冷原子荧光法间接测定水中氰化物

本文详细研究了氰化物蒸馏条件及其稳定性问题，建立了一个冷原子荧光法间接测定水中氰化物的方法，并用于海水及氰化液中痕量ＣＮ－的测定，结果令人满意。ＣＮ－检出限为０．０２μｇ／ｍＬ，回收率９５％～９８％，变异系数７．３％～８．９％。     

一种高灵敏测定水中游离氯的新方法

探讨了在中性水溶液中，游离氯催化过氧化氢氧化副攻瑰苯胺的褪色反应及其动力学条件，建立了一种高灵敏、选择性好测定水中痕量Ｃｌ２的新方法，测定范围为０．０１５￣１．０μｇ／１０ｍｌ，成功地用于水中Ｃｌ２的测定。     

间氯偶氮安替比林流动注射分析测定药物及水中钙

基于间氯偶氮安替比林可与钙在碱性介质中形成灵敏的兰色络合物这一显色反应，本文在自行组装的带微型计算机的流动注射分析仪上，以分光光度计作检测器，建立了测定微量钙的流动注射分光光度法。最佳显色反应条件：０．０８ｍｏｌ／Ｌ ＮａＯＨ－０．０１２％显色剂２．０％三乙醇胺溶液，测定波长为６３０ｎｍ。以三乙醇胺为掩蔽剂，方法选择性较高。钙的线性范围为１．０￣１５．０μｇ／ｍｌ，检测限０．５μｇ／ｍｌ，进样频率     

安替比林基重氮氨基—2,4—二硝基苯间接分光光度法测定痕量氰化物

１引言氰化物是环境监测和食品检验中必测的剧毒物之一。研究表明，在ｐＨ＝１０．５～１２．８的条件下，氰离子使银与安替比林基重氮氨基－２，４－二硝基苯（ＡＰＤＮＢＴ）络合物褪色，其褪色程度与氰离子的浓度呈良好的线性关系，从而建立了新的间接测定氰离子的分光光度方法。对于浓度低于０．０５ｍｇ／Ｌ时氰离子的测定，提出了标准加入分光光度法，提高了低含量氰离子测定的准确度和可靠性。２实验部分２．１仪器和试剂７２２型光栅分光光度计，ｐＨｓ－２型酸度计；银标准溶液为１５．０ｍｇ／Ｌ，氰离子标准溶液为５．０ｍｇ／Ｌ…     

食品包装材料与容器涂料中甲醛的示波极谱测定方法的研究

在ｐＨ５．０的０．０２ｍｏｌ／Ｌ乙酸－乙酸钠介质中,甲醛与硫酸肼的反应产物在－１．０４Ｖ处产生一个灵敏的吸附还原波,其峰高（ｉｐ）与甲醛浓度在０．０１～１．０ｍｇ／Ｌ范围内呈良好的线性关系。方法操作简便、快速、灵敏、选择性好。用于食品包装材料、容器内壁涂料中游离甲醛的测定,均获得与国标法一致的效果。     

氧化藏红T褪色催化荧光法测定痕量钒

研究了在酸性介质中柠檬酸存在下，痕量钒（Ｖ）催化溴酸钾氧化藏红Ｔ的褪色反应及其动力学条件，建立了催化荧光测定痕量钒的新方法。催化反应在沸水浴中进行８ｍｉｎ，为假零级反应，反应的表观活化能力为９９．２１ｋＪ／ｍｏｌ，反应速度常数为０．１２／ｓ；该方法的检出限为２．２×１０＾－８ｇ／Ｌ；线性范围为０．２￣２．４μｇ／Ｌ研究了共存离子的影响，用于人发和煤灰中痕量钒的测定，结果令人满意。     

