Use of an electronic tongue and HPLC with electrochemical detection to differentiate molds in culture media.

A study was conducted to further evaluate an electronic tongue, using high-performance liquid chromatography (HPLC) with electrochemical (EC) and UV detection as a reference method. The electronic tongue consisted of four working electrodes made of different metals and arranged in a standard three-electrode configuration. Pulses of voltage were applied to the metals, and the current responses were sampled and collected in a data matrix. The objectives of the present investigation were to examine the ability of the electronic tongue to distinguish between two mold species growing in three different media, and to obtain support for the hypothesis that the device actually discriminates between different redox-active metabolites produced by the molds. Peak areas in EC and UV HPLC chromatograms were collected in a data matrix. The electronic tongue data and the EC and UV data were then subjected to principal component analysis (PCA). A number of peaks in the HPLC-EC chromatograms indicated that the growth media contained redox-active metabolites. Moreover, PCA of peak areas in EC chromatograms revealed differences between the distribution of redox-active metabolites produced by the two species and between the three culture media. The same pattern was apparent in a PCA score plot of electronic tongue data. The peaks in the UV and EC chromatograms differed, and these were also shown by the PCA score plots.

Quantitative light microscopic autoradiography. Emulsion sensitivity and latent image fading.

Emulsion sensitivity, latent image fading, and the effects of temperature, humidity, radiation dose and chemography on them were measured for NTB2 autoradiographic emulsion using quantitative methods. Sensitivity of NTB2 emulsion increased as the temperature during exposure increased, with the greatest increase per degree occurring between -20 degrees C. At 4 degrees C, emulsion sensitivity remained constant with time and radiation dose. Direct measurement of latent image fading showed no latent image fading for 60 weeks on slides exposed at 4 degrees C with Drierite. Slides exposed at 27 degrees C showed significant latent image fading and great variation between samples. High humidity decreased emulsion sensitivity and increased latent image fading. No evidence of either positive or negative chemography was found. The practical use of autoradiography requires an internal standard on each slide to correct for fluctuations in temperature and humidity during exposure time.

Use of an electronic tongue to analyze mold growth in liquid media.

The feasibility of employing an electronic tongue to measure the growth of mold in a liquid medium was studied. We used the electronic tongue developed at Linköping University, which is based on pulsed voltammetry and consists of an array of different metal electrodes. Instead of focusing on a single parameter, this device provides information about the condition or quality of a sample or process. Accordingly, the data obtained are complex, and multivariate methods such as principal component analysis (PCA) or projection to latent structures (PLS) are required to extract relevant information. A gas chromatographic technique was developed to measure ergosterol content in mold biomass and was subsequently used as a reference method to investigate the ability of the electronic tongue to measure the growth of mold in liquid media. The result shows that the electronic tongue can monitor mold growth in liquids. In PLS analysis, the electronic tongue signals correlate well with the amount of ergosterol in the mold biomass as well as the microbially induced changes in the pH of the medium.

Determination of low molecular weight organic acids in soil solution by HPLC.

An HPLC method employing an ion exclusion column was developed for the determination of low molecular weight organic acids in soil solution. The method includes extensive sample pretreatment using ultrafiltration and cation exchange. The method showed linear calibration graphs (r>0.99) and the limits of detection in the range 0.1-26 muM. The recovery of eleven added acids ranged from 89 to 102%. Soil solutions of five horizons of a podzolised soil were analysed. The results showed that these compounds made up 1-3% of the dissolved organic carbon and 0-14% of the acidity. Identification of the major acids was also carried out by capillary zone electrophoresis.

The use of 13C NMR spectroscopy in forensic drug analysis.

13C NMR spectroscopy has been used for analysis of fourteen compounds which, according to Swedish laws are defined as narcotic drugs or are substances often found in combination with these drugs. The carbon-13 NMR method seems to be well suited for analysis of complex forensic drug mixtures because no preliminary separation of components is required.

Determination of the carboxyl content in humic substances by methylation.

The carboxyl content of different fulvic acids was estimated by means of a methylation technique. The procedure involved methylation by diazomethane followed by base catalyzed hydrolysis, esterification with propionyl chloride and gas chromatographic analysis of the methyl ester formed. After optimization of each step, the whole sequence of reactions was performed using only a few milligrams of starting material. The method was applied to two fulvic acid samples of different origin (surface water and groundwater, respectively). The carboxylic content was estimated to about 3.5 meq/g material for the surface water fulvic acid and about 4.5 meq/g material for the groundwater fulvic acid. This estimates approximately 80% of the total content of acidic groups obtained for the same materials by using potentiometric titration.

