Automatic flow procedure for the determination of glycerol in wine using enzymatic reaction and spectrophotometry

An automatic flow procedure for the determination of glycerol in wines by employing a flow system based on multicommutation and enzymatic reaction is described. Glycerol dehydrogenase was immobilized on aminopropyl glass beads and packed into a column that was coupled to the flow system. The NADH produced by the enzymatic reaction was monitored by spectrophotometry at 340 nm and its radiation absorption presented a relationship with glycerol concentration. The system manifold comprised a set of three-way solenoid valves controlled by a microcomputer, which was furnished with electronic interfaces and runs a software that was designed to carry out on-line sample dilution, reagent addition, and data acquisition. The procedure allows the determination of glycerol in wine samples without any prior pretreatment. The procedure presented as profitable features a linear response range between 2.0 and 10.0 g l⁻¹ glycerol (R=0.998), a detection limit of 0.006 g l⁻¹ glycerol, a relative standard deviation of 1.8% (n=14) for a typical wine sample presenting 5.3 g l⁻¹ glycerol, a sampling throughput of 33 determinations per hour, and a NAD⁺ consumption of 0.8 mg per determination. The results were compared with those obtained using a reference method and no significant difference at 90% confidence level was observed.     

Sequential injection system for the spectrophotometric determination of reducing sugars in wines

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described. The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with 2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the interference of some coloured compounds. In this way, direct sample introduction into the system was possible, without any previous treatment of the wine samples. The proposed method can be applied to the determination of reducing sugars in two concentration ranges: from 2 to 25 g l(-1) (table wines) and from 20 to 140 g l(-1) (Port wines). To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational parameters were changed in the controlling software. A sampling-rate of 14-18 samples per hour was obtained with good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) <2.1%). The results obtained from 19 wine samples were comparable to those obtained by the reference method.     

Selective determination of arsenite by flow injection spectrophotometry

This paper describes the application of the well-known Molybdenum Blue method for selective determination of arsenite in a flow injection system. Selectivity is achieved by on-line separation of the main interferents phosphate, arsenate and silicate using a strong anion-exchange microcolumn located in the aspiration line of injection valve. Arsenite passing through the microcolumn unretained is determined using Molybdenum Blue method following in-line oxidation to arsenate by permanganate. A thorough investigation of optimal experimental conditions for both, the separation of interferents and sensitive detection of arsenite is presented. The method developed permits arsenite to be determined in the concentration range 5-500 microg/l with high precision and reliability. A sample throughput of 20 hr(-1) is achieved. Phosphate, arsenate and silicate do not interfere at concentration levels significantly higher than that of arsenite. The application to real water samples reveals excellent recovery of spiked samples and the absence of matrix interferences.     

Flow injection spectrophotometric determination of reducing sugars using a focalized coiled reactor in a domestic microwave oven

A flow injection (FI) spectrophotometric procedure for determining reducing sugars content in sugar cane juices using a focalized PTFE coiled reactor positioned at the output antenna of a domestic microwave oven at 700 W is proposed. In this system, sample solution converge to 1.0 mol l(-1) NaOH and 5.2 mmol l(-1) K(3)Fe(CN)(6) solutions previously mixed and the decrease of hexacyanoferrate(III) concentration was monitored at 420 nm. Under best analytical conditions, there was a direct relationship between absorbance decrease and reducing sugar content (fructose plus glucose concentrations) in the concentration range from 50 to 1200 micromol l(-1) with a detection limit of 15 micromol l(-1). The relative standard deviations (rds) were less than 1.4% for ten injection of 400 and 800 micromol l(-1) fructose solution and the analytical frequency was 70 h(-1). A paired t-test showed that all results obtained for sugar cane juices using this FI procedure and the Somogyi-Nelson batch procedure agree at the 95% confidence level.     

