Good laboratory practice sample analysis

Creating consensus recommendations for good laboratory practices associated with clinical-sample analysis for environmental and occupational medicine. 

Due to increased levels of sensitivity of analytical techniques and a range of legal requirements (including Good Laboratory Practices and issues in potential litigation), particular care must be taken in collecting and handling samples to both avoid contamination and maintain a chain of custody of samples and sample records. There are a vast variety of techniques now employed in analysis, as outlined below. 

Upon arrival, the sample should be logged in the laboratory record book indicating time of arrival, sample temperature, and pH. The sample should in all cases be analyzed for residual chlorine and, if present, oxidized with sodium thiosulfate before it is employed for toxicity evaluation. A portion of the sample should also be removed for alkalinity and hardness analyses. Often it is necessary to coarse filter the sample to remove floe or suspended debris before testing however, this practice may reduce the sample s toxicity. The remainder of the sample should be kept at 4°C for a period not exceeding 72 h after initial sample collection. It is desirable to employ two separate 24 h composite samples for performing a 96 h acute larval fathead minnow test. This would allow renewal after 48 h exposure. In the 7 day tests with Ceriodaphnia and Pimephales, three separate 24 h composite samples should be employed for daily renewal of the various exposure solutions. Toxicity data summary sheets should include daily routine physico-chemical measurements and sample information. It is essential that good laboratory practices be used in all aspects of sample collection, treatment, and analysis to obtain quality and defensible results. 

Samples of process flavors were analyzed for the presence of five PHAs IQ, MelQ, MelQx, DiMelQx, and PhIP. The samples were analyzed using die method developed by Gross (1990) and modified by Knize and Salmon (1998). The analysis of the samples complied with the FDA s Good Laboratory Practice regulations (21 CFR Part 58). 

In this section we provide some practical considerations to chemists not familiar with the use of immunoassays for food contaminants. We focus primarily on the use of 96-well microtiter ELISA. Regardless of the type of sample and analysis, good laboratory practices (GLPs) and international standards organization (ISO) standards, where they apply, need to be followed to ensure the quality of results and the minimization of variability. Like any other analytical protocol, the analysis of contaminants by immunoassay is a combination of three sequential steps sample collection and preparation, sample analysis, and data processing followed by the interpretation of results. 

The means for obtaining high quality, cost effective analytical services are described. These services are essential for accurate and economical analysis with rapid turn around time. Good laboratory practices, including computerized sample tracking, instrument calibration, maintenance of equipment and written documentation of the analytical methods assure high quality of the analytical data. 

This exercise affords an opportunity to introduce good laboratory practices when conducting an analysis using a spectrophotometer. Each student is given at least one unknown groundwater sample with which to measure the concentration of Fe(III) and the concentration of Fe(II). 

---