Suction sampling

Unless stated otherwise, clothing was sampled using the apparatus detailed in Figure 26.1 and Figure 26.2 (suction sampled). 

The first step was to directly compare existing procedures, namely, suction sampling and swabbing. Table 25.1 gives comparison data. The results reveal that NG was detected on all three swab samples and that it was not present on the third suction sample. The initial suction sampling removes a high proportion of the NG whereas the second swabbing shows a substantial level of NG (-40%) when compared to the initial swab sample. Suction... 

The revised suction sampling device was tested by comparison with the previous device. Results are presented in Table 25.5. This represents a good recovery of NG when compared to Table 25.4 and illustrates that the device is effective. However, in this instance only one membrane filter was present in the suction line consequently, like is not being compared with like. The improved recovery may be due to a combination of factors. 

The results show that suction sampling removes nearly all the detectable NG present whereas swabbing removes considerably less. The swabbing prior to suction sampling probably had a detrimental effect on the number of inorganic particles recovered. 

Table 25.6 Comparison of Swab and Suction Sampling Techniques...

Jacket 1 Swabbed first, then suction sampled 1,080 495 8 2 8 7... 

Jacket 2 Suction sampled first, then swabbed 1,555 ND 27 None 16 None... 

Suction sampling of clothing for FDR examination has been used by this laboratory since 1979. As discussed previously, the suction sampling apparatus described was modified from that previously used to increase its efficiency and to make it compatible with explosive residue examination. Such sampling is efficient and easy to use but suffers from the disadvantage that the Deldrin filter holder is too expensive to be regarded as disposable. 

The suction sampling and analysis techniques were repeated to determine if organic and inorganic FDR could be detected on clothing worn during the firing of one round of ammunition from a revolver. The results are listed in Table 26.6. 

Clothing is sampled by suction using the revised suction sampling device (see Figure 25.2). Samples taken are stored at -20°C until required. The Del-drins are reusable and are washed according to the procedure given in reference 219. 

Borges, P. A. and Brown, V. K. 2003. Estimating species richness of arthropods in Azorean pastures the adequacy of suction sampling and pitfall trapping. Graellsta, 59 7-24. 

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