Sensitive Synchronous Spectrofluorimetric Methods for the Determination of 1- and 2-Naphthol in Micellar Media

Abstract

The interaction of 1-naphthol and 2-naphthol with several quaternary ammonium salts was studied. Spectrofluorimetric methods were developed for the determination of both naphthols in hexadecyltrimethylammonium bromide micellar medium. The detection limits are 1.4 and 10.2 ng/ml for 1-naphthol, and 6.2 and 5.1 ng/ml for 2-naphthol employing the conventional and synchronous spectrofluorimetric methods, respectively. The use of the first-derivative spectrum allows for the simultaneous determination of both naphthols. The recoveries of 1-naphthol and 2-naphthol in natural waters are acceptable.     

Spectrofluorimetric determination of thiabendazole in a micellar medium

A sensitive, selective Spectrofluorimetric method has been developed for the determination of thiabendazole in a sodium dodecylsulphate micellar medium. The method features a linear determination range of 0.020-15 g and a detection limit of 0.2 ng/ml, with a relative standard deviation of less than 3%. By using a straightforward extraction procedure with ethyl acetate and hydrochloric acid, the method provided average thiabendazole recoveries above 96% from apple, pear and potato samples.     

Fluorimetric determination of 1-naphthol and mixtures of carbaryl and 1-naphthol in micellar media

Summary The interaction of 1-naphthol with different types of anionic, cationic and non-ionic surfactants has been studied spectrofluorimetrically in order to obtain a sensitivity enhancement in the determination of this compound. At neutral pH, cetyl trimethyl ammonium bromide (CTAB) provides a 2-fold sensitivity enhancement of 1-naphthol and exhibits a weak interaction with carbaryl. In strong alkaline medium carbaryl is hydrolyzed to 1-naphthol and in the presence of CTAB micells, a 5-fold sensitivity enhancement and a limit of detection of 0.2 g·ml^–1 with a 101±3% percentage of recovery is obtained. These facts permit the development of an accurate method for the fluorimetric analysis of 1-naphthol and carbaryl mixtures, comprising the determination of the sum of both compounds (pH 12, 0.1% w/v CTAB, _em=449 nm, _ex=341 nm) and of the concentration of 1-naphthol (neutral pH, 0.4% w/v CTAB, _em=449 nm, _ex=312 nm).     

Simultaneous chemiluminescent determination of carbaryl and 1-naphthol in soils using a flow-injection system

A flow-injection method coupled with the luminol chemiluminescence (CL) detection was developed for the simultaneous determination of carbaryl and 1-naphthol in soils. The method is based on the inhibition of luminol oxidation by the presence of 1-naphthol with the consequent reduction in the CL intensity. The conversion of carbaryl into 1-naphthol was made by the alkaline hydrolysis with NaOH. Under the optimised conditions, the method permits the determination of carbaryl and 1-naphthol over the range 25–400 ng mL^?1 with high determination coefficient using both peak area and height, and high sample throughput (40 h^?1). The detection limits applying the International Unión of Pure and Applied Chemistry (IUPAC) criteria were 65 ng g^?1 and 123.5 ng g^?1 for peak height and area, respectively. A simple extraction procedure employing chloroform as the solvent and sonication was effective for the complete extraction of the analytes present in soils. The method was validated by the analysis of spiked samples, with recoveries between 88.7 and 103.1%. The Flow Injection-Chemiluminescence (FI-CL) method has proven to be simple, fast and accurate for the quantification of carbaryl and its main degradation product in soils.     

Spectrofluorimetric determination of traces of bromide

A Spectrofluorimetric method for the determination of traces of bromide has been developed. The method is based on the bromination of fluorescein after bromide and hypochlorite form bromine, giving the less fluorescent eosin. The fluorescence decrease is used as the analytical signal. The calibration graph is linear over the range 10 to 80 g/1. The detection limit is 3 g/1 and the relative standard deviation 1.0%. The method has been satisfactorily applied to the determination of bromide in natural waters.     

High-performance liquid chromatographic determination of carbaryl and 1-naphthol in biological fluids

A simple and sensitive method for the simultaneous analysis of carbaryl and 1-naphthol in whole blood by reversed-phase high-performance liquid chromatography and fluorescence detection is described. Spiked blood (heparinized) containing an internal standard was hemolyzed and extracted with ethyl acetate. After centrifugation the extractant was removed and taken to dryness. Reconstitution and subsequent high-performance liquid chromatography-fluorescence analysis yielded linear standard curves for carbaryl and 1-naphthol. Linear response vs. concentration profiles were obtained for carbaryl and 1-naphthol extracted from buffer solutions as well. A simple chemical hydrolysis study of carbaryl is included to illustrate the effectiveness of the extraction procedure and assay.     

