Ultratrace determination of phosphorus in ultrapurified water by a slope comparison method

The analytical method for the determination of phosphorus in ultrapurified water was developed. Ultrapurified water was evaporated to concentrate phosphorus and the final sample volume for analysis was 10 ml. In 0.55 mol 1(-1) HCl, orthophosphate forms molybdophosphate, and then the molybdophosphate forms ion associate with Malachite Green (MG), which can be collected on a tiny membrane filter (diameter: 5 mm, and effective filtering diameter: 2 mm). After the ion associate on the membrane filter is dissolved together with the membrane filter in I ml of methyl cellosolve (MC), the absorbance of MC solution is measured at 627 nm by a flow injection-spectrophotometric detection technique. When 10 ml of the sample solution was used for the procedures and absorbance measurement, the calibration graph is linear up to about 500 ng 1(-1) of phosphorus and the detection limit was 8 ng 1(-1) (S/N = 3). For the determination of phosphorus in an ultrapurified water, 10-40 ml of sample solutions were transferred into poly(tetrafluoroethylene) (PTFE) beaker and evaporated to 5 ml or to dryness. To them, 0.003 mol 1(-1) HCl was added to get 10 ml of final solution, which was used as sample. Phosphate is determined by comparing the slope of the varied sample volume after evaporation/concentration with a slope of the standard calibration graph (a slope comparison method: SCM). The SCM enables to evaluate the concentration of phosphate in ultrapurified waters more sensitively and accurately

Spectrophotometric Determination of Anionic Surfactants in River Water with Cationic AZO Dye by Solvent Extraction- Flow Injection Analysis

Anionic surfactants in water were determined by a spectrophotometric flow injection technique coupled with solvent extraction. The ion associate which formed between an anionic surfactant and an cationic azo dye was extracted into an organic solvent and the absorbance was measured. The carrier was distilled water, and the reagent solution contained an cationic azo dye and sodium sulfate, the pH of which being adjusted to 5 with acetate buffer. A phase separator with a poly(tetrafluoroethylene) porous membrane (0.8μm pore size) was used to separate the organic phase. Six derivatives of cationic azo dyes and several extracting solvents were examined; a pair of 1-methyl-4-(4-diethylaminophenylazo)- pyridinium cation and chloroform turned out best. The sampling rate was 30 samples per hour. Calibration graphs were linear up to 2×10(-6)M or 3×10(-5)M of anionic surfactant when injection volume was 300 or 100μl, respectively. The relative standard deviation(n=10) was 1.5% for 300μl of 1×10(-6)M sodium dodecylsulfate. The detection limit was as little as 1×10(-8)M of anionic surfactant. Anionic surfactants in river water were determined satisfactorily

Synthesis of cross-linked chitosan functionalized with threonine moiety and its application to on-line collection/concentration and determination of Mo, V and Cu

A novel chitosan-based resin functionalized with threonine moiety was synthesized, and applied to the collection/concentration of Mo, V and Cu in environmental water samples, followed by their determination using inductively coupled plasma-atomic emission spectrometer (ICP-AES). The synthesized resin, cross-linked chitosan-threonine (CCTS-Thr), showed good adsorption behavior toward trace amounts of Mo, V and Cu in a wide pH range. The adsorbed elements can be easily eluted using 2 mol L-1 of nitric acid, and their recoveries were found to be 90-100%. The CCTS-Thr was packed in a mini-column, which was then installed in a computer-controlled auto-pretreatment system (Auto-Pret System) for on-line trace elements collection and determination by ICP-AES. Experimental parameters related to the improvement of sensitivity and reproducibility were optimized. The limits of detection (LODs) for target metals were found to be in sub-ppb level. The proposed method with CCTS-Thr resin was successfully applied to the determination of Mo, V and Cu in environmental water samples. The recovery test showed that common matrices which exist in environmental water samples did not interfere with the determination.</p

Kinetic-spectrophotometric method for the determination of trace amounts of bromide in seawater

A novel simple, sensitive and rapid kinetic-spectrophotornetric method is proposed for the determination of trace amounts of bromide. The method is based on its catalytic effect on the oxidation of methylene blue (MB) by hydrogen peroxide in strongly acidic solution. The oxidation reaction is activated by large amounts of chloride and can be monitored spectrophotometrically by measuring the decrease in the absorbance of MB at 746 run. The determination of bromide is performed by a fixed-time method at the first 100 s from the initiation of the reaction. Unlike other kinetic-spectrophotornetric methods for the determination of bromide, the proposed method does not require heating the solution. Bromide can be determined in the range from 80 to 960 mu g l(-1) with the detection limit of 35 mu g l(-1). The relative standard deviation of ten replicate determination of 480 mu g l(-1) bromide was 1.4%. The influence of potential interfering ions was studied. The proposed method was satisfactorily applied to the determination of bromide in seawater without interfering effect from chloride ion.</p

