A simple spectrophotometric method for the determination of copper in industrial, environmental, biological and soil samples using 2,5-dimercapto-1,3,4-thiadiazole.

A simple spectrophotometric method is presented for the rapid determination of copper at a trace level using 2,5-dimercapto-1,3,4-thiadiazole (DMTD) as a new spectrophotometric reagent. The method is based on the reaction of non-absorbent DMTD in a slightly acidic (0.002-0.014 mol dm(-3) sulfuric acid) aqueous solution with copper(II) to produce a highly absorbent greenish-yellow chelate product that has an absorption maximum at 390 nm. The reaction is instantaneous and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 5.65 x 10(4) dm3 mol(-1) cm(-1) and 10 ng cm(-2) of CuII, respectively. Linear calibration graphs were obtained for 0.1-20 microg cm(-3) of CuII; the stoichiometric composition of the chelate is 1:2 (Cu:DMTD). A large excess of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere in the determination. The method was successfully used for the determination of copper in several Standard Reference Materials as well as in some environmental water samples, biological samples, soil samples and solutions containing both copper(I) and copper(II) and complex synthetic mixtures. The method has high precision and accuracy (s = +/-0.01 for 0.5 microg cm(-1)).     

Determination of chromium, copper and lead in river water by graphite-furnace atomic absorption spectrometry after coprecipitation with terbium hydroxide.

Coprecipitation with terbium hydroxide quantitatively recovered trace amounts of chromium(III), copper(II) and lead(II) at pH 8.4 - 10.8, 8.0 - 11.5 and 8.7 - 11.5, respectively. The precipitate was dissolved in 0.85 mol dm(-3) nitric acid, and the analytes were determined by graphite-furnace atomic absorption spectrometry (GF-AAS). The presence of terbium (up to 7 g dm(-3)) did not interfere with the determination. The detection limits were 0.3 microg dm(-3) for chromium, 0.4 microg dm(-3) for copper and 0.5 microg dm(-3) for lead, when the analytes in 200 cm3 of the sample solution were concentrated into 10 cm3. The ions added to river or seawater were quantitatively recovered. Chromium and copper in a contaminated river water were successfully determined.     

Determination of the equilibrium formation constants of two U(VI)-peroxide complexes at alkaline pH

The formation of uranyl-peroxide complexes was studied at alkaline media by using UV-Visible spectrophotometry and the STAR code. Two different complexes were found at a H(2)O(2)/U(VI) ratio lower than 2. A graphical method was used in order to obtain the formation constants of such complexes and the STAR program was used to refine the formation constants values because of its capacity to treat multiwavelength absorbance data and refining equilibrium constants. The values obtained for the two complexes identified were: UO(2)(2+) + H(2)O(2) + 4OH(-) UO(2)(O(2))(OH)(2)(2-) + 2H(2)O: log β°(1,1,4) = 28.1 ± 0.1 (1). UO(2)(2+) + 2H(2)O(2) + 6OH(-) UO(2)(O(2))(2)(OH)(2)(4-) + 4H(2)O: log β°(1,2,6) = 36.8 ± 0.2 (2). At hydrogen peroxide concentrations higher than 10(-5) mol dm(-3), and in the absence of carbonate, the UO(2)(O(2))(2)(OH)(2)(4-) complex is predominant in solution, indicating the significant peroxide affinity of peroxide ions for uranium and the strong complexes of uranium(VI) with peroxide.     

4-(N,N-diethylamino) benzaldehyde thiosemicarbazone in the spectrophotometric determination of palladium

4-(N,N-diethylamino)benzaldehyde thiosemicarbazone(DEABT) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium (II) in a potassium hydrogen phthalate-hydrochloric acid buffer of pH 3.0, to form a yellow complex. Beer's law is obeyed in the concentration range up to 3.60 microgmL(-1). The optimum concentration range for minimum photometric error as determined by Ringbom plot method is 0.36 - 3.24 microg mL(-1). The yellow Pd(II)-DEABT complex shows a maximum absorbance at 408 nm, with molar absorptivity of 3.33 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity of the complex from Beer's data, for D = 0.001, is 0.0032 microg cm(-2). The composition of the Pd(II)-DEABT complex is found to be 1:2 (M:L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes and model mixtures with a fair degree of accuracy.     

