双波长分光光度法同时测定灌木饲料中的铁和铝

利用铁、铝与邻苯二酚紫（PCV）形成的络合物的最大吸收波长相差30nm的光谱性质，建立了同时测定铁和铝的双波长分光光度法，并对络合物的形成条件及相互干扰情况进行研究，方法用于灌木饲料样品中铁和铝测定。     

双波长光度法同时测定水中微量铁和铜

提出了以5 Br PADAP为显色剂,在pH3.0的缓冲溶液中,用双波长光度法同时测定=590.水中微量铁和铜的最佳条件。选择的测定铁和铜的波长对分别为λFe1=503.5nm,λFe2=555.0nm,服从比耳定律的线性范围和检出限分别为0～16μg/25ml和0nm,λCu1=604.0nm,λCu20～24μg/25ml,0.008和0.006μg·ml-1,加标回收率分别为89.2%～105.4%和88.4%～102.0%。通过测定不同的水样,结果满意。     

双试剂双波长光度法同时测定硅石中的铁和钛

研究以邻二氮菲(Phen)和二安替比林甲烷(DAM)为显色剂同时测定硅石中的铁和钛,在pH值为0.99～1.26的酸性条件下,Phen和DAM可分别与铁和钛生成稳定的有色络合物.分别在波长510 nm和390 nm测其吸光度,用双波长计算法,同时测定试液中的铁和钛.铁量在0～100μg/(50 mL),钛量在0～150μg/(50 mL),符合比耳定律.铁和钛的加标回收率分别为99.8%～101.3%和98.8%～101.6%.     

流动注射—双显色剂双波长分光光度法同时测定铝与铁

本文将流动注射与双波长双光束分光光度计联用，选择铬天菁Ｓ和亚硝基Ｒ盐双显色剂使ＡＩ（Ⅲ）和Ｆｅ（Ⅱ）同时显色。建立了同时测定铝、铁的流动注射－双波长等吸收法。方法用于岩矿样品中铝、铁的测定，结果满意。     

流动注射－双显色剂双波长分光光度法同时测定铝与铁

本文将流动注射与双波长双光束分光光度计联用，选择铬天菁Ｓ和亚硝基Ｒ盐双显色剂使Ａｉ（Ⅲ）和Ｆｅ（Ⅱ）同时显色。建立了同时测定铝、铁的流动注射－双波长等吸收法。方法用于岩矿样品中铝、铁的测定，结果满意。     

主次波长光度法测定天然水中碘

在溴和甲酸钠存在下，碘与淀粉作用生成蓝色物质，本文根据着色溶液吸光度（Ａ），入射波长（λ）及显色物质浓度（Ｘ）的相互关系研究天然水中测定碘的主次波长新光度法，该法具有较高分析精密度，检出限较单波长比色法低，样品分析结果表明：ＲＳＤ≤４．３％?加标回收率为９７％～１０７％。方法检出限０．００１μｇ／ｍＬ。     

双波长光度法测定水中的微量铁

建立了双波长光度法——Fe（Ⅱ）-TAB—NO2-显色光度法测定水中的微量铁。在碱性介质中,铁（Ⅱ）与硫代巴比妥酸-NO2-体系友生显色反应形成-种蓝色配阴离子,该配阴离子具有两个吸收峰分别位于658nm和384nm,且体系的吸光度A658、A384及其二者之和A均与铁（Ⅱ）含量在0—30μg／（25mL）范围内具有良好的线性关系。方法的加标回收率为94％～104％,测定结果的相对标准偏差为3．4％～4．8％（n=5）。     

紫尿酸双波长叠加光度法测定水中微量铁

在碱性介质中,铁（Ⅱ）与紫尿酸发生显色反应形成一种蓝色配阴离子,该配阴离子具有两个吸收峰,分别位于630nm和350nm,吸光度A630,A350之和△A与铁（Ⅱ）的含量在0-2μg／mL范围内线性关系良好,据此建立了测定微量铁的紫尿酸双波长叠加光度法,该法用于水中微量铁的测定,测定结果与火焰原子吸收法（FAAS）相吻合,加标回收率为98％-102％,测定结果的相对标准偏差为1．2％-2．9％（n=5）。     

双波长分光光度法测定微量铜

报道了以５－（５－硝基－２－吡啶偶氮）－２－４－二氨基甲苯（５－ＮＯ２－ＰＡ－ＤＡＴ）为显色剂,应用双峰双波长光度法测定铜（Ｉ）的新方法。实验结果表明,在ｐＨ４．０￣ｐＨ６．０的乙酸－乙酸钠缓冲溶液中和盐酸羟胺和乙醇存在下,铜（Ｉ）可与试剂形成稳定的１：２红色配合物。     

Determination of effective wavelengths for discrimination of fruit vinegars using near infrared spectroscopy and multivariate analysis