流动注射催化光度法测定微量Sb(Ⅲ)

基于在B-R缓冲溶液介质中,Sb(Ⅲ)对H2O2氧化孔雀石绿褪色反应具有催化作用,建立了流动注射催化动力学光度法测定微量元素Sb(Ⅲ)的新分析方法,该方法的线性范围为0.010～2.0μg/mL,检出限为7.8×10-3μg/mL,r=0.9996。对0.1μg/mL Sb(Ⅲ)测定的RSD=0.97%n=11,进样频率为22.8次/h。用于环境水样中微量Sb(Ⅲ)的测定,回收率为97.3%～97.7%。     

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...     

The determination of trace lead in drinking water by flow injection spectrophotometry

Lead is the non-essential trace element in the human body, and it has been confirmed that drinking water is one of the sources of lead in human body. In the research, based on the sensitive colour reaction of lead with I^?–EV⁺–PVA, a simple, sensitive, accurate and portable method for the determination of trace lead in drinking waters was proposed. Chemicals and physicals had been optimized in detail. The apparent molar absorption coefficient was up to 7.4 × 10⁵ mol L^?1 cm^?1. The developed method provided a linearity range over 5–80 μg L^?1. The regression deviation was between 0.71% and 2.33%. The 3σ detection limit was 0.9 μg L^?1. Close to the quantitation limit for the analyte the relative standard deviation was 1.10% (n = 10) at 40 μg L^?1. The method developed here for analysis of lead yielded results that were comparable with those of the GFAAS.     

基于不稳定反应的流动注射催化光度法测定铁

近年来,由于含铁水处理剂的广泛应用,水体中铁含量逐渐增高.含铁量高的水在管道内易生长铁细菌,增加水的浑浊度,使水产生特殊的色、嗅、味,易污染衣物、器皿,影响某些工业产品的质量.因此,研究准确快速测定水中铁的分析方法具有重要意义.     

Two-step solvent extraction flow injection system for the determination of anionic surfactants by spectrophotometry

 An automated flow injection procedure for the determination of anionic surfactants with two-step extraction was developed, based on the official methylene blue method. A washing step was used for on-line treatment of the extracted products with methylene blue to eliminate interferences. An improved gravitational phase separator was used to overcome the limitations of the membrane separator, and an effective separation of the two phases was performed by gravity separation in a conical cavity constructed of PTFE and stainless steel. Use of PTFE pump tubing allowed reliable and reproducible withdrawal and propulsion of organic extractant at low flow-rates. The calibration graphs were linear up to 6.0 mg/l of sodium dodecyl sulfonate in aqueous solution when 100 μl of sample was injected, a relative standard deviation of 4.6% (n=7) was achieved. The recoveries of the procedure were in the range of 89–107%. The results obtained for anionic surfactants in waste water samples agreed well with those obtained by the standard methylene blue batch method. Received: 1 December 1995/Revised: 1 April 1996/Accepted: 9 April 1996     

停留-反相流动注射阻抑光度法测定超痕量铋(Ⅲ)

基于在B-R缓冲溶液介质中,Bi(Ⅲ)对H2O2氧化孔雀石绿(MG)褪色反应的显著阻抑作用,建立了一种停留-反相流动注射阻抑光度法测定超痕量Bi(Ⅲ)的新分析方法,该方法的线性范围为0.001～0.54 ng/L,检出限为9.9×10-4ng/L,相关系数为0.9992。对0.001 ng/LBi(Ⅲ)平行测定11次的标准偏差为1.3%,进样频率为20.9次/h。该方法可直接用于人发和水中的超痕量Bi(Ⅲ)的测定,回收率为96.0%～102.0%。     

Comparison of a DS-horizontal chamber and a new Smin chamber in TLC separation

The chromatographic characteristics of a popular DS-horizontal chamber (Chromdes, Poland) and an S_min chamber with a minimum gas volume (Institute of Petrochemical Synthesis of the Russian Academy of Sciences) have been experimentally evaluated.     

o-Dianisidine: a new reagent for selective spectrophotometric, flow injection determination of chlorine.

