8 - Sample Preparation Techniques for Liquid Scintillation Analysis

Abstract

It is a sad but very true observation that sample preparation is considered an inconvenient step on the way to obtaining results. Consequently, it is only when the results obtained are different to those expected that the cry “There's something wrong with the cocktail” is heard. While this may or may not be true, the technique of sample preparation in general is only rarely considered responsible for the unexpected results. Correct sample preparation in liquid scintillation analysis (LSA) is essential for both accurate and reproducible analysis, and no amount of instrumental sophistication can ever fully compensate for the problems attendant to a badly prepared sample. Good sample preparation guarantees that the sample will be stable during the analysis, and therefore provides a solid foundation for accurate results. Sample preparation encompasses a wide variety of methods and techniques, and includes dissolution, distillation, extraction, solubilization, digestion, suspension, and combustion. All of these methods of sample preparation hold pitfalls for the unwary and some expertise is generally required. Common to all sample preparation methods is the liquid scintillation counting (LSC) cocktail, and this is the medium that holds the sample during the analysis process. The LSC cocktail is both fundamental to and necessary for the analysis; therefore correct cocktail selection is a critical step in sample preparation.