Synthesis of chitosan-based resins modified with tris(2-aminoethyl)amine moiety and its application to collection/concentration and determination of trace mercury by inductively coupled plasma atomic emission spectrometry

A novel chitosan-based chelating resin modified with tris(2-aminoethyl)amine moiety (CCTS-TAA) was synthesized. and its characteristics in the collection/concentration of mercury was examined. The synthesized resin showed good adsorption toward mercury in a wide pH range, and the adsorbed mercury can be easily eluted by using 2 M HNO3 without any addition of complexing agent. The resin was then packed in a mini-column and the mini-column was installed on a computer-controlled automated-pretreatment (Auto-Pret) system coupled with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) for on-line mercury collection and determination at trace level.</p

Slope comparison method (SCM) for the determination of trace amounts of silicate in ultrapurified water

A sensitive analytical method for the determination of trace amounts of silicate in ultrapurified water was developed. The method is based on the formation of an ion associate of molybdosilicate with malachite green (MG) and the collection of the ion associate on a tiny membrane filter (diameter: 5 mm, and effective filtering diameter: 1 mm). The ion associate formed on the membrane filter is dissolved together with the membrane filter in 1 ml of methyl cellosolve (MC) and the absorbance of MC solution is measured at 627 nm by a flow injection-spectrophotometric detection technique. In this method, silicate in the original sample (ultrapurified water) is concentrated as the ion associate into a small volume of MC to get high sensitivity. As sample concentration takes place, the small amounts of silicate contained in the reagents used also become concentrated as the ion associate into MC. The original sample volumes are varied and evaporated to an identical volume. Therefore, the reagent added is fixed to the same volume. The absorbance increase linearly with increase in the original sample volume will be due only to silicate in the original samples (ultrapurified water). The resulting slopes obtained by varying the sample volumes are compared with the slope of the calibration graph, and thus named the slope comparison method (SCM). The SCM facilitates a more sensitive and accurate evaluation of silicate concentration in the samples than either common calibration method (CCM) or standard addition method (SAM) because it compensates for the influence of trace amounts of silicate contained in chemicals, reagent solution and solvent used. The calibration graph was constructed from 0 to 0.25 ng ml(-1) of Si and the detection limit was 10 pg ml(-1) (ppt) when 30 ml of samples was used. The standard deviation and relative standard deviation from six measurements of the reagent blanks were 0.0012 and 3.5%, respectively

Use of weak ion association in the separation of inorganic anions by capillary electrophoresis with specific application to simultaneous-trace determination of bromate and iodate in drinking water

In this work weak ion association was used to effect selectivity and detection of inorganic anions with environmental or health significance by capillary electropheresis, CE. Tetrabutylammonium ion was used as a pairing anion to separate mixtures containing closely or co-migrating inorganic anions at pHs 3.8 and pH 7. Despite taking a longer analysis time, better resolution is achieved at pH 7 than 3.8. Trace level of bromate and iodate present in drinking water were determined after online pre-concentration by field enhanced sample injection (FESI) technique. Consequently an internal standard (SCN-) was employed, which entailed the use of tetrabutylammonium ion as a pairing cation to resolve the internal standard from a co-migrating broad peak. The LODs (S/N = 3) were 7.8 x 10-10 M (10 ppb) and 1.2 x 10-9 M (0.21 ppb) for bromate and iodate, respectively. The method was subsequently used to determine bromate and iodate levels in drinking water.  KEY WORDS: Weak ion association, Selectivity, Capillary electrophoresis, Tetrabutylammonium ion, Bromate, Iodate, Drinking water  Bull. Chem. Soc. Ethiop. 2008, 22(1), 1-9

Direct photometric detection of inorganic anions by capillary zone electrophoresis using stacking effect of sulfate ion on sample ions

Stacking effect of sulfate ion on the analysis of inorganic anions by capillary zone electrophoresis was examined during the sample injection period. A used silica capillary was dynamically coated with tetradecyltrimethylammonium bromide (TDTMA(+)Br(-)) to control the electroosmotic flow. Analyte anions were directly detected by photometry at 214 nm. Five kinds of anions, namely bromide, nitrite, nitrate, molybdate, and tungstate, were detected. Anion separation was developed using 4×10(-3) M sodium sulfate in the carrier solution. Peak heights for anions increased along with additional Na(2)SO(4). The stacking effect was more effective for the anions with high mobility than those with low mobility. Calibration graphs for nitrate and nitrite showed good linearity in the concentration range of 10(-6) to 10(-5) M