铁(Ⅲ)-硫氰酸根-乙基罗丹明B缔合体系微乳液分光光度法测定铝合金中铁

提出了微乳液分光光度法测定铝合金中铁含量的方法。在比色管中,先后加入0.5 mol·L^-1硫酸溶液3.00 mL、铁（Ⅲ）标准溶液,2 mol·L^-1硫氰酸钾溶液3.00 mL、5 g·L^-1阿拉伯树胶溶液0.8 mL、微乳液0.70 mL及1×10^-3 mol·L^-1乙基罗丹明B溶液3.00 mL使反应生成铁与硫氰酸盐的络阴离子和乙基罗丹明B的缔合物。微乳液和阿拉伯树胶对此显色体系具有显著的增溶作用。铁（Ⅲ）的质量浓度在0.026～0.36 mg·L^-1范围内与其吸光度呈线性关系。反应体系的吸收峰位于波长620 nm处,在此波长条件下测定其表观摩尔吸光率为1.08×10⁵ L·mol^-1·cm^-1。方法用于测定铝合金试样中铁量,测定值的相对标准偏差（n=5）小于2%。     

分光光度法测定4种芒果中的铁含量

用高氯酸-硝酸(1+4)混合酸湿法消解处理一定量芒果样品(鸡心芒、台农芒、金煌芒或黄金大芒),蒸至近干,加水定容至25mL。分取1.50mL样品溶液,加100g·L-1盐酸羟胺溶液1.00mL将铁(Ⅲ)还原至二价。基于亚铁离子与铁氰化钾之间生成蓝色化合物的反应,用分光光度法测定样品溶液中的铁含量。铁的质量浓度在0.04~10.09mg·L-1范围内与其吸光度呈线性关系,检出限(3S/N)为0.02mg·L-1。加标回收率在98.7%~100%之间,测定值的相对标准偏差(n=6)均小于0.60%。几种芒果中微量铁元素含量的多少依次为台农芒、黄金大芒、金煌芒、鸡心芒。     

双酶显色-紫外-可见分光光度法测定牛奶中组胺与腐胺的含量

建立了基于二胺氧化酶-辣根过氧化物酶双酶显色的紫外-可见分光光度法测定牛奶中组胺与腐胺含量的方法。取10 mL牛奶样品,加入10 mL 2%（质量分数）硝酸铅标准溶液,混匀,再加入20 mL 0.1%（质量分数）三氯乙酸标准溶液,混匀,离心,取上清液,将溶液pH调至7.2,得到待测样品溶液。移取1.0 g·L^-1二胺氧化酶标准溶液100μL,加入100μL待测样品溶液,于50℃水浴中反应15 min。反应结束后,依次加入1.0 g·L^-1辣根过氧化物酶标准溶液50μL,0.5 g·L^-1四甲基联苯胺标准溶液200μL和2 mol·L^-1盐酸溶液50μL,采用紫外-可见分光光度计测定体系的吸光度。结果显示：样品溶液由无色变为蓝色又变为黄色;组胺、腐胺的浓度分别在2.5～150μmol·L^-1和5～200μmol·L^-1内与其对应的吸光度呈线性关系,检出限（3S/N）分别为0.652 2μmol·L^-1和1.134 1μmol·L     

Folin-Ciocalteu比色法测定库拉索芦荟花中多酚

建立Folin-Ciocalteu比色法测定库拉索芦荟花中多酚含量的方法。利用多功能微孔板分光光度计对Folin-Ciocalteu法检测库拉索芦荟花多酚的显色反应条件进行优化，再用紫外可见分光光度计对其方法稳定性、重现性及准确性进行验证。结果表明，向库拉索芦荟花样品溶液中加入Folin-Ciocalteu试剂1.0 mL、50 g/L碳酸钠溶液2.0 mL，用水定容至10 mL，于40℃避光显色60 min，测定反应体系在765 nm处的吸光度，多酚质量浓度在6.3～62.6μg/mL范围内与吸光度具有良好的线性关系，线性相关系数为0.999 6。样品测定值的相对标准偏差为1.42%(n=6)，测定方法的平均回收率为95.52%。该方法适用于库拉索芦荟花中多酚含量的测定。     

