from standard concentrations of 0.05to1.0 mg L−1.The calibration curve of Pesticides and PCBs was obtained from standard concentrations of 0.005to 0.2 mg L−1. All residuals were within ± 20% and correlation coefficients square (R2) were higher or equal to 0.98.

Representative standard curve of each group is given in Fig 2.

LOD &LOQ

The LOD for individual PAH was calculated as 0.03 and LOQ was calculated as 0.1mg L−1. The LOD for individual PAH and pesticides was calculated as 0.003 and LOQ was calculated as 0.01mg L−1. 

Recovery 

 The recovery was found to be between 70-120% for each individual compounds spiking at two different level before extraction. The results are presented in Table No.2.

Precision

Precision in this validation was calculated from the 3 replicate determinations at lower spiking level. The results of repeatability as obtained were presented in terms of the relative standard deviation (%RSD) in Table No.3. Over all the Relative standard deviation values were found to be within 10%.

Conclusion

In the present study, the three major group of residue PAH, PCB and Pesticides were simultaneously estimated by employing the SPE followed by GCMSMS analysis. This rapid and reproducible method succeeds over the conventional method in following aspects 1) Total time require to complete total analysis. 2) Use of Instruments 3) Solvent consumption. In addition, the new method is also cost effective in commercial purview.

Table and Figures

Table:1 Compounds in PAH,PCB and Pesticide mix

Sl no PAH’S PCB’S PESTICIDES
1 Napthalene 2,Chlorobiphenyl a-HCH
2 Acenapthylene 2,3 Dichlorobiphenyl g-HCH
3 Acenapthene 2,2′,5-Trichlorobiphenyl b-HCH
4 Fluorene 2,4′,5-Trichlorobiphenyl d-HCH
5 Phenanthrene 2,2′,3,5′-Tetrachlorobiphenyl Aldrin
6 Anthracene 2,2′,5,5′-Tetrachlorobiphenyl Dieldrin
7 Fluoranthene 2,3′,4,4′-Tetrachlorobiphenyl O,p’-DDD
8 Pyrene 2,2′,3,4,5′-Pentachlorobiphenyl P,p’-DDD
9 Benz (a) anthracene 2,2′,4,5,5′-Pentachlorobiphenyl O,p’-DDT
10 Chrysene 2,3,3′,4,6′-Pentachlorobiphenyl O,p’-DDT
11 Benzo (b) Fluoranthene 2,2′,3,4,4′,5-Hexachlorobiphenyl O,p’-DDE
12 Benzo (k) Fluoranthene 2,2′,3,4,5,5′-Hexachlorobiphenyl P,p’-DDE
13 Benzo (a) pyrene 2,2′,3,5,5′,6-Hexachlorobiphenyl a-Endosulfan
14 Indeno(1,2,3-cd)Pyrene 2,2′,4,4′,5,5′-Hexachlorobiphenyl b-Endosulfan
15 dibenz(ah)anthracene 2,2′,3,3′,4,4′,5-Heptachlorobiphenyl Endosulfan-Sulfate
16 benzo(ghi)perylene 2,2′,3,4,4′,5,5′-Heptachlorobiphenyl Ethion
17 _ 2,2′,3,4,4′,5′,6-Heptachlorobiphenyl Chlorpyrifos
18 _ 2,2′,3,4′,5,5′,6-Heptachlorobiphenyl Phorate
19 _ 2,2′,3,3′,4′,5,5′,6-Nonachlorobiphenyl Butachlor
20 _ _ Alachlor
21 _ _ Me-Parathion
22 _ _ Malathion
23 _ _ PhorateSulfoxide
24 _ _ Phorate -Sulfone
25 _ _ Malathion
26 _ _ Methyl Paraxon
27 _ _ Malaoxon
28 _ _ Monochrotophos
29 _ _ 2,4D methyl ester

