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Sample collection, transport and storage

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  P83-84

2026-09-21

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Sample collection, transport and storage

If the analyte is very volatile (e.g. propane, butane) and a quantitative analysis is required, a blood sample should be collected directly into the vial in which the analysis will be carried out. Many other volatile compounds are relatively stable in blood and other tissues if simple precautions are taken. In the case of blood, the container used for the sample should be glass, preferably with a cap lined with metal foil. Plastic containers should be avoided because some plastics such as poly(ethylene) and poly(propylene) are permeable to volatile organic compounds. Attention should be given to the types of tubes used for sample collection. Gross contamination with volatile aromatic compounds (ethylbenzene, toluene, xylene) and butanol was found in blood collected into certain types of blood-collection tubes (Dyne et al. 1996). Contamination with butan-1-ol or 2-methylpropan-2-ol occurs commonly in blood collected into tubes coated with EDTA. Carbon disulfide has been detected in blood collected in tubes sealed with soft-rubber stoppers (Weller and Wolf 1989). Volatile substances by their very nature volatilise readily from samples. Volatilisa tion is a concentration- and temperature-driven process and hence the greater the air space above a sample and the higher the temperature, the more readily will the substance volatilise. Thus sample tubes should be as full as possible and should only be opened when required for analysis and then only when cold (4C). An anti coagulant (sodium ethylenediaminetetraacetic acid (EDTA) or lithium heparin) should be used. Specimen storage between 2C and 8C (i.e. normalrefrigeratortemperature)isrecommended and 1% (w/v) sodium fluoride should be added to minimise enzymic activity. If a necropsy is to be performed, tissues (brain, lung, liver, kidney and subcutaneous fat) should be obtained in addition to standard toxicological specimens (femoral blood, urine, stomach contents and vitreous humour). Tissues should be stored before analysis in the same way as for blood but no preservative should be added. To avoid cross-contamination, products implicated in the incident (and stomach contents if ingestion is suspected) should be packed, transported and stored entirely separately from (other) biological specimens even when stored in refrigerators or freezers. Investigation of deaths that occurred during or shortly after anaesthesia should include the analysis of the inhalation anaesthetic(s), in order to exclude an error in administration. Clinical therapies and poor procedures during sample collection can also give rise to volatile compounds. For example, halothane or chlorobutanol may be used in therapy or inadvertently added to the sample as a preservative. Use of aerosol disinfectant preparations when collecting specimens may contaminate the sample if an aerosol propellant is used. Contamination of blood samples with ethanol or propan-2-ol may occur if an alcohol-soaked swab is used to cleanse skin prior to venepuncture.