A cation-exchange column (TSK IC-Cation, 4.6 mm i.d., 10 mm) was used as a reaction/concentration/separation medium in an HPLC system. Cr(VI) and 1,5-diphenylcarbazide (DPC) were on-line mixed and reacted in a flow tube. When the reagents flowed into the column, both DPC and the complex were concentrated on the column, and the higher DPC concentration accelerated the remaining Cr(VI) to quickly complete the reaction with the DPC on the column. After the complexation and preconcentration, the complex and the extra DPC were eluted by a mixed solution containing lanthanum chloride and 1-propanol. The absorbance of the Cr(III)-DPCO complex at 540 nm was continuously monitored. In addition, the dissolved Cr(III) could be oxidized to Cr(VI) by 185-nm irradiation using a low pressure ultraviolet (UV) lamp for 8 min, and then analyzed by the present method as total chromium, thus the quantitative speciation analysis of Cr(III) and Cr(VI) was realized. In the range of 1 ng dm -3 -100 μg dm -3 Cr(VI) concentration, the calibration curve was linear. The analytical time was 8 min for Cr(VI) and 24 min for total Cr. The detection limit (3σ) of the method was 0.6 ng dm -3 for Cr(VI) and 0.8 ng dm -3 for total chromium when using a 3.9-cm 3 water sample. The present method could be successfully applied to the speciation analysis of dissolved chromium in natural water, and the leaching test of Cr(III) and Cr(VI) from stainless steel.
A sensitive, simple and low-cost determination method for the total iron concentration in boiler water systems of power generation plants was developed by solid phase spectrometry (SPS) using 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ) as a coloring agent. The reagents and 0.08 cm 3 of a cation exchanger were added to a 50-cm 3 boiler water sample, then mixed for 30 min to adsorb/concentrate the produced Fe(TPTZ)2 2+ colored complex on the solid beads, resulting in a 625 times concentration of the target analyte without any other procedure. The detection limit of 0.1 μg dm -3 was obtained, and the optimum conditions for the digestion procedure and color developing reaction was investigated and reported. According to the application of this method to real samples, the present SPS method is the best one because of the shorter analysis time, simpler operation and use of very low-cost equipment compared to the conventional methods, such as TPTZ solution spectrophotometric method after a 16 times concentration, ICP-MS and AAS.
However, the background coloration due to the HA degradation and the acid dissociation of SA could not be ignored in this pH region. We recently clarified the AzB complexation mechanism from both 2014 © The Japan Society for Analytical Chemistry † To whom correspondence should be addressed. Boric acid reacts with 5-fluorosalicylaldehyde (F-SA) and 8-amino-1-naphthol-3,6-disulfonic acid (HA) to form the boric acid-fluoroazomethine H complex (F-AzB) that is now being used for the flow-injection analysis (FIA) of boric acid. At pH 6.5, the F-AzB complexation proceeded fairly fast, whereas the fluoroazomethine H (F-AzH) formation was slow. Thus, highly sensitive measurement of F-AzB was possible if the reaction time was controlled using the FIA method to decrease the background absorbance of F-AzH at the analytical wavelength. The optimum conditions for the color developing reaction were investigated for single and dual channel systems. The former system was simple, applicable to the determination of boron in reversed osmosis (RO) desalination water with a detection limit (LOD) of 4 μg B dm -3 . For the latter system, the calibration range was 0.005 to 10 mg B dm -3 with an LOD of 1 μg B dm -3 , which can be applicable to natural water analyses of boron. These methods could analyze 15 -20 samples in one hour. The results of the boron concentration measurement for water samples from an RO desalination plant, industrial wastewater and river water were in fairly good agreement with those obtained by other methods.
A new, simple and sensitive solid-phase spectrometry (SPS) that is easily applicable to the on-site analysis of targeted chemical components in water at μg dm -3 or sub-μg dm -3 levels is proposed in this study. The main features of the SPS are the simplicity of operation, high sensitivity and applicability to real samples without the need for any pretreatment procedures. A portable spectrophotometer, consisting of an LED light source, a grating and a CCD, was used for the solid-phase light measurements. The universal applicability of the proposed system to on-site analysis was evaluated by determining phosphate, chromium(VI) and iron(II) in natural water.
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