Diazinon detection limits

Azinphos ethyl (h/ f 20-25), malathion (h/ f 40-45) and diazinone (h/ f 47-52) yielded white chromatogram zones on a blue background immediately. Before in situ quantitation the chromatogram was dried in the air until no film of moisture could be seen on the layer surface. It was then dried completely in a stream of warm air whereby the blue coloration of the background changed to brown (Fig. 1). The visual detection limits were 200 ng substance per chromatogram zone. 

The purpose of this chapter is to describe the analytical methods that are available for detecting, and/or measuring, and/or monitoring diazinon, its metabolites, and other biomarkers of exposure and effect to diazinon. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used for environmental samples are the methods approved by federal agencies and organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that modify previously used methods to obtain lower detection limits, and/or to improve accuracy and precision. 

In one studyOPPs were extracted with SPME (85 /rm of polyacrylate coating) by the immersion technique at 75°C for 60 min. Desorption was done in a desorption device by supercritical fluid carbon dioxide (temperature 50°C pressure 306 atm) prior to online introduction into LC. The detection limits were 300 /rg/l for diazinon, 40 /rg/l for EPN, and 60 /rg/1 for chlorpyrifos, with recoveries ranging from 62 to 64%. 

The residues of four pesticides (diazinon, caibaryl, malathion, fenitrothion) were recovered from sesame seeds and baseline resolved on a Cjg column (2 = 225 nm) using a 50/50 acetonitrile/water (0.1% acetic acid) mobile phase [969]. Excellent separation and elution were achieved in 21 min. Linearity was obtained over the range 2-4500 ng/mL with detection limits of 5-50 ng/mL (analyte dependent). 

The first field test was successful. Both dimethoate and malathion declined exponentially (Figure 9) and exhibited efficiency factors comparable to the efficiency factors found in the pilot tests. An efficiency factor could be calculated for baygon, but not for diazinon. Some sediment was present into the bottom of the holding tank which could have been slowly releasing baygon and diazinon in the bulk liquid. Nevertheless, after 24 hours of treatment, all pesticides were below the limit of detection. 

Food Chain Bioaccumulation. Diazinon has an estimated low bioconcentration potential (BCF=77) (Kenaga 1980) in aquatic organisms, which is generally confirmed by measured BCF values obtained from laboratory studies with fish and other aquatic invertebrates (El Arab et al. 1990 Keizer et al. 1991 Sancho et al. 1993 Tsuda et al. 1989, 1995). Further information on measured BCF values for additional edible fish and shellfish would be helpful, as would information on tissue residues of diazinon and its major degradation products in edible species. No information was found on studies associated with plant uptake, but diazinon is rarely detected above EPA tolerance limits (Hundley et al. 1988). Bioaccumulation in aquatic food chains does not appear to be important, and no further information on biomagnification is required. 

Diazinon was determined in bovine liver and rumen content by GC/flame photometric detection (FPD) by Holstege et al. (1991) using a method with a limit of detection (LOD) reported to be 0.01-0.05 pg/g using a 5 g sample. Recoveries were reported to be 95% from rumen content and 88% from liver. In another study, diazinon was determined by GC/FPD and GC/mass spectrometry (MS) in avian liver and kidney using a method with a LOD of 0.02 ppm and 100% recovery at the 0.05 ppm level. Brown et al. (1987) used GC/FPD to determine diazinon in animal fat. No data were reported for the LOD, but the recovery was stated to be 90% (6% RSD) at 0.4 ppm. 

Diazinon can be measured in air after pre-concentration from air onto some adsorbent material with subsequent extraction. Following extraction from the adsorbent, separation and detection methods include GC/MS (Hsu et al. 1988 Kuwata and Yasuhara 1994), GC/NPD (Williams et al. 1987), and GC/FPD in the P mode (NIOSH 1994). The method of Williams et al. (1987) applicable to both diazinon and diazoxon. The NIOSH method (Method 5600, NIOSH 1994) has been fully validated for use in occupational settings where regulatory exposure limits are of concern. 

Three standardized methods were found in the Official Methods ofAnalysis of the Association of Official Analytical Chemists (AOAC 1990). The first of these methods is based on the extraction of crops (kale, endive, carrots, lettuce, apples, potatoes, and strawberries) with ethyl acetate and isolation of the residue followed by a sweep codistillation cleanup prior to GC/thermionic detection (Method 968.24). The second of these methods utilizes Florisil column chromatography clean-up followed by GC/FPD (Method 970.53). In the third method (Method 970.52), the sample is extracted with acetonitrile, and the residue is partitioned into petroleum ether followed by Florisil clean-up and GC/KC1 thermionic detection. Identifications are based on combinations of gas, thin-layer, and paper chromatography. The recovery for diazinon in this method is stated to be greater than 80% no data on limits of detection were given. 

Prepared by bulk polymerization, an MIP for the detection of dicrotophos based on the Eu3+ complex has recently been presented [58]. The authors used reversible addition fragmentation chain transfer (RAFT) polymerization followed by ring closing methathesis (RCM) to obtain the star MIP with arms made out of block copolymer. The star MIP containing Eu3+ exhibited strong fluorescence when excited at 338 nm with a very narrow emission peak (half width -10 nm) at 614 nm. This MIP was sensitive to dicrotophos in the range of 0-200 ppb, but showed saturation above this limit. Cross-reactivity of this MIP was evaluated with respect to structurally similar compounds dichlorvos, diazinon and dimethyl methylphosphonate. In these tests no optical response of the polymer was detected even at concentrations much higher than the initial concentration of dicrotophos (>1000 ppb). 

Table XI. Calculated Lower Limit of Ultraviolet Detectability (ng) for the Diazinon, Parathion, and Baytex Systems...

The spectrophotometric characteristics of the OPH-CnTPPCi complex are more sensitive to exposure to OPH substrates than those of the OPH-CnTPPSi complex resulting in a lower limit of detection. The characteristic peak for the interaction of CuTPPCi with immobilized OPH is at 412 nm. The absorbance intensity of this peak decreases upon exposure of the surface to diazinon, malathion, conmaphos, and... 

Diazinon samples were analyzed with a Tracer 222 Gas Chromatograph equipped with a flame photometric detector in the phosphorous mode. The diazinon standard employed was obtained from EPA, Research Triangle Park. The limit of detection of the instrument was 0.3 ng with a maximum injection volume of 10 ul. since all environmental samples were extracted in 30 ml of solvent and were not concentrated, the sensitivity per sample was 900 ng. 

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