汞-邻菲啰啉-刚果红缔合体系光度法测定痕量汞

在含有汞(Ⅱ)试液中,先后加入乙酸-乙酸钠缓冲溶液(pH 5.7)、1.0×10-3mol.L-1邻菲啰啉溶液0.8 mL、4.0×10-4mol.L-1刚果红溶液1.2 mL及10 g.L-1阿拉伯树胶(GA)溶液0.8 mL使反应生成汞与邻菲啰啉和刚果红的络合物。在此缔合体系中,GA对显色反应兼有增敏和增稳作用。汞(Ⅱ)质量浓度在1.0 mg.L-1范围内与其吸光度呈线性关系。反应体系的吸收峰位于540 nm波长处,在此波长条件下测定其表观摩尔吸光系数为8.49×104L.mol-1.cm-1。此方法已应用于测定河水中汞量,求得相对标准偏差(n=5)小于2.0%,平均回收率为100.4%。     

新显色剂对-二甲氨基偶氮氯膦的合成及其与钍显色反应的研究

合成了新显色剂对-二甲氨基偶氮氯膦,研究了它与Th(Ⅳ)的显色反应.结果表明:Th(Ⅳ)在0～30μg/25mL范围内与该试剂形成的配合物在674,612和538nm³个波长处吸光度绝对值之和与溶液中Th(Ⅳ)的浓度呈线性关系,故可利用该3个波长下吸光度绝对值叠加的方法测定Th(Ⅳ),其ε值达1.74×10⁵L·mol^-1·cm^-1.由于显色反应在较强酸性介质中进行,本法有良好的选择性,大多数共存离子不干扰钍的测定,用于测定岩矿中的微量钍,结果满意.     

二溴对甲基偶氮甲磺光度法测定钙

1 引言二溴对甲基偶氮甲磺曾用于钡和锶的测定.近来的研究发现,该试剂也能与钙发生显色反应,与其它测钙的试剂不同,大量的镁存在对显色反应也不干扰.用于环境水样中钙的测定,干扰少,结果满意.2 实验部分2.1主要试剂和仪器 7530G分光光度计,721型分光光度计.钙标准溶液:1g/L;磷酸:3 mol/l;二溴对甲基偶氮甲磺(3-[(4-甲基-2-磺酸基苯)偶氮]-6-[(2,6-二溴-4-甲基苯)偶氮]-4,5-二羟基-2,7-基萘二碳酸,自制):0.O5%水溶液.2.2 试验方法 吸取含50μg钙的标准溶液于25mL比色管中,加入3mol/l磷酸2.0ml,以水稀释至15mL左右.加入二溴对甲基偶氮甲磺溶液2.5ml,用水稀释至刻度.以试剂空白为参比,用1cm比色皿于632nm测量吸光度.3 结果与讨论3.1 络合物吸收光谱 结果表明,试剂最大吸收位于554nm处,络合物的最大吸收位于632nm处,对比度△λ=78nm.3.2 介质的选择 该试剂在盐酸、硝酸、高氯酸、磷酸、硫酸一定的酸度介质中均能与钙形成稳定的络合物,由于磷酸介质可以掩蔽水样中常见的Fe~(3+),在0.06～0.5mol/L磷酸体系中吸光度基本不变,试验中选用0.24mol/L磷酸体系.     

碘量紫外分光光度法测定碳氢燃料过氧化值

建立测定碳氢燃料过氧化值的碘量紫外分光光度法。样品溶于乙醇中，加入0.50 mL冰乙酸，用饱和碘化钾-乙醇溶液定容至10 mL，避光显色90 min，过氧化物在酸性条件下与碘化钾反应生成黄色的I₃^-，在360 nm处测定吸光度，计算过氧化氢的含量。过氧化氢的质量浓度在0.106 1～1.061μg/mL范围内与吸光度线性关系良好，相关系数为0.999 8，方法检出限为0.015μg/mL。样品加标回收率为97.3%～103.6%，测定结果的相对标准偏差小于5%(n=6)。该法适用于测定碳氢燃料的过氧化值。     