A flow injection analysis (FIA) procedure for the determination of free chlorine in industrial formulations and water samples is proposed. The manifold is provided with a gas-diffusion unit which permits the removal of interfering species and also the preconcentration of chlorine. The determination of chlorine is performed on the basis of the oxidation by o-dianisidine as a chromogenic reagent to a coloured product which can be monitored at 445 nm. The method (for a preconcentration step of 60 s) is linear over the range 0.04-1.00 mg l(-1) of chlorine, the limit of detection is 0.04 mg l(-1), the reproducibility of the procedure (as RSD of the slope) is 3.7% for a series of four independent calibrations, the precision (as RSD of a series of 30 continuous FIA peaks of 0.56 mg l(-1) of chlorine) is 1.4% and the sample throughput is 40 h(-1). A detailed comparative study of the analytical characteristics of a single mono-channel reverse FIA assembly and the same system but provided with a Fluoropore membrane filter of 0.5 microm pore size was performed to check the advantages of the new approach in terms of sensitivity, selectivity and limit of detection.     

Rapid determination of protein in plant material by flow injection spectrophotometry with trinitrobenzenesulfonic acid

The rapid determination of protein in plant material based on spectrophotometric determination of amino acids in protein hydrolysates with trinitrobenzenesulfonic acid has been adapted to flow injection analysis. With the manifold described, a routine sampling rate of 120 samples/h is possible, though this, as well as sensitivity, can easily be varied. The method was calibrated against the Kjeldahl method and a good correlation was obtained between the two methods over a wide range of protein values for beans.     

Focussed microwave-assisted sample preparation: total phenol determination in petroleum refinery effluents by flow injection spectrophotometry

This paper reports the development of a new approach for total phenol distillation using a focussed microwave oven, aiming its determination in petroleum refinery effluents and sour waters. In the procedure, 25 ml of sample is distilled during 15 min at 210 W power. At these conditions, recoveries as high as 95% are obtained, making possible the determination of total phenol in the samples without any interference and in a time significantly lower than that required by the reference method. In the course of the research, the influence of the distilled volume was investigated and a Doehlert matrix was employed for the multivariate optimization of the irradiation power and time. Quantification of phenol was spectrophotometrically performed in a FIA system, exploring classical reaction of phenol with 4-amineantipyrine and ferricyanide. Aqueous standards solutions of phenol could be directly injected in the FIA system for calibration purposes, making the procedure very simple and low time-consuming. A detection limit of 10 μg l⁻¹ was achieved as well as a quantification limit of 33 μg l⁻¹, becoming the procedure very suitable to be applied in the control of total phenols in effluents from petroleum industry.     

Fast microwave-assisted free sugars washing and hydrolysis pre-treatment for the flow injection determination of starch in food

The approach used consists of a flow injection (FI) manifold assisted by a focused microwave digestor for both fast washing of free sugars and acceleration of the hydrolysis step prior to the determination of starch in food. The action of microwaves reduces both the times for removal of free sugars to a 5 min single washing cycle with ethanol/water and that of the subsequent starch hydrolysis to a 10 min step. The sugars formed in the starch hydrolysis are in-line derivatised and photometrically monitored at λ=460 nm. In this way, automation of pre-treatment and determination is achieved with the minimum of both cost and time. The precision of the overall method, expressed as relative standard deviation, is 3.75% and the total analysis time is 38 min. Comparison of the results, obtained in applying the method to flour and bread, is in agreement with those provided by the manual method.     

Titrimetric semimicro determination of reducing sugars in wines and liquors

Summary A semimicro modification of the method ofFehling-Causse-Bonnams is described for the determination of invert sugar in wines and liquors. A relative standard deviation of 4 parts per thousand is obtained by closely adhering to a standardized procedure which is also required for the attainment of accuracy.

