Spectrophotometric determination of bromate by sequential injection analysis

A simple and rapid on-line spectrophotometric method for the determination of bromate is proposed. The method is based on the reaction of bromate and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-bromo-PADAP) with SCN⁻, a red complex is formed and monitored at 550 nm. The linear range found is between 0.18 and 3.00 mg l⁻¹ with a detection limit of 0.15 mg l⁻¹. The sampling rate was calculated to be 45 samples per hour. The proposed method has a precision of less than 0.8%.     

At-line determination of formaldehyde in bioprocesses by sequential injection analysis

A sequential injection analysis (SIA) method for the at-line determination of formaldehyde in a cultivation process of Pichia pastoris is presented. A genetically modified yeast strain was used for cultivation processes wherein methanol feed induced the production of the recombinant protein 1-3del I-TAC. Recurring measurements of culture medium, its blank and including standard addition were performed with Nash reagent using an automated syringe device and photometric detection. The apparatus was coupled via a laboratory-made flow-through adapter to a continuous filtered and cell-medium flow from the bioreactor. At-line monitoring of formaldehyde was performed at two cultivations, each of 250 h during fed-batch phases with glycerol and methanol as carbon sources. High reliability, robustness and reproducibility of the method, the software and the instrumentation as well as the high selectivity of the reaction were demonstrated.     

Preconcentration and atomic absorption determination of iron by sequential injection analysis

A sequential injection analysis (SIA) assembly for the atomic absorption determination of Fe(III) in natural waters is proposed. Iron is preconcentrated on a microcolumn packed with a chelating resin (Chelex 100) that is inserted in the manifold. The sample is passed through the column and the iron retained by the resin is subsequently eluted with 2 M HNO(3). The proposed SIA system affords automatic preconcentration, elution, detection of Fe(III), data acquisition and treatment. When 9 ml of iron solution containing 0.4 or 1 mg l(-1) was passed through the resin, the retention efficiency was 93.1 +/- 0.6 and 7.4 +/- 3.0% respectively, and when 27 ml of iron solution of 0.2 mg l(-1) was preconcentrated, the retention was 8.4 +/- 2.9%. The detection limits thus achieved is 12 mug l(-1) when 9 ml of sample are preconcentrated and 6 mug l(-1) for 27 ml.     

流动注射化学发光法测定佐米曲谱坦

在碱性条件下,佐米曲谱坦对鲁米诺-K3[Fe(CN)6]化学发光体系有较强的抑制作用,据此建立了佐米曲谱坦的流动注射化学发光分析法。该法的化学发光抑制值ΔI与佐米曲谱坦质量浓度在2.0×10-6~1.2×10-4g/mL范围内,呈良好的线性关系,检出限为7.6×10-7g/mL。对2.5×10-5g/mL佐米曲谱坦测定的相对标准偏差为1.2%(n=11)。方法适用于佐米曲谱坦片中佐米曲谱坦的测定。     

流动注射化学发光法测定司帕沙星的研究

在酸性介质中,司帕沙星对NaNO2-H2O2发光体系有很强的增强作用,并且其增强化学发光强度与司帕沙星的物质的量浓度在一定范围内呈线性关系。基于此,采用流动注射技术,建立了一种简单、快速测定司帕沙星的方法。线性范围为1.0×10-7~8.5×10-4mol/L,检出限为6.5×10-8mol/L。利用该法测定了司帕沙星片剂中的司帕沙星,回收率在98.8%~104.4%之间。     

流动注射化学发光法测定那格列奈

在碱性介质中,那格列奈对Luminol-H2O2体系的化学发光有很强的抑制作用,据此建立了流动注射化学发光抑制法测定那格列奈的新方法.该法的化学发光抑制值△I与那格列奈的质量浓度在2.0×10-8～1.0×10-6 g/mL范围内,呈良好的线性关系,检出限为1.4×10-8 g/mL;对4.0×10-7 g/mL那格列奈连续进行11次平行测定,相对标准偏差为1.0%;通过对荧光光谱的研究,对机理进行了初步探讨.     

