用分光光度法连续测定血清中微量铜、锌的研究

研究了在ＴｒｉｔｏｎＸ－１００存在下,在ＰＨ８．０的乙醇介质中,用５－Ｂｒ－ＰＡＤＡＰ作为显色剂,应用分光光度法连续测定血清中的铜,锌。本法具有较高的灵敏度,Ｃｕ＾２＋－５－Ｂｒ－ＰＡＤＡＰ的ε为８．５０＊１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１,Ｚｎ＾２＋－５－Ｂｒ－ＰＡＤＡＰ的ε为９．６５＊１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１。铜线性范围为０－０．４５ｍｇ．Ｌ＾－１,锌线性范围为０－０．４０ｍｇ．     

Development of a differential pulse voltammetric method for the determination of Silymarin/Vitamin E acetate mixture in pharmaceuticals

Differential pulse voltammetric method was developed for determination of Silymarin (SMR)/Vitamin E acetate (VEA) mixture in pharmaceuticals. SMR and VE gave well-resolved diffusion-controlled anodic peaks at +756 and +444mV, respectively (versus Ag/AgCl) in Britton-Robinson buffer at pH 2.8. The solution conditions and instrumental parameters were optimized for their quantitative determination. The linear response was obtained in the range 0.1-4.0mgL(-1) with a detection limit of 0.03mgL(-1) for SMR and 0.05-4.0mgL(-1) with a detection limit of 0.01mgL(-1)for VEA.     

Investigating chemical constraints to the measurement of phosphorus in soils using diffusive gradients in thin films (DGT) and resin methods

The effect of potential chemical constraints on the performance of two relatively new soil P testing methods, anion exchange membrane (AEM) and diffusive gradients in thin films (DGT), were evaluated. Exposures to ranges of anion (Cl(-), NO(3)(-), SO(4)(2-) and HCO(3)(-)) concentrations relevant to agricultural soils had minimal effect on P recoveries using DGT. It has also been shown previously that DGT P recoveries are unaffected by varying pH (3-9). In contrast, increasing NO(3)(-) and SO(4)(2-) concentrations in solution reduced the recovery of P using the resin method (anion exchange membrane, AEM) by 24% at 50mgL(-1) NO(3)(-) and by 47% at 12mgL(-1) SO(4)(2-) when the P concentration of the test solution was 2mgL(-1). Phosphorus sorption by the resin decreased with increasing Cl(-) concentrations until there was a 100% decrease at 300mgL(-1) Cl(-) when the P concentration of the test solution was 2mgL(-1) and a 92% reduction at 700mgL(-1) Cl(-) when the P concentration of the test solution was 0.2mgL(-1). There was also a small but significant effect of carbonate species on P sorption to the resin at carbonate concentrations that can occur in agricultural soils. Changing the pH of the solution had minimal effects on the resin P measurements in solutions above pH 4, but below pH 4, resin P measurements decreased dramatically. A poor coefficient of determination for the regression fit between DGT and resin measurements on eight agricultural soils suggested that these two methods are measuring different amounts of P for different soils. Resin P measurements increased significantly, but non-uniformly across soils, when the soil:water ratio was decreased but this did not result in an improved relationship with DGT P. There was a minimal effect on measured P using either Cl(-) or HCO(3)(-) as counter ions on the resin.     

Simultaneous determination of vitamin B12 and its derivatives using some of multivariate calibration 1 (MVC1) techniques

Resolution of binary mixtures of vitamin B12, methylcobalamin and B12 coenzyme with minimum sample pre-treatment and without analyte separation has been successfully achieved by methods of partial least squares algorithm with one dependent variable (PLS1), orthogonal signal correction/partial least squares (OSC/PLS), principal component regression (PCR) and hybrid linear analysis (HLA). Data of analysis were obtained from UV-vis spectra. The UV-vis spectra of the vitamin B12, methylcobalamin and B12 coenzyme were recorded in the same spectral conditions. The method of central composite design was used in the ranges of 10-80mgL(-1) for vitamin B12 and methylcobalamin and 20-130mgL(-1) for B12 coenzyme. The models refinement procedure and validation were performed by cross-validation. The minimum root mean square error of prediction (RMSEP) was 2.26mgL(-1) for vitamin B12 with PLS1, 1.33mgL(-1) for methylcobalamin with OSC/PLS and 3.24mgL(-1) for B12 coenzyme with HLA techniques. Figures of merit such as selectivity, sensitivity, analytical sensitivity and LOD were determined for three compounds. The procedure was successfully applied to simultaneous determination of three compounds in synthetic mixtures and in a pharmaceutical formulation.     