Table:2 Result for %Recovery at different spiking level

PAH’S % Recovery     at 0.1ppb % Recovery at 0.5ppb PESTICIDES % Recovery at 0.02ppb % Recovery at 0.1ppb
Napthalene 100.8 80.67 a-HCH 83.55 97.56
Acenapthylene 77.13 79.02 g-HCH 88.15 85.76
Acenapthene 82.92 76.17 b-HCH 96.4 88.52
Fluorene 82.68 105.27 d-HCH 98.9 100.79
Phenanthrene 81.37 77.78 Aldrin 102.5 108.32
Anthracene 80.89 77.78 Dieldrin 86.75 85.17
Fluoranthene 99.7 91.81 O,p’-DDD 93.7 84.29
Pyrene 93.81 83.27 P,p’-DDD 97.55 92.76
Benz (a) anthracene 88.36 90.14 O,p’-DDT 99.6 83.51
Chrysene 76.22 90.14 O,p’-DDT 91.05 79.76
Benzo (b) Fluoranthene 71.38 91.87 O,p’-DDE 105.5 94.22
Benzo (k) Fluoranthene 82.2 91.88 P,p’-DDE 81.1 78.93
Benzo (a) pyrene 75.72 86.35 a-Endosulfan 82.35 89.69
Indeno(1,2,3-cd)Pyrene 72.09 80.43 b-Endosulfan 89.6 86.92
dibenz(ah)anthracene 83.78 75.94 Endosulfan-Sulfate 93.6 87.68
benzo(ghi)perylene 80.23 72.78 Ethion 112.4 104.92
PCB’S % Recovery at 0.02ppb  % Recovery at 0.1ppb  Chlorpyrifos 106.1 100.69
2,Chlorobiphenyl 92.35 97.13 Phorate 105.2 90.06
2,3 Dichlorobiphenyl 98.65 100.67 Butachlor 83.55 79.45
2,2′,5-Trichlorobiphenyl 105.15 87.62 Alachlor 81.4 82.34
2,4′,5-Trichlorobiphenyl 108.25 84.43 Me-Parathion 81.9 77.54
2,2′,3,5′-Tetrachlorobiphenyl 86.5 80.4 Malathion 81.75 77.68
2,2′,5,5′-Tetrachlorobiphenyl 82.3 83.37 PhorateSulfoxide 107.45 108.01
2,3′,4,4′-Tetrachlorobiphenyl 82.2 87.62 Phorate -Sulfone 100.15 88.94
2,2′,3,4,5′-Pentachlorobiphenyl 83.4 84.91 Malathion 98.7 95.96
2,2′,4,5,5′-Pentachlorobiphenyl 86.35 84.03 Methyl Paraxon 107.8 107.2
2,3,3′,4,6′-Pentachlorobiphenyl 91.75 103.11 Malaoxon 99 88.97
2,2′,3,4,4′,5-Hexachlorobiphenyl 90.15 86.56 Monochrotophos 90.9 95.3
2,2′,3,4,5,5′-Hexachlorobiphenyl 82.85 75.79 2,4D methyl ester 82.75 97.89
2,2′,3,5,5′,6-Hexachlorobiphenyl 80.1 74.02
2,2′,3,3′,4,4′,5-Heptachlorobiphenyl 84.25 79.15
2,2′,3,4,4′,5,5′-Heptachlorobiphenyl 84.8 74.56
2,2′,3,4,4′,5′,6-Heptachlorobiphenyl 76.45 85.78
2,2′,3,4′,5,5′,6-Heptachlorobiphenyl 75.75 72.81
2,2′,3,3′,4′,5,5′,6-Nonachlorobiphenyl 79.95 78.83

