Sampling, Sample Preparation and Preservation

Abstract

Proper collection and handling of water samples is an essential part of producing meaningful analytical results, especially at the trace levels now reported. Aspects which must be considered include sample size and container, sample labels, sampling technique, sample preservation from time of collection until receipt by the laboratory, transport and storage of samples, and recordkeeping. The characteristics of the agricultural chemical to be analyzed, study objectives and design, and the nature of the water to be sampled are important factors in determining how each of this aspects should be addressed. For many agricultural chemicals, requirements for sample containers and sampling techniques can be simplified compared to those often used in other types of groundwater monitoring programs. Regardless of the specific procedures utilized, the challenge of collecting water samples in an environment where dust and surface soils may contain residues three to four orders of magnitude higher than the sensitivity of the analytical method dictates that samples always be collected by conscientious and trained personnel. Care must always be taken to avoid contamination by attention to cleanliness of the sampler, sample bottles, sampling equipment, and storage containers. Samples (or empty sample bottles) should not be transported in vehicles also used to transport agricultural chemicals or stored in containers or freezers previously containing agricultural chemicals. Sample labels and study records must be adequate to provide necessary information and fulfil any applicable regulatory requirements.