A Kalman filter for calibration,evaluation of unknown samples and quality control in drifting systems : Part 4. Flow Injection Analysis

The application of state estimation in flow injection analysis is described. The linear calibration graphs normally provided often suffer from drifting parameters. The entire system is absed on a set of algorithms for prediction, filtering, smoothing, evaluation, control and optimization. Selection and verification of the calibration model and the noise covariances used are investigated. The experimental results demonstrate the applicability of the calibration system in practice as a simple intelligent analyzer. The spectrophotometric determination of chloride in aqueous samples serves as the example.     

Highly sensitive chemiluminescence flow sensor for ascorbic acid

A highly sensitive chemiluminescence(CL) flow sensor is proposed for the determination of ascorbic acid. The analytical reagents luminol and iron(II) are immobilized on anion-exchange and cation-exchange resins, respectively, and can be eluted by sodium sulphate. The calibration graphs are linear in the range 1 × 10^–9 to 1 × 10^–6 g mL^–1 and the detection limit is 4.0 × 10^–10 g mL^–1. The sensor has been applied successfully to the determination of ascorbic acid in vegetables.     

Linear calibration in ion chromatography by calculating total amounts of sample from measured conductivity data

Calibration graphs in ion chromatography are generally not linear, if a suppressor column and a conductivity detector are employed. The main reason for this is that the dissociation equilibrium of the eluent (which is a weak acid after eluent suppression) is shifted by H⁺ ions from the sample, which are formed in the suppressor column. Therefore a formula is derived in which the suppression of the eluent dissociation by the sample is considered. Application of this formula for chloride, nitrate and sulphate samples in succinate and carbonate eluents results in linear calibration graphs in the range 0–40 mg l^? when peak areas are used.     

Spectrophotometric determination of catecholamines with metaperiodate by flow-injection analysis

A flow-injection Spectrophotometric method for the determination of adrenaline and isoprenaline, based on the reaction with metaperiodate, is described. The calibration graphs are linear up to 2 × 10⁻⁴ M. Flow injection allows the measurement of 120 samples per hour. The method was successfully applied to the determination of both catecholamines in pharmaceuticals.     

Flow injection fluorimetric determination of thiamine and copper based on the formation of thiochrome

The reaction, involving the oxidation of thiamine by copper(II) in basic solutions to fluorescent thiochrome, has been adapted to the determination of thiamine by flow-injection analysis. Linear calibration graphs are obtained between 0.30 and 6.02 mug/ml with a sampling rate of 50 samples/hr and a relative standard deviation of 0.53%. This reaction has also been adapted to the determination of copper(II) over the range 0.5-5.0 mug/ml. The applicability of both methods for determination of thiamine and copper is demonstrated by investigating the effect of potential interferences and by the analysis of real samples (pharmaceuticals for thiamine and ores and alloys for copper).     

Solvent effect on the determination of sulfamethazine by room-temperature photochemically induced fluorescence

Room-temperature photochemically-induced fluorescence (RTPF) was applied to the determination of sulfamethazine (SMT) in methanol, ethanol and 2-propanol. Optimal ultraviolet irradiation times ranged between 2 and 6 min. Linear calibration graphs were obtained over a concentration range of more than one order of magnitude. The relative standard deviations were within the range 1.4-2.2%. Limits of detection were between 40 and 80 ng/ml. The method was evaluated for its applicability to the analysis of SMT in pharmaceutical formulations.     

Non-aqueous fluorimetric determination of scandium in silicate rocks

A method for the fluorimetric determination of scandium with 1,2,7-trihydroxyanthraquinone in dimethylformamide medium is described. The calibration graphs obtained by the normal, synchronous, and synchronous first and second derivative techniques are linear between 12 and 225 ng/ml, and the detection limit is 2 ng/ml. The method is applied to the determination of Sc(III) in two simulated and two naturally occurring rocks.     

