Roger N. Reeve

Direct on-filter assay of subtilisin-typeproteolytic enzymes for rapid analysis of analyte captured from the workplaceatmosphere

A simple assay for some proteolytic enzymes has been developed which can be performed directly on the surface of a cellulose nitrate filter used to capture the analyte during workplace monitoring for health and safety purposes. Following air sampling the analysis is performed on the filter which is retained within the air sampler. This involves two steps: first, a 15 min incubation in which the captured enzyme is dissolved and then digests an alkaline-phosphatase-labelled antibody immobilised as a small dot on the surface of the filter; and second, is a 10 min incubation with substrate solution, which follows an in situ wash under a vacuum. During the incubation colour develops on the spot at the location of the immobilised enzyme antibody conjugate. The intensity of the spot can be assessed visually within the sampler to ascertain the presence or absence of captured enzyme, or alternatively quantitative results can be obtained using an optical scanner. The limit of detection is 5 ng per filter for subtilisin (20 ng for visual discrimination between this standard and the zero). The assay is stable to the effects of ambient air sampling at 31 min(-1) for 18 h.

Enzyme-linked immunosorbent assay for ondansetron captured from airborne samples

A simple and relatively rapid enzyme-linked immunosorbant assay method for the anti-emetic drug ondansetron has been developed for its quantitation in solution. This has been optimised for use with samples that have been obtained following extraction of filters after the drugs capture from air samples in the workplace. The assay has the sample throughput (40 duplicate samples in 3 h), specificity, sensitivity (LOD of 10.5 ng drug ml-1) and precision (RSD < 11%) necessary for its use in determining airborne concentrations of ondansetron in such samples as part of an occupational health and hygiene monitoring programme.