Spectrophotometric Determination of Zinc Using 7-(4-Nitrophenylazo)-8-Hydroxyquinoline-5-Sulfonic Acid

A sensitive and selective spectrophotometric method is proposed for the rapid determination of zinc(II) using an 8-hydroxyquinoline derivative, 7-(4-nitrophenylazo)-8-hydroxyquinoline-5-sulfonic acid (p-NIAZOXS), as a new spectrophotometric reagent. The reaction between the p-NIAZOXS and zinc(II) is instantaneous at pH 9.2 (borax buffer) and the absorbance remains stable for over 24 h. The method allows the determination of zinc over the range of 0.05-1.0 mug mL-1 with a molar absorptivity of 3.75x10(4) L mol-1 cm-1 and features a detection limit of 15 ng mL-1. The proposed method has been successfully applied to the determination of zinc in several pharmaceutical preparations and copper alloys. The precision (R.S.D. < 2%) and the accuracy obtained were satisfactory

Spectrophotometric Determination of Zinc Using 7-(4-Nitrophenylazo)-8-Hydroxyquinoline-5-Sulfonic Acid

A sensitive and selective spectrophotometric method is proposed for the rapid determination of zinc(II) using an 8-hydroxyquinoline derivative, 7-(4-nitrophenylazo)-8-hydroxyquinoline-5-sulfonic acid (p-NIAZOXS), as a new spectrophotometric reagent. The reaction between the p-NIAZOXS and zinc(II) is instantaneous at pH 9.2 (borax buffer) and the absorbance remains stable for over 24 h. The method allows the determination of zinc over the range of 0.05-1.0 mug mL-1 with a molar absorptivity of 3.75x10(4) L mol-1 cm-1 and features a detection limit of 15 ng mL-1. The proposed method has been successfully applied to the determination of zinc in several pharmaceutical preparations and copper alloys. The precision (R.S.D. < 2%) and the accuracy obtained were satisfactory

Spectrophotometric determination of uranium using 2-(2- Thiazolylazo)-p-Cresol (TAC) in the presence of surfactants

A sensitive and selective spectrophotometric method is proposed for the rapid determination of uranium using 2-(2- Thiazolylazo)-p-Cresol (TAC). The reaction between TAC and uranium (VI) is instantaneous at pH 6.5 and the absorbance remains stable for over 3 h. N-cetyl-N,N,N-trimethylamonium bromide (CTAB) and triton X-100 are used for increasing the sensitivity and solubility of the system respectively. The method allows the determination of uranium in the range from 0.30 to 12.0 mug mL-1 with a molar absorptivity of 1.31 x 10(4) L mol-1 cm-1 and features a detection limit of 26 ng mL-1 at 588 nm. The selectivity of the reagent was improved by the use of (1,2-cyclohexylenedinitrilo) tetraacetic acid (CyDTA) as masking agent. The proposed method has been successfully applied to the determination of uranium in mine drainage waters. The precision (R.S.D. < 2%) and the accuracy obtained were satisfactory

Spectrophotometric determination of uranium using 2-(2- Thiazolylazo)-p-Cresol (TAC) in the presence of surfactants

A sensitive and selective spectrophotometric method is proposed for the rapid determination of uranium using 2-(2- Thiazolylazo)-p-Cresol (TAC). The reaction between TAC and uranium (VI) is instantaneous at pH 6.5 and the absorbance remains stable for over 3 h. N-cetyl-N,N,N-trimethylamonium bromide (CTAB) and triton X-100 are used for increasing the sensitivity and solubility of the system respectively. The method allows the determination of uranium in the range from 0.30 to 12.0 mug mL-1 with a molar absorptivity of 1.31 x 10(4) L mol-1 cm-1 and features a detection limit of 26 ng mL-1 at 588 nm. The selectivity of the reagent was improved by the use of (1,2-cyclohexylenedinitrilo) tetraacetic acid (CyDTA) as masking agent. The proposed method has been successfully applied to the determination of uranium in mine drainage waters. The precision (R.S.D. < 2%) and the accuracy obtained were satisfactory

Flow injection spectrophotometric determination of phenolic compounds in wastewaters using peroxidase of zucchini (Cucurbita pepo)

The silver diethyldithiocarbamate (SDDC) method, has been employed for the determination of arsenic in different materials. The disagreeable odor of the pyridine, the lower stability and reproducibility of the complex are justifications for many works related to the alternatives of the method. The SDDC/pyridine system was substituted for system using triethanolamine 5% v/v in chloroform with many advantages. The method was used for arsenic determination in hair samples with good recovery. Many kinds of digestions was studied.Pelo uso de técnicas mais baratas, como a do SDDC, é possível determinar níveis traços de arsênio em cabelo; entretanto esta técnica apresenta alguns inconvenientes como baixa estabilidade e o odor desagradável da piridina. A piridina foi substituída por trietanolamina/CHCl3 e as características analíticas do complexo foram estudadas. O complexo foi estável por 270 minutos, a faixa de aplicação da lei de Beer foi de 0,0 a 25,0 mg As, a repetibilidade foi de 0,028 mg As, o limite de detecção foi de 18,6 mg de As/L e a sensibilidade (e)? de 1,12 104 L.mol-1.cm-1. O método foi aplicado à amostras de cabelo. A lavagem das amostras foi feita com extran e água desionizada e seca em estufa (40-60ºC). 0,1000 g de amostra foi submetida à 11 métodos de digestão. O melhor método foi o que usou uma solução 1:1 de HNO3 e H2SO4 concentrados em temperatura de 100-110ºC com evaporação até fumos de SO3. O tempo de abertura é um inconveniente neste tipo de digestão

Determinação de Mn, Cu e Zn em matrizes salinas após separação e pré-concentração usando Amberlite XAD-7 impregnada com Vermelho de Alizarina S

The aim of this work was to explore the possibility of the application of a non-ionic resin obtained by impregnation of Alizarin Red S (VAS) in Amberlite XAD-7 for manganese, copper and zinc separation and preconcentration in saline matrices. For these system, the metals were quantitatively retained, in the pH range 8.5-10.0, by using 0.50 g of solid phase, stirring time of five minutes and a total mass up to 200 mug of each cation. The sorbed elements were subsequently eluted and a fifty-fold, ten-fold and ten-fold preconcentration factor for to Zn, Cu and Mn were obtained, respectively