A rapid and sensitive extractive spectrophotometric determination of copper(II) in pharmaceutical and environmental samples using benzildithiosemicarbazone.

Benzildithiosemicarbazone (BDTSC) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of copper(II). BDTSC reacts with copper(II) in the pH range 1.0-7.0 to form a yellowish complex. Beer's law is obeyed in the concentration range 0.5-0.4 microg cm(-3). The yellowish Cu(II)-BDTSC complex in chloroform shows a maximum absorbance at 380 nm, with molar absorptivity and Sandell's sensitivity values of 1.63 x 10(4) dm3 mol(-1) cm(-1) and 0.00389 microg cm(-2), respectively. A repetition of the method is checked by finding the relative standard deviation (RSD) (n = 10), which is 0.6%. The composition of the Cu(II)-BDTSC complex is established as 1:1 by slope analysis, molar ratio and Asmus' methods. An excellent linearity with a correlation coefficient value of 0.98 is obtained for the Cu(II)-BDTSC complex. The instability constant of the complex calculated from Edmond and Birnbaum's method is 7.70 x 10(-4) and that of Asmus' method is 7.66 x 10(-4), at room temperature. The method is successfully employed for the determination copper(II) in pharmaceutical and environmental samples. The reliability of the method is assured by analyzing the standard alloys (BCS 5g, 10g, 19e, 78, 32a, 207 and 179) and by inter-comparison of experimental values, using an atomic absorption spectrometer.     

Flow injection analysis of hydrogen peroxide using glass-beads modified with manganese(III)-tetra(4-carboxyphenyl)porphine derivative and its analytical application to the determination of serum glucose.

A flow injection analysis system of hydrogen peroxide was developed. The present system is based on measuring of the absorbance of a quinoid dye formed by the following reaction catalyzed by peroxidase: Phenol + 4-Aminoantipyrine + 2H2O2 --> Peroxidase --> Quinoid dye + 4H2O. A column packed with aminopropyl-glass beads modified with amanganese(III)-tetra(4-carboxyphenyl)porphine derivative (Mn-TCPP(G) column), which has peroxidase-like activity, was used in place of an immobilized peroxidase column in the above reaction. The linear range of the calibration curve was 0.4-80 microg/ml hydrogen peroxide. The relative standard deviation of this system was 2.97% (n = 100, 10 microg/ml hydrogen peroxide 20 microl injection). The Mn-TCPP(G) column has sufficiently stability for the continuous injection of hydrogen peroxide untill 100 times. The advantageous feature of the Mn-TCPP(G) column was a less-electrostatic interaction between the mother glass beads and the anionic chromogen or quinoid dye formed and the stability in terms of the storage, temperature and moisture. The determination of serum glucose was achieved by attaching an immobilized glucose oxidase column to this system without deproteinization.     

Selective determination of hydrogen peroxide by adduct formation with a dinuclear iron(III) complex and flow injection analysis/tandem mass spectrometry

A highly selective method for the determination of hydrogen peroxide is presented. In a flow injection analysis (FIA) instrument, the analyte is brought into contact with a dinuclear heptadentate iron(III) complex. The formation of the peroxide adduct is quantified using electrospray tandem mass spectrometry (ESI-MS/MS). Selected reaction monitoring (SRM) based on the transition from the triply charged peroxide adduct with m/z = 251.2 to the triply charged fragment ion of m/z = 240.5 is performed. The limit of detection for hydrogen peroxide is 10(-7) mol dm(-3), limit of quantification is 3 x 10(-7) mol dm(-3), and a linear range of 2.5 decades starting at the limit of quantification is observed.     

