Flow injection determination of aluminium by spectrofluorimetric detection after complexation with N-o-vanillidine-2-amino-p-cresol: the application to natural waters

An on-line flow injection spectrofluorimetric method for the direct determination of aluminium in water samples is described. The method is based on the reaction of aluminium with N-o-vanillidine-2-amino-p-cresol (OVAC) in acidic medium at pH 4.0 to form a water-soluble complex. The excitation and emission wavelengths were 423.0 and 553.0 nm, respectively, at which the OVAC-Al complex gave the maximum fluorescence intensity at pH 4.0 in a 50% methanol-50% water medium at 50 °C. An interference from fluoride ions was minimised by the addition of Be²⁺. Other ions were found not to interfere at the concentrations likely to be found in natural waters. The proposed methods were validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. Under these conditions, the calibration was linear up to 1000 μg L⁻¹ (r = 0.999). The limit of detection (3σ) for the determination of Al(III) was 0.057 μg L⁻¹ and the precision for multiple determinations of 3 ng mL⁻¹ Al(III) prepared in ultra-pure water was found to be 0.62% (n = 10).The Schiff base ligand could be used to determine ultra-trace aluminium from natural waters. Analysis of environmental certified reference materials showed good agreement with the certified values. The procedure was found to be equally applicable to both freshwater and saline solutions, including seawater.     

Environmental monitoring of phenolic pollutants in water by cloud point extraction prior to micellar electrokinetic chromatography

Many aromatic compounds can be found in the environment as a result of anthropogenic activities and some of them are highly toxic. The need to determine low concentrations of pollutants requires analytical methods with high sensitivity, selectivity, and resolution for application to soil, sediment, water, and other environmental samples. Complex sample preparation involving analyte isolation and enrichment is generally necessary before the final analysis. The present paper outlines a novel, simple, low-cost, and environmentally friendly method for the simultaneous determination of p-nitrophenol (PNP), p-aminophenol (PAP), and hydroquinone (HQ) by micellar electrokinetic capillary chromatography after preconcentration by cloud point extraction. Enrichment factors of 180 to 200 were achieved. The limits of detection of the analytes for the preconcentration of 50-ml sample volume were 0.10 μg L⁻¹ for PNP, 0.20 μg L⁻¹ for PAP, and 0.16 μg L⁻¹ for HQ. The optimized procedure was applied to the determination of phenolic pollutants in natural waters from San Luis, Argentina. Figure Schematic representation of the cloud point extraction process.     

Some observations on the automation by flow injection analysis of the spectrophotometric determination of amino acids and proteins witho-phthalaldehyde

Automation by flow injection analysis with Spectrophotometric detection of the determination of total amino acids and proteins witho-phthalaldehyde is not straightforward. The use of spectrophotometry, instead of spectrofluorimetry, and of N-acetyl-L-cysteine, instead of the conventional mercaptoethanol is advantageous because of the lower variability of absorptivities with respect to fluorescence yields, and the larger stability of the derivatives. Under adequate working conditions and with leucine as reference, the procedure can be used for the evaluation of total amino acids. A similar procedure is proposed for the analysis of proteins in a sample. Limits of detection are 1 × 10^–5 M for amino acids, and 1 × 10^–6 M for proteins, respectively.     

Spectrofluorimetric determination of traces of indium with 5-chiorosalicylidene-o-aminophenol

A Spectrofluorimetric method for microdetermination of indium, based on the formation of a fluorescent 21 (ligand:metal) complex between In (III) and 5-chlorosalicylidene-o-aminophenol at an apparent pH of 4.70 in an aqueous-ethanol medium (50% v/v ethanol) is proposed. The calibration graph is linear over the range 10.0–80.0 g/l, the relative standard deviation 2.7% and the detection limit 1.5 g/l. The method has been applied to the determination of indium in synthetic samples and natural waters.     

沉积物中铝含量的流动注射分光光度法测定

本文根据自行设计的一套流动注射（ＦＩＡ）双光束分光光度计装置，研究了河底沉积物中微量铝测定的适宜条件，设备简单，操作容易。灵敏度较普通光度法提高近１倍，进样速率为８０－９０次／ｈ，相对标准偏差小于０．９％。     

Isomerization processes in inclusion compounds: Xylenes in deoxycholic acid

The isomerization processes induced by UV photons in inclusion compounds of the host-guest type are examined, with special attention to the photophysics of the energy transfer process between the host and the guest, as well as to the influence of the host molecular cavity symmetry and the guest molecular symmetry. In particular, the experimental study has been carried out on the isomerization processes ofp-,m-, ando-xylene inside the molecular cavities of deoxycholic acid. The results have been compared with those obtained by irradiating the xylenes in an inert solution of hexane. The main difference is the elimination of by-products when the photochemical process is carried out in the solid state inclusion compound; however, the high purity of the isomerization product corresponds to a decrease in its yield with respect to the reaction in solution, due to the energy transfer process from the host to the guest moiety.     

