Determination of hydrocarbons in water – interlaboratory method validation before routine monitoring

The clarification of hydrocarbon input into the Baltic sea via rivers is one of the priority issues of the 4th Pollution Load Compilation (PLC-4) within the framework of international Baltic Sea marine monitoring. An interlaboratory comparison was conducted to check the applicability of a new method for the determination of hydrocarbons by solvent extraction and gas chromatography. Surrogate oil solutions with known hydrocarbon content were distributed among the participants for preparation of water samples of different hydrocarbon concentration. In using these concentrations as assigned values and by setting target values for precision, the proficiency of participating laboratories could be tested as a qualifying step before involvement in PLC-4 routine monitoring. The results of the exercise indicate that hydrocarbons in water samples can be monitored as a mandatory test item within the framework of PLC-4. Received: 31 October 2000 Accepted: 3 January 2001