Chromatograms organophosphorus pesticides

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.)...

A multiresidue method for analyzing 28 common organophosphorus pesticides and three of their main metabolites (paraoxon-ethyl, paraoxon-methyl, and malaoxon) in a variety of crop samples has been developed (59). The use of LC-DAD techniques allowed identification of both organophosphorus pesticides and metabolites by means of standard and spectral comparisons, respectively. A typical chromatogram for fortified apple extract is shown in Figure 4. 

Sulfur is found in many industrial wastes, marine algae, and sediment samples. Sulfur may mask the region of chromatogram, overlapping with peaks of interest. For example, in pesticides analysis, sulfur can mask over many pesticides such as lindane, aldrin, and heptachlor. Sulfur has a solubility similar to the organochlorine and organophosphorus pesticides and it cannot be separated by Florisil cleanup method. 

Figure 4.31 Dual chromatograms from a single injection of a reference standard containing organophosphorus pesticides.

The sensitivity of detection is usually between 0.2 and 0.5 pg per chromatogram zone. This is also true for pesticides based on organophosphorus acids [9]. 

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