Table:3 Result for % RSD of recoveries

PAH’s % Recovery SET 1 % Recovery SET 2 % Recovery SET 3 % RSD of recovery
Napthalene 100.8 104.11 92.13 6.25
Acenapthylene 77.13 78.65 80.1 1.89
Acenapthene 82.92 77.09 75.98 4.74
Fluorene 82.68 76.13 70.73 7.82
Phenanthrene 81.37 74.26 76.99 4.63
Anthracene 80.89 88.57 73.12 9.55
Fluoranthene 99.7 97.03 86.79 7.21
Pyrene 93.81 82.06 80.83 8.37
Benz (a) anthracene 88.36 90.44 75.32 9.67
Chrysene 76.22 76.99 72.66 3.07
Benzo (b) Fluoranthene 71.38 76.83 71.25 4.35
Benzo (k) Fluoranthene 82.2 79.31 73.31 5.79
Benzo a pyrene 75.72 78.61 76.31 1.99
Indeno(1,2,3-cd)Pyrene 72.09 74.76 75.19 2.27
Dibenz(ah)anthracene 83.78 77.78 72.38 7.31
Benzo(ghi)perylene 80.23 81.28 76.2 3.38
2-Chlorobiphenyl 92.35 86.1 91.05 3.67
2,3-Dichlorobiphenyl 98.65 93.65 92.25 3.55
2,2′,5-Trichlorobiphenyl 105.15 94.85 88.15 8.92
2,4′,5-Trichlorobiphenyl 108.25 94.45 93.15 8.49
2,2′,3,5′-Tetrachlorobiphenyl 86.5 97.45 87.35 6.74
2,2′,5,5′-Tetrachlorobiphenyl 82.3 91.05 90.45 5.56
2,3′,4,4′-Tetrachlorobiphenyl 82.2 95.6 92.6 7.8
2,2′,3,4,5′-Pentachlorobiphenyl 83.4 81.00 83.35 1.66
2,2′,4,5,5′-Pentachlorobiphenyl 86.35 84.35 91.15 4.00
2,3,3′,4,6′-Pentachlorobiphenyl 91.75 93.6 97.85 3.31
2,2′,3,4,4′,5-Hexachlorobiphenyl 90.15 87.00 84.7 3.13
2,2′,3,4,5,5′-Hexachlorobiphenyl 82.85 86.4 80.55 3.54
2,2′,3,5,5′,6-Hexachlorobiphenyl 80.1 83.8 80.9 2.39
2,2′,3,3′,4,4′,5-Heptachlorobiphenyl 84.25 79.55 86.05 4.03
2,2′,3,4,4′,5,5′-Heptachlorobiphenyl 84.8 84.5 86.2 1.07
2,2′,3,4,4′,5′,6-Heptachlorobiphenyl 76.45 79.65 75.45 2.84
2,2′,3,4′,5,5′,6-Heptachlorobiphenyl 75.75 86.2 75.65 7.65
2,2′,3,3′,4′,5,5′,6-Nonachlorobiphenyl 79.95 75.5 73.7 4.21
2,4 D 83.55 87.45 91.25 4.4
a-HCH 88.15 86.1 86.05 1.38
g-HCH 96.4 88.2 81.4 8.47
b-HCH 98.9 93.2 83.75 8.32
d-HCH 102.5 94.75 105.95 5.68
Aldrin 86.75 80 87.2 4.76
Dieldrin 93.7 90.85 94.55 2.08
O,p’-DDD 97.55 92.85 85.85 6.39
P,p’-DDD 99.6 89.8 87.85 6.81
O,p’-DDT 91.05 93.65 99.45 4.54
Pp’-DDT 105.5 94.05 94.95 6.49
O,p’-DDE 81.1 82.65 78.4 2.66
P,P-DDE 82.35 88.45 89.9 4.61
a-Endosulfan 89.6 99.4 100.1 6.09
b-Endosulfan 93.6 96.35 94.15 1.54
Endosulfan-Sulfate 112.4 100.5 108.4 5.65
Ethion 106.1 93.2 91 8.43
Chlorpyrifos 105.2 99.4 87.45 9.3
Phorate 83.55 92.35 85.45 5.32
Butachlor 81.4 92.5 92.95 7.36
Alachlor 81.9 79.5 78.25 2.32
Atrazine 81.75 77.9 74.9 4.39
Me-Parathion 107.45 99.6 106.9 4.19
Malathion 100.15 114.7 111.4 7.01
PhorateSulfoxide 98.7 99.7 99.05 0.51
Phorate -Sulfone 107.8 90.25 105.4 9.41
Methyl Paraxon 99.0 98.0 102.0 2.09
Malaoxon 90.9 88.15 89.6 1.54
Monocrotofos 82.75 83.6 76.0 5.15

Fig:1 Total ion chromatogram 

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Fig 2Calibration curve of one representative compound of each group

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Conducted By: Piali Ganguly