Roger Abraham Bunce

A simple near-patient test for nicotine and its metabolites in urine to assess smoking habit

We describe a disposable, near-patient urine test to monitor cigarette smoking. A plastic device contains the sealed dried reagents to measure nicotine and its metabolites, by a colorimetric assay. The device can be used to give a qualitative assessment of tobacco consumption, simply by observing a colour change. Alternatively, the test can be quantified by measuring the light absorbance with a simple colorimeter, and a concentration of nicotinic metabolites obtained with reference to a cotinine standard. A correction factor for the concentration of the urine sample, based on light absorbance, allows the result to be expressed as a ratio to urine concentration. This method correlates with reported daily cigarette consumption (r = 0.69, p < 0.0001) and compares favourably with cotinine, as measured by gas chromatography (r = 0.89, p < 0.0001). The method provides a simple-to-use, inexpensive way to monitoring tobacco consumption in extralaboratory situations.

Camera luminometer for use with luminescent assays

An instrument, a camera luminometer, has been developed that detects light emission from luminescent reactions using high-speed instant photographic film (ASA 20000). The luminometer simultaneously monitors light emission from 63 reaction vessels in the form of a 7 × 9 array. It also incorporates a multiple pipette, which enables luminescent reactions to be simultaneously initiated directly above the instant film. Photographic results are interpreted visually and semi-quantitative assessment is possible. This may be improved by interposing a stepped neutral density filter between each reaction vessel and the film. The application of this instrument is illustrated by an enhanced luminescent enzyme immunoassay for serum ferritin and chemiluminescent assays for Co(II), Cr(III), peroxide and luminol. The film has a limited exposure latitude and so the assays operate as threshold tests with the following detection limits: ferritin, 1 ng; Co(II), 5 pmol; Cr(III), 500 fmol; peroxide, 500 pmol; and luminol, 500 fmol.

Disposable analytical devices permitting automatic, timed, sequential delivery of multiple reagents

Abstract Most extra-laboratory immunoassay devices require multiple manual reagent addition and timing steps, and current “one-step” devices do not permit the use of enzyme labels and washing stages. The limitations of both of these types of analytical system have been overcome and the advantages combined in a range of novel, simple, disposable devices that automate the sequential initiation and timing of reagent additions and wash steps. This is achieved either by “switching” porous tracks together by the hydration and expansion of a compressed foam switching element, or by using liquidic circuits cut in or printed onto a single sheet of porous material. The feasibility of the concepts has been demonstrated using dyes to visualize reagent flow.

Application of robotics In the clinical laboratory

The basic types of robot are explained, and the performances and costs of some commercial examples are given. The potential advantages and problems of introducing robots into clinical laboratories are identified and the specifcation of a suitable robot is developed. None of the commercially available robots meets all aspects of the specificalion, and currently the purchase of a robot is considered premature for most clinical laboratories.