Near infrared (NIR) spectroscopy based on effective wavelengths (EWs) and chemometrics was proposed to discriminate the varieties of fruit vinegars including aloe, apple, lemon and peach vinegars. One hundred eighty samples (45 for each variety) were selected randomly for the calibration set, and 60 samples (15 for each variety) for the validation set, whereas 24 samples (6 for each variety) for the independent set. Partial least squares discriminant analysis (PLS-DA) and least squares-support vector machine (LS-SVM) were implemented for calibration models. Different input data matrices of LS-SVM were determined by latent variables (LVs) selected by explained variance, and EWs selected by x-loading weights, regression coefficients, modeling power and independent component analysis (ICA). Then the LS-SVM models were developed with a grid search technique and RBF kernel function. All LS-SVM models outperformed PLS-DA model, and the optimal LS-SVM model was achieved with EWs (4021, 4058, 4264, 4400, 4853, 5070 and 5273 cm⁻¹) selected by regression coefficients. The determination coefficient (R²), RMSEP and total recognition ratio with cutoff value ±0.1 in validation set were 1.000, 0.025 and 100%, respectively. The overall results indicted that the regression coefficients was an effective way for the selection of effective wavelengths. NIR spectroscopy combined with LS-SVM models had the capability to discriminate the varieties of fruit vinegars with high accuracy.     

Rapid decolorization of water soluble azo-dyes by nanosized zero-valent iron immobilized on the exchange resin

Nanosized zero-valent iron (NZVI) supported on the cation exchange resin was synthesized and applied to decompose some water soluble azo dyes. The decomposition efficiency for azo dyes was evaluated by using the aqueous suspensions and parked column of this material. Batch experiments indicated that this novel material exhibited excellent degradation ability for 0.05 g·L1 of Acid Orange 7, Acid Orange 8, Acid Orange 10, Sunset Yellow, and Methyl Orange, with decolorization ratio up to 95% in 4 min; pH value was the key factor for degradation and H was one of the reactants; adsorption of azo dyes onto the material existed at the beginning but reduced gradually until disappearing completely. For the packed column system, 58%~90% of azo dyes were decomposed in the 1st circle of solution passing through the column, and the adsorption onto the materials could accelerate the degradation azo dyes with the increasing reaction time. During the degradation process, Fe2 , the product of NZVI, was exchanged to the resin again and could be reduced to Fe0 by KBH4 for reusing. The 10th refreshed NZVI possessed reductive activity up to 90% of the newly systhesized NZVI. Decomposing pollutants in the aqueous solution with columns packed with NZVI immobilized on the cation exchange resin is a promising technology that can solve the reclaiming and refreshing problem of NZVI.     

Determination of composition and instability constants of maltol complexes with iron(iii) ions

Complexation of maltol (MH) with Fe³⁺ ions in aqueous solutions was studied. The compositions of [FeMa]²⁺, [FeMa₂]⁺, and [FeMa₃] complexes were determined by the method of isomolar series, and their instability constants were calculated. The values of the latter were confirmed by the method of apparent deviation from the Bouger—Lambert—Beer law. An increase in the Ma : Fe³⁺ ratio from 1 to 3 decreases the instability constants of the complexes. The [FeMa₃] complex can be considered as a basis for the antianemic drug with a prolonged effect.     

Determination of total and dissolved amount of iron in water samples using catalytic spectrophotometric flow injection analysis

A flow injection spectrophotometric method has been developed for the determination of dissolved and total amounts of iron in tap and natural water samples. The method for the determination of iron employs a sample acidification step in order to decompose iron hydroxide and iron-complexes into free iron, Fe(III) and Fe(II). The amounts of free iron were detected using a catalytic action of Fe(III) and Fe(II) on the oxidation of N,N-dimethyl-p-phenylenediamine in the presence of hydrogen peroxide. Increase in absorbance of oxidized product was detected spectrophotometrically at 514 nm. The proposed method allows 0.02 and 0.06 μg l⁻¹ of LOD and LOQ, respectively, with relative standard deviation (RSD) below 2%. The accuracy and the precision of the method were evaluated by the analysis of the standard reference material, river water. The developed method was successfully applied to real water samples.     

Determination of cyanobacterial cyclic peptide hepatotoxins in drinking water using CE

Four cyanobacteria hepatotoxins microcystin LR, microcystin RR, microcystin YR, and nodularin were simultaneously determined in drinking water using CZE and MEKC coupled with UV detection. The toxins were satisfactorily separated in both CZE and MEKC modes. Detection limits were in the range of 0.82–4.81 μg/mL, with R² values of 0.994–0.999. The linearity range tested for the standards was 5–100 μg/mL and RSD percentages were in the range of 1.0–2.5% for retention time and 3.0–10.2% for peak area. When a known amount of standard was spiked into a known volume of water and extracted, recoveries were 90.3% (RR), 101.5% (nodularin), 90.6% (YR), and 88.2% (LR). The use of SPE enabled cleanup and pre‐concentration of a real sample to achieve a 100‐fold concentration factor. Detection limits after SPE of the real sample spiked with microcystins were 0.090 μg/L (RR), 0.076 μg/L (YR), and 0.110 μg/L (LR), with RSD percentage values of 9.9–11.7% for peak area and 2.2–3.3% for retention time. The technique developed provides an alternative method for determining microcystins at levels of concentration that will be able to meet WHO drinking water guidelines for microcystins.     

