High volume filtration sampling

Alfheim, I., A. Jebens, and S. Johansen, Sampling Ambient Air for Mutagenicity Testing by High-Volume Filtration on Glass-Fibre Filters and on XAD-2, Environ. Int., 11, 111-118 (1985). 

Samples with particulate matter may present quite serious problems, and it may be desirable to remove particles, for example, by centrifugation, and examine this fraction by procedures applicable to solid phases which are discussed in Section 2.2.5. Tangential-flow high-volume filtration systems have been used for analysis of particulate fractions (>0.45 jum) where the analytes occur in only low concentration (Broman et al. 1991). Attention has already been drawn to artifacts resulting from reactions with cyclohexene added as an inhibitor to dichloromethane. It has also been suggested that under basic conditions, Mn2+ in water samples may be oxidized to Mn(III or IV) which in turn oxidized phenolic constituents to quinones (Chen et al. 1991). Serious problems may arise if mercuric chloride is added as a preservative after collection of the samples (Foreman et al. 1992) since this has appreciable solubility in many organic solvents, and its use should therefore be avoided. 

Sampling of airborne particles was carried out at the rooftop level of a 6-story building of the National Institute of Public Health surrounded with arterial roads in central Tokyo (30 m above the ground) between lO and 22 October, 2000. Airborne particles smaller than 10 pm in aerodynamic diameter were collected on quartz fiber filters with a high-volume air sampler with 10-pm cut-off stage for 24 h from 1224 m of the air. Three quarters of the filter samples spiked with 2-NFL internal standard were cut into small pieces and put into dichloromethane to extract SOF from the airborne particle. The extracted SOF solution was isolated by filtration and washed sequentially with 5% sodium hydroxide, 20% sulfuric acid solution, and purified water. After removal of water, the sample solution was concentrated by drying under nitrogen and was dissolved into 1 mL of acetonitrile for subsequent analysis. 

HPLC has been used increasingly in the analysis of food samples to separate and detect additives and contaminants. HPLC can separate a large number of compoimds both rapidly and at high sensitivity, reduce separation times, and reduce the volume of sample needed. HPLC is ideally suited for compounds of limited thermal stability, but requires sample pretreatment such as extraction and filtration. In addition, HPLC requires careful selection of mobile phase and sample pumping rate [24]. 

Half an hour should be sufficient time for extraction offlavonol glycosides because of the high surface area of powdered material and the large volume of solvent. Another method of extraction is to add solvent to the sample in two to three aliquots, decant each through Whatman no. 1 filter paper at the end of a specified time, and combine the filtrates. 

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