Screening methods are often used to determine the presence or absence of a specific analyte, groups of analytes, classes of compounds or other indicators of chemical compounds in order to determine if further analysis or action is necessary. The determination whether to proceed with further action is useful in reducing the number of negative results for which the screening method serves as a surrogate.

The use of screening methods, whether to generate qualitative or semi-quantitative results, is increasingly becoming a useful tool for regulatory monitoring, process control, and site characterization. The appropriate use of a screening method, or any other method for that matter, is dependent upon the Data Quality Objectives (DQOs) that are defined by the user of the data.

Persons responsible for assessing the quality of the data generated by the use of screening methods should have detailed Quality Control guidelines by which to assess data quality.

1.1 This guide covers general considerations for the Quality Control practices for use with screening methods for organic and inorganic constituents in water. Methods are provided by various standard setting bodies, governmental agencies, as well as many domestic and international manufacturers.

1.2 This guide provides general QC procedures that are applicable to a broad range of screening methodologies. These procedures help to ensure the quality of data that is generated. Additional, method-specific or project specific requirements may be necessary. This guide also includes general considerations regarding proper utilization of screening methods.