乙醇敏化钛黄与蛋白质作用的共振光散射光谱研究及其分析应用

研究了在乙醇存在下钛黄（TY）与蛋白质作用的共振光散射（RLS）光谱特征 。基于RLS的增强,建立了一种测定蛋白质的新方法。考察了各种影响因素,在优 化条件下确定了RLS强度与蛋白质浓度之间的关系。当TY浓度为4 * 10~(-5)mol· L~(-1)时,牛血清白蛋白（BSA）、人血清白蛋白（HSA）和溶菌酶(lysozyme)的线 性响应范围分别为0.1～6.0 μg·mL~(-1), 0.1～5.0 μg·mL~(-1), 0.2～3.0 μg·mL~(-1),检出限分别为12.7 ng·mL~(-1), 11.6 ng·mL~(-1)和18.8 ng· mL~(-1)。三种合成样品五次平行测定的回收率和相对标准偏差（RSD）分别为96. 0%～102.3%和0.8%～3.2%。将该方法与经典的Bradford方法分别用于人血清试样中 蛋白的测定,两种方法的分析结果经F-检验和双总体T-检验证明无显著性差异。     

Flow-Injection Fluorometric Determination of Novalgin in Pharmaceutical Preparations

A flow-injection configuration for the fluorometric determination of Novalgin (dipyrone) is proposed. The procedure is based on the oxidation of Novalgin by cerium(IV). The fluorescence native of cerium(III) formed in the oxidation of Novalgin is monitored. Lineal calibration graphs were obtained between 0.5 and 4 μg/ml, with a sampling rate of 40 samples/h and relative standard deviations between 0.93 and 2.8%. The applicability of the method to the determination of Novalgin in pharmaceutical preparations was demonstrated by investigating the effect of potential interferences and by analysis of commercial preparations.     

Monoparameter sensors for the determination of the antioxidants butylated hydroxyanisole and n-propyl gallate in foods and cosmetics by flow injection spectrophotometry.

A flow-through optosensor with solid phase UV spectroscopic detection is proposed for the direct determination of single antioxidants, namely butylated hydroxyanisole (BHA) and n-propyl gallate (n-PG), without previous derivatization. The methods are based on the transient retention behaviour of these compounds in a flow-through cell packed with C-18 silica using ethanol-water mixtures as a carrier, and on the intrinsic absorbance monitored at 290 and 283 nm, respectively. After recording the analytical signal, the antioxidants were easily and quickly desorbed from the solid support by the same carrier. For BHA, calibration graphs were linear over the range 1.0-300.0 mg L-1 using area as the analytical parameter. The relative standard deviation (RSD) was between 0.5 and 1.6%. For n-PG, calibration graphs were linear over the range 1.0-300.0 mg L-1 in area and the RSD was between 1.4 and 1.5%. The methods were applied to the determination of these antioxidants in several food and cosmetics samples, and were validated using the standard additions method and an HPLC reference method.     

Flow-injection successive determination of cysteine and cystine in pharmaceutical preparations

A flow-injection configuration is proposed for the individual determination of cysteine and cystine and for the mixtures of both analytes. The procedure is based on the inhibitory effect of cysteine on the oxidation of thiamine to thiochrome by mercury(II). Linear calibration graphs were obtained between 1.0 x 10(-5) and 1.0 x 10(-4)M, with a sampling rate of 22 samples/hr and relative standard deviation of 1.14%. The inclusion of a selecting valve in the configuration, to pump water or hydroxylamine, allows the successive determination of these two analytes. The applicability of the method to the determination of cysteine and cystine in pharmaceutical preparations was demonstrated by investigating the effect of potential interferences and by the analysis of commercial preparations.     

