Examination of precipitation chemistry and improvements in precision using the Mg(OH)"2 preconcentration inductively coupled plasma mass spectrometry (ICP-MS) ... [An article from: Analytica Chimica Acta]

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Description:
The chemistry of magnesium precipitation preconcentration of Fe, Mn, and Co from seawater was investigated, and this analytical technique was adapted for use with the Element-2 inductively coupled plasma mass spectrometer (E2 ICP-MS). Experiments revealed that the scavenging efficiency of Mn using the precipitation protocol described here was ~95% and similar to that previously observed with Fe. In contrast, the scavenging efficiency of Co was three-fold lower than that of Fe and Mn, resulting in poor recovery. An increase in sample size to 13mL led to several desired effects: (1) an increase in the Fe and Mn signals allowing a final dilution of samples to 0.5mL and the use of an autosampler, (2) an increase in precision to ~1-2.5% R.S.D., and (3) an increase in signal relative to the blank. Experiments suggest metal concentration from seawater occurs during the formation of Mg(OH)"2 precipitate, whereas P was scavenged by adsorption onto the Mg(OH)"2 particles. Example vertical profiles are shown for dissolved Fe and Mn from the Equatorial Pacific.