This guide describes quality assurance protocols for the determination of the anions and cations in atmospheric wet deposition which include the minimum recommended requirements for the preparation of calibration standards and suggested procedures for validating laboratory measurement results. Specimens to be used in all tests shall consist of reagent grade chemicals, water, and standard solutions. Common techniques for chemical analysis include automated colorimetry; ion chromatography, flame atomic absorption spectrophotometry, electrometry, and inductively coupled plasma spectrometry. Analytical precision and bias determinations shall be done for evaluation of the reference materials. Samples for reanalysis may be selected from the evaluation of control charts and the calculation of ion and conductivity percent differences.