锰（Ⅱ）—苯酚红—高碘酸钾—邻菲Luo啉体系催化光度法测定痕量锰的研究

研究了在碱性介质中，以邻菲Ｌｕｏ啉为活化剂，锰（Ⅱ）催化高碘酸钾氧化苯酚红褪色指标反应及其动力学条件，建立了测定痕量锰的新方法。锰的浓度在０．０．０７μｇ／ｍＬ范围内为线性关系，检测限为３．０ｎｇ／ｍＬ。用于盐酸试剂中痕量锰的测定，结果良好。     

溴水氧化氰根光度法测定微量氰化物

在磷酸介质中,氰根被饱和溴水氧化为溴化氰,剩余的溴水用磺基水杨酸除去。溴化氰与碘化钾反应生成单质碘,碘与淀粉显色,从而测定氰化物。其最大吸收波长λｍ ａｘ＝ ５６５ｎｍ ,ＣＮ－ 在０～１５μｇ／２５ｍ Ｌ范围内呈良好线性关系,表观摩尔吸光系数为３．１×１０４Ｌ·ｍ ｏｌ－ １·ｃｍ － １。已用于测定废水中的氰化物。     

表面活性剂增敏铍试剂Ⅱ荧光法测定痕量锰

在碱性条件下，Ｍｎ（Ⅱ）与铍试剂Ⅱ形成１；２的荧光络合物，其荧光峰为λｅｘ＝λｅｍ＝３６７／４６７（ｎｍ），表面活性剂十二烷基苯磺酸钠对体系具有强烈增敏作用，基于此建立了痕量锰的测定方法。本文研究了测定的最佳条件，即０．０１％铍试剂Ⅱ４．０ｍＬ，０．１ｍｏｌ／ＬＮａＯＨ６．０ｍＬ，１％ＳＤＢＳ ４．０ｍＬ，反应温度为９０℃，时间１０ｍｉｎ，线性范围为０－１６０μｇ／Ｌ，回归方程Ｘ（μｇ／Ｌ）＝２．     

溴酸钾—碘离子体系催化动力学电位法测定痕量铜

以ＫＢｒＯ３氧化Ｉ＾－的反应为指示反应，用碘离子选择电极跟踪Ｉ＾－。在适宜条件下，该指示反应为一级反应。反应速度可用电位的变化ΔＥ表示。当时间固定，ΔＥ与铜浓度在０￣３ｍｇ／Ｌ范围内呈线性关系，检出限为０．２μｇ／Ｌ。该方法已成功地用于土豆和红薯中痕量铜的测定。     

Continuous flow derivatization system coupled to capillary electrophoresis for the determination of amino acids

A derivatization system coupled to capillary electrophoresis for the determination of amino acids using 1,2-naphthoquinone-4-sulfonate as a labeling agent is described. In this system, amino acids are derivatized on-line in a three-channel flow manifold for sample, reagent and buffer solutions. The reaction takes place in a PTFE coil heated at 80 degrees C. The resulting solution, which contains the amino acid derivatives, is introduced into the electrophoretic system by means of an appropriate interface. Subsequently, amino acid derivatives are separated at 25 kV using a 40 mM sodium tetraborate aqueous solution with 30% (v/v) isopropanol solution as a running buffer. The electropherograms are monitored spectrophotometrically at 230 nm. The method has been applied to the determination of amino acids in feed samples and pharmaceutical preparations. A good concordance of the predicted values with those given by a standard amino acid analyzer is shown.     

Indirect determination of cyclamate by an on-line continuous precipitation-dissolution flow system

A continuous-flow procedure is proposed for the indirect determination of sodium cyclamate by an atomic absorption spectrometric method in artificial sweeteners mixtures and soft drinks. Sulfamic group is oxidized to sulfate and it is continuously precipited with lead ion in a flow manifold. The lead sulfate formed is retained on a filter, washed with diluted ethanol and dissolved in ammonium acetate for on-line atomic absorption determination of lead, the amount of which in the precipitate is proportional to that of cyclamate in the sample. The proposed method allows the determination of sodium cyclamate in the range 1–90 μg ml⁻¹ with a relative standard deviation of 3.1% at a rate of ca. 35 samples per h. The 3σ detection limit is 0.25 μg ml⁻¹. The method is very selective, no compounds normally found in the analysed samples and other artificial sweeteners had any effect on the determination of cyclamate.     