Resolution of mixtures of three nonsteroidal anti-inflammatory drugs by fluorescence using partial least squares multivariate calibration with previous wavelength selection by Kohonen artificial neural networks

A spectrofluorometric method for the quantitative determination of flufenamic, mefenamic and meclofenamic acids in mixtures has been developed by recording emission fluorescence spectra between 370 and 550 nm with an excitation wavelength of 352 nm. The excitation–emission spectra of these compounds are deeply overlapped which does not allow their direct determination without previous separation. The proposed method applies partial least squares (PLS) multivariate calibration to the resolution of this mixture using a set of wavelengths previously selected by Kohonen artificial neural networks (K-ANN). The linear calibration graphs used to construct the calibration matrix were selected in the ranges from 0.25 to 1.00 μg ml⁻¹ for flufenamic and meclofenamic acids, and from 1.00 to 4.00 μg ml⁻¹ for mefenamic acid. A cross-validation procedure was used to select the number of factors. The selected calibration model has been applied to the determination of these compounds in synthetic mixtures and pharmaceutical formulations.     

Determination of zinc in foods by fluorescence spectroscopy in micellar media

The effect of cationic [cetyltrimethylammonium bromide (CTAB), Zephiramine], non-ionic (Triton X-100, Brij-35) and anionic (sodium lauryl sulphate) surfactant micelles on the fluorescence intensity of the zinc 5,7-dichloro-2-methylquinolin-8-ol chelate is described. In Brij-35 or CTAB micellar media, the fluorescence is about 25 times greater than that obtained in ethanol-water. The relationship between fluorescence intensity and experimental variables was studied in order to develop a procedure for the fluorimetric determination of zinc. Linear calibration graphs were obtained in the ranges 3–100 and 50–400 ng Zn ml^?1. The detection limit is 3 ng ml^?1. The method was successfully applied to the determination of zinc in food samples and drinking waters.     

高效液相色谱法测定铝酸钠溶液中的有机酸

建立了铝酸钠溶液中有机酸的高效液相色谱测定方法。铝酸钠溶液样品经简单处理后,在Kromasil C18色谱柱上,以KH2PO4-H3PO4-甲醇-水为多元流动相,等度洗脱,在10 min内可完成草酸、酒石酸、乙酸、丁二酸、丁烯二酸和戊二酸等有机酸的分离测定。方法线性关系良好（r=0.9952-0.9999）,样品加标回收率在80.2%-127.6%之间,相对标准偏差均在6.9%以下。     

Spectrophotometric determination of sulphate in sodium hydroxide solutions by flow-injection analysis

A spectrophotometric flow-injection procedure is described for the determination of sulphate in sodium hydroxide solutions. Sulphate catalyses the reaction between zirconium and methylthymol blue to form a complex measured at 586 nm. Optimal reaction conditions are discussed. The calibration graph is linear over the range 0.05–0.5 g l^?1 sulphate with a relative standard deviation of 0.02. The sample throughput is 20 h^?1. Sulphate is easily determined in 1 M sodium hydroxide; the results agree with those obtained by the conventional gravimetric method and by ion chromatography.     

Flow-injection fluorimetric determination of trimeprazine and trifluoperazine in pharmaceutical preparations

A flow-injection configuration for the fluorimetric determination of trimeprazine and trifluoperazine is proposed. The procedure is based on oxidation of the drugs by cerium(IV). The fluorescence of cerium(III) formed in the oxidation of trimeprazine or trifluoperazine is monitored. Lineal calibration graphs were obtained between 2 x 10(-7) and 1 x 10(-5)M for both trimeprazine and trifluoperazine with a sampling rate of 60 samples/hr. The relative standard deviations were over the ranges 0.78-1.16 and 0.84-0.97% for trimeprazine and trifluoperazine respectively. The applicability of the method to determination of trimeprazine and trifluoperazine was demonstrated by investigating the effect of potential interferences and by analysis of commercial pharmaceutical preparations.     

Spectrofluorimetric flow injection method for the individual and successive determination of L-cysteine and L-cystine in pharmaceutical and urine samples.