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Zusammenfassung Ein Halbmikroverfahren der Methode vonFehling-Causse-Bonnams wird für die Bestimmung von Invertzucker in Wein und Likören beschrieben. Der relative mittlere Fehler konnte durch Konstanthaltung der Versuchsbedingungen auf 0,4% beschränkt werden, eine Maßregel, die für die Erzielung richtiger Ergebnisse erforderlich ist. Die zur Entfärbung verwendete Pflanzenkohle adsorbiert auch etwa 2% des reduzierenden Zuckers pro 50 mg Kohle und der dadurch bedingte Korrektionsfaktor muß durch Kontrollanalysen mit Invertzuckerlösungen bekannten Gehaltes für jede Kohlesorte bestimmt werden.

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Résumé On décrit un procédé semi-micro pour la méthode deFehling-Causse-Bonnams pour le dosage du sucre interverti dans le vin et les liqueurs. L'erreur relative moyenne a pu être limitée à 0,4% par maintien constant des conditions de l'expérience; cette mesure est nécessaire pour l'obtention de résultats corrects. Le charbon végétal utilisé pour décolorer adsorbe environ 2% de sucre réducteur pour 50 mg de charbon et le facteur de correction qui en résulte doit, dans les analyses de contrôle, être déterminé pour chaque qualité de charbon avec des solutions de sucre interverti de teneur connue.

     

Rapid flow injection method for the determination of sulfite in wine using the permanganate-luminol luminescence system

A simple, rapid and sensitive chemiluminescence method for the determination of sulfite has been developed by combining flow-injection analysis and its sensitizing effect on the known chemiluminescence emission produced by the oxidation of luminol in alkaline medium; in this work permanganate has been proposed as oxidizing reactive. The optimum conditions for the chemiluminescence emission were established. The chemiluminescence was proportional to the sulfite concentration over the range 1.6 × 10⁻⁵ and 4.0 × 10⁻⁴ mol L⁻¹. The detection limit was 4.7 × 10⁻⁶ mol L⁻¹ of sulfite. The method has been satisfactorily used for the determination of free and bound sulfite in wines.     

Continuous-flow determination of reducing sugars in serum by reaction with periodate ions,with use of a flow-through periodate-sensitive electrode

A continuous-flow method for the determination of reducing sugars in serum is described. The sample reacts with an excess of periodate in a flow system and the decrease in periodate

activity is monitored with a periodate-sensitive flow-through electrode. The recorded potential peak heights are indirectly linearly related to the reducing sugar concentration expressed as glucose, in the range 50–290 mg/100 ml. The analysis is completely automated and requires no sample pretreatment, and samples can be analyzed at the rate of 30 per hour with average errors and relative standard deviation of about 1–2%. Comparison with an enzymatic method for serum gave satisfactory results.     

An automatic flow injection analysis procedure for photometric determination of ethanol in red wine without using a chromogenic reagent

An automatic reagentless photometric procedure for the determination of ethanol in red wine is described. The procedure was based on a falling drop system that was implemented by employing a flow injection analysis manifold. The detection system comprised an infrared LED and a phototransistor. The experimental arrangement was designed to ensure that the wine drop grew between these devices, thus causing a decrease in the intensity of the radiation beam coming from the LED. Since ethanol content affected the size of the wine drop this feature was exploited to develop an analytical procedure for the photometric determination of ethanol in red wine without using a chromogenic reagent. In an attempt to prove the usefulness of the proposed procedure, a set of red wines were analysed. No significant difference between our results and those obtained with a reference method was observed at the 95% confidence level. Other advantages of our method were a linear response ranging from 0.17 up to 5.14 mol L⁻¹ (1.0 up to 30.0%) ethanol (R=0.999); a limit of detection of 0.05 mol L⁻¹ (0.3%) ethanol; a relative standard deviation of 2.5% (n=10) using typical wine sample containing 2.14 mol L⁻¹ (12.5%) ethanol; and a sampling rate of 50 determinations per hour.