紫外分光光度法测定聚硫密封胶中二氧化钛

基于强酸性溶液中钛氧离子与H2O2发生显色络合反应的原理,建立了浓硫酸–硫酸铵消解–紫外分光光度法测定聚硫密封胶中TiO_2含量的方法。通过对酸液和显色剂用量,以及显色络合物稳定性的系统考察,确定浓硫酸用量为2 mL,双氧水用量为3 mL,检测波长为403 nm。二氧化钛质量浓度在0~130μg/mL范围内与其吸光度呈良好的线性关系,线性方程为A=5.047 8c–0.019 31,r~2=0.999 2,检出限为0.08μg/mL。检测结果的相对标准偏差为0.89%(n=5),3水平加标平均回收率为101.7%。该方法线性范围较宽、检出限低、重复性好,可用于聚硫密封胶中二氧化钛的定量分析。     

紫外光谱法测定印制线路板废水中的铜

白杨素在紫外区内具有强吸收,Cu2+加入后会导致其吸光度显著下降,且吸光度的降低与Cu2+的浓度呈良好的线性关系,基于此建立了紫外光谱法测定Cu2+的新方法。通过对缓冲溶液体积、p H、白杨素浓度等进行考察和优化,在p H 8.28、9.0×10-2mol/L的六亚甲基四胺(HM TA)-HCl缓冲溶液中,4.0×10-8~1.0×10-6mol/L范围内,Cu2+浓度与吸光度降低成正比,线性方程为ΔA=0.508 c-0.0147(10-6mol/L)(R=0.99604),检出限为7.08 nmol/L(S/N=7),对4.0×10-8mol/L Cu2+溶液平行测定7次,ΔA的相对标准偏差为4.0%。对印制线路板废水中的铜进行了测定,测得结果与EDTA滴定法基本一致。     

Improved detection of salicylic acids using terbium-sensitized luminescence in aqueous micellar solutions of cetyltrimethylammonium chloride

The determination of salicylic, p-aminosalicylic and 5-fluorosalicylic acids was investigated using terbium-sensitized luminescence in aqueous solutions. Formation of a ternary chelate between terbium, EDTA and the salicylic acid requires dissociation of the phenol group which is adjacent to the dissociated carboxylic group. The reaction is obtained in alkaline solutions and is enhanced in the presence of cetyltrimethylammonium chloride. As evidenced by absorbance and fluorescence measurements, the cationic surfactant plays an important role in the formation of the ternary chelate and then terbium luminescence depends mainly on the extent of chelate formation. Linearity is found over more than four orders of magnitude and detection limits are in the range (2-4) x 10(-10) mol l-1 for the three acids.     

Spectrophotometric determination of sulfur dioxide in air, using thymol blue

A simple and sensitive spectrophotometric method was developed for the determination of trace amounts of sulfur dioxide. The method is based on the reaction of SO2 with a known excess of ICI as the oxidant. The unreacted ICI iodinates thymol blue under acidic conditions. The lambdamax of thymol blue is at 545 nm under acidic conditions, and on lodination lambdamax shifts to 430 nm. This shift results in a decrease in the absorbance at 545 nm. The amount of uniodinated thymol blue present depends on the concentration of unreacted ICI, which in turn depends on the SO2 concentration. The system obeys Beer's law in the range 0-30 microg SO2 in a final volume of 25 mL, having a molar absorptivity of 3.2 x 10(4) L/mol cm with a relative standard deviation (RSD) of 2% at 24 microg SO2 (n = 10). The uniodinated dye can be extracted into 5 mL isoamyl alcohol under acidic conditions for measurement of absorbance. The extraction method obeys Beer's law in the range 0-5 microg SO2, having a molar absorpitivity of 4.16 x 10(4) L/mol x cm with an RSD of 1.9% at 4 microg SO2 (n = 10). The method has been successfully applied to the determination of atmospheric SO2.     

Spectrophotometric Determination of Carboxylic acids with 2-Mitrophenylhydrazine in Aqueous Solution

Abstract

Carboxylic acids were determined spectrophotometrically by converting them into 2-nitrophenylhydrazides. The coupling reaction of carboxylic acids with 2-nitrophenylhydrazine was effected by a water-soluble carbociimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and proceeded efficiently in aqueous solution buffered at pH 4.5 with pyridine and hydrochloric acid. The yields of hydrazides from acetic and benzoic acids were nearly quantitative. The reaction mixture was then made strongly alkaline, and after heating to reduce the blank absorbance, the absorbance of the hydrazide was measured at around 540 nm. Calibration curves of various carboxylic acids were linear between 0.02 and 0.5 μmol through the origin.     

