A proficiency testing system for the determination of volatile halogenated hydrocarbons at μg/L concentration level in water

Fourteen laboratories participated in the Austrian proficiency testing scheme (PTS) for monitoring of volatile halogenated hydrocarbons in ground water from July 1996 to January 1998. The PTS enabled to supervise the analytical performance in the mug/L range and revealed that the participating laboratories analysed with average recoveries ranging from 91% to 98%. The inter-laboratory standard deviation was found to range from 10% to 30%. Accompanying quality assurance measures showed that both, stock solutions in methanol and artificially prepared aqueous samples containing halogenated hydrocarbons are stable for at least 111 days and 81 days, respectively. As far as storage conditions are concerned, 60 mL of head space of air above 600 mL of sample solution had only a minimal impact on the concentration of six most volatile halogenated hydrocarbons after 63 days. The sample preparation procedure was found to be well suited for the operation of the PTS. It was possible to prepare homogeneous synthetic samples with known concentration within a bandwidth of +/- 10%. Moreover, the batch-wise sample preparation procedure was designed in such a way that no compound could evaporate despite its volatility. The present study revealed that permanent proficiency testing is a useful and powerful tool to make environmental monitoring more reliable and effective.