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

On-line preconcentration using dual mini-columns for the speciation of chromium(III) and chromium(VI) and its application to water samples as studied by inductively coupled plasma-atomic emission spectrometry

On-line preconcentration system for the selective, sensitive and simultaneous determination of chromium species was investigated. Dual minicolumns containing chelating resin were utilized for the speciation and preconcentration of Cr(III) and Cr(VI) in water samples. In this system, Cr(III) was collected on first column packed with iminodiacetate resin. Cr(VI) in the effluent from the first column was reduced to Cr(III), which was collected on the second column packed with iminodiacetate resin. Hydroxyammonium chloride was examined as a potential reducing agent for Cr(VI) to Cr(III). The effects of pH, sample flow rate, column length, and interfering ions on the recoveries of Cr(III) were carefully studied. Five millilitres of a sample solution was introduced into the system. The collected species were then sequentially washed by 1 M ammonium acetate, eluted by 2 M nitric acid and measured by ICP-AES. The detection limit for Cr(III) and Cr(VI) was 0.08 and 0.15 mu g l-1, respectively. The total analysis time was about 9.4 min. The developed method was successfully applied to the speciation of chromium in river, tap water and wastewater samples with satisfied results. </p

Synthesis of cross-linked chitosan modified with the glycine moiety for the collection/concentration of bismuth in aquatic samples for ICP-MS determination

A chelating resin, cross-linked chitosan modified with the glycine moiety (glycine-type chitosan resin), was developed for the collection and concentration of bismuth in aquatic samples for ICP-MS measurements. The adsorption behavior of bismuth and 55 elements on glycine-type chitosan resin was systematically examined by passing a sample solution containing 56 elements through a mini-column packed with the resin (wet volume; I ml). After eluting the elements adsorbed on the resin with nitric acid, the eluates were measured by ICP-MS. The glycine-type chitosan resin could adsorb several cations by a chelating mechanism and several oxoanions by an anion-exchange mechanism. Especially, the resin could adsorb almost 100% Bi(III) over a wide pH region from pH 2 to 6. Bismuth could be strongly adsorbed at pH 3, and eluted quantitatively with 10 ml of 3 M nitric acid. A column pretreatment method with the glycine-type chitosan resin was used prior to removal of high concentrations of matrices in a seawater sample and the preconcentration of trace bismuth in river water samples for ICP-MS measurements. The column pretreatment method was also applied to the determination of bismuth in real samples by ICP-MS. The LOD of bismuth was 0.1 pg ml(-1) by 10-fold column preconcentration for ICP-MS measurements. The analytical results for bismuth in sea and river water samples by ICP-MS were 22.9 +/- 0.5 pg ml(-1) (RSD, 2.2%) and 2.08 +/- 0.05 pg ml(-1) (RSD, 2.4%), respectively.</p

Development of novel detection reagent for simple and sensitive determination of trace amounts of formaldehyde and its application to flow injection spectrophotometric analysis

In this paper, a novel detection reagent for formaldehyde determination is proposed, and is applied to a simple and highly sensitive flow injection method for the spectrophotometric determination of formaldehyde. The method is based on the reaction of formaldehyde with methyl acetoacetate in the presence of ammonia. The increase in the absorbance of the reaction product was measured at 375 nm. An inexpensive light emitting diode (LED)based UV detector (375 nm) was, for the first time, used. Under the optimized experimental conditions, formaldehyde in an aqueous solution was determined over the concentration range from 0.25 to 20.0 x 10(-6) M with a liner calibration graph; the limit of detection (LOD) of 5 x 10(-8) M (1.5 mu g L-1) was possible. The relative standard deviation of 12 replicate measurements of 5 X 10(-6) M formaldehyde was 1.2%. Maximum sampling throughput was about 21 samples/h. The effect of potential interferences such as metals, organic compounds and other aldehyde was also examined. The analytical performance for formaldehyde determination was compared with those obtained by the conventional acetylacetone method, which uses visible absorption spectrophotometry. Finally, the proposed method was successfully applied to the determination of formaldehyde in natural water samples

Functionalization of chitosan with 3-nitro-4-amino benzoic acid moiety and its application to the collection/concentration of molybdenum in environmental water samples