Spectrophotometric and first-derivative spectrophotometric determination of cadmium witho-hydroxybenzenediazoaminoazobenzene (HDAA)

The synthesis ofo-hydroxybenzenediazoaminoazobenzene (HDAA) is described. Cadmium forms with HDAA in the presence of Triton X-100 a 13 complex, which gives a maximum absorption at 520nm with an apparent molar absorptivity of 1.97 × 10⁵1 · mol^–1 · cm^–1 in pH 10 borax buffer solution and 1.52 × 10⁵1 · mol^–1 · cm^–1 in ammoniacal medium. In both media, Beer's law is followed in the range of 0 –10 g of cadmium in 25ml of solution and the coefficients of variation do not exceed 1.5%. A derivative method has been employed to determine cadmium in certain waste water samples without separation.     

Flow injection analysis for the determination of thiabendazole and fuberidazole in water by spectrofluorimetry

Flow-injection analysis (FIA) is proposed for determining thiabendazole (TBZ) and fuberidazole (FBZ) by Spectrofluorimetry. A pH 2 aqueous solution was found to be the optimal solvent for the rapid, precise and sensitive fluorescence analysis of both fungicides. Linear dynamic graphs were established over a concentration range of two orders of magnitude. Limits of detection were 0.7ng/ml for TBZ and 0.1 ng/ml for FBZ. Relative standard deviations were 0.5 and 0.8% for TBZ and FBZ, respectively. The method was applied to the determination of both compounds in spiked river and tap water samples, with satisfactory recoveries.On leave from the Department of Analytical Chemistry and Food Technology, University of Castilla-La Mancha, E-13071-Ciudad Real, Spain     

流动注射分光光度法测定矿物浸提液中的游离氰化物

在氢氧化钠介质中游离的氰化物与苦味酸钠反应生成玫瑰红酸钠，并进行升温改善反应条件。双流路系统与单流路相比，峰形规范、光滑，能有效消除鬼峰，优化了显色条件，工作波长为５１０ｎｍ。按生产工艺要求的线性范围为４．０￣４０．０ｍｍｏｌ／Ｌ。进样频率为１３０次／ｈ。已成功地用于矿物浸提液中游离氰化物的现场分析。     

Quinonimines and aminoquinones, the reaction products of 3,6-di(tert-butyl)-o-benzoquinone with primary and secondary amines

Reactions of 3,6-di(tert-butyl)-o-benzoquinone with primary amines occur by the nucleophilic 1,4-addition mechanism and lead to the corresponding 2-hydroxy-p-quinonimines, which exist in solutions in equilibrium with tautomeric 4-amino-o-quinones. The thermodynamic parameters of this prototropic isomerism were determined by NMR spectroscopy. In the case of a secondary amine (piperidine), a derivative of 4-amino-o-quinone was obtained; the corresponding o-semiquinone complexes were studied in solution by ESR spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1151–1155, July, 2006.     

The separation and determination of nitrophenol isomers by high-performance capillary zone electrophoresis

o-Nitrophenol, m-nitrophenol, and p-nitrophenol could well be separated by capillary zone electrophoresis (CZE) by only adjusting the run buffer with methanol. Efficiency up to 10⁵ theoretical plates per meter was achieved. The effects of several important factors were investigated to find optimum conditions. The linear range, regression equation, and the recovery were given. This method possessed the advantages of simplicity, rapidity, and good reproducibility; it can be developed for the separation of practical samples in environment analysis.     

流动注射-分光光度法在线全自动测定正磷酸盐

通过将GB/T6913-2008分光光度法在线化,设计研制了正磷酸盐流动注射自动在线监测仪;优化了显色剂浓度、载流液浓度、采样环长度等实验参数,建立了水中正磷酸盐流动注射全自动在线分析方法,并考察了其实际使用效果.结果表明,当待测水样中PO34浓度在0～15.0 mg/L范围内时,吸光度和浓度呈良好的线性关系,检出限为...     