Fluorometric determination of carbaryl in micellar Media

A new method is proposed for the fluorometric determination of carbaryl, based on the basic hydrolysis of the pesticide to 1-naphtholate at pH 12 and enhancement of the relative quantum yield of this latter compound by the presence of non-ionic surfactants. The procedure is quick and easy and presents a limit of detection of 1.4 ng/ml. The interaction of carbaryl with non-ionic surfactants has been studied both spectrophotometrically and fluorometrically, in different media. To determine carbaryl in real samples prior extraction into xylene and back-extraction with 1 M sodium hydroxide is necessary to avoid the strong quenching effect of the matrix.     

Direct fluorimetric determination of carbaryl insecticide and its hydrolysis product 1-naphthol

Direct fluorimetric determinations are described for Carbaryl (1-naphthyl-N-methylcarbamate) and 1-naphthol in the range 0–1 μg ml^-1 in the same solution. Spectra, quantum efficiencies and relative sensitivities are reported.     

Spectrofluorimetric flow-injection determination of cerium in carbon and low alloy steels

Cerium can be determined spectrofluorimetrically (_em 350 nm, _ex 260 nm) based on the relatively intense native fluorescence of the cerium(III) aquo-ion. The main potential interference in the analysis of steel from iron(III), cerium(IV) and chromium(VI) are removed by use of a carrier solution containing 2.5% w/v hydroxylammonium chloride. The slight residual interference from iron(II) can be corrected by a matrix matching factor linearly related to the amount of iron present. The calibration graphs are linear over the range 0–7 g ml^–1 based on 250 l injection volumes. The sampling rate was 30 h^–1. The relative standard deviation was 2.0% (n=5) at 3 g ml^–1 cerium. The system has been applied to the determination of cerium in carbon or low alloy steels.     

Synthesis of 4,8-dimethoxy-1-naphthol via an acetyl migration

Based on acetyl migration, an efficient synthesis of 4,8-dimethoxy-1-naphthol (1) has been achieved with high overall yield. Compared with the reported method, there were several advantages. First, the reaction conditions were mild. Second, the workup of each step was much simpler. Third, juglone as the starting material in the synthesis was readily available. The solvent and reaction temperature greatly influenced the migration process.     

抑制化学发光法检测甲萘威的研究

研究发现甲萘威对鲁米诺-过氧化氢-叶绿素铜钠体系的化学发光具有强烈抑制作用,由此建立了流动注射-抑制化学发光检测甲萘威的新方法,并利用荧光猝灭法探讨了甲萘威对该体系化学发光的抑制机理.实验表明叶绿素铜钠对甲萘威的荧光猝灭过程是静态猝灭过程,二者以摩尔比1:1结合,形成稳定的络合物,平衡常数为5.43× 104 L·mo...     

聚合物负载的手性联二萘酚的合成及其在不对称催化中的应用进展

作为一种有机配体, 手性1,1'-联二萘酚(BINOL)被广泛应用于过渡金属催化的均相不对称有机反应. 为克服均相催化剂不易回收重复使用等缺陷, 人们深入研究了聚合物负载手性BINOL催化剂的方法. 总结了近年来聚合物负载手性BINOL催化剂的合成及其在不对称有机催化中的应用, 并对负载型BINOL催化剂进行了展望.     

微分脉冲溶出伏安法测定2,4-二硝基-1-萘酚

以Britton-Robinson(pH=8.0)缓冲液为底液,富集电位为-0.05V,富集时间为30s,电位扫描速率20mV/s,产生2个完全分离的峰,在-0.58±0.01V(vs.Ag/AgCl)处产生的峰灵敏度高且峰形好,故以此峰为定量峰。2,4_二硝基_1_萘酚浓度在6.00×10-8～2.00×10-6mol/L时与峰电流呈良好的线性关系,线性相关系数为0.9996。检出限为4.00×10-9mol/L,信噪比S/N约为10。     

Determination of propazine by differential pulse polarography in micellar and emulsified media

