Frederick J. Rowell

Detection of nitro-organic and peroxide explosives in latent fingermarks by DART- and SALDI-TOF-mass spectrometry

The ability of two mass spectrometric methods, surface-assisted laser desorption/ionization-time of flight-mass spectrometry (SALDI-TOF-MS) and direct analysis in real time (DART-MS), to detect the presence of seven common explosives (six nitro-organic- and one peroxide-type) in spiked latent fingermarks has been examined. It was found that each explosive could be detected with nanogram sensitivity for marks resulting from direct finger contact with a glass probe by DART-MS or onto stainless steel target plates using SALDI-TOF-MS for marks pre-dusted with one type of commercial black magnetic powder. These explosives also could be detected in latent marks lifted from six common surfaces (paper, plastic bag, metal drinks can, wood laminate, adhesive tape and white ceramic tile) whereas no explosive could be detected in equivalent pre-dusted marks on the surface of a commercial lifting tape by the DART-MS method due to high background interference from the tape material. The presence of TNT and Tetryl could be detected in pre-dusted latent fingermarks on a commercial lifting tape for up to 29 days sealed and stored under ambient conditions.

Direct determination of some phenothiazine sedatives in greyhound urine by fluoroimmunoassay

Antibodies have been raised in rabbits to a chlorpromazine sulfoxide-bovine serum albumin immunogen and the resulting antiserum used to develop a magnetizable solid-phase antibody fluoroimmunoassay for the detection of sulfoxide metabolites of commonly used phenothiazine and thioxanthine neuroleptics. These assays were used to screen metabolite levels in the urine of a greyhound following oral medication with chlorpromazine in order to assess the potential of these assays as simple screens for detecting exposure of racing greyhounds to such sedatives. The urine samples were also screened for neuroleptic content using an established radioreceptor assay and by TLC. The immunoassay described represents a relatively simple, sensitive and group-specific alternative method for screening for medication with phenothiazine and structurally similar sedatives in urine samples.

Classification of fresh edible oils using a coated piezoelectric sensor array-based electronic nose with soft computing approach for pattern recognition

An electronic nose based on an array of six bulk acoustic wave polymer-coated piezoelectric quartz (PZQ) sensors with soft computing-based pattern recognition was used for the classi-fication of edible oils. The electronic nose was presented with 346 samples of fresh edible oil headspace volatiles, generated at 45°C. Extra virgin olive (EVO), nonvirgin olive oil (NVO) and sunflower oil (SFO) were used over a period of 30 days. The sensor responses were visualized by plotting the results from principal component analysis (PCA). Classification of edible oils was carried out using fuzzy c-means as well as radial basis function (RBF) neural networks both from a raw data and data after having been preprocessed by fuzzy c-means. The fuzzy c-means results were poor (74%) due to the different cluster sizes. The result of RBF with fuzzy c-means preprocessing was 95% and 99% for raw data input. RBF networks with fuzzy c-means preprocessing provide the advantage of a simple architecture that is quicker to train.

Radial basis neural network for the classification of fresh edible oils using an electronic nose

An electronic nose utilising an array of six-bulk acoustic wave polymer coated Piezoelectric Quartz (PZQ) sensors has been developed. The nose was presented with 346 samples of fresh edible oil headspace volatiles, generated at 45°C. Extra virgin olive (EVO), Non-virgin olive oil (OI) and Sunflower oil (SFO), were used over a period of 30 days. The sensor responses were then analysed producing an architecture for the Radial Basis Function Artificial Neural Network (RBF). It was found that the RBF results were excellent, giving classifications of above 99% for the vegetable oil test samples.

Simple dip strip ELISA for airborne estrogenic steroids

An ELISA for the potent estrogenic steroids, ethinyl estradiol (ETED), 17-β-estradiol (ED) and estrone (ES) has been developed and used to determine the recovery of ED and ETED following spiking from seven filters commonly used in samplers for ascertaining personal exposure of workers to airborne biochemicals. Best results were obtained with cellulose nitrate (CN) and polytetrafluoroethylene (PTFE) filters. The assay reagents have also been used to develop a simple dip strip assay that can be used to determine the presence of steroids on the filters. Steroids captured from the air on the surface of filters within a conventional personal exposure sampler are extracted with specific antiserum. A spot of hapten-protein conjugate is immobilised on a small square of CN filter attached to a plastic strip. This is immersed in the sampler solution where unbound antibodies bind to the hapten on the spot. The strips are then transferred to a 96 well filter plate located within a filter manifold. Following washing, strips are incubated with alkaline phosphatase-labelled second antibody and the spots were developed by addition of substrate. The intensity of the developed blue spot is inversely proportional to the amount of steroid originally captured on the filter. A batch of over 50 samplers can be screened within 1 h. Spots on strips from filters on which 10 ng of ED, ES or ETED are present can be visually discerned from strips from filters where no steroid is present.

