GC ECD

The sfe of chlorpyrifos methyl from wheat followed by on-line Ic/gc/ecd has been investigated (93). Extraction profiles were generated to determine the maximum analyte recovery and the minimum extraction time. Using pure CO2, a 65% recovery of chlorpyrifos methyl spiked onto wheat at 50 ppb was reported. When 2% methanol was added to the CO2, the recovery from a one gram sample averaged 97.8% (n = 10, 4.0% RSD). 

Chlorphenylid, Flucofuron and Sulcofuron Waters (Tentative Methods based on methylation and GC-ECD, ion-pair HPLC and hydrolysis of Sulcofuron to 4-chloro-3-trifluoromethylaniline by GC-ECD), 1993... 

Figure 10.13 GC clrromatogram obtained after on-line LC-GC(ECD) of a human milk sample analysed for PCBs (attenuation X 64). Peak identification is as follows (1) PCB 28 (2) PCB 118 (3) PCB 153 (4) PCB 138 (5) PCB 180 (6) PCB 170 (7) PCB 207. Reprinted from Journal of High Resolution Chromatography, 20, G. R. van der Hoff et al, Determination of organochlorine compounds in fatty matiices application of normal-phase LC clean-up coupled on-line to GC/ECD , pp. 222-226, 1997, with permission from Wiley-VCH.

G. R. van der Hoff, R. A. Baumann, P. van Zoonen and U. A. Th. Brinkman, Determination of organocWoiine compounds in fatty matrices application of normal-phase PC clean-up coupled on-line to GC/ECD , 7. High Resolut. Chromatogr. 20 222-226(1997). 

Figure 15.1 Separation of pesticides from butter by using LC-GC-ECD. Peak identification is as follows 1, HCB 2, lindane 5, aldrin 7, o,p -DDE 10, endrin 11, o,p -DDT 13, p,p -DDT peaks 3, 4, 6, 8, 9, 12, 14, 15 and 16 were not identified. Adapted from Journal of High Resolution Chromatography, 13, R. Barcarolo, Coupled EC-GC a new method for the on-line analysis of organchlorine pesticide residues in fat , pp. 465-469, 1990, with permission from Wiley-VCH.

In this core, concentrations of PCBs (determined as Aroclor 1254 and 1260, by high resolution gas chromatography, electron capture detection and high resolution gas chromatography-low resolution mass spectrometry) were <30 ng and those of total DDT (p,p DDT + p,p DDD + p,p DDE) <5 ng g Campesan et al. (21) in 11 sediment samples from Valle di Brenta, determined by GC-ECD the following mean concentrations (ng gd.w.) ... 

Urine Acidify and heat to hydroloyze add NaOH to pH=11 extract with benzene-diethyl ether reacidify and dry with sodium sulfate derivatize with hexamethyl disilizane on GC column (PNP) GC/ECD 50 pg/L (50 ppb) 95.4 Cranmer 1970 EPA1980d... 

Urine Acidify and heat to hydrolyze add NaOH extract with anhydrous ethyl ether derivatize with diazoethane concentrate add hexane concentrate and cleanup on silica gel elute with benzene-hexane (PNP) GC/ECD 20 pg/L (20 ppb) 85-98 Shafiketal. 1973b... 

Water Extract with benzene plus anhydrous potassium carbonate concentrate cleanup on silica gel GC/ECD 0.1 pg/L 79 Lee etal. 1984 > r m... 

Water, plant tissue, animal Extract with hexane cleanup with hexane/acetonitrile GC/ECD 0.1 pg/L (water) 0.01 mg/kg (tissue) 100 Kadoum1968... 

Food (butter fat) Extract and cleanup on semipreparative HPLC column elute with methylene chloride-hexane GC/ECD No data No data Gillespie and Walters 1986... 

Analysis of methyl parathion in sediments, soils, foods, and plant and animal tissues poses problems with extraction from the sample matrix, cleanup of samples, and selective detection. Sediments and soils have been analyzed primarily by GC/ECD or GC/FPD. Food, plant, and animal tissues have been analyzed primarily by GC/thermionic detector or GC/FPD, the recommended methods of the Association of Official Analytical Chemists (AOAC). Various extraction and cleanup methods (AOAC 1984 Belisle and Swineford 1988 Capriel et al. 1986 Kadoum 1968) and separation and detection techniques (Alak and Vo-Dinh 1987 Betowski and Jones 1988 Clark et al. 1985 Gillespie and Walters 1986 Koen and Huber 1970 Stan 1989 Stan and Mrowetz 1983 Udaya and Nanda 1981) have been used in an attempt to simplify sample preparation and improve sensitivity, reliability, and selectivity. A detection limit in the low-ppb range and recoveries of 100% were achieved in soil and plant and animal tissue by Kadoum (1968). GC/ECD analysis following extraction, cleanup, and partitioning with a hexane-acetonitrile system was used. 