A silver nanoparticle-based method for determination of antioxidant capacity of rapeseed and its products

A novel silver nanoparticle-based (AgNP) method and two modified procedures, ferric reducing antioxidant power (FRAP) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH), were used for determination of antioxidant capacities of the ethanolic, methanolic, methanolic-aqueous (1?:?1 v/v) and aqueous extracts of rapeseed and its products. The AgNP method based on the electron-transfer reaction between silver ions and antioxidants in an optimized ammonium buffer medium (pH = 8.4) and determination of silver nanoparticle formation has been elaborated. The novel AgNP method was validated using sinapic acid, gallic acid, caffeic acid, ascorbic acid and quercetin as standard antioxidant solutions in concentration ranges of 0.03-0.21 μmol mL(-1), 0.02-0.20 μmol mL(-1), 0.01-0.18 μmol mL(-1), 0.03-0.30 μmol mL(-1) and 0.001-0.009 μmol mL(-1). The calculated detection (DL = 0.01, 0.02, 0.009, 0.02 and 0.0004 μmol mL(-1) for sinapic, gallic, caffeic, ascorbic acids and quercetin, respectively) and quantification limits (QL = 0.04, 0.06, 0.03, 0.08 and 0.001 μmol mL(-1) for sinapic, gallic, caffeic, ascorbic acids and quercetin, respectively) confirm linearity concentration ranges for determination of antioxidant capacity by AgNP assay. The average antioxidant capacities of the studied rapeseed samples ranged between 14.7 and 126.2 μmol sinapic acid per gram for the proposed AgNP method, 7.4-112.7 μmol sinapic acid per gram for the FRAP method and 39.1-339.8 μmol sinapic acid per gram for DPPH assay. The methanol-water mixture (1:1 v/v) was the most efficient solvent for extraction of antioxidants from the studied rapeseed samples. There are significant, positive correlations between the novel AgNP and the modified FRAP, DPPH and FC methods for all extracts of the studied rapeseed samples (r = 0.7564-0.8516, p < 0.001). Satisfactory values of precision (RSD = 1.2-4.4%) and accuracy (recovery = 95.6-104.6%, except methanolic extracts) demonstrate the benefit of the proposed AgNP method for analysis of the antioxidant capacity of rapeseed samples. Results of the principal component analysis (PCA) indicate that there are differences between the total amounts of antioxidants in rapeseed samples extracted by different solvents.     

Spectrophotometric determination of selenium by use of thionin

A simple, rapid, and sensitive spectrophotometric method has been developed for the determination of selenium in real samples of water, soil, plant materials, human hair, and synthetic cosmetic and in pharmaceutical preparations. The method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine. The liberated iodine bleaches the violet color of thionin, and which is measured at 600 nm. This decrease in absorbance is directly proportional to selenium concentration and obeys Beer's law in the range 1-5 micro g selenium in a final volume of 10 mL (0.1-0.5 microg mL(-1)). The molar absorptivity and Sandell's sensitivity of the method were found to be 7.33 x 10(4) L mol(-1) cm(-1) and 0.0011 microg cm(-2), respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination is described.     

Spectrophotometric determination of trace iron by using its catalytic effect on the N-phenylanthranilic acid-potassium periodate reaction.

The analytical features of the reaction between N-phenylanthranilic acid (PAA) and potassium periodate in acidic medium are explored with the aim of improving the catalytic kinetic determination of iron in water samples. In the presence of Fe(II, III), PAA is oxidized by potassium periodate in a formic acid medium to form a violet-colored compound. The reaction is followed spectrophotometrically by measuring the increase in the absorbance of the oxidation product at 525 nm. The variables that affected the reaction rate were investigated and the reaction conditions were established. Calibration graphs are linear in the range of concentrations 2 - 500 ng mL(-1). As low as 10(-8) mol L(-1) Fe(II, III) can be easily determined by the fixed time method. The established catalytic method was successfully applied to the determination of iron in tap water and in pharmaceutical samples.     

