Volatilization sampling, pesticide

The sorbents, Chromosorb 102 and XAD-2, which are styrene-divinyl benzene cross-linked porous polymers, proved to be most useful in our studies. Capacity of the sorbent sampling tubes was not a problem with the pesticides we studied since most were not extremely volatile. Sampling humid atmospheres of the pesticides also did not affect the sorbent capacity since these porous polymers are hydrophobic. 

Determination of Priority Pollutant Non-Volatile Organochlorine Pesticides in Contaminated Groundwater Comparison of Sample Preparation Methods—pLLE versus Solid-Phase Extraction Techniques ... 

Contractors at Sites B, D, G, I, and J had incomplete sampling practices and as a result were not able to evaluate PPE levels based on monitoring data. Eor example, both contractors SSAHPs at Site I lacked provisions for monitoring site hazards such as metals, pesticides, herbicides, and semi-volatile organic compounds (SVOCs) that could not be evaluated with a PID. Since worker exposures to the range of hazards on site had not been characterized, PPE was not selected based on its performance relative to the nature and level of site hazards. 

Chlorophenoxy acids are relatively polar pesticides which are usually determined by LC because volatile derivatives have to be prepared for GC analysis. This group of herbicides can be detected by multiresidue methods combined with automated procedures for sample clean-up, although selectivity and sensitivity can be enhanced by coupled-column chromatographic techniques (52). The experimental conditions for Such analyses are shown in Table 13.1. 

When pure P-endosulfan was allowed to equilibrate in the apparatus, the ratio of the P-isomer to the a-isomer in the gas phase became 8 92 at 20 , suggesting that the P-isomer converts to the a-isomer (Rice et al. 1997). Several investigators have reported rapid initial losses of endosulfan residues from treated plant surfaces due to volatilization (Archer 1973 Terranova and Ware 1963 Ware 1967). One research group (Willis et al. 1987) attributed the limited runoff losses found in soybean fields treated with endosulfan to early losses of the compound during application and to volatilization/degradation of the compound from plant surfaces. Air sampling performed in a wind tunnel under defined conditions (20 air velocity 1 m/sec relative humidity 40-60%) showed that 60% of the initial dose of endosulfan is volatilized from Trench bean surfaces after 24 hours (Rudel 1997). Influences of various pesticide application formulations were not tested. 

Although SPME was applied initially for the analysis of relatively volatile environmental pollutants in waters, rapid developments have enabled SPME to be successfully applied for the analysis of pesticides in water, wine and more complex food samples such as honey, fruit juice and pears, vegetables and strawberries. With food samples, most analysts recognize the need for some sample pretreatment in order to minimize matrix effects. The matrix can affect the SPME efficiency, resulting in a reduced recovery of pesticides. The most common method is simply to dilute the sample or sample extract with water. Simpltcio and Boas comminuted pears in water prior to the determination of pesticides. Volante et al. extracted over 100 pesticides... 

Lord and Pawliszyn" developed a related technique called in-tube SPME in which analytes partition into a polymer coated on the inside of a fused-silica capillary. In automated SPME/HPLC the sample is injected directly into the SPME tube and the analyte is selectively eluted with either the mobile phase or a desorption solution of choice. A mixture of six phenylurea pesticides and eight carbamate pesticides was analyzed using this technique. Lee etal. utilized a novel technique of diazomethane gas-phase methylation post-SPE for the determination of acidic herbicides in water, and Nilsson et al. used SPME post-derivatization to extract benzyl ester herbicides. The successful analysis of volatile analytes indicates a potential for the analysis of fumigant pesticides such as formaldehyde, methyl bromide and phosphine. 

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

Localized, or field-scale, studies generally assess pesticides drifting off-target during application or from post-application volatilization over short sampling intervals. The... 

Figure 8.4 Apparatus for sample preparation using physical separation. A - fractionation tube and trap for assisted distillation (A septum injector, B carrier gas inlet, C Florisil trap for collecting volatile pesticides) B, Shapiro-type freeze concentrator and C, apparatus for solvent sublation.

Namiesnik et al. [33] have reviewed the analysis of soils and sediments for organic contaminants. They discuss methods of sample preparation and isolation-preconcentration prior to instrumental determination. Compound classes discussed include volatile organic compounds, polychlorobiphenyls, polyaromatic compounds, pesticides and polychlorodibenzo-p-dioxins and polychlorodibenzofurans. 

Endrin is relatively nonvolatile with a vapor pressure of 2.0xl0 7 mm Hg (EPA 198 la Worthing and Walker 1983). Despite its low volatility, initial loss of agriculturally applied endrin through volatilization was found to be comparable to more volatile pesticides (Nash 1983). No recent data on atmospheric concentrations of endrin could be found in the available literature. Endrin was detected in air samples collected at 4 of the 102 NPL sites where endrin has been detected in some environmental medium however, concentrations were not available (HazDat 1996). 

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