A flow injection configuration is proposed for the determination of L-cysteine and L-cystine individually and for mixtures of both analytes. The procedure is based on the rapid oxidation of L-cysteine by thallium(III) with concomitant formation of fluorescent thallium(I). The inclusion of a selecting valve and of a copper-coated cadmium column in the configuration allows the successive determination of two analytes. Linear calibration graphs were obtained between 5 x 10(-6) and 5 x 10(-5) mol dm-3 of L-cysteine and between 2 x 10(-6) and 2 x 10(-5) mol dm-3 of L-cystine. The applicability of the method to the determination of L-cysteine and L-cystine in pharmaceutical preparations was demonstrated by investigating the effect of potential interferents and by the analysis of commercial preparations. The method was successfully applied to the determination of L-cysteine and L-cystine in urine samples.     

Capillary electrophoresis determinations of trace concentrations of inorganic ions in large excess of chloride: soft modelling using artificial neural networks for optimisation of electrolyte composition

In this work, using a combination of experimental design (ED) and artificial neural networks (ANN), the composition of a triethanolamine-buffered chromate electrolyte was optimised for determination of sulphate anions in the presence of high chloride excess. The optimal electrolyte, allowing a baseline-resolved separation of sulphate from chloride present in a 1500 multiple excess in less than 170 s, consists of 10 mmol/L CrO(3), 2 mmol/L hexamethonium hydroxide, 10% methanol, and triethanolamine added to adjust the pH to 8.0. The method is suitable to a wide concentration range of chloride (4-1757 mg/L) and sulphate (4-590 mg/L) with linear calibration plots (R(2) = 0.9937-0.9999). Relative standard deviations are less than 2.0% for both anions for migration times and peak areas. The detection limits (hydrodynamic injection of 1 s) were 0.6 mg/L for sulphate and 0.5 mg/L for chloride. The method was successfully applied to determination of sulphate in mineral waters containing a high chloride concentration and to determination of sulphate traces in an anticancer drug injection preparation containing a physiological level of chloride. It was shown that alpha-cyclodextrin as an electrolyte additive has a significant potential for further increasing the separation selectivity for inorganic anions.     

Spectrophotometric and fluorimetric determination of nomifensine maleate

Three methods have been developed for the determination of nomifensine maleate alone and in capsules: a spectrophotometric, an iodine charge-transfer, and a spectrofluorimetric method. All three give linear calibration graphs, over the ranges 20-100, 1-5 and 0.1-0.5 microg/ml, respectively, with coefficients of variation of 0.8, 1.3 and 1.3%, respectively.     

Simultaneous spectrophotometric determination of nitroaniline isomers after cloud point extraction by using least-squares support vector machines

Cloud point extraction has been used for the preconcentration of m-nitroaniline, o-nitroaniline and p-nitroaniline and later simultaneous spectrophotometric determination using polyethylene glycol tert-octylphenyl ether (Triton X-100) as surfactant. The resolution of a ternary mixture of the nitroaniline isomers (after extraction by cloud point) by the application of least-squares support vector machines (LS-SVM) was performed. The chemical parameters affecting the separation phase and detection process were studied and optimized. Under the optimum experimental conditions (i.e. pH 7.0, Triton X-100=0.6%, equilibrium time 20 min and cloud point 75 degrees C), calibration graphs were linear in the range of 0.2-20.0, 0.1-15.0 and 0.1-17.0 microg ml(-1) with detection limits of 0.08, 0.05 and 0.06 microg ml(-1) for m-nitroaniline, o-nitroaniline and p-nitroaniline, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graphs concentrations of nitroaniline isomers. The root mean square error of prediction (RMSEP) for m-nitroaniline, o-nitroaniline and p-nitroaniline were 0.0146, 0.0308 and 0.0304, respectively. This procedure allows the simultaneous determination of nitroaniline isomers in synthetic and real matrix samples good reliability of the determination was proved.