Sensitive Voltammetric Determination of Captopril Using a Carbon Paste Electrode Modified with Nano-TiO2/Ferrocene Carboxylic Acid

A carbon paste electrode (CPE) modified with ferrocene carboxylic acid (FcCA) and TiO2 nanoparticles was constructed by incorporating TiO2 nanoparticles and ferrocene carboxylic acid into the carbon paste matrix.The electrochemical behavior of captopril (CAP) at the surface of the modified electrode was investigated using electroanalytical methods.The modified electrode showed excellent electrocatalytic activity for the oxidation of CAP in aqueous solutions at physiological pH values.Cyclic voltammetric curves showed that the oxidation of CAP at the surface of the modified electrode reduced its overpotential by more than 290 mV.The modified electrode was used for detecting captopril using cyclic voltammetry and square wave voltammetry techniques.A calibration curve in the range of 0.03 to 2400μmol/L was obtained that had a detection limit of 0.0096 μmol/L (3σ) under the optimized conditions.The modified electrode was successfully used for the determination of captopril in pharmaceutical and biological samples.     

Extraction of copper(II) carboxylates with chloroform under substoichiometric conditions

The features are considered of binding carboxylic acids (HR) as dimeric solvated copper(II) complexes at the copper(II) extraction with chloroform under substoichiometric conditions, with excess of the metal ion in the aqueous phase. The fundamental difference in the optimization of the quantitative extraction of copper(II) in the form of any carboxylate with a maximum ratio of Cu:R and the total binding with carboxylic acids to form the copper complex of the minimum stoichiometry was noted. It was found that quantitative binding of HR occurred at the extraction of mixed-ligand acetate-carboxylate copper(II) complexes without control over the aqueous phase acidity when acetic acid medium or copper(II) acetate was used, but not copper chloride, nitrate, perchlorate, or sulfate. The possibility of determination by extraction-photometric method by the color of the Cu(II) complex was shown that was suitable only to those carboxylic acids, whose logarithm of the partition coefficient in the water-chloroform mixture was higher than three.     

高碘酸钾氧化中性红褪色催化动力学光度法测定痕量硒(Ⅳ)

基于3.2×10-4mol/LH2SO4介质中,痕量硒(Ⅳ)催化KIO4氧化中性红的褪色反应,建立了测定痕量硒(Ⅳ)的动力学光度法。在固定加热时间段(6min)后,于530nm处测定中性红的吸光度降低值监控反应速率。方法检出限为0.36μg/L,校准曲线的质量浓度线性范围为0～8.0μg/L。实验了酸度、反应物浓度、温度、反应时间、干扰离子等因素的影响。研究了反应的最佳条件,并测定了一些动力学参数,催化反应的表观活化能为81.60kJ/mol。11次重复测定0.1μg/25mL和0.2μg/25mLSe(Ⅳ)的相对标准偏差分别为2.1%和1.9%。方法用于食品和人发样品中痕量硒(Ⅳ)的测定,相对标准偏差为0.33%～3.8%,加标回收率为96.0%～103.0%。     

Transport and separation of carboxylic acids through bulk liquid membranes containing tributylamine

In this study, transport and separation of carboxylic acids (formic, acetic, propionic, and butyric acids) from their aqueous solutions through bulk liquid membrane (BLM) containing tributylamine (TBA) and the parameters affecting the transport were investigated. The influence of the parameters on the separation process such as the stirring of membrane phase, the stripping phase type and concentration, the feed phase type, and the feed:membrane:stripping phase ratio (F/M/S phase ratio) were examined. In the experiments, 10% (w/w) acid solutions (formic, acetic, propionic, and butyric acids) were used as the feed phase, different concentrations of NaOH solutions within the range of 0–2?N were used as the stripping phase, and 0.5?mol/lt TBA, dissolved in oleyl alcohol, was used as the membrane phase. It was determined that the stirring of the membrane phase increases the transport of acids. In the case of 2 N NaOH solution in the stripping phase and F/M/S phase ratio 1:2:1 gave the best recovery (96.75%) for butyric acid. It was observed that BLM was an effective technique for the separation of carboxylic acids from aqueous solutions.