流动注射化学发光法测定氨苄西林的研究

氨苄西林在NaOH溶液中降解后,其产物可在酸性条件下与KMnO4发生化学发光反应,甲醛的存在可使发光强度增强。据此,采用流动注射技术,建立了一种测定氨苄西林的化学发光分析法。方法的检出限为9.1×10-9g/mL,相对标准偏差为1.8%(n=11,ρ=3.4×10-6g/mL),线性范围为4.0×10-8~2.0×10-5g/mL。利用该法测定了氨苄西林胶囊中的氨苄西林,其回收率在87%~106%。     

Determination of nitrite by sequential injection analysis of electrokinetic flow analysis system

A new sequential injection analysis (SIA) method of an electrokinetic flow analysis (EKFA) system for the determination of nitrite-nitrogen is presented in this paper. The proposed system mainly consisted of an electroosmotic pump, two solenoid valves and a spectrophotometer etc. All the pump and valves were controlled by a personal computer automatically. The determination method of nitrite-nitrogen was based on the reaction among nitrite, sulfanilamide and naphthylethylenediamine to form a colored compound, which was measured at 540 nm. The linear calibration range of nitrite-nitrogen was 10-800 mug l(-1). The detection limit was 1 mug l(-1) (K=3, n=11). The analytical method can provide a throughput of 33 samples per h.     

Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis.

A new catalytic spectrophotometric method is reported for the simultaneous determination of nitrite and nitrate by flow injection analysis, based on the catalytic effect of nitrite on the redox reaction between pyrogallolsulfonephthalein and potassium bromate in acidic media. Nitrate can also be on-line reduced to nitrite with a modified copper-coated cadmium reduction column. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of pyrogallolsulfonephthalein at 465 nm. Various analytical parameters such as effects of acidity, reagent concentrations, flow rates, sample sizes, lengths of the reaction coil and temperatures were studied and were optimized. Under the optimized conditions, the calibration graph was linear for 2.4 to 160 ng ml(-1) of nitrite and 4.0 to 100 ng ml(-1) of nitrate. The influences of potential interfering cations and anions for nitrite and nitrate determination were studied. The method is successfully applied for food and water samples. Up to ten samples can be analyzed per hour.     

Fluorescence determination of the pesticide asulam by flow injection analysis.

This paper presents the analytical determination of the pesticide Asulam based on its native fluorescence. The method was optimized in either a flow injection analysis (FIA) assembly or in batch. The maximum fluorescence intensity was observed for basic pH solutions and at a lamda(ex) of 258 nm and a lamda(em) of 342 nm. The influence of different empirical parameters, such as the pH, the presence of surfactants, solvent polarity or solved oxygen amount, was studied. The calibration range was fitted with a linear equation from 0.01-3 mg l(-1) Asulam and 0.005-15 mg l(-1) Asulam for batch and continuous-flow, respectively. The RSD for both procedures was 1.0%. After testing the influence of a large series of potential interferents, the method was applied to water samples from different locations.     

顺序注射催化动力学光度法测定织物和室内空气中痕量甲醛

在磷酸介质中 ,甲醛可以催化溴酸钾氧化　花青的反应使其退色 ,据此建立了顺序注射催化动力学光度法测定织物和室内空气中痕量甲醛的新方法。方法的线性范围 0 .5～ 7.0 μg mL ,检出限 0 .1 μg mL。用于树脂整理特殊织物和室内空气中痕量甲醛的测定 ,回收率在 97.0 %～ 1 0 5 .0 %之间。     

Spectrofluorimetric determination of aluminum in drinking waters by sequential injection analysis

