Arsenic species analysis by ion chromatography-bianode electrochemical hydride generator-atomic fluorescence spectrometry.

In this work, a novel hyphenated technique ion chromatography-bianode electrochemical hydride generator-atomic fluorescence spectrometry (IC-BAECHG-AFS) system was developed for on-line simultaneous analysis of arsenite (As(III)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)). Parameters that might affect hydride generation efficiency were investigated and the interference of various ions was also examined. Under the optimal conditions, the hydride generation efficiency of bianode electrochemical hydride generator (BAECHG) was close to the hydride generation efficiency of chemical hydride generator (CHG). The linear ranges were 5-200 microg L(-1) for As(III), DMA and MMA and 10-200 microg L(-1) for As(V). The limits of detection (LOD, S/N=3) were 3.04, 4.27, 3.97 and 9.30 microg L(-1) for As(III), DMA, MMA and As(V), respectively. The relative standard deviations (RSD, n=7) of As(III), DMA, MMA and As(V) were 4, 3, 5 and 4%, respectively. The proposed method was also applied to the determination of the four arsenic species in dental pulp inactivative agent (type I). The recoveries of the four arsenic compounds were in the range of 91.6-103.2%.

N-Methyl-piperazinediium penta-chloridoanti-monate(III) monohydrate.

The asymmetric unit of the title compound, (C(5)H(14)N(2))[SbCl(5)]·H(2)O, consists of an N-methyl-piperazinediium cation, a penta-chloridoanti-monate anion with the Sb(III) ion in a slightly distorted square-pyramidal coordination environment, and one solvent water mol-ecule. The crystal structure is stabilized by inter-molecular N-H⋯Cl, O-H⋯Cl and N-H⋯O hydrogen bonds.

Redetermination of ethyl-ene-diammonium bis-(p-methyl-benzene-sulfonate) monohydrate.

In the asymmetric unit of the title compound, C(2)H(10)N(2) (2+)·2C(7)H(7)O(3)S(-)·H(2)O, there are two independent 4-methyl-benzene-sulfonate anions, one ethyl-enediammonium cation and a water mol-ecule. The present redetermination was carried out to improve the treatment of disorder, which was not refined in the previous study [Ahn & Kim (1985 ▶). J. Korean Chem. Soc.29, 335-340]. One of the sulfonate groups is disordered over two positions, with site-occupancy factors of 0.588 (14) and 0.412 (14). Inter-molecular N-H⋯O and O-H⋯O hydrogen bonds hold the three components together, affording a layer structure extending parallel to the (001) plane.

Fabrication of electrolytic cell for online post-column electrochemical derivatization in ion chromatography.

An electrolytic cell (EC), composed of two ruthenium-plated titanium electrodes separated by cation-exchange membranes, was fabricated and evaluated for online postcolumn derivatization in ion chromatography (IC). Folic acid (FA) and methotrexate (MTX) were preliminarily used as prototype analytes to test the performance of EC. After separation by an anion exchange column, FA and MTX, which emit very weak fluorescence when excited, were electrochemically oxidized online in the anode chamber of the EC. The compounds with strong fluorescence, which are oxidation products, were detected by the fluorescence detector. The phosphate buffer solution (100 mM KH(2)PO(4)) served as an optimal eluent for anion exchange chromatographic separation and a suitable supporting electrolyte for electro-oxidation, leading to ideal compatibility between IC separation and the postcolumn electrochemical derivatization. For the presently proposed method, the linear ranges were from 0.01 mg L(-1) to 5 mg L(-1) for both FA and MTX. The detection limits of FA and MTX were 1.8 and 2.1 µg L(-1), and the relative standard deviations (RSD, n=7) were 2.9% and 3.6%, respectively. The method was applied for the simultaneous determination of FA and MTX in the plasma of patients being treated for rheumatoid arthritis. The determination of MTX in the urine of the patients of diffuse large B cell lymphoma was also demonstrated.