Direct determination of iron and manganese in wine using the reference element technique and fast sequential multi-element flame atomic absorption spectrometry

A procedure is proposed for the direct determination of manganese and iron in wine employing fast sequential flame atomic absorption spectrometry and the reference element technique to correct for matrix effects. Cobalt, silver, nickel and indium have been tested as reference elements. The results demonstrated that cobalt and indium at a concentration of 2 and 10mgL(-1) were efficient for quantification of manganese and iron, respectively. Under these conditions, manganese and iron could be determined with quantification limits of 27 and 40microg L(-1), respectively. The proposed method was applied to the determination of manganese and iron in 16 wine samples. The content of manganese varied from 0.78 to 2.89mgL(-1) and that of iron from 0.88 to 9.22mgL(-1). The analytical results were compared with those obtained by inductively coupled plasma optical emission spectrometry after complete mineralization using acid digestion. The statistical comparison by a t-test (95% confidence level) showed no significant difference between the results.     

Determination of sorbate and benzoate in beverage samples by capillary electrophoresis-Optimization of the method with inspection of ionic mobilities

The aim of this study was to develop a fast capillary electrophoresis method for the determination of benzoate and sorbate ions in commercial beverages. In the method development the pH and constituents of the background electrolyte were selected using the effective mobility versus pH curves. As the high resolution obtained experimentally for sorbate and benzoate in the studies presented in the literature is not in agreement with that expected from the ionic mobility values published, a procedure to determine these values was carried out. The salicylate ion was used as the internal standard. The background electrolyte was composed of 25mmolL(-1) tris(hydroxymethyl)aminomethane and 12.5mmolL(-1) 2-hydroxyisobutyric acid, at pH 8.1. Separation was conducted in a fused-silica capillary (32cm total length and 8.5cm effective length, 50mum I.D.), with short-end injection configuration and direct UV detection at 200nm for benzoate and salicylate and 254nm for sorbate ions. The run time was only 28s. A few figures of merit of the proposed method include: good linearity (R(2)>0.999), limit of detection of 0.9 and 0.3mgL(-1) for benzoate and sorbate, respectively, inter-day precision better than 2.7% (n=9) and recovery in the range 97.9-105%. Beverage samples were prepared by simple dilution with deionized water (1:11, v/v). Concentrations in the range of 197-401mgL(-1) for benzoate and 28-144mgL(-1) for sorbate were found in soft drinks and tea.     

Analysis of elements in wine using near infrared spectroscopy and partial least squares regression

The use of visible (VIS) and near infrared spectroscopy (NIRS) to measure the concentration of elements in Australian wines was investigated. Both white (n=32) and red (n=94) wine samples representing a wide range of varieties and regions were analysed by inductively coupled plasma mass spectrometry (ICP-MS) for the concentrations of calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), sodium (Na), sulphur (S), iron (Fe), boron (B) and manganese (Mn). Samples were scanned in transmittance mode (1mm path length) in a monochromator instrument (400-2500nm). The spectra were pre-treated by second derivative and standard normal variate (SNV) prior to developing calibration models using partial least squares (PLS) regression method with cross-validation. The highest coefficients of determination in cross-validation (R(val)(2)) and the lowest errors of cross-validation (SECV) were obtained for Ca (0.90 and 9.80mgL(-1)), Fe (0.86 and 0.65mgL(-1)) and for K (0.89 and 147.6mgL(-1)). Intermediate R(val)(2) (<0.80) and SECV were obtained for the other minerals analysed. The results showed that some macro- and microelements present in wine might be measured by VIS-NIRS spectroscopy.     