A selective procedure for the determination of Al³⁺ in drinking and natural waters is proposed. The analytical procedure is based both on the complex formation between Al³⁺ and 8-hydroxyquinoline-5-sulfonic acid (HQS) and on a fluorimetric detection of the complex. The reaction was carried out in presence of thioglycolic acid as a masking agent. This procedure has been adapted to a sequential injection analysis (SIA) system. Operative conditions both for batch and SIA procedures were investigated including reagent concentration, volumes, pH and wavelengths used for the fluorimetric detection. Batch procedure allows determination of Al³⁺ at ppb level (LOQ: 2.8 μg l⁻¹) within a working range of 2.2-300 μg l⁻¹. The SIA procedure was successfully employed for the determination of Al³⁺ in several commercial drinking and tap waters.     

Quasi-simultaneous determination of antioxidative activities against superoxide anion and nitric oxide by a combination of sequential injection analysis and flow injection analysis with chemiluminescence detection

A method that combines sequential injection analysis (SIA), flow injection analysis and chemiluminescence (CL) detection was developed for the quasi-simultaneous determination of antioxidative activities against superoxide anion and nitric oxide (NO). The antioxidative activity was expressed as the decrease in luminol CL intensity caused by the quenching of or NO by an antioxidant. The SIA system consisted of two syringe pumps, two selection valves, two holding coils, an HPLC pump to deliver luminol solution, and a CL detector. Operation of the syringe pumps and multiport valves was controlled automatically using a personal computer with appropriate software. A hypoxanthine (HX)-xanthine oxidase (XOD) system was used for the generation of , and (±)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexenamide (NOR1) was employed as NO donor agent. The repeatability of the method was evaluated with 35.2 μg ml⁻¹ L-ascorbic acid, and the relative standard deviations (RSD) of the antioxidative activities were less than 3.8%. The quasi-simultaneous determination of the antioxidative activities in one sample was completed within 2.0 min. The antioxidative activities of some antioxidants and commercially available supplements containing certain antioxidants were successfully determined using this system. The proposed system is rapid and reproducible, and thus may be useful for the screening of functional foods, supplements and pharmaceutical formulations that exhibit antioxidative activity. Figure The system that utilizes a combination of SIA and FIA with CL for the quasi-simultaneous determination of antioxidative activity against a NO and b . SP1, 2: syringe pump, HC1, 2: holding coil, MV1, 2: multi-port valve, P: pump, D: chemiluminescence detector, I: integrator, M1, 2: mixing tee, NOR1: (±)-(E)-4-methyl-2-[(E)- hydroxyimino]-5-nitro-6-methoxy-3-hexenamide, HX: hypoxanthine, XOD: xanthine oxidase.     

Simultaneous determination of nitrate and nitrite by flow injection analysis

An automatic method for the simultaneous determination of nitrate and nitrite by flow injection analysis is described. Nitrate is reduced to nitrite with a copperized cadmium column. Nitrite is diazotized and coupled with N-(l-naphthyl)ethylenediammonium dichloride. The merging zones approach is used to minimize reagent consumption. The injector system is arranged so that two peaks are obtained, one corresponding to nitrite and the other to nitrite plus nitrate. A sampling rate of about 90 samples per hour is possible; the precision is better than 0.5% for nitrite in the range 0.1–0.5 mg l^t and 1.5% for nitrate in the range 1.0–5.0 mg l^t     

Chemiluminescence determination of bufrenorphine hydrochloride by flow injection analysis

A direct, simple and rapid flow-injection method is described for determining buprenorphine hydrochloride (10^?8–10^?4 M) based on its chemiluminescent oxidation with potassium permanganate in polyphosphoric acid. The limit of detection is 1 × 10^?8 M (0.5 pmol per injection) and the log-log calibration is linear up to 1 × 10^?4 M; the r.s.d. is 0.7% for a 10 μg ml^?1 solution (n = 10). The method is directly applicable to aqueous solutions of tablets containing the drug (0.2 mg/tablet).     

