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-1 (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.

A flow-batch manipulated Ag NPs based SPR sensor for colorimetric detection of copper ions (Cu2+) in water samples.

Using flow-batch analysis, a highly sensitive and selective method for automatic colorimetric detection of copper ions (Cu2+) was produced on the basis of the surface plasma resonance (SPR) of silver nanoparticles (Ag NPs). The Ag NPs were catalytically etched by thiosulfate in the presence of Cu(NH3)42+, resulting in a color change of the solution induced by the absorbance decrease at 401nm of the SPR peak of Ag NPs. The proposed method showed high selectivity for Cu2+ over various metallic ions, including Fe3+, Mn2+, Co2+, Ni2+, Zn2+, Pb2+, Ba2+, Cd2+, Bi3+, Sb2+, As3+, Hg2+, Cr3+ and K+. The linear range was 0.5-35µg/L with a coefficient of 0.9954. The limit of detection was as low as 0.24µg/L. The relative standard deviation (RSD, n=7) for the determination of Cu2+ spiked samples at concentrations of 10µg/L was 1.21% and for 25µg/L was 1.03%. The proposed method was successfully applied to analyze Cu2+ in lake water, tap water, rainwater and bottled water samples, as well as leaf samples for food packaging. The results were in good agreement with those obtained by graphite furnace atomic absorption spectrometry, the classical technique.