EDTA specimen contamination

Analysis of Pb is routinely performed by either ICP-Qj, electrothermal atomic absorption spectrometry. EDTA anticoagulated blood is the specimen of choice for Pb analysis, because Pb is concentrated in the erythrocytes. Sodium heparin may also be used however, samples that are not analyzed within 48 hours are frequently clotted and must be rejected. Care must be taken when obtaining capillary blood. Surface contamination, insufficient collection volume, and inadequate mixing with EDTA result in frequent sample rejection. Urinalysis can also be performed urine quantification correlates with exposure. 

The 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 2-propanol may also occur if an alcohol-soaked swab is used to cleanse skin prior to venepuncture. Gross contamination with technical xylene (a mixture of o-, m-, and p-xylene together with ethylbenzene) has been found in blood collected into Sarstedt Monovette Serum Gel blood collection tubes contamination with toluene (up to 22 mg 1 ), 1-butanol, ethylbenzene, and xylene has been found in batches of these same tubes. Contamination with 1-butanol or 2-methyl-2-prop-anol occurs commonly in blood collected into tubes coated with EDTA. Care should be taken when handling frozen tissue prior to analysis as any compounds present in ambient air may condense on the cold surface and give rise to false positives. Processing blank frozen tissue can control for this possibility. 

The overall abundance of nickel in the human environment requires a strict contamination control in the preanalytical phase (specimen collection, transport, and storage) as well as in the analytical phase. Collection of urine and blood specimens should take place in a noncontaminated area after the individual has showered and changed into street clothing. Urine should be voided directly into acid-washed plastic containers. Standard collection equipment, e.g., Vacutainer and Monovetten (EDTA-K as anticoagulant), can be used after checking all sources for possible contamination for blood sampling. 

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