Vapour phase Fourier transform infrared spectrometric determination of L-cysteine and L-cystine

A novel and selective procedure for the determination of l-cysteine and l-cystine based on vapour-generation Fourier transform infrared spectrometry is described. Potassium iodate solution was injected into a glass vessel containing l-cysteine and/or l-cystine. The evolved CO was swept by a stream of nitrogen to an infrared gas cell. The vapour phase FTIR spectra were continuously recorded, as a function of time, between 2240 and 2000cm(-1), which includes the CO absorption band. The maximum absorbance at 2170cm(-1) was selected as a measurement criterion. The calibration curve was linear over the range 6-300mgL(-1). The method provided a limit of detection of 2mgL(-1) of l-cysteine, a throughput of 12samples h(-1) and an R.S.D. of 1.76% for five independent analyses of a 75mgL(-1)l-cysteine solution. For the measurement of l-cysteine and l-cystine separately, after measuring total concentration of l-cysteine and l-cystine, l-cysteine was masked with p-benzoquinone at a pH of 3 and individual l-cystine was determined. The amount of l-cysteine was obtained by difference. The method was applied to the determination of l-cysteine and l-cystine in pharmaceutical and urine samples. Results obtained for real samples compared well with those obtained by a reference spectrometric method.     

Molecularly imprinted polymer-based solid-phase extraction combined with molecularly imprinted polymer-based sensor for detection of uric acid

The development of an easy-to-use, rapid, robust and inexpensive technique is required which can measure the basal concentration of uric acid (UA) lower than 1.0 x 10(-7)M ( approximately 0.017 mgL(-1)) in biological samples to attend the problem of hypouricemia. In the present work an artificial receptor for UA, silica gel-bonded molecularly imprinted polymer (MIP), was used as a sorbent for molecularly imprinted solid-phase extraction (MISPE) in column chromatography. The use of a sensor based on a MIP-modified hanging mercury drop electrode (HMDE), as reported from our laboratory, could estimate UA with detection limit as low as 0.024 mgL(-1) under the optimized conditions of differential pulse, cathodic stripping voltammetric (DPCSV) measurement. However, in the current investigation, with the use of the combination of MISPE followed by detection with a MIP-based HMDE sensor, the minimum detectable concentration could go down to 0.0008 mgL(-1) (RSD=0.63%, S/N=3). The same MIP receptor for both MISPE and the corresponding sensor was able to enhance the preconcentration of analyte substantially so as to attain the desired level of sensitivity; and that to without any interference (cross-reactivity) from other structurally related analogues including the major interferent like ascorbic acid prevalent in the aqueous environment of biological samples.     

Amino modified mesostructured silica nanoparticles for efficient adsorption of methylene blue

In this work, mesostructured silica nanoparticles (MSN(AP)) with high adsorptivity were prepared by a modification with 3-aminopropyl triethoxysilane (APTES) as a pore expander. The performance of the MSN(AP) was tested by the adsorption of MB in a batch system under varying pH (2-11), adsorbent dosage (0.1-0.5gL(-1)), and initial MB concentration (5-60mgL(-1)). The best conditions were achieved at pH 7 when using 0.1gL(-1) MSN(AP) and 60mgL(-1)MB to give a maximum monolayer adsorption capacity of 500.1mgg(-1) at 303K. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Harkins-Jura isotherms and fit well to the Freundlich isotherm model. The adsorption kinetics was best described by the pseudo-second order model. The results indicate the potential for a new use of mesostructured materials as an effective adsorbent for MB.     

Multicomponent kinetic spectrophotometric determination of pefloxacin and norfloxacin in pharmaceutical preparations and human plasma samples with the aid of chemometrics

A spectrophotometric method for the simultaneous determination of the important pharmaceuticals, pefloxacin and its structurally similar metabolite, norfloxacin, is described for the first time. The analysis is based on the monitoring of a kinetic spectrophotometric reaction of the two analytes with potassium permanganate as the oxidant. The measurement of the reaction process followed the absorbance decrease of potassium permanganate at 526nm, and the accompanying increase of the product, potassium manganate, at 608nm. It was essential to use multivariate calibrations to overcome severe spectral overlaps and similarities in reaction kinetics. Calibration curves for the individual analytes showed linear relationships over the concentration ranges of 1.0-11.5mgL(-1) at 526 and 608nm for pefloxacin, and 0.15-1.8mgL(-1) at 526 and 608nm for norfloxacin. Various multivariate calibration models were applied, at the two analytical wavelengths, for the simultaneous prediction of the two analytes including classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), radial basis function-artificial neural network (RBF-ANN) and principal component-radial basis function-artificial neural network (PC-RBF-ANN). PLS and PC-RBF-ANN calibrations with the data collected at 526nm, were the preferred methods-%RPE(T) approximately 5, and LODs for pefloxacin and norfloxacin of 0.36 and 0.06mgL(-1), respectively. Then, the proposed method was applied successfully for the simultaneous determination of pefloxacin and norfloxacin present in pharmaceutical and human plasma samples. The results compared well with those from the alternative analysis by HPLC.     

