Effects of Chemical Preservative and Temperature Storage Conditions on Cations and Anions in Natural Water

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Abstract
The effect of storage on cation and anion concentrations in freshwater samples was investigated experimentally using chemical preservation treatments (mercuric chloride and/or acidification with hydrochloric acid) combined with three separate temperature levels (20°C, 4°C, or frozen). Two storage times were used, 21 days and approximately 90 days. Results were interpreted using analysis of variance and comparison of various means with results at day 0. Cations (Ca2+, Mg2+, Na+, K+) were analysed at two different laboratories, yielding comparable results. Cation concentrations are generally resistant to change and are best untreated or preserved with mercuric chloride at any of the three temperatures. for anions, storage at 4°C with no chemical preservatives proved good or adequate. the main conclusions resulting from a large number of ANOVA tables and tables of means are presented, together with a summary table for all experimental treatments and chemical components studied: Na+, K+, Ca2+, Mg2+, PO3− 4, SiO4− 4, SO2− 4, Cl−, NH+ 4, total organic carbon. Particular storage treatments, such as removal of suspended matter by filtration and the use of iodised bottles for preserving phosphate, are important for some analyses. the biggest changes in ion concentrations occurred between days 21 and 90+; early analysis of stored samples is recommended.