Pesticide analyzer

Observing the amount and variety of pesticides analyzed by GC chromatography we decided to observe 14 of the most represented pesticides Prometryn, Deltamethrin, Fenitrothion, Tebuconazole, Buprofezin, Malathion, Myclobutanyl, Atrazine, Acetochlor, Bifenthrin, Alachlor, Pendimethalin, Dichlonuid and Trifluralin. 

Of the 22 pesticides analyzed in water, 21 were found to be present in some or all of the samples analyzed cyanazine was the only undetected compound. Figure 2 shows the concentration of individual and total pesticides and their frequency of detection in the water samples collected from each of the six sampling sites monitored. 

Analytical Procedures. The extraction procedure used for solution studies was based on the method supplied by Union Carbide Corporation ( ), and was reported In previous work ( ). Samples were analyzed using a Microtek GC with a Tracer NP detector as described by Lemley and Zhong ( ). Conditions used for the various pesticides analyzed and the retention times obtained are detailed In Table I. In all cases a 4 foot x 4 mm I.D. glass column packed with 1.5% SP-2250/1.95% SP-2401 on 100/120 mesh Supelcoport was used. A glass Injector was used for the analysis of carbofuran and 3-hydroxycarbofuran. Procedures were varied slightly for analysis of methomyl. The first three Inches of the column were packed with 1.5% OV-17 on 100/120 mesh Supelcoport, and a glass Injector was used without glass wool at the end. 

With regard to current-use pesticides, few pesticides have standards and/or guidelines established by the health organizations. For example, of the 88 pesticides analyzed in the Lake Erie Basin by the NAWQA of the USGS,... 

In general, earlier results showed that DDT residues were the highest among various pesticides analyzed, followed by CHLs, HCHs, and HCB, in that order. On the other hand, higher levels of CHLs than DDTs were detected in mussels during 1997-1999 (Boonyatumanond et al., 2002). These results may indicate that the usage of DDT in several locations in Thailand decreased after the ban, whereas CHLs were being widely used until its ban in the year 2000. 

The other study on human cord blood collected in a Kuala Lumpur hospital (Benjamin Tan and Mustafa, 2003) reported that only chlopyrifos was found in 18% of the samples at levels of ND-1.15ng mL-1 while other pesticides analyzed, such as lindane, diazinon, endrin, and endosulfans were not detected. In the same study, bisphenol-A and nonylphenols were detected in more than 80% of the samples at concentration levels of ND-4.05 and ND-15.17ng mL-1, respectively. Several alkylphenols were also found in these blood samples. 

Figure 4. First fully automated pesticide analyzer...

The next pesticide analyzer is described by Singer, et al (6) and used post-column derivatization for a nitrosamide-specific reaction. Following chromatographic separation and UV detection, the stream was air-segmented and treated with the Griess Reagent (Figure 11). The... 

This brief summary of the state of current instrumentation for the total automation of pesticide analyses will hopefully entice the reader to apply these principles of mechanized unit operations to his own analytical problems. There are enough creative scientists in this field, each trying to lighten his workload, that it seems safe to make this prediction by 1984 we ll have a pesticide analyzer which will take our unmeasured, untreated sample into one end of the instrument and give us final answers, printed in correct concentration units, twice as fast as today, with one tenth the sample size, and with half the CV s. If an analyst makes up his mind to do so, he can likely automate anything. 

GC/MS-SIM analysis coupled with QuEChERS method (section 9.2.1.1) is performed using the analytical conditions reported in Table 9.6. Pesticides analyzed are reported in Table 9.7 with their GC retention time and the m/z ion used for quantification. 

Results from a more limited study were recently reported by Kelly ( 3). Iowa scientists analyzed water samples from 128 wells involving 58 public water supplies between May 1984 and March 1985. One or more synthetic chemicals were found in 57 wells representing 33 water supplies. Trihalomethanes, as a group, were the most commonly occurring substances. The most frequently detected single product was atrazine, found in 24 wells. Overall, only 6, of 34 pesticides analyzed, were detected. None were above established standards or standards that could be set by methodology discussed later in this report. The highest level reported for any pesticide was 16.6 ppb for alachlor. 

The solution to the problem of analyzing large numbers of samples in environmental screeing projects has been found in the development of automated pesticide analyzers. Also, the range of automatic injection devices for HPLC now available reduces operator involvement in analyzing large numbers of samples. 

Of all organochlorine pesticides analyzed during the period of 1997-1999 at 313 sites, only DDT and its metabolites were detected in almost all sites under study, with geometric mean values varying from 0.005 to 0.119 mg/kg. Regions having no DDT residues have not been observed (Kaloyanova-Simeonova, F., et al., 2001). 

Laboratory Services Branch (USB) method E3389 of the Canadian Ministry of the Environment s Laboratory Services Branch is used for testing drinking water. The principle of the method is LC-UV after SPE followed by desorption of the OPPs with ethyl acetate. The sample extracts are evaporated to dryness and reconstituted in 1 ml acetonitrile. Limits of quantification range from 0.5 /rg/l for phorate to 28 /rg/1 for temephos. The other pesticides analyzed with this method are azinphos-methyl, chlorpyriphos, diazinon, dimethoate, parathion, malathion, terbufos. 

Reference 9 describes a collaborate survey of over 28 laboratories testing the new Tentative Standard Method for Chlorinated Hydrocarbon Pesticides in distilled water. This method calls for two successive extractions utilizing a hexane, semi-automatic extraction as described by Kawa-hara et al, 10) and modified by Schaefer et al, (11) Three different chlorinated hydrocarbon pesticide mixtures were tested only three of eighteen pesticides analyzed showed a total error of less than 50%. This calculation of the total error was based upon Table 100 (3) which described the accuracy and precision of the new method (9). 

A matrix has been shown to affect the signal for most of the pesticides analyzed in multiple matrices, despite the high resolution offered by UHPLC and sample treatment based on QuEChERS, pressurized solvent extraction, SPE, or a combination of both [75,77,78,80,82,83,89,90]. The most common way to overcome this issue has been quantifying with a matrix matched in agreement with the SANCO guidelines [91], which has been the quantification strategy followed by many authors. The high number of pesticides analyzed in multi-residue analysis does not make feasible the use of standard addition, which would increase the analysis time and materials needed or the use of labeled internal standards, which would make the analysis very expensive as well as increase the number of transitions to follow when triple... 

GC are therefore expected in the direction of fully automated sample preparation and sample introduction systems. Some instrumentation nowadays is already tailor-made for a given application. More can be expected in the future and development may result in specific instruments, such as a pesticide analyzer, a PCB analyzer, or a sugar analyzer. 

Bassett, M.V. et al.. The application of tris buffer and copper sulfate for the preservation of phenylurea pesticides analyzed using U.S. EPA Method 532 in the UCMR survey. Environ. Sci. Technol., 36,1809, 2002. 

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