In-field determination of trace dissolved manganese in estuarine and coastal waters with automatic on-line preconcentration and flame atomic fluorescence spectrometry.

An automatic on-line preconcentration and detection system for analysis of trace dissolved manganese (Mn) in estuarine and coastal waters was established, using preconcentration with IDA chelating resin and detection with flame atomic fluorescence spectrometer (FAFS). The rinse (pre-eluent) solution was optimized, for removing the interference ions while retaining the target element. It was found that the interference ions affected the chelating efficiency of Mn, causing variation of the detection blank and sensitivity. This effect varied when sample volume presented as preconcentration time changed. The influence at preconcentration times of 120 s, 30 s and 10 s were carefully investigated and reported. Ten folds of the foreign trace metals Zn, Cu, Ni, Fe, and Al did not show obvious interference on Mn preconcentration and detection. The method detection limit was 0.9 nmol L (n = 7, preconcentration time 120 s). The linear detection range could be adjusted with designed preconcentration time. In addition to high precision and accuracy, the proposed analytical system had the advantages of high integration, and required normal site preparation, low energy supply and simple auxiliary equipment, which was appropriate for in-field operation. Compared with other common in-field applied molecular spectrometry instruments, the inherent high selectivity and multi-element applicability of FAFS highlighted the superiority and potential of the proposed analytical system. It was successfully applied to in-field vehicle-board determination of dissolved Mn in coastal waters around Xiamen, Fujian, China, and it was also used to analyze natural water samples collected from the Jiulongjiang Estuary, Fujian, China.