Determination of lead in water using laser ablation–laser induced fluorescence

The detection sensitivity of laser-induced breakdown spectroscopy (LIBS) is improved by coupling it with a laser-induced fluorescence method. A waterjet sample containing 500 ppm of Pb as an analyte was ablated by a 266 nm, frequency-quadrupled Q-switchedNd:YAG laser at an energy of ~ 260 μJ. After a short delay the resulting plume was re-excited with a 283.306 nm, nanosecond pulse dye laser at energies ranging from 45 to 100 nJ. The limit of detection (LOD) of lead in water was determined both by the single-pulse LIBS technique and Laser Ablation coupled with Laser-Induced Fluorecence (LA–LIF) method. It was found to be 75 ppm in the case of single-pulse LIBS and 4.3 ppm for LA–LIF. When the resonant pulse was detuned from the transition wavelength the LA–LIF signal disappeared demonstrating the resonant selectivity of this technique.     

Determination of pH value of isoelectric solution and identification of passive iron surface phases using immersion method

Using the method of phase modeling, the pH values of solutions corresponding to the uncharged surface of passive iron and ferric oxide γ-Fe₂O₃ (pH₀) are compared. According to the theory of connected places, the charge of metal oxide surface is determined by the adsorption or desorption of hydrogen ions leading to a change in the potential drop at the oxide/solution interface. Preliminarily passivated iron electrode was washed with twice-distilled water and placed into 0.5 M NaNO₃ solution with various pH values; the variation in the potential (ΔE) with time was studied. The pH₀ value for passive electrode under the open-circuit conditions was determined by the dependence of ΔE on the pH value (pH₀ 6.2 ± 0.1). The pH₀ value was close to that for γ-Fe₂O₃ (pH₀ 6.2), which was determined by the method of potentiometrical titration of oxide suspension in the nitrate solution. The introduction of surface-active ions Ba²⁺ and Cl^? changes the charge of passive iron surface: Ba²⁺ ions increase the electrode potential, while Cl^? ions decrease it. Comparing the pH₀ values for passive electrode and metal oxides, one can identify the composition of passive electrode surface.     

双波长双指示剂催化动力学光度法测定痕量铁

铁是人体健康所必须的微量元素,它对人体的生理功能有一定影响.如果体内可利用的铁不能满足血红蛋白正常合成的需要,致使红细胞增殖能力下降,就会造成缺铁性贫血.相反,体内铁含量过高,又易产生癌症~([1]).     

Ion-pair adsorption film colorimetry of iron (III) in water samples and human serum

The anionic chelate of iron(III)-2,2-dihydroxyazobenzene (H₂L), [FeL₂]^–, formed 1 1 ion-pair with crystal violet cation (CV⁺), CV⁺ [FeL₂]^–, and was adsorbed on a surface of transparent polyvinyl chloride (PVC) film plasticized with di-n-octyl phthalate. Enrichment of the blue violet species of the ion-pair onto the transparent PVC film has enabled a highly sensitive and simple method for the determination of iron(III). The detection limits are 1 × 10^–8 mol dm^–3 (0.6 ppb) by spectrophotometry at 592 nm, and 4 × 10^–8 mol dm^–3 (2 ppb) by visual colorimetry. The method has been successfully applied to the determination of iron in water samples and human serum. No preparatory procedures for the separation of serum protein and other coexisting substances are required, since ion-pair adsorption process provides a new method to prevent interference of serum matrix.     

Photoinduced degradation by iron(III): removal of triphenyltin chloride from water

The photoredox process taking place in iron(III) aquacomplexes was used to cause the complete degradation of triphenyltin (TPT). TPT elimination was proved to come only from attack by hydroxyl radicals generated upon irradiation at 365 nm of Fe(H₂O)₅OH²⁺, the iron(III) species present under the experimental conditions ([Fe(III)] in the range (3–6) × 10^?4 mol l^?1). The first step is the formation of an adduct between hydroxyl radicals and the benzene ring. The main process is a stepwise dephenylation of the starting TPT. Hydroxylated phenyltin derivatives were also formed, but only as minor photoproducts. The process was shown to be efficient with artificial light as well as with solar light. Copyright © 2001 John Wiley & Sons, Ltd.