ION CHROMATOGRAPHY OF ORGANIC-RICH NATURAL-WATERS FROM PEATLANDS .2. NA+, NH4+, K+, MG-2+ AND CA-2+

Organic-rich natural waters from peat bogs in continental (Switzerland) and maritime (Shetland Islands, Scotland) environments were analysed for Na+, NH4+, K+, Mg2+ and Ca2+ using ion chromatography. These cations were determined simultaneously in surface and pore water samples from the continental bogs using a 250-mul injection loop in an isocratic separation. Using this loop, detection limits of the order of 1 ng/g were achieved. An organics-removal cartridge (Dionex OnGuard P) was used to remove humic materials. Analyses of deionized water filtered through these cartridges showed acceptably low blank values (e.g., ca. 5 ng/g) and appeared to have no significant effect on the measured cation concentrations. For the maritime bog waters, the low concentrations of NH4+ (ca. 1 mug/g) compared with Na+ (ca. 100 mug/g) required improved peak separation. This was accomplished by using a gradient separation beginning with 40 mM HCl-1 mM D,L-2,3-diaminopropionic acid monochloride (DAP) and switching to 40 mM HCl-12 mM DAP after 2 min. Using a 25-mul injection loop, Na+, NH4+, K+, Mg2+ and Ca2+ were determined simultaneously in less than 25 min. In this instance, even with Na+/NH4+ > 100, there was no interference from Na+ in the determination of NH+ (baseline separated).