Luminol Chemiluminescence with Heteropoly Acids and its Application to the Determination of Arsenate, Germanate, Phosphate and Silicate by Ion Chromatography

Abstract

A flow‐injection chemiluminescence (CL) method has been proposed for sensitive determination of arsenate, germanate, phosphate and silicate, after separation by ion chromatography (IC). The post‐column detection system involved formation of heteropoly acid in a H2SO4 medium before the CL reaction with luminol in an NaOH medium. For separation, heteropoly acid formation and the CL detection reaction, pH requirements were not compatible. When present as a heteropoly acid complex with molybdenum(VI), ger‐ manium(IV) and silicon(IV) caused CL emission from oxidation of luminol, and such a CL oxidation of luminol was observed analogously for arsenic(V) and phosphorus(V) but with the addition of metavanadate ion to the acid solution of molybdate. Good sensitivity for the three analytes arsenic(V), ger‐ manium(IV) and phosphorus(V) could be given by a single set of reagent conditions, chosen carefully. Another set was suitable for determining phosphorus(V) and silicon(IV). The minimum detectable concentrations of arsenic(V), germanium(IV), phosphorus(V) and silicon(IV) were 10, 50, 1 and 10 μg l−1, respectively. Linear calibrations for arsenic(V), germanium(IV), phosphorus(V) and silicon(IV) were established over the respective concentration ranges of 10–1000, 50–25000, 1–1000 and 50–1 μg l−1. The proposed IC–CL method was successfully applied to analyses of a seaweed reference material, rice wine and water samples.

Flow Chemiluminescence Determination of Antimony(III,V) Using a Rhodamine B-Cetyltrimethylammonium Chloride Reversed Micelle System Following Liquid-Liquid Extraction

“…9 However, many inorganic anions like the antimony(V) chloro-complex anion, [SbCl6] -, do not cause luminol CL and thus applications of flow injection CL methods for anion determination have been limited. 10 In order to extend the use of the CL method for practical analysis, on the other hand, rhodamine compounds as a series of xanthene dyes are attracting increasing attention as highly sensitive and selective CL reagents. As is well known, rhodamine B (RB) has been applied in analytical chemistry, 11,12 mostly in spectrophotometry 13 and fluorescence analysis.…”

Principles and Applications of Ion Chromatography

“…However, its use in ion chromatography is limited due to the requirements that must be met by the analyzed substance to be detected. It is applied to detect arsenates, silicates, and phosphates [61]; chromium ions [62]; nitrogen anions [63]; and copper [64].…”

A multisyringe flow-through sequential extraction system for on-line monitoring of orthophosphate in soils and sediments

“…Actually, a 20% increase in the analytical signals was detected whenever the molybdate reagent for HL containing 0.125 % (w/v) oxalic acid in 0.3 M H 2 SO 4 was utilized for analyzing a 1.0 mg P l -1 standard containing 200 mg Si l -1 in 1.0 M NaOH. It is known that the interference of silicate on the orthophosphate MB determination can be minimized by increasing both the acidity of the reaction medium and the concentration of the masking organic acid [36][37][38][39]. The effect of the concentration of sulfuric acid was thus evaluated from 0.3 to 1.5 M while that of oxalic acid from 0.125 to 0.25 (w/v).…”

“…The effect of the concentration of sulfuric acid was thus evaluated from 0.3 to 1.5 M while that of oxalic acid from 0.125 to 0.25 (w/v). Yet, since the acidity has opposite effects on the selectivity and sensitivity of the molybdophosphate formation [36][37][38], the molybdate reagent was finally prepared in a 1.0 M H 2 SO 4 medium containing 0.25 (w/v) oxalic acid. Under these experimental conditions, silicate was tolerated up to 400 mg Si l -1 at the 10% interference level.…”