A robust multisyringe system for process flow analysis. Part II. A multi-commuted injection system applied to the photometric determination of free acidity and iron(III) in metallurgical solutions

A new software-controlled volume-based system for sample introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one or two additional commutation valves, the multi-commuted injection of precise sample volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Three configurations were implemented in order to achieve two different tasks: the single injection of a sample in a two- or three-channels manifold, and the dual injection into different streams. The two channel flow system using the single injection was applied to the determination of free acidity in diluted samples containing high levels of iron(III), by employing the single point titration methodology. The precipitation of ferric hydroxide was prevented using the ammonium and sodium salts of oxalate and acetate as buffer titrant. Methyl Red was employed as indicator. The procedure allows determination of acid concentration in solutions with a Fe(III)/H+ molar ratio up to 0.2. Samples with higher Fe(III)/H+ molar ratios were spiked with a known strong acid at dilution. The three-channel configuration was applied to the determination of ferric ions, using, as reagent, a merging mixture of sulfuric acid and potassium thiocyanate. The double injection system was implemented in series in a single (three-channel) manifold in such a way that a different injection volume and a changed reagent were used for each analyte. It was applied to the separated or sequential determination of free acidity and ferric ions. In this configuration, iron(III) was determined using 0.5-0.7% (w/v) sodium salicylate solution as reagent. The systems can operate at up to 100, 84 and 78 injections per hour, respectively. Determinations on synthetic and process samples compared well with the reference values and procedures. Recoveries of 95-102% with a maximum RSD value of 5.4% were found for acidity. The respective values obtained for iron determinations were 96-105% and 4.3%.     

Spectrofluorimetric determination of diquat by manual and flow-injection methods

A reliable, highly sensitive and selective method is described for the determination of the herbicide diquat in different materials. It involves the formation of a stable radical obtained by reduction of diquat with sodium dithionite. The radical is a very fluorescent species (φ_F=0.37), and there is a linear relationship between diquat concentration and fluorescence intensity over the range 3–900 μg l^?1. The limit of detection is 0.4 μg l^?1. The method can be successfully adapted as a flow system using a two-channel manifold, the peak height being proportional to the diquat concentration over the range 18–4000 μg l^?1. Manual and flow-injection methods were successfully applied to the determination of diquat in commercial herbicides, waters, potatoes, flowers and soils. Both procedures were also been applied to the determination of diquat in serum and urine without prior preparation of the samples and with good results.     

Flow system exploiting multicommutation to increase sample residence time for improved sensitivity. Simultaneous determination of ammonium and ortho-phosphate in natural water

A flow system for the simultaneous determination of ammonium and phosphate in river water at the mug ml(-1) level employing a low expensive LED-based photometer is described. The manifold of the flow system comprised four analytical pathways containg a set of three-way solenoid valves and an automatic injector commutator. The signal measurements of both analytes were carried out using two LED-based photometers attached to the flow cells. A microcomputer running a programme written in quickbasic 4.5 provided facilities to control the system and to carry out simultaneously two analytical procedures also performing data acquisition. For the determination of ortho-phosphate the method based on reaction with molybdate and ascorbic acid was employed, while for ammonium the method based on reaction with hypochlorite and salicylic acid was selected. The four-pathway structure of the manifold allowed the sample incubation time to be increased to 130 s to permit the reaction to occur without a decrease in sample throughput. The usefulness of the system was ascertained by analyzing a set of water samples. Applying the paired t-test to results obtained employing reference methods, no significant difference at the 95% confidence level was observed for both analytes. Other profitable features such as an analytical throughput of 112 analyte determination per hour; relative standard deviations of 1.1 and 0.7% (n=6) ammonium and phosphate, respectively, reagent consumption of 0.3 mg ammonium molybdate, 0.75 mg salicylic acid, 3.3 mg ascorbic acid and sodium hypochlorite per determination; detection limits of 7.0 mug l(-1) NH(4)(+) and 17.0 mug l(-1) PO(4)(3-) were also achieved.     

