Development of continuous dispersive liquid-liquid microextraction performed in home-made device for extraction and preconcentration of aryloxyphenoxy-propionate herbicides from aqueous samples followed by gas chromatography-flame ionization detection.

In this study, a rapid, simple, and efficient sample preparation method based on continuous dispersive liquid-liquid microextraction has been developed for the extraction and preconcentration of aryloxyphenoxy-propionate herbicides from aqueous samples prior to their analysis by gas chromatography-flame ionization detection. In this method, two parallel glass tubes with different diameters are connected with a teflon stopcock and used as an extraction device. A mixture of disperser and extraction solvents is transferred into one side (narrow tube) of the extraction device and an aqueous phase containing the analytes is filled into the other side (wide tube). Then the stopcock is opened and the mixture of disperser and extraction solvents mixes with the aqueous phase. By this action, the extraction solvent is dispersed continuously as fine droplets into the aqueous sample and the target analytes are extracted into the fine droplets of the extraction solvent. The fine droplets move up through the aqueous phase due to its low density compared to aqueous phase and collect on the surface of the aqueous phase as an organic layer. Finally an aliquot of the organic phase is removed and injected into the separation system for analysis. Several parameters that can affect extraction efficiency including type and volume of extraction and disperser solvents, sample pH, and ionic strength were investigated and optimized. Under the optimum extraction conditions, the extraction recoveries and enrichment factors ranged from 49 to 74% and 1633 to 2466, respectively. Relative standard deviations were in the ranges of 3-6% (n = 6, C = 30 µg L(-1)) for intra-day and 4-7% (n = 4, C = 30 µg L(-1)) for inter-day precisions. The limits of detection were in the range of 0.20-0.86 µg L(-1). Finally the proposed method was successfully applied to determine the target herbicides in fruit juice and vegetable samples.

Use of a Rapid Ethylene Glycol Assay: a 4-Year Retrospective Study at an Academic Medical Center.

Ethylene glycol (EG) is a common cause of toxic ingestions. Gas chromatography (GC)-based laboratory assays are the gold standard for diagnosing EG intoxication. However, GC requires specialized instrumentation and technical expertise that limits feasibility for many clinical laboratories. The objective of this retrospective study was to determine the utility of incorporating a rapid EG assay for management of cases with suspected EG poisoning. The University of Iowa Hospitals and Clinics core clinical laboratory adapted a veterinary EG assay (Catachem, Inc.) for the Roche Diagnostics cobas 8000 c502 analyzer and incorporated this assay in an osmolal gap-based algorithm for potential toxic alcohol/glycol ingestions. The main limitation is that high concentrations of propylene glycol (PG), while readily identifiable by reaction rate kinetics, can interfere with EG measurement. The clinical laboratory had the ability to perform GC for EG and PG, if needed. A total of 222 rapid EG and 24 EG/PG GC analyses were documented in 106 patient encounters. Of ten confirmed EG ingestions, eight cases were managed entirely with the rapid EG assay. PG interference was evident in 25 samples, leading to 8 GC analyses to rule out the presence of EG. Chart review of cases with negative rapid EG assay results showed no evidence of false negatives. The results of this study highlight the use of incorporating a rapid EG assay for the diagnosis and management of suspected EG toxicity by decreasing the reliance on GC. Future improvements would involve rapid EG assays that completely avoid interference by PG.

[Observations on the cost effectiveness of various methods of electrolyte determination]. / Betrachtungen zur ökonomischen Effizienz von verschiedenen Methoden zur Elektrolytbestimmung.

New analytical methods have to be considered also with respect to their economic efficiency. Here we present the application of an economic analysis based on the rules of applied economics in our institute for clinical chemistry and laboratory medicine. We started with an analysis of laboratory structure and economic efficiency in 1988, which since then has been followed by a continuously performed laboratory controlling system. The results of unit costing show the different cost groups, which add up to the cost of a single electrolyte determination. Regarding the transferability of our data to other laboratories, one has to consider that the main cost groups besides personnel cost are the apportionment of the overhead cost and the depreciation cost; both may vary markedly between each laboratory. Variable cost (reagents and consumables) differ widely from flame photometry to enzymatic electrolyte determination, but they amount only to 3-15% of the total cost.