Determination of manganese in some medicinal plants and their infusions by a catalytic spectrophotometric method

The catalytic effect of manganese (II) on the oxidation of the azo dye 3-Methyl-6-(2-hydroxyethoxy)-2-[2-methoxy-4-N (N, N diethylamino) phenylazo] benzothiazolium methylsulphate, with potassium periodate in the presence of 1,10-phenanthroline in weakly acidic media was studied. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 560 nm. Under the optimum conditions (4 x 10(-5) mol dm(-3) azo dye, 4 x 10(-4) mol dm(-3) potassium periodate, 1 x 10(-4) mol dm(-3) 1,10-phenanthroline, 0.1 mol dm(-3) buffer--pH 3.0, 70 degrees C, 8 min) manganese (II) in the range 0.1-5 ng cm(-3) could be determined by the fixed-time method with a detection limit of 0.035 ng cm(-3). The developed method is highly sensitive, selective, and simple. The method was applied successfully to the determination of total manganese in some medicinal plants and to analyse their infusions for trace amounts of total manganese and free manganese (II) ions without separation.     

Spectrophotometric determination of urea in dermatologic formulations and cosmetics

A rapid, relatively sensitive, and low-cost method for the determination of water-soluble urea content in dermatological therapy products and cosmetics is proposed using a new spectrophotometric assay with water as the only extraction solvent. Spectrophotometric methods involve addition of a known excess of bromate to urea in an acid medium, followed by the determination of residual bromine and chlorine reacting with methyl orange and measurement of absorbance at 505 nm. The absorbance increases linearly with urea concentration (r = 0.9998). The systems obey Beer's law for 6 - 90 microg ml(-1). The calculated apparent molar absorbance values are found to be 4.537 x 10(3) dm(3) mol(-1) cm(-1) and the Sandell's sensitivity is 0.013 microg cm(-2). The variables affecting the rate of the reaction were investigated. The relative standard deviation for five-replication determination of 60 microg ml(-1) urea was 2.1% and the detection limit of the method is 0.34 ng ml(-1).     

壳聚糖-铜复合物修饰电极对过氧化氢电催化性能的研究

将壳聚糖与铜盐通过配位结合制得壳聚糖-铜复合物(CTS-Cu),并用其修饰玻碳电极,使用循环伏安法和计时安培法研究了该修饰电极对H2O2的电催化性能,对其催化机理进行了探讨.优化的实验条件为:以0.1 mol/L.磷酸缓冲溶液(PBS,pH 7.0)为反应介质,CTS-Cu修饰液中的铜离子浓度为6 mmol/L,工作电...     

磁性量子点电致化学发光法测定李氏禾提取液中的过氧化氢

利用巯基乙酸水热法合成出表面修饰—COOH的CdTe量子点,并将CdTe量子点(QDs)连接在Fe3O4纳米粒子表面,制备出CdTe/Fe3O4磁性量子点。通过磁力将磁性量子点修饰于石墨电极表面。在pH7.5的PBS缓冲溶液中,H2O2可使CdTe量子点产生电致化学发光,H2O2浓度在4～100μmol/L范围内与CdTe量子点的电致化学发光强度呈良好的线性关系,检出限为0.24μmol/L。据此建立了测定样品中过氧化氢含量的电致化学发光分析法,并成功地应用于李氏禾草汁原液中过氧化氢含量的测定。该研究借助纳米Fe3O4的磁力特征,使敏感膜易于形成和更新分离,简化了实验操作,同时起到增强发光强度的作用。     

Spectrophotometric determination of oxalate ion with N,N'-diethyl-N,N'-[[4,4'-dihydroxy-1,1'-binaphthalene]-3,3'-diyl]bisbenzamide and copper(II).

A simple and rapid spectrophotometric method for the determination of oxalate ion was established by the fading of a colored complex between N,N'-diethyl-N,N'-[[4,4'-dihydroxy-1,1'-binaphthalene]-3,3'-diyl]bisbenzamide and copper(II). Beer's law was obeyed in the concentration range of 0.1 - 2.0 microg cm(-3) for oxalate ion, with an effective molar absorptivity at 533 nm and the relative standard deviation being 8.0 x 10(3) dm(3) mol(-1) cm(-1) and 1.0% (n = 5), respectively. This proposed method has excellent reproducibility, and was applied to recovery tests of oxalate ion in tap water and human urine; the results were satisfactory. This is suggested that the method is based on the reaction of copper(II) to copper(I) with oxalate ion.     

