Sampling and analyses

Avoid contamination of samples

At sampling, it is important to handle the samples so that they are not affected by external factors. First and foremost this involves ensuring that the compounds to be analysed are not altered or lost between sampling and analysis, for example through organising rapid transport to the laboratory (within a day) preferably in chilled conditions. The conditions during the actual sampling are also important since certain compounds can be volatile, while others can adhere to the sampling equipment if the wrong materials are used. It is equally important to ensure that the sample is not contaminated in any way. There is a high risk of samples becoming contaminated if the inside of the bottle or cap is touched, or if the cap is left on the ground during sampling. Similarly, it is important to avoid contaminating the sampling equipment used through considering how it is stored before use and also during the actual  sampling. The concentrations to be analysed are often very low, which increases the risk of inadvertently contaminating the sample.

Detailed instructions on how sampling should be carried out and what to be aware of usually accompany the sampling bottles sent out by the laboratory in charge of carrying out analyses.  

For general guidance on sampling techniques and the design of sampling programmes for different types of water, see the standards issued by ISO (SS-EN ISO 5667-1:2007 and SS-EN ISO 5667-1:2007/AC:2007), which can be purchased through SIS (Swedish Standards Institute)