Spectrophotometric determination of aniline in aqueous solution by azo-dye formation with diazotized p-nitroaniline

A simple, sensitive, and rapid Spectrophotometric method for the trace determination of aniline in aqueous solution is described. The method is based on coupling aniline with diazotizedp-nitroaniline in the presence of ethanol and sodium hydroxide to form an intense red water-soluble azo-dye which shows maximum absorption at 505 nm and greater stability and sensitivity in the presence of cetyltrimethylammonium bromide. Beer's law is obeyed over the aniline concentration range 0.2–2.4g/ml in the solution measured; the molar absorptivity is 3.46×10⁴l· mole^–1·cm^–1, and the relative standard deviation 1–2%, depending on the aniline concentration.     

Flow screen-printed amperometric detection of p-nitrophenol in alkaline phosphatase-based assays

p-Nitrophenyl phosphate is one of the most widely used substrates for alkaline phosphatase in ELISAs because its yellow, water-soluble product, p-nitrophenol, absorbs strongly at 405 nm. p-Nitrophenol is also electroactive; an oxidative peak at 0.97 V (vs. an Ag pseudoreference electrode) is obtained when a bare screen-printed carbon electrode is used. When an amperometric detector was coupled to a flow-injection analysis system the detection limit achieved for p-nitrophenol was 2×10⁻⁸ mol L⁻¹, almost two orders of magnitude lower than that obtained by measuring the absorbance of the compound. By use of this electrochemical detection method, measurement of 7×10⁻¹⁴ mol L⁻¹ alkaline phosphatase was achieved after incubation for 20 min. The feasibility of coupling immunoassay to screen-printed carbon electrode amperometric detection has been demonstrated by performing an ELISA for detection of pneumolysin, a toxin produced by Streptococcus pneumoniae, which causes respiratory infections. The method is simple, reproducible, and much more sensitive than traditional spectrophotometry.     

流动注射光度法测定肉制品中的亚硝酸盐

流动注射光度法测定肉制品中的亚硝酸盐许汉英＊赵志明梁春王宝东（吉林进出口商品检验局长春１３００６２）关键词肉制品，亚硝酸盐，ＦＩ－分光光度法１９９６－１１－２８收稿，１９９７－０５－２２修回食品及环境样品中亚硝酸盐的测定有分光光度法［１～３］，极谱法...     

Rapid spectrofluorimetric determination of lisinopril in pharmaceutical tablets using sequential injection analysis

The present work reports for the first time a simple and rapid method for the spectrofluorimetric determination of lisinopril (LSP) in pharmaceutical formulations using sequential injection analysis (SIA). The method is based on reaction of LSP with o-phthalaldehyde (OPA) in the presence of 2-mercaptoethanol (borate buffer medium, pH=10.6). The emission of the derivative is monitored at 455 nm upon excitation at 346 nm. The various chemical and physical conditions that affected the reaction were studied. The calibration curve was linear in the range 0.3–10.0 mg L^–1 LSP, at a sampling rate of 60 injections h^–1. Consumption of OPA reagent was significantly reduced compared with conventional flow injection (FI) systems, because only 50 L of OPA was consumed per run. The method was found to be adequately precise (s_r=2% at 5 mg L^–1 LSP, n=10) and the 3 detection limit was 0.1 mg L^–1. The method was successfully applied to the analysis of two pharmaceutical formulations containing LSP. The results obtained were in good agreement with those obtained by use of high-performance liquid chromatography (HPLC), because the mean relative error, e_r, was <1.8%.     

Indirect electrochemical destructive oxidation of aromatic compounds with reactive oxygen species

The indirect destructive electrooxidation of benzene, phenol, and N-methyl-p-aminophenol with active oxygen species generated in situ from O₂, H₂O₂, and H₂O in aqueous solutions with various pH values has been carried out using different cell designs with Pt, Pb/PbO₂, and Ru-Ti oxide anodes. The indirect oxidation of the aromatic compounds mineralizes them into CO₂ and H₂O or converts them into simple monocarboxylic or dicarboxylic acids, which can be utilized by microorganisms in subsequent biotreatment.     

在线预浓集流动注射测定苯酚

基于ＶＳ－Ⅱ阴离子交换纤维对苯酚的吸附，建立了以ＶＳ－Ⅱ阴离子交换纤维柱在线预浓集、流动注射４－氨基安替比林分光光度测定苯酚的方法，方法的线性范围为０．０１－１．４０ｍｇ／Ｌ；进样频率可达９０次／ｈ，应用于环境污染水中苯酚的测定，结果满意。