Maintaining quality control in field sampling involves preparation in three stages: 1) Pre-sampling preparation of sampling and safety plans, sampling equipment and sampling containers; 2) On-site collection of site specific and quality control samples; 3) Post sampling preparation of laboratory and chain-of-custody forms as well as preparation of samples for shipment.
Sampling begins with the development of site sampling and safety plans. The sampling plan is used to determine the location, type and number of samples to be collected. On the site, the sampling plan may be adjusted to reflect field conditions. The safety plan is used to establish levels of protection required for specific activities and any other emergency information necessary. Once these determinations are made, field equipment (which includes both sampling supplies and personal protective clothing) can be prepared. For each sample collected, a lab specified volume of aqueous or solid material must be collected to ensure an adequate volume of sample for analysis. Samples are collected in specified types of jars so that the container itself does not influence sample results. When packing sampling equipment, care is given to each item so that samples will not be contaminated with off-site material.
Quality control samples are collected to assure reliable analytical results. These quality control samples include: a trip blank, used to determine contamination which may result from storage, transport or site activities; a field blank, used to determine previously existing container contamination and contamination which may result from ambient on-site conditions; an equipment blank, used to determine contamination in sampling equipment; an additional sample volume for a laboratory matrix spike/matrix spike duplicate sample, used by the laboratory to determine spike recoveries for analysis of matrix effects and laboratory data accuracy; unidentified (“blind”) duplicate samples, used to check laboratory precision; and background samples, used for comparison when determining the type and amount of contamination present. Preserve samples as required in the field. Decontaminate all field equipment to prevent cross-contamination of samples collected.
After sampling, complete all required laboratory forms. Maintain chain-of-custody on samples at all times. Pack jars in individual plastic bags to reduce cross-contamination if breakage occurs. Wrap jars individually with bubble plastic and place in coolers with ice for shipment. Ship samples for overnight delivery.