A chitosan resin functionalized with 3-nitro-4-amino benzoic acid moiety (CCTS-NABA resin) was newly synthesized for the collection/concentration of trace molybdenum by using cross-linked chitosan (CCTS) as base material. The carboxyl group of the moiety was chemically attached to amino group of cross-linked chitosan through amide bond formation. The adsorption behavior of molybdenum as well as other 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the elements collected on the resin with 1 M HNO3, the eluates were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES). The CCTS-NABA resin can adsorb several metal ions, such as vanadium, gallium, arsenic, selenium, silver, bismuth, thorium, tungsten, tin, tellurium, copper, and molybdenum at appropriate pHs. Among these metal ions, only molybdenum could be adsorbed almost completely on the resin at acidic regions. An excellent selectivity toward molybdenum could be obtained at pH 3-4. The adsorption capacity of CCTS-NABA resin for Mo(VI) was 380 mg g(-1) resin. Through the column pretreatment, alkali and alkaline earth metals in river water and seawater samples were successfully removed. The CCTS-NABA resin was applied to the adsorption/collection of molybdenum in river water and seawater samples. The concentrations of molybdenum in river water samples were found in the range of 0.84 and 0.95 ppb (ng g(-1)), whereas molybdenum in seawater was about 9 ppb. The validation of the proposed method was carried out by determining molybdenum in the certified reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-NABA resin; the results showed good agreement with the certified-values. </p

Simple flow-injection system for the simultaneous determination of nitrite and nitrate in water samples

A novel spectrophotometric reaction system was developed for the determination of nitrite as well as nitrate in water samples, and was applied to a flow-injection analysis (FIA). The spectrophotometric flow-injection system coupled with a copperised cadmium reductor column was proposed. The detection was based on the nitrosation reaction between nitrite ion and phloroglucinol (1,3,5-trihydroxybenzene), a commercially available phenolic compound. Sample injected into a carrier stream was split into two streams at the Y-shaped connector. One of the streams merged directly and reacted with the reagent stream: nitrite ion in the samples was detected. The other stream was passed through the copperised cadmium reductor column, where the reduction of nitrate to nitrite occurred, and the sample zone was then mixed with the reagent stream and passed through the detector: the sum of nitrate and nitrite was detected. The optimised conditions allow a linear calibration range of 0.03-0.30 mug NO2--N ml(-1) and 0.10-1.00 mug NO3--N ml(-1). The detection limits for nitrite and nitrate, defined as three times the standard deviation of measured blanks are 2.9 ng NO2--N ml(-1) and 2.3 ng NO3--N ml(-1), respectively. Up to 20 samples can be analyzed per hour with a relative standard deviation of less than 1.5%. The proposed method could be applied successfully to the simultaneous determination of nitrite and nitrate in water samples.</p

Synthesis of cross-linked chitosan possessing N-methyl-D-glucamine moiety (CCTS-NMDG) for adsorption/concentration of boron in water samples and its accurate measurement by ICP-MS and ICP-AES

A chitosan resin derivatized with N-methyl-(D)-glucamine (CCTS-NMDG) was synthesized by using a cross-linked chitosan (CCTS) as base material. The N-methyl-D-glucamine (NMDG) moiety was attached to the amino group of CCTS through the arm of chloromethyloxirane. The adsorption behavior of 59 elements on the synthesized resin was systematically examined by using the resin packed in a mini-column, passing water samples through it and measuring the adsorbed elements in eluates by ICP-MS. The CCTS-NMDG resin shows high ability in boron sorption with the capacity of 0.61 mmol ml(-1) (= 2.1 mmol g(-1)). The sorption kinetics of this resin was faster than that of the commercially available resins. Other advantages of the synthesized resin are: (1) quantitative collection of boron at neutral pH regions; (2) complete removal of large amounts of matrices; (3) no loss of efficiency over prolonged usage; (4) effective collection of boron in wide range concentration using a mini column containing 1 ml resin; (5) complete elution of boron with 1 mol 1(-1) nitric acid. The resin was applied to the collection/concentration of boron in water samples. Boron in tap water and river water was found to be in the range of 6-8 mu g 1(-1). The limit of detection (LOD) of boron after pretreatment with CCTS-NMDG resin and measurement by ICP-MS was 0.07 mu g 1(-1) and the limit of quantification (LOQ) was 0. 14 mu g 1(-1) when the volume of each sample and eluent was 10 ml.</p