A comparison of methods for concentrating mutagens in drinking water--recovery aspects and their implications for the chemical character of major unidentified mutagens.

A comparison of techniques for concentrating mutagenic compounds in drinking water has shown that XAD-2 adsorption and dichloromethane extraction have acceptable and almost identical enrichment properties, while purging at an elevated temperature is inappropriate in this context. Quantitatively, the most important drinking water mutagens could only be adsorbed (extracted) after acidification of the water, and even then recovery was far from complete. Recovery experiments with known mutagens from pulp mill effluents have shown that none of the major chlorination-stage mutagens identified thus far can explain the mutagenic activity of extracts from neutral or acidified chlorinated drinking water.

Impact of bleached kraft mill effluents on drinking water quality.

Bleaching effluents from kraft pulp mills contain large quantities of chlorinated organic compounds, some of which are mutagenic. Mutagenic chloro-organic compounds are also formed as by-products in chlorination of drinking water. The work reported here was a combined field and laboratory study aimed at comparing the evidence of health risks from pulp mill contaminants in drinking water, with corresponding evidence from normal, chlorine disinfection by-products. The study was performed in a Swedish river basin with a large, public water works located downstream from a bleached kraft mill. Chemical analyses (gas chromatography and determination of adsorbable organic halogen) and bioassays for mutagenic activity (bacterial and mammalian cell bioassays) were performed on samples of river water, drinking water and laboratory produced drinking water. The study showed that the bleached kraft effluents caused a considerable, long-range transport of chloro-organic substances in the receiving waters, and a substantial increase in the total amount of organic chlorine in drinking water produced downstream from the mill. As regards Ames mutagenic compounds, however, chlorination of naturally occurring humic substances during the chlorine disinfection step in drinking water production, proved to be a far more important source. The contribution of volatile chloro-organic compounds from the kraft mill was also much smaller than the contribution from normal disinfection by-products. The chromosome aberration tests gave no clear evidence of a positive response for any of the samples tested.

Abnormal glucose levels found in transportation accidents.

BACKGROUND: The Federal Aviation Administration's Office of Aerospace Medicine is responsible for the certification of pilots with diabetic conditions. The present study evaluated the use of postmortem vitreous humor and urine glucose levels in transportation accident fatalities as indicators of potentially incapacitating medical conditions or performance impairment. METHODS: Vitreous humor and/or urine from 192 accident fatalities were analyzed for glucose using a hexokinase method. Cases with values below the lower limit of detection (10 mg x dl(-1)) and above 3 standard deviations (SD) from the mean were not included in the final statistics. All cases more than 5 SD above the mean were deemed abnormal and a full case history was evaluated based on the available medical history. RESULTS: The mean vitreous humor glucose concentration was 30+/-21 mg x dl(-1) (N=98), while it was 27+/-16 mg x dl(-1) in urine (N=127). Of the 192 cases, 9 were identified as having abnormal glucose levels. Abnormal glucose levels were found in 5 of the 8 cases with a known diabetic condition. Glycosuria or low renal threshold was reported in 2 fatal pilots; 1 of these pilots had an abnormal glucose level. CONCLUSIONS: Hyperglycemia can be established from the vitreous humor and urine glucose levels. All of the abnormal glucose cases detected were previously identified during the medical certification process or had a medical reason for the abnormal level. Elevated vitreous humor and urine glucose levels have proven useful in identifying individuals with a pre-existing diabetic condition that might have been a factor in the accident.

Stress reduction. A spectrum of strategies in pediatric oncology nursing.

It is important to provide resources to promote effective coping mechanisms for dealing with the stresses encountered by children, families, and staff in a pediatric oncology setting. Knowledge of how such resources can be used to the maximum advantage must be combined with the utilization and development of support services.

Direct liquid chromatographic separation of enantiomers on immobilized protein stationary phases. IV. Molecular interaction forces and retention behaviour in chromatography on bovine serum albumin as a stationary phase.

Chromatography with the use of immobilized bovine serum albumin as a stationary phase and aqueous buffer systems as eluents has proved to be a highly selective method, capable of separating structurally very closely related compounds. Retention can be effectively regulated by changes in at least three independent parameters of the mobile phase, which may be used for an optimization of separation factors. Particularly, the enantioselective properties of the chiral stationary phase have been demonstrated to be useful for the analytical resolution of a variety of racemates into enantiomers. From the variation of the retention behaviour with substituent effects, as well as the mobile phase composition, some indications regarding the molecular interaction forces regulating the substrate-protein equilibria have been obtained.