Kinetic dual standard additions method for the determination of two mutually interfering analytes: Molybdate and tungstate

A kinetic dual standard additions method for determination of two mutually interfering analytes is proposed. The deviations of absorbance from additivity in kinetic systems, caused by synergistic effects of catalysts, are compensated with the defined synergistic catalytic coefficient. The hydrogen peroxide-iodide kinetic reaction catalysed by molybdate and tungstate was studied with the stopped-flow injection technique and the conditions for simultaneous determination of Mo and W established. The molybdenum and tungsten contents in different samples were determined with recoveries of 97.6 102.1% and 96.9 98.6%, and relative standard deviations of 2.3 3.4% and 1.6 2.6%, respectively.     

金属离子对动力学反应的协同诱导效应及在多组分分析中的应用

研究铁(II)和锑(III)对Cr2O7^2^--I^-动力学反应体系的协同诱导效应, 提出协同诱导系数的概念。将此系数引入前述停流FIA-动力学双组分同时测定方法中,有效地补偿了由于双组分间协同效应而引起的对吸光度加合性的偏离, 同时线性测定范围亦显著扩大, 从而为动力学体系中多组分的测定提供了一种有效的方法。测定了废水、合成样品及标准样品中铁和锑的含量, 结果满意。     

Fast simultaneous determination of niobium and tantalum by Kalman Filter analysis with flow injection chemiluminescence method.

A fast and highly efficient Kalman Filter analysis-flow injection chemiluminescence (FI-CL) method was developed to simultaneously determine trace amounts of niobium and tantalum in geological samples. The method, without the boring process of separation and dear instruments, is suitable for field scene analysis. The mixed chemiluminescence kinetic curve was analyzed by a Kalman Filter (KF) in this method to realize the simultaneous determination of niobium and tantalum. Possible interference elements in the determination were investigated. Under the selected conditions, the detection limits (3sigma, n = 11) of niobium(V) and tantalum(V) were 2.1 x 10(-3) microg g(-1) and 4.0 x 10(-3) microg g(-1), respectively, and the relative standard deviations were 4.9% and 3.3% (n = 9). The method was applied to the determination of niobium and tantalum in geological samples with satisfactory results.     

分光光度法同时测定两个干扰组份的研究 I.多波长数据线性回归法及其应用于同时测定微量锰和锌的探讨

In this paper, a linear regression method of multiwavelength data is proposed. The method, based on the difference of molar absorptivity between two coloured chelates at murti-wavelengths, can be applied to simultaneous spectrophotometric determination of two-interfering-component systems in the visible region. As an example, the availability as well as the optimum condition for simultaneous determination of Mn and Zn with 5-Br-PADAP in the presence of nonionic surfactant Triton X-100 have been studied. Measure the absorbance at 15 wavelengths over the range of 540-584 nm and treat the data with the suggested method, the linear correlation coefficients (γ) are found to be 0.998 in the synthetic mixtures containing microamounts of Mn and Zn with the concentration ratio from 1:10 to 10:1. The recoveries of both elements are 95-120% with the relative standard deviations (N=5) less than 17%. the method has been successfully used for direct determination of Mn and Zn in tap water. The new method proposed in this work is simple, fast and can be used for the analysis of two-interfering-component systems.     

Spectrophotometric determination of palladium(II) with 2-diethylaminoethanethiol hydrochloride and the simultaneous determination of rhodium and palladium

2-Diethylaminoethanethiol hydrochloride is proposed for spectrophotometric determination of palladium(II). The sensitivity of the reaction is 0.0085 smg/cm² and the yellow colored complex shows absorption maxima at 258 mμ and 303 mμ. Color development is slow in the cold but complete after heating for 