固相萃取-高效液相色谱法测定畜牧粪便中13种抗生素药物残留

建立了固相萃取-反相高效液相色谱法测定畜牧粪便中5种磺胺类、4种四环素类、2种喹诺酮类以及氯霉素和呋喃唑酮的检测方法.采用乙腈和0.01 mol/L草酸作为流动相分离4种四环素类和氯霉素,乙腈和0.025 mol/L醋酸铵作为流动相分离5种磺胺类和其它3种抗生素.结果表明,检测的13种抗生素出峰时间稳定,峰形较好,检出限0.01～0.05 mg/L,定量下限0.03～0.167 mg/L,采用柠檬酸缓冲液酸化的乙腈对猪粪便样品前处理,采用EDTA-McIlvaine提取液对鸡粪便样品前处理,两类样品均通过HLB固相萃取小柱纯化富集,回收率为54%～103%.该方法成功用于天津市4个畜牧养殖基地的20个畜牧粪便样品中抗生素的检测.结果表明,均有不同浓度的抗生素检出,浓度范围0.3～173 mg/kg.     

A microanalytical method for ammonium and short-chain primary aliphatic amines using precolumn derivatization and capillary liquid chromatography

A new microscale method is presented for the determination of ammonium and primary short-chain aliphatic amines (methylamine, ethylamine, propylamine, n-butylamine and n-pentylamine) in water. The assay uses precolumn derivatization with the reagent o-phthaldialdehyde (OPA) in combination with the thiol N-acetyl-L-cysteine (NAC), and capillary liquid chromatography with UV detection at 330 nm. The described method is very simple and rapid as no preconcentration of the analytes is necessary, and the volume of sample required is only 0.1 mL. Under the proposed conditions good linearity has been obtained up to a concentration of the analytes of 10.0 mgL(-1), the limits of detection being of 8-50 microgL(-1). No matrix effect was found, and recoveries between 97 and 110% were obtained. The precision of the method was good, and the achieved variation coefficients were below 12%. The reliability of the proposed approach has been tested by analyzing a microsample of fogwater collected from leaf surfaces.     

Capillary electrophoretic method for the determination of inorganic and organic anions in real samples. Strategies for improving repeatability and reproducibility

Selectivity and robustness of the pyromellitic acid (PMA) based background electrolyte was improved in order to increase its applicability for routine analysis of inorganic and organic anions in real samples. An electrolyte composed of 6.75 mM PMA, 0.5 mM hexamethonium hydroxide as electroosmotic flow (EOF) modifier, Ca(2+) 0.05 mM as complexation agent and pH adjusted to 7.6 with TEA 1M allows for the separation of 22 inorganic and organic anions in less than 17 min. Good RSDs for within-day migration time reproducibility (0.03-0.9%) and day-to-day analyses (0.04-1.4%) were obtained by the use of two internal standards, allowing for an accurate compound identification. The detection limits ranged from 0.1 to 0.4 mgL(-1) (S/N=3) for hydrodynamic injection (1250 mbars). The applicability of the proposed method was demonstrated by the analysis of inorganic and organic anions in diverse real samples. The recoveries obtained ranged from 93 to 106%.     

Flow-injection determination of copper(II) based on its catalysis on the redox reaction of cysteine with iron(III) in the presence of 1,10-phenanthroline

A redox reaction of cysteine with iron(III) proceeds slowly in the presence of 1,10-phenanthroline (phen). However, this reaction is accelerated in the presence of copper(II) as a catalyst, producing an iron(II)-phen complex (lambda(max)=510 nm). A sensitive spectrophotometric flow-injection method is proposed for the determination of copper(II) based on its catalytic action on this redox reaction. The dynamic range was 0.1-10 ng ml(-1) of copper(II) with a relative standard deviation of 1.0% (n=10) for 1.0 ng ml(-1) of copper(II) at a sampling rate of 30 h(-1). The detection limit (S/N=3) is 0.04 ng ml(-1). The proposed method was successfully applied to the determination of copper in river water as a certified reference material.     

