George G. Guilbault

Recent developments in piezoelectric immunosensors. A review

The development of piezoelectric (PZ) devices as immunosensors is reviewed. The recent advances in sensor design have stimulated great interest in PZ technology and facilitated diverse applications in a variety of matrices. Methods of antibody immobilization on crystals and several applications are reported including microgravimetric immunoassays, microbial toxins and other contaminants.

Flow-injection determination of ethanol by fiber-optic chemiluminescence measurement

Abstract A new approach for the determination of ethanol in beverages is presented. The hydrogen peroxide generated in the enzymatically catalyzed oxidation of ethanol is measured by the luminol chemiluminescence reaction using potassium hexacyanoferrate(III) as a catalyst. Alcohol oxidase is immobilized on aminopropyl glass beads packed in a glass column. The chemiluminescence measurement is made using an optical fiber to transport the luminescence from the flow cell to the detector in conjunction with a flow system. This assay system responds linearly in the ethanol concentration range 3 × 10−6-7.5 × 10−4 M with a precision of 2.4% and an analysis time of 1.5 min.

A piezoelectric detector for organophosphorus pesticides in the air

Abstract A quartz piezoelectric crystal coated with a substrate has been used for the detection of organophosphorus pesticides via selective sorption. The crystal is incorporated in a mixer circuit to allow read-out by either an ammeter or a recorder, and is sufficiently sensitive to allow detection of organophosphorus pesticides at levels of less than 10 p.p.b. AT-cut quartz crystals with fundamental frequencies of 9.0 MHz were coated with oxime substrates and subsequently investigated and evaluated for response to organophosphorus pesticides. This detector has a potential for use both as an air pollution sensor and a highly selective gas chromatography detector.

Creatinine-selective enzyme electrodes

Abstract Two selective creatinine enzyme electrodes have been developed for the determination of creatinine in the range 1–100 mg dl −1 . The electrodes were prepared using a new microbial enzyme (creatinine deiminase) immobilized on collagen and pig intestine membranes, in cojunction with an ammonia electrode. The electrodes are quite stable, have a response time of 2–10 min, and are sufficiently sensitive to detect normal levels of creatinine in blood serum.

PIEZOELECTRIC CRYSTAL SENSOR FOR THE DETERMINATION OF FORMALDEHYDE IN AIR

Formaldehyde in air was detected and assayed with a piezoelectric quartz crystal coated with a 7,10-dioxa-3,4-diaza-1,5,12,16-hexadecatetrol/chromotropic acid solution. Water vapor and several gaseous interferents were removed by passing the sampling stream through a column of anhydrous magnesium perchlorate. The response curves were linear in the concentration ranges 0.4-4.5 and 0.4-3.6 ppm v/v CH(2)O with and without the scrubber column, respectively. A single coating was used for 12 days (500 assays) without significant loss in sensitivity. With a single-point daily recalibration, the useful lifetime of the coating is about 2 months.

A fiber optic biosensor for sulfite analysis in food.

The sulfite fiber optic biosensor developed herein is based on the enzymatic oxidation reaction of sulfite catalyzed by sulfite oxidase (SOD). The consumption of O(2) is measured with an O(2) fiber optic sensor which monitors the fluorescence quenching of the indicator, perylene, by molecular oxygen. Perylene is immobilized into a polymer matrix and attached to the end of a fiber bundle forming an O(2) sensor. The enzyme, sulfite oxidase is immobilized on a pre-activated membrane and mounted onto the O(2) sensor. Several analytical characteristics of this sulfite biosensor were investigated including dynamic range, reversibility, reproducibility, stability and selectivity. The sulfite contents of various food samples, e.g. dried fruits, potato flakes, lemon juice were determined and the results obtained were in good agreement with the standard AOAC method.

Determination of some first transition metal group elements by electron spin resonance

Abstract An e.s.r. method is described for the determination of chromium(III), vanadyl(II), and iron(III). The measurement is based on the linear relationship that exists between the peak heights of the spectra of these ions and their concentration. Iron(III) ion has a very broad line in aqueous solution, but in organic solvents its line becomes much narrower, and suitable for analytical purposes. Nickel (II) has no observable spectra in aqueous solution; cobalt(II) has a relatively sensitive signal only in the presence of excess cyanide ion. The reproducibility of the calibration curves is about ±0.4–0.6%. The accuracy of the determination varies between 2 and 4%. The effect of about 30 different diverse substances (anions and ligands) on the peak heights was studied. The maximum concentrations of these ions that have no effect on the e.s.r. spectra are summarized.

Flow Injection Analysis of Glucose by Fiber Optic Chemiluminescence Measurement

Abstract A flow injection system was developed for the determination of glucose based on fiber optic chemiluminescence measurements. The hydrogen peroxide produced from the glucose oxidase catalyzed reaction was quantified by measuring the intensity of luminol chemiluminescence in the presence of excess ferricyanide. Glucose oxidase was immobilized on aminopropyl glass using glutaraldehyde and packed in a reactor. The chemiluminescence was transported to the detector using an optical fiber. The system responds linearly to glucose in the concentration range 0.20 mM up to 2.5 mM, with a relative precision of 5%. Several fruit juices were analyzed for their glucose content and the results were compared with a standard AOAC procedure.

Enzyme electrodes for the sugar substitute aspartame

An aspartame selective electrode has been developed for the rapid determination of this artificial sweetener in various dry powder mixes. The aspartase enzyme has been immobilized over an ammonia gas sensing electrode. The Potentiometric responses of a soluble and a chemically immobilized enzyme device have been evaluated. The latter offers greater stability, more than 7 days, with a linear dependence of the response from 1 mmol/1 to 10 mmol/1 aspartame. Successful determinations of aspartame in commercially available powder mixes have been obtained with no special sample pretreatment.

A piezoelectric crystal detector for determination of acetoin in air

Abstract A method is presented for the determination of acetoin (3-hydroxy-2-butanone) in air with a piezoelectric crystal detector coated with semicarbazide. The response time is about 5 min, is fully reversible, and is selective for acetoin in the presence of the interferences normally found in air. The detector has a sensitivity of 12.4 Hz 1 μl−1 for acetoin and the response varies linearly with concentration in the 50– μl l−1 range.