Simultaneous spectrophotometric determination of phosphate and silicate ions in river water by using ion-exclusion chromatographic separation and post-column derivatization

The simultaneous spectrophotometric determination of phosphate and silicate ions in river water was examined by using ion-exclusion chromatography and post-column derivatization. Phosphate and silicate ions were separated by the ion-exclusion column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the H⁺-form (TSKgel Super IC-A/C) by using ultra pure water as an eluent. After the post-column derivatization with molybdate and ascorbic acid, so-called molybdenum-blue, both ions were determined simultaneously by spectrophotometry. The effects of sulfuric acid, sodium molybdate and ascorbic acid concentrations and reaction coil length, which have relation to form the reduced complexes of molybdate and ions, on the detector response for phosphate and silicate ions were investigated. Under the optimized conditions (color-forming reactant, 50 mM sulfuric acid-10 mM sodium molybdate; reducing agent, 50 mM ascorbic acid; reaction coil length, 6 m), the calibration curves of phosphate and silicate ions were linear in the range of 50-2000 μg L⁻¹ as P and 250-10,000 μg L⁻¹ as Si. This method was successfully applied to water quality monitoring of Kurose-river watershed and it suggested that the effluent from a biological sewage treatment plant was significant source of phosphate ion in Kurose-river water.     

Continuous-flow synthesis of activated vitamin D3 and its analogues

An efficient, two-stage, continuous-flow synthesis of 1α,25-(OH)(2)-vitamin D(3) (activated vitamin D(3)) and its analogues was achieved. The developed method afforded the desired products in satisfactory yields using a high-intensity and economical light source, i.e., a high-pressure mercury lamp. In addition, our method required neither intermediate purification nor high-dilution conditions.     

水为洗脱剂的静电离子色谱-增强电导检测法测定常见的无机阴离子（英文）

To enhance the conductivity detection sensitivity of common anions(Na-anions) in electrostatic ion chromatography(EIC) by elution with water,a conductivity enhancement column packed with strong acid cation exchange resin in the H-form was inserted between an octadecyl silane(ODS)-silica separation column modified with zwitterionic surfactant(CHAPS: 3-{(3-cholamidopropyl)-dimethylammonio}propanesulfonate) and a conductivity detector.Specifically,the Na-anion pairing is converted to H-anion pairing after the EIC separation and then detected sensitively by the conductivity detector.The effects of conductivity enhancement and suppression in the EIC by the enhanced conductivity detection were characterized for the common strong acid anions such as SO2-4,Cl-,NO-3,I-and ClO-4 and weak acid anions such as F-,NO-2,HCOO-,CH3COO-and HCO-3.For the conductivity enhancement effect in the EIC,it is found that the conductivity of measured for all strong acid anions(Na-anions) was enhanced according to the theoretical conductivity predicted for H-anions and that of the measured for weak acid anions was suppressed depending on their pKa of H-anions.For the calibration linearity in the EIC,the strong acid anions were linear(r2=0.99-1.00) because the degree of dissociation is almost 1.0 over all the concentration range and that of the weak acid anions was non-linear because the degree of dissociation decreased by increasing the concentration of the weak acid anions.In conclusion,the EIC by enhanced conductivity detection was recognized to be useful only for the strong acid anions in terms of conductivity detection and calibration linearity.