A rapid, qualitative ELISA test for the specific detection of morphine in serum or urine

We describe a competitive inhibition ELISA technique, with a visual end-point, to detect free morphine in blood or urine. It has a sensitivity of 2 X 10(-7) mol/l using 5 microliter samples. No significant cross-reactivity was observed with other opiate derivatives. The assay has applications as a specific screen for morphine in drug abusers, or to study the metabolism of the drug in the body (as the metabolite, morphine-3-glucuronide, does not cross-react significantly with morphine in the assay).

Enzyme linked immunosorbent assay for detecting benzodiazepines in urine

A relatively simple ELISA technique was developed for the detection of a range of benzodiazepines (BZs) in urine. The assay employs a mouse anti-oxazepam antibody that is highly specific for the BZs. The limit of detection using 10 microliters samples of urine was 0.3 microgram ml-1 oxazepam. N-Desmethyldiazepam showed equal cross-reactivity to oxazepam, 11 BZs cross-reacted weakly and flurazepam and chlordiazepoxide did not cross-react at levels reported to be found in urine. No cross-reactivity was observed with drugs of abuse and a range of therapeutic drugs commonly found in urine. The assay was used as a screen to detect the presence of BZs in urine from 88 addicts that had been screened by the EMIT technique and a radioreceptor assay (RRA) for BZs. The ELISA produced two false negatives that were EMIT and RRA positive whereas the EMIT produced four different false negatives that were positive by both ELISA and RRA. Thirty-three positives were common to all three assays. The ELISA was also used to monitor nitrazepam-like activity in the urine of a greyhound receiving 5 mg oral medication and the results were compared with those obtained by RRA. Both assays were able to detect nitrazepam-like activity for up to 10 h post-administration.

A rapid fluorescence ELISA for ceftazidime

A simple and rapid ELISA with a fluorescent end-point has been developed for the measurement of the cephalosporin antibiotic, ceftazidime. The ELISA can be applied to the analysis of the drug in solutions that have been eluted from filters following the capture of air samples in the workplace and in biological fluids. The assay has good precision and shows insignificant interference from a range of other cephalosporins and penicillins. A comparison has been made between this assay and a similar ELISA method using spectrophotometric detection. The use of fluorescence detection improves the limit of detection from 3.5 × 10–9 mol dm–3 to 6.5 × 10–10 mol dm–3, and reduces the overall assay time from 45 to 25 min. The current method of choice is HPLC, which is slow and insensitive in comparison with the assay described.

Rapid enzyme-linked immunosorbent assay (ELISA) with a visual end-point for detecting quinine in urine, serum and dried blood spots

A rapid and simple assay has been developed for the detection of quinine in biological fluids (e.g., urine, serum and dried blood spots). The assay has a coloured end-point and a limit of sensitivity of 3 µg l–1, using 5-µl samples. No cross-reactivity is observed with examples of commonly administered drugs. The assay was used to screen samples of dried blood spots and urine from a volunteer after taking a dose of 300 mg of quinine. The assay requires no sophisticated laboratory equipment or instrumentation to give a qualitative assessment of the presence of quinine, but may be used with a simple portable microtitre plate reader to give quantitative measurements if required.

Rapid and sensitive assay for some protease enzymes using a fluorosubstrate-immobilized bioreactor

Protease enzymes are commonly used in industry; exposure of the workforce to these enzymes may lead to respiratory sensitization. Assays are therefore needed which can be coupled to air sampling devices to produce real-time monitoring systems which are sufficiently sensitive and rapid to provide an early warning system that indicates that the airborne concentrations of enzyme have exceeded occupational exposure limits. Current methods based on spectrophotometric end-points are too slow and insensitive for this application. An assay is reported that is based on the release of fluorescein covalently attached to porcine thyroglobulin which is itself immobilized onto glass beads in a bioreactor. Exposure of the bioreactor to the enzymes, subtilisin, trypsin, alcalase and esperase produces a fluorescent peak in a flow through cell within 3–4 min. The resulting signal is linear (r= 0.999, n= 5) over the range 2–50 ng for subtilisin and the reproducibility of the assay (sr) at 5 ng is 0.8% for this enzyme.