Colorimetric determination of iron in infant fortified formulas by sequential injection analysis

 A procedure is described for the colorimetric determination of iron in infant fortified formulas based on sequential injection analysis (SIA). Iron(III) complexation with thiocyanate is used as colour developing reaction. The system enables the determination of iron in the samples (after digestion by dry ashing and treatment with 0.2 mol/L nitric acid in the range of 0.50–20.0 mg/L, consuming 140 μL of the sample and 8 mg thiocyanate per determination. The reactor geometry and the adjustment of the ionic content of the calibration solutions is important for the accuracy of the results. A regression line according to the equation [Fe(III) (mg/L)]_SIA=−0.3(±0.4)+1.03(±0.04) [Fe(III) (mg/L)]_FAAS was obtained after comparative analysis of a set of 12 samples. The measurement rate was 34 s, thus allowing to analyze 100 samples per hour with a relative standard deviation lower than 2%. Received: 30 July 1996/Revised: 1 October 1996/Accepted: 4 October 1996     

Spectrophotometric determination of magnesium in pharmaceutical preparations by cost-effective sequential injection analysis

A simple and rapid, inexpensive spectrophotometric method was proposed for magnesium assay in pharmaceutical preparations by sequential injection analysis (SIA). The method is based on the reaction between o-cresolphthalein complexone (CPC) and Mg(II) in alkaline media, yielding a pink colored complex with absorption maximum at 570 nm. Since the formation constant between Ca-CPC and Mg-CPC is similar, initially a sample/standard solution was aspirated into the holding coil followed by a mixture of masking-buffer solutions. This was done because masking of calcium should be accomplished before Mg-CPC complexation. Then the reagent was introduced into the reaction coil to produce a colored complex, which is measured spectrophotometrically at 570 nm. In this way the interference of calcium was reduced. Furthermore, all the parameters that affect the reaction were evaluated. The calibration curve is linear over a range of 0-20 mg l⁻¹ of Mg(II) with a detection limit of 0.24 mg l⁻¹. A sample throughput of 80 samples per hour and relative standard deviation <2.0% were achieved. The proposed method was successfully applied for the assay of magnesium in three different compositions of pharmaceutical preparations (tablets). The results were found to be in good agreement with the manual flame atomic absorption spectrophotometry (FAAS) and UV-Vis spectrophotometry methods and with the claimed values by the manufactures. The t-test shows no significant difference at 95% confidence level.     

Sensitive determination of indomethacin in pharmaceuticals and urine by sequential injection analysis and optosensing

A selective and sensitive method based on coupling of sequential injection analysis (SIA) and optosensing was developed and applied to the determination of indomethacin in pharmaceutical and urinary samples. After alkaline hydrolysis, the fluorescent product generated from indomethacin is inserted in the flow system, transitorily retained on an active solid support (Sephadex QAE A-25) filling the flowcell, and monitored at 283/371 nm (lamda ex / lamda em). The system was calibrated for two sample volumes, 100 and 1000 microL. It showed a linear dynamic range of 0.5-6.5 ng/mL, with an LOD of 0.15 ng/mL and an RSD of 3.9% (n=10) when the highest sample volume was used. The proposed fluorometric SIA optosensor was applied to the determination of indomethacin in both pharmaceuticals and urine samples, and satisfactory results were obtained.     

Differential kinetic determination of furfural and vanillin by flow injection analysis

A photometric method for simultaneous determination of furfural and vanillin based on the different reaction rate of these compounds with p-aminophenol is proposed. The linear range of determination is 0.5–6.0 μg/ml for the individual determination and 0.5–4.0 μg/ml for the simultaneous one, with an r.s.d. of ± 1.9 and ± 0.2% for furfural and vanillin, respectively, in the most unfavorable case. The presence of organic compounds, such as other aldehydes, acids, ketones, etc., is well tolerated. The resolution of mixtures of these analytes has been carried out with good results.