McLachlen et al also opted to study analyte stability in of Milli-Q-water at room temperature over three weeks. The surface water samples collected, however, are shipped as liquids (unfrozen) at 4 °C. Whilst it has been reported short term that it may be beneficial to store samples at 4 °C in comparison to -18 °C , in environmental samples there is a risk that microbiological action could potentially degrade or transform analytes in question . This is an important consideration if shipping takes several days to reach the analysis lab. Samples may be kept for a prolonged time (e.g. 1-2 weeks) at 4 °C before spiking of internal standards and/or before the extraction protocols take place . Whilst the matrix and microbiological communities will vary between temporal and spatial graphic location, a stability study on the matrix in question should be done.