Possibilities and limitations of color quench correction methods for gross alpha/beta measurements

Gross alpha/beta activity determination is utilized as a very popular Liquid Scintillation Counting (LSC) technique widely used in routine monitoring of drinking, surface and waste waters. Since quenching phenomena are most problematic effect during LSC measurements, the objectives of this paper are to present, consider and evaluate two methods for color quench correction as a proposal for supplement to the ASTM D 7283-06 method for gross α/β determination. The first method is PSA adjustment: application of previously established dependence of optimal PSA discriminator between alpha and beta events on quench level of sample. The second method assumes counting on usual optimal PSA setting and application of previously determined quench calibration curves in order to correct count rates in alpha and beta channels afterwards. Application on obtained activity results of few artesian well water samples and colored spiked samples, based on the measured SQP(E) value of samples, has been demonstrated, as the opportunity to compare the validity, reliability and limitations of both methods. All samples have been counted on low-background liquid scintilllation counter Quantulus 1220™.