Houdbaarheid en conservering van grondwatermonsters voor anorganische analyses

The storage life and the possibilities for preservation of inorganic analyses of groundwater samples have been investigated. Groundwater samples, with and without preservation with acid, from four locations in the Netherlands have been analysed ten times over a period of three months on six components, viz. dissolved organic carbon (DOC), ammonium (NH4), total-phosphorus (Total-P), chloride (Cl), nitrate (NO3) and sulphate (SO4). It appears that, under the regular conditions for storage of samples, only for low concentrations of nitrate a significant decrease with time in the nitrate content occurs. For the samples with added preservation acid, differences between 'preserved' and 'not preserved' are only absent for chloride. In all other cases differences between 'preserved' and 'not preserved' are small, except for nitrate, and predominantly located in the range of very low concentrations. The magnitudes of the differences between 'preserved' and 'not preserved' are strongly matrix dependent