Synthesis of a novel chemiluminescent reagent for the determination of hydrogen peroxide in snow waters

7-(4,6-Dichloro-1,3,5-triazinylamino)-4-methylcoumarin (DTMC) was synthesized as a completely new chemiluminescent reagent, and with it a novel chemiluminescence method was developed for the determination of hydrogen peroxide in the absence of any added catalyst or co-oxidant. The chemiluminescence intensity of the DTMC-H(2)O(2) system could be enhanced by the addition of cation surfactants. The chemiluminescence intensity was directly proportional to the concentration of H(2)O(2) in the range 1.0 x 10(-7)-4.0x10(-4) mol l(-1), and the detection limit was 4.0 x 10(-8) mol l(-1). The relative S.D. was 4.9% for 1.0 x 10(-6) mol l(-1) of H(2)O(2) (n=10). The selectivity of this method was high, and most of the transition metal ions have no effect on the determination. The proposed method has been applied to the determination of trace amounts of hydrogen peroxide in snow water. A possible mechanism of the chemiluminescence reaction is also discussed.     

Determination of hydrogen peroxide by iron(III) complex of thiacalix[4]arenetetrasulfonate on a modified ion-exchanger with peroxidase-like catalytic activity.

An iron(III) complex of thiacalix[4]arenetetrasulfonate on a modified anion-exchanger (Fe3+-TCAS(A-500)) has shown high peroxidase-like activity at pH 5 - 6 for the reaction of quinoid-dye formation between 3-methyl-2-benzothiazolinone hydrazone and N-(3-sulfopropyl)aniline in the presence of hydrogen peroxide. Utilizing the peroxidase-like activity of Fe3+-TCAS(A-500) for this reaction, a method using Fe3+-TCAS(A-500) was applied for the spectrophotometric determination of hydrogen peroxide. The calibration curve by the method using Fe3+-TCAS(A-500) was linear over the range from 1 to 10 microg of hydrogen peroxide in a 1 ml sample solution. The apparent molar absorptivity for hydrogen peroxide was 2.4 x 10(4) l mol(-1) cm(-1). which was about 80% of that by peroxidase under the same conditions. This determination method of hydrogen peroxide using Fe3+-TCAS(A-500) was applied for the determination of glucose in diluted normal and abnormal control serum I and II.     

Rapid quantitative determination of hydrogen peroxide by oxidation decolorization of methyl orange using a Fenton reaction system

In this study, a sensitive and rapid method for hydrogen peroxide (H(2)O(2)) determination has been developed with the aid of oxidation decolorization of methyl orange (MO) by using Fenton reactions, because the decolorization extent of MO solution (at the maximum absorption wavelength of 507 nm) is proportion to the concentration of H(2)O(2). Under optimum conditions, this spectrophotometric method for the H(2)O(2) analysis yields a dynamic range of H(2)O(2) concentration from 5.0 x 10(-7) to 1.0 x 10(-4) mol L(-1) (r=0.997) and a detection limit (3 sigma/k) of 2.0 x 10(-7) mol L(-1). This method for the determination of H(2)O(2) (0.04 mmol L(-1)) is able to tolerate the interference from NaCl (0-5.0 mmol L(-1)), Na(2)SO(4) (0-5.0 mmol L(-1)), MgCl(2) (0-5.0 mmol L(-1)), sodium humate (0-0.1 mmol L(-1)), benzene (0-0.2 mmol L(-1)), toluene (0-0.2 mmol L(-1)), chlorobenzene (0-0.2 mmol L(-1)) and chloroform (0-0.2 mmol L(-1)). The analysis results for practical rainwater samples are in good agreement with the classical N,N-diethyl-p-phenylenediamine (DPD) method for H(2)O(2) determination.     