An electroanalytical study of the herbicide propazine's reduction process in micellar solutions and oil-in-water emulsions is reported. The anionic surfactant sodium pentanesulphonate was chosen as the most suitable. The differential pulse polarograms of micellar solutions had two reduction peaks below pH 2.0, whereas only one peak was obtained above pH 2.O. Ethyl acetate was chosen as the organic solvent to form propazine emulsions. Unlike in micellar solutions, the DPP polarograms of propazine emulsions showed only one peak even at pH < 2.0, suggesting that propazine hydrolysis was hindered in the emulsified medium. The limiting current is diffusion-controlled and the electrode process is irreversible. Propazine can be determined by differential pulse polarography over the 1.0 × 10^–1 – 1.0 × 10^–1moll^–1 and 1.0 × 10^–15 – 4.0 × 10^–1 moll^–1 concentration ranges and the limit of detection was 2.8 × 10^–1 moll^–1. Of the potential interferents simazine, methoprotryne and terbutryn (alls-triazines), thiram (a dithiocarbamate), dinoseb (nitrophenolic), and heptachlor (chlorinated cyclo-diene herbicide), only the first two were significant (10% error for equimolar concentrations). The method was applied to the determination of propazine in spiked drinking water. At a concentration level of 2.0 × 10^–1 moll^–1 a recovery of 94 ± 6% was obtained, after tenfold concentration on Sep-Pak.     

Simultaneous kinetic determination of chlorpyrifos and carbaryl based on differential degradation processes in alkaline oxidative medium

A kinetic method for the simultaneous determination of chlorpyrifos and carbaryl is described. The method is based on the degradation of these compounds in alkaline hydrogen peroxide medium by measuring the absorbance at two different reaction times and at two different wavelengths. A homemade stopped-flow system coupled with a diode-array detector and the proportional equation method was used. Resolution was achieved over chlorpyrifos: carbaryl ratios ranging from 61 to 14, with relative errors of 4 and 3%, respectively. The method was successfully applied to the analysis of a commercial formulation.     

Spectrofluorimetric determination of nucleic acids as 8-hydroxyquinoline/ yttrium ternary complexes

The formation of nucleic acids/8-hydroxyquinoline/yttrium(III) ternary complexes and their fluorescent properties have been studied. The nucleic acids studied include native and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 7.6–8.5, controlled by NH₃-NH₄C1 buffer, ternary complexes are formed that fluoresce at different wavelengths with different nucleic acids. Based on the fluorescence reactions, sensitive spectrofluorimetric methods for nucleic acids are proposed. In optimal conditions, the calibration curves were linear in the range 0.5–4.0 gml^–1 for calf thymus DNA, 0.5–2.5 g ml^–1 for fish sperm DNA and 0.5–4.0 g ml^–1 for yeast RNA. The limits of determination (3 ) were 0.030 g ml^–1 for calf thymus DNA, 0.020 g ml^–1 for fish sperm DNA and 0.090 g ml^–1 for yeast RNA. Corresponding to the interferences of coexisting substances, six synthetic samples were constructed and the results of determination were satisfactory.     

Studies on the Conformation of Poly(1-naphthol) Assembled by Horseradish Peroxidase in Aqueous Micelle

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Synthesis of New and Novel N-Protected 1-Aminoalkyl-2-naphthol Derivatives

A series of three-component reactions has been carried out using HClO₄-SiO₂ as a versatile heterogeneous catalyst. A series of new and novel N-protected 1-aminoalkyl-2-naphthol derivatives have been prepared under thermal solvent-free reaction conditions. In all cases, the reaction conditions were very simple and high-yielding.     

2,6-Bis[(o-hydroxy)phenyliminomethyl]-1-hydroxybenzene as a reagent for the selective spectrofluorimetric determination of aluminium

A spectrofluorimetric method for the determination of aluminium at ng/ml level has been developed. The method is based on the formation of a fluorescent 11 complex between Al(III) and 2,6-bis[(o-hydroxy)phenyliminomethyl]-1-hydroxybenzene at an apparent pH of 5.0 in an aqueous-ethanol medium (70% v/v ethanol). The influence of reaction variables is discussed. The range of concentration of the method is 1.0–10.0 ng/ml aluminium, the relative standard deviation 1.5% and the limit of detection 0.1 ng/ml. The advantages of the proposed method include high sensitivity and selectivity. The method has been applied to the determination of aluminium in natural waters.