Experimental and computational study of species formed during electrochemical stripping oxidation of copper in chloride media determination of copper(II) in the ng l(-1) range by stripping potentiometry

A novel glassy carbon electrode design, permitting medium exchange in batch mode without loss of electrode potential control, has been used for the study of copper(I) and copper(II) species formed during constant current stripping oxidation of copper in chloride media. It was found that copper(II) species dominated at chloride concentrations below about 1 mM and that soluble copper(I) species dominated at chloride concentrations above about 100 mM. In the concentration range 1-100 mM, soluble copper(I) and copper(II) species are formed as well as solid copper(I) chloride, the latter giving rise to a split peak as it is further oxidised to copper(II). The experimental results agreed satisfactorily with computer calculated equilibria data using the haltafall program. The medium exchange procedure has, furthermore, been used for the determination of copper(II) in seawater reference samples, 7.5 M ammonium acetate/2.5 M acetic acid being used as stripping medium. The detection limit, after 15 min of electrolysis, was found to be 6 ng l(-1) (0.10 mM) and the relative precision 6-10%.     

Determination of carbohydrates by capillary electrophoresis with electrospray-mass spectrometric detection.

A method for the determination of underivatized carbohydrates using capillary electrophoresis (CE) with detection by electrospray ionization-mass spectrometry (ESI-MS) presented. Highly alkaline carrier electrolytes based on volatile organic bases like is diethylamine (DEA) combined with MS detection in the negativ-ion mode proved to be the optimum solution for the separation and detection of these analytes. Optimization of the carrier electrolyte composition has been performed with respect to its pH, ionic strength as well as the addition of an organic modifier. The influence of the DEA concentration in the sheath liquid on parameters like peak shapes or signal-to-noise (S/N) ratios was also investigated. Limits of detection (LOD) were in the range of 0.5-3.0 mgL(-1) and calibration was linear over an order of magnitude for almost all solutes investigated. Finally, the applicability of this method for the analysis of real samples was demonstrated with wine samples.     

Pre-concentration procedure for determination of copper and zinc in food samples by sequential multi-element flame atomic absorption spectrometry

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box-Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3sigma(b)/S, LOD) of 0.1 microg L(-1), precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% (N=10), for copper concentrations of 10 and 50 microg L(-1), respectively. Zinc is determined with a LOD of 0.15 microg L(-1) and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 microg L(-1), respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a - Wheat Flour and SRM 8433 - Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 microg g(-1) and zinc from 8.7 to 22.9 microg g(-1).     

Determination of copper and zinc in serum by derivative atomic absorption spectrometry using the microsampling technique

A method has been developed for the determination of copper and zinc in the serum of rats by derivative microsampling flame atomic absorption spectrometry (D-MFAAS). The microsampling volume, solution uptake rate and other figures of merit of the proposed methodology were studied. For a 100 microl volume, the characteristic concentrations and detection limits (3s) of D-MFAAS were 0.023 and 0.013 microg ml(-1) for copper and 0.0066 and 0.0080 microg ml(-1) for zinc, which were 4.5-6.5-fold better than those of microsampling flame atomic absorption spectrometry (MFAAS). The detection limits and sensitivities of D-MFAAS were 6.4- and 16-fold for 300 microl volume for copper, 14- and 13-fold for 250 microl volume for zinc, better than those of MFAAS. The method demonstrates high tolerance to interferences, and the analytical results obtained for a certified reference material, GBW 08551 Pork Liver, were in good agreement with the certified values. The recovery with the standard additions method was good, in the range 97.6-101.5%, and precisions (relative standard deviations) obtained for a diluent sample containing 0.5 microg ml(-1) copper and 0.7 microg ml(-1) zinc were 4.0% and 3.5% (n = 15) for copper and zinc, respectively.     

Magnesium optical one-shot sensor based on a coumarin chromoionophore

The characterization of a new irreversible optical absorption-based one-shot sensor for magnesium is described. The magnesium photoactive probe is 7-diethylamino-3-(3,4-ethylendioxybenzoyl)coumarin immobilized in a plasticized polymeric membrane. The magnesium selectivity can be explained in terms of size and charge density of magnesium and charge-separated resonance forms contribution in the excited state of coumarin. The selectivity obtained for magnesium over a variety of naturally occurring species in natural waters meets the requirements for the determination of this ion in water. The one-shot sensor responds between 0.14 and 14mgL(-1) with a sensor-to-sensor reproducibility of 1.3% as [Formula: see text] , at the medium level of the range. The performance of the optical one-shot sensor was tested in the analysis of magnesium in different types of natural waters and soft drinks validating results against a reference procedure.