Filter sorbent sampling

A universal sampler applicable to the majority of pesticides would be an ideal sampling device. In this study, personal sampling and analytical methods were developed and validated in the laboratory for determining workplace exposure to several pesticides. The major objectives of the study were to standardize on specific sampling media and to develop and validate methods using filter/ sorbent sampling trains. 

The collection efficiency of a filter sampler was demonstrated by sampling test atmospheres with a backup collector at the proposed sampling rate and time, and analyzing the collected samples. For sorbents or filter/sorbent sampling trains, the breakthrough volume was determined (to demonstrate capacity) at 80% relative humidity. 6... 

Filter/Sorbent Methods. The methods developed using filter/ sorbent sampling trains are listed in Table III. The sampling train consists of a 37-mm diameter filter contained in a cassette filter holder followed by a sorbent tube as described above. Samples are collected at 1 liter/min to obtain the prescribed sample volume. After sampling is completed, the filter is removed from the filter holder and placed in a glass vial with the front sorbent section and capped. The combined sample is extracted with toluene and the resulting solution is analyzed by gas chromatography. 

Figures 2 through 4 are graphical representations of the tests performed on the filter/sorbent sampling trains to test for sorbent capacity or breakthrough, and to best determine aerosol/vapor partitioning.

As a result of developing and validating filter/sorbent sampling methods, some additional criteria for testing were formulated and added to the original method testing criteria for these sampling trains. These are summarized below ... 

Sampling SVOCs/POMs in Air 2.4.2.1 Filter/Sorbent Sampling... 

The second approach laboratory analysis of air and/or soil samples (note the air sample can be obtained by gas samphng bag, filter, sorbent, and wet-contaminant collection methods). 

Recovery of the pesticide from the sampling media was determined with spiked samples greater than 90% recovery was desired. For filter/sorbent methods we have found that the sample losses due to volatilization are minimized if the filter and sorbent are combined after sampling. The combined sample is then analyzed. This requires that the recoveries from filter and sorbent be statistically the same. 

Figure 5. A denuder-filter-sorbent system for PAH sampling. (Reproduced with permission from reference 63. Copyright 1988.)...

Air sampling for occupational exposure to pesticides normally consists of measurement of pesticide concentrations in the worker s breathing zone, with a portable air-sampling pump and a sampling train which includes some type of collection device. The latter device, or sampling media, selected are based on the physical and chemical properties of the compound to be measured. Field workers may be exposed to chemical vapors, solid particulates or water-based aerosols. Examples of sampling media include membrane filters, sorbent tubes, polyurethane foam and charcoal. A discussion of pesticide exposure provides a useful review of methods for respiratory exposure measurement (Nigg etal, 1990). 

The extraction of methylimidazole from food is based on the cation exchange of the analyte onto the sorbent (Fig. 6.15). The food sample is prepared by homogenizing in methanol, filtering the sample, and evaporating the filtrate to dryness. The extract is reconstituted in water and filtered. The sample is now ready for application to the strong cation-exchange resin. 

An on-line concentration, isolation, and Hquid chromatographic separation method for the analysis of trace organics in natural waters has been described (63). Concentration and isolation are accompHshed with two precolumns connected in series the first acts as a filter for removal of interferences the second actually concentrates target solutes. The technique is appHcable even if no selective sorbent is available for the specific analyte of interest. Detection limits of less than 0.1 ppb were achieved for polar herbicides (qv) in the chlorotriazine and phenylurea classes. A novel method for deterrnination of tetracyclines in animal tissues and fluids was developed with sample extraction and cleanup based on tendency of tetracyclines to chelate with divalent metal ions (64). The metal chelate affinity precolumn was connected on-line to reversed-phase hplc column, and detection limits for several different tetracyclines in a variety of matrices were in the 10—50 ppb range. 

Impingers and bubblers. Figure 8.5, containing liquids have been used extensively for collecting high boiling, reactive or polar substances that cannot be quantitatively recovered from solid sorbents [8,72]. They are most frequently used as personal sampling systems and in combination with filters and various... 

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