Flow-injection determination of lead by hydride generation and conductometric detection

Plumbane produced from the lead analyte in a flow-injection manifold by reaction with sodium borohydride is passed through a porous poly(tetrafluoroethylene) membrane in a gas-diffusion cell. The hydride reacts with bromine in the acceptor stream resulting in ionization which is detected by conductivity measurement. Direct mixing of the carrier with a reagent stream yields a limit of detection of approximately 1 mg/L. An improved detection limit of about 200 microg/L can be achieved by the incorporation of an auxiliary stream containing persulphate as oxidizing agent. The application of the method to the determination of lead in road dust and soil samples is demonstrated.     

Selenium determination by HG-ICPAES: Elimination of iron interferences by means of an ion-exchange resin in a continuous flow system

 An accurate procedure for the elimination of iron interferences in the determination of selenium in geological materials by the Hydride Generation – Inductively Coupled Plasma Atomic Emission Spectrometry technique (HG-ICPAES) is proposed. A selective removal of iron is achieved by on-line incorporation of a microcolumn filled with strongly acidic cation exchange resin (Dowex 50W-X8). The microcolumn manifold used was interfaced with the hydride generation manifold by a flow injection sample injection valve. After the removal of the iron, a 500 μl sample was injected into a carrier stream of water. This was merged with hydrochloric acid and sodium tetrahydroborate in order to generate the corresponding selenium hydride. The system was found to have a limit of detection of 0.4 ng ml^-1 and a relative standard deviation of 2% for 20 ng ml^-1 selenium. The application of the method on different Geochemical Standard Reference Samples demonstrated that results were statistically indistinguishable from certified values. Received: 7 March 1996 / Revised: 30 May 1996 / Accepted: 4 June 1996     

Use of basic amphiprotic organic solvents containing neutral-surfactant aggregates as pseudostationary phase in non-aqueous capillary electrophoresis

A new approach to non-aqueous capillary electrophoresis based on the addition of anionic carboxylic surfactants to the basic amphiprotic organic solvent in which form neutral-surfactant aggregates was developed with a view to improving the electrophoretic resolution of charged substances. These aggregates acts as a new pseudostationary phase. The presence of these aggregates allows the effective separation of four tetracyclines with increased selectivity. The efficiency of sodium caprylate, sodium laurate and sodium palmitate as surfactants was examined. The latter two proved more effective than the former as they provided migration times reproducible to within 7% or better in all cases. The additional use of an alcohol allows peak shape to be controlled, which expands the potential of this electrophoretic technique even further. The proposed method was used to determine tetracyclines in water samples. The sensitivity of the determination was improved by using a flow manifold coupled at-line to the capillary electrophoresis system in order to preconcentrate the analytes. The limits of detection thus achieved ranged from 50 to 90 μg/l. Under optimal operating conditions, recoveries ranged from 97 to 104%, and precision from 5.4 to 7.0%.     

Sequential injection analysis of lead using time-based colorimetric detection and preconcentration on an anionic-exchange resin.

The development of a sequential injection analysis manifold for the colorimetric determination of lead in water samples is described The concentration of lead was assessed from its catalytic effect on the reaction of resazurine reduction caused by sulfide in an alkali medium. To that effect, the reaction zone was stopped at the detector, and the time interval required for the attainment of an absorbance decrease of 0.800 at the wavelength of 610 nm was estimated. Interference of other transition metals of the samples was minimized by adding potassium iodide to the sample and retaining the iodocomplexes formed in an on-line anionic resin (AGI X8). Elution was made with a 2 mol/L sodium hydroxide solution. The relationship [SIA] microg/L = 0.99 (+/- 0.11) x [ETAAS] microg/L + 0 (+/- 4) was obtained upon comparing the results given by the proposed system and by electrothermal atomization atomic absorption spectrometry (ETAAS) after the analysis of ten water samples.