Evaluation of uncertainty of measurement from method validation data: an application to the simultaneous determination of retinol and alpha-tocopherol in human serum by HPLC.

An isocratic RP-HPLC method for the determination of retinol and alpha-tocopherol in serum, with fluorescence and UV/VIS detection, respectively, was developed and validated according to international guidelines. Detection (retinol 0.015 mg/L, alpha-tocopherol 0.

Quality specifications for the determination of copper, zinc, and selenium in human serum or plasma: evaluation of an approach based on biological and analytical variation.

Background: Trace element external quality assessment schemes monitor laboratory performance and provide a stimulus for improvement in accuracy. However, monitoring of participant performance varies according to the scheme and can lead to conflicting conclusions.

Methods: Quality specifications based on biological intra- and interindividual variability were calculated and compared to those currently used by various trace element external quality assessment schemes for plasma or serum copper, zinc, and selenium concentrations.

Salivary uric acid at the acidic pH of the stomach is the principal defense against nitrite-derived reactive species: sparing effects of chlorogenic acid and serum albumin.

A complex antioxidant system is present in human saliva, with uric acid being the most concentrated component. Ascorbic acid, present at low concentrations in saliva, is actively secreted into the gastric lumen. We report that ascorbic acid added to human saliva at pH 2 was consumed within a few minutes, regenerating HNO(2), whereas uric acid was consumed relatively slowly in a nitrite-dependent manner.

Differences in national legislation for the implementation of lead regulations included in the European directive for the protection of the health and safety of workers with occupational exposure to chemical agents (98/24/EC).

Background: The European Council Directive 98/24 on the protection of the health and safety of workers exposed to chemical agents sets out provisions for environmental and biological monitoring, making specific reference to binding limit values and health surveillance measures for those with exposure to lead

Objectives: To compare how the Directive has been implemented at a national level in EU countries and to determine whether workers receive equivalent protection.

Methods: Information on selected key issues was collected from 14 EU countries by means of a structured questionnaire.

Results: National occupational exposure limit values generally reflect that set by the Directive (0.

Estimate of uncertainty of measurement from a single-laboratory validation study: application to the determination of lead in blood.

Background: Lead is an environmental pollutant, and human exposure is assessed by monitoring lead concentrations in blood. Because the main source of environmental exposure has been the use of leaded gasoline, its phase-out has led to decreased lead concentrations in the general population. Therefore, validated analytical methods for the determination of lower lead concentrations in blood (<150 microg/L) are needed.

Comparison of procedures for evaluating laboratory performance in external quality assessment schemes for lead in blood and aluminum in serum demonstrates the need for common quality specifications.

Background: The different scoring methods used by eight European External Quality Assessment Schemes (EQASs) for occupational and environmental laboratory medicine were compared to develop suitable quality specifications as a step toward harmonization.

Methods: Real results for blood lead and serum aluminum assays, reported by participants in Italian and United Kingdom EQASs, were evaluated according to individual scheme scoring criteria. The same results were then used to produce z scores using scheme-based between-laboratory SDs as the estimate of variability to determine whether simple performance-derived quality specifications produced better agreement among schemes.

[Chemical compound safety: typology of competency accreditation for assay centers and analytical laboratories].

The use of chemicals warrants many benefits on which modern society is entirely dependent. On the other hand, the lack of reliable information about the impact of the use of chemicals raises increasing concern. In order to guarantee the safety of chemicals it is mandatory to proceed to risk assessment, which in turn consists of hazard evaluation and exposure estimation.