Organophosphorus pesticides detectors

Methyl parathion was determined in dog and human serum using a benzene extraction procedure followed by GC/FID detection (Braeckman et al. 1980, 1983 DePotter et al. 1978). An alkali flame FID (nitrogen-phosphorus) detector increased the specificity of FID for the organophosphorus pesticides. The detection limit was in the low ppb (pg/L). In a comparison of rat blood and brain tissue samples analyzed by both GC/FPD and GC/FID, Gabica et al. (1971) found that GC/FPD provided better specificity. The minimum detectable level for both techniques was 3.0 ppb, but GC/FPD was more selective. The EPA-recommended method for analysis of low levels (<0.1 ppm) of methyl parathion in tissue, blood, and urine is GC/FPD for phosphorus (EPA 1980d). Methyl parathion is not thermally stable above 120 °C (Keith and Walters 1985). 

Five organophosphorus pesticides were chosen that could be iso-thermally and simultaneously analyzed by gas chromatography using an N-P TSD detector. They are all currently commercially used and exhibit a wide range of physicochemical properties (Table I). Also influencing the choice of these pesticides was the fact that volatilization data measured from soil and water under controlled laboratory conditions are scarce for methyl parathion, parathion, and diazinon (14-17), and are not available for malathion and mevinphos. Technical mevinphos (60% E-isomer, Shell Development Co.), diazinon (87.2%, Ciba-Geigy Corp.), and malathion (93.3%, American Cyanamld), and analytical grade methyl parathion (99%, Monsanto) and parathion (98%, Stauffer Chemical Co.) were used. 

Figure 14. Chromatograms of organophosphorus pesticides obtained from a small-bore fused silica column (0.2 mm i.d., 1 m long) packed with 5-pm Spherisorb ODS. A, UV detection at 254 nm and B, dual-flame thermionic detector. Peaks correspond to 1, solvent containing phosphorus impurities 2, guthion, 89 ng of phosphorus 3, zolone, 71 ng of phosphorus and 4y ethion, 144 ng of phosphorus. Mobile-phase conditions 15% water and 85% methanol (v/v) at a flow rate of 1.6 pL/min. (Reproduced from reference 58. Copyright 1983 American Chemical Society.)...

J.J. Rippeth, T.D. Gibson, J.P. Hart, I.C. Hartley and G. Nelson, Flow-injection detector incorporating a screen-printed disposable amperomet-ric biosensor for monitoring organophosphorus pesticides, Analyst, 122 (1997) 1425-1429. 

Highly selective to compounds containing nitrogen and phosphorus Nitrogen-phosphorus detector Organophosphorus pesticides (EPA 8141) Acrylonitrile (EPA 8031) Acetonitrile (EPA 8033) Nitrosamines (EPA 8070) Hydrocarbons, fats, oils, waxes may interfere with organophosphorus pesticides. 

Second detector confirmation is another compound confirmation technique. Two detectors with selectivity to different functional groups are connected in series to one column or in parallel to two columns. For example, two detectors, a UV/VIS detector and a fluorometer, connected in series to the HPLC column are used in the EPA Method 8310 for analysis of PAH compounds. If the second detector is connected to a second column of a dissimilar polarity, then the confirmation becomes even more reliable. An example of such a configuration is organophosphorus pesticides analysis the samples may be initially analyzed with an NPD, and then confirmed on a different column with an ECD or a FPD. 

Other important GC detectors include the thermionic detector, the electrolytic conductivity or Hall detector, and the photoionization detector. The thermionic detector is similar in construction to the FID. With the thermionic detector, nitrogen- and phosphorus-containing compounds produce increased currents in a flame in which an alkali metal salt is vaporized. The thermionic detector is widely used for organophosphorus pesticides and pharmaceutical compounds. 

Cho Y, Matsuoka N, Kamiya A. Determination of organophosphorus pesticides in biological samples of acute poisoning by HPLC with diode-array detector. Chem Pharm Bull (Tokyo) 1997 45 737. ... 

Specification of the GC Detectors Used for Organophosphorus Pesticides Determination ... 

Skopec, Z. V., Clark, R., Harvey, P. M. A., and Wells, R. J., Analysis of organophosphorus pesticides in rice hy supercritical fluid extraction and quantification using an atomic emission detector, J. Chromatogr. Set, 31, 445-449, 1993. 

S-selective mode it is useful to characterize the organosulfur compounds in complex petroleum mixtures, as the much higher levels of coeluting hydrocarbon peaks give minimal response. Operated in P-selective mode it is a sensitive detector for organophosphorus pesticide trace residues in complex environmental mixtures. Only the sulfur mode response range is illustrated in Fig. 12.13. 

The popularity of the BCD can be attributed to the high sensitivity to organohalogen compounds, which include many compounds of environmental interest, including polychlorinated biphenyls and pesticides. It is the least selective of the so-called selective detectors but has the highest sensitivity of any contemporary detector. The NPD or thermionic ionization or emission detector is a modified FID in which a constant supply of an alkali metal salt, such as rubidium chloride, is introduced into the flame. It is a detector of choice for analysis of organophosphorus pesticides and pharmaceuticals. The FPD detects specific luminescent emission originating from various excited state species produced in a flame by sulfur- and phosphorus-containing compounds. 

Gas Chromatographic Methods to Determine Organophosphorus Pesticides Using the Nitrogen Phosphorus Detector and the Elame Photometric Detector... 

Organophosphorus pesticides Nitrogen phosphorus and mass spectrometric detectors GC-MS [206]... 

Scheide EP, Guilbault GG. 1972. Piezoelectric detectors for organophosphorus compounds and pesticides. Anal Chem 44(11) 1764-1768. 

Pesticides and Fungicides. Modern pure food regulations require that the food processor be responsible for their finished products. Since so many pesticides and fungicides are used in agriculture, their detection and quantitative analysis are difficult (5, 22). Organophosphorus and chlorinated hydrocarbons are the most common pesticides. When GLC is used for halogens, electron capture or microcoulometric detectors are used for phosphorus, a thermionic flame photometric detector is required. 

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