流动注射胶束电化学发光测定过氧化氢的研究

建立了一种简易、快速检测过氧化氢的流动注射电化学发光法。本法基于铂丝阳极在 1.3 V(vs.Ag Cl/Ag)时 ,在含有 Na2 CO3 -Na HCO3 缓冲溶液的 KCl支持电解质中现场产生试剂 ,当注入过氧化氢溶液后即产生电化学发光。加入 Triton X-10 0形成的胶束能增强这一体系的发光强度。该法测定过氧化氢的线性范围为 1.0×10 -7～ 1.0× 10 -5 mol/L,对 4.0× 10 -7mol/L的过氧化氢进行 11次测定的相对标准偏差为 2 .6%。用这一方法对雨水中的过氧化氢进行了测定 ,结果满意。     

Kinetic determination of iodide in pharmaceutical and food samples

A kinetic method for the determination of iodide based on its inhibitory effect on the Pd(III) catalysed reaction between ethylenediaminetetraacetic acid (EDTA)-Co(III) and the hypophosphite ion is described. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance at 540 nm. Under the optimum experimental conditions of 2.6 x 10(-3) mol dm(-3)Co(III)-EDTA, 0.4 mol dm(-3)H2PO2-, pH 3.2 (adjusted with Britton-Robinson buffer), 0.57 micrograms ml(-1) Pd(III) and 20 +/- 0.2 degrees C, iodide was determined in the range 2-28 ng ml(-1). The method was applied to the determination of iodide in pharmaceutical products, iodinated salts, cow's milk and infants' powdered milk.     

Catalytic determination of silver(I) by extractive flow injection analysis

A new catalytic method for the determination of silver(I) was developed based on a metal exchange reaction between ethylenediaminetetraacetatomercury(II) (Hg(II)-EDTA) in the aqueous phase and bis(diethyldithiocarbamato)copper(II) (Cu(II)-DDTC) in the organic phase. This exchange reaction (Cu(II)-DDTC(org)+Hg(II)-EDTA-->Hg(II)-DDTC(org)+Cu(II)-EDTA, where org denotes the organic phase) was observed to proceed slowly and the Cu(II)-DDTC complex transferred quantitatively to Hg(II)-complex in the organic phase in the equilibrium state. In this system, silver(I) acts as the catalyst and can be determined by measuring the decrease in the absorbance of the Cu(II)-DDTC complex (lambda(max)=435 nm). The reaction was applied to the extractive flow injection analysis of silver(I). The present method allows the determination of silver(I) at 10(-7) mol dm(-3) level with the sampling frequency of 30 h(-1). The relative standard deviation of 0.28% (n=10) was obtained at 4.0x10(-7) mol dm(-3) of silver(I).     

A rapid and sensitive extractive spectrophotometric determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using pyridoxal-4-phenyl-3-thiosemicarbazone.

A rapid and sensitive extractive spectrophotometric method has been developed for the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using pyridoxal-4-phenyl-3-thiosemicarbazone (PPT) as an analytical reagent. The reagent forms a red-color complex with the metal at pH 3.0, which is extracted into benzene. The absorbance is measured at 460 nm. The method adheres to Beer's law up to a concentration range of 0.4-6.4 microg cm(-3). The molar absorptivity and Sandell's sensitivity are 2.20 x 10(4) dm3 mol(-1) cm(-1) and 4.85 x 10(-3) microg cm(-2), respectively. The correlation coefficient of the Pd(II)-PPT complex is 0.99, which indicates an excellent linearity between two variables. The detection limit of this method is 0.05 microg cm(-3). The instability constant of the Pd(II)-PPT complex calculated from Edmond and Birnbaum's method is 2.90 x 10(-5) and that of Asmus' method is 2.80 x 10(-5) at room temperature. The concurrent repetition of the method is checked and the relative standard deviation (RSD) (n = 5) was derived as 1.84 percent. The present method was applied to the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts. The results were compared by employing an atomic-absorption spectrometer.     

Determination of trace amounts of cobalt(II) by flow injection-solid phase spectrometry (FI-SPS) with 5-Br-PADAB.

Flow injection-solid phase spectrometry (FI-SPS) has been applied to the determination of cobalt(II) in water samples. The complex formed between cobalt and 5-Br-PADAB was on-line protonated and concentrated on an AG 50W-X2 cation-exchanger in a flow-through cell. The increase in absorbance caused by the accumulation of the complex in the resin was continuously measured. The interference by copper could be effectively eliminated by using EDDP as a masking agent. The detection limit was 40 ng dm(-3) with a 4.0 cm3 sample solution.