HPLC has been recommended as a cleanup and fiactionation procedure for food samples prior to analysis by GC/ECD (Gillespie and Walters 1986). The advantages over the AOAC-recommended Florisil colunrn are that it is faster, requires less solvent, and gives better resolution. HPLC coupled with various detectors MS, MS/MS, UV/electrochemical detector, or UV/polarographic detection has been tested as a rapid, simplified separation and detection system to replace GC (Betowski and Jones 1988 Clark et al. 1985 Koen and Huber 1970). Recoveries, detection limits, and precisions were generally good, but further work is needed before the techniques are adopted for general use. 

The method of choice for the determination of a- and P-endosulfan in blood, urine, liver, kidney, brain, and adipose tissue is gas chromatography equipped with an electron capture detector (GC/ECD) (Coutselinis et al. 1976 Demeter and Heyndrickx 1979 Demeter et al. 1977 Le Bel and Williams 1986). This is because GC/ECD is relatively inexpensive, simple to operate, and offers a high sensitivity for halogens (Griffith and Blanke 1974). After fractionation of adipose tissue extracts using gel permeation chromatography, detection limits of low-ppb (1.2 ng/g) were achieved for endosulfan and other chlorinated pesticides using GC/ECD (Le Bel and Williams 1986). 

P-Endosulfan has also been measured in hand rinsings using GC/ECD (Kazen et al. 1974). Sample preparation involves hand rinses with hexane followed by concentration, fractionation, and clean-up with Florisil . Sensitivity, recovery, and precision data were not reported. 

Positive identification of low-ppb (pg/L) levels of endosulfan in human blood has been achieved by GC equipped with a microcoulometric detector (GC/MC) (Griffith and Blanke 1974). Although GC/MC is specific and nearly as sensitive as GC/ECD for detecting endosulfan in blood, GC/MC is more difficult to operate. Both isomers of endosulfan can be measured in blood using a method described by Guardino et al. (1996). According to the authors, endosulfan can be recovered and measured with an approximate limit of quantitation (LOQ) of 0.2 pg/L (sub-ppb). 

GC/MS has been employed by Demeter et al. (1978) to quantitatively detect low-ppb levels of a- and P-endosulfan in human serum, urine, and liver. This technique could not separate a- and P-isomers, and limited sensitivity confined its use to toxicological analysis following exposures to high levels of endosulfan. More recently, Le Bel and Williams (1986) and Williams et al. (1988) employed GC/MS to confirm qualitatively the presence of a-endosulfan in adipose tissue previously analyzed quantitatively by GC/ECD. These studies indicate that GC/MS is not as sensitive as GC/ECD. Mariani et al. (1995) have used GC in conjunction with negative ion chemical ionization mass spectrometry to determine alpha- and beta-endosulfan in plasma and brain samples with limits of detection reported to be 5 ppb in each matrix. Details of commonly used analytical methods for several types of biological media are presented in Table 6-1. 

Liver Addition of water to sample followed by homogenization extraction with benzene, clean-up on silica column and HPLC GC/ECD No data No data Demeter and Heyndrickx 1979... 

Hand rinsings Rinsing of hands twice with hexane solvent volume reduction fractionation and clean-up on Florisal GC/ECD No data No data Kazen et al. 1974... 

GC/ECD or a halogen-specific detector (HSD) (Method 8080) is the technique recommended by EPA s Office of Solid Waste and Emergency Response for determining a- and [3-endosulfan and endosulfan sulfate in water and waste water at low-ppb levels (EPA 1986a). At these low concentrations, identification of endosulfan residues can be hampered by the presence of a variety of other pesticides. Consequently, sample clean-up on a Florisil column is usually required prior to analysis (EPA 1986a). 

Methods 508, 508.1, and 525.2 (EPA 1997a, 1997b, 1997c) are applicable to drinking water and ground-water and can determine a- and [3-endosulfan and endosulfan sulphate at concentrations as low as 7 ppt using liquid solid extraction (LSE) and GC/ECD. 

GC/ECD and GC/MS (EPA Method 608) are the methods recommended for determining a-endosulfan, (3-endosulfan, and endosulfan sulfate in municipal and industrial discharges (EPA 1991a). Sample clean-... 

A procedure has been developed for the analysis of a- and (3-endosulfan and endosulfan sulfate in fish, water, and sediments (Chau and Terry 1972 Musial et al. 1976). This procedure involves the acetylation of endosulfan residues into their diacetates and subsequent quantification by GC/ECD. Detection limits of low-ppb levels of endosulfan were reported. This approach is rapid and simple, and minimum sample preparation is required (Chau and Terry 1972 Musial et al. 1976). 

Water waste water Extraction of sample with methylene chloride and olean-up on Florisil oolumn GC/ECD 0.49 [jg/L ( endo-sulfan) 6.1 pg/L ( "endosulfan) 2.7 pg/l (endosulfan sulfate) No data EPA 19860 (Method 8080)... 

Municipal and industrial discharge Extraction of sample with methylene ohloride water removal exchange to hexane volume reduotion olean-up on Florisil column and removal of elemental sulfur GC/ECD GC/MS 0.014 pg/L ( "endo-sulfan) 0.004 pg/L ( "endosulfan) 0.066 pg/L (endosulfan sulfate) 97 ( "endosulfan) 93 ( "endosulfan) 89 (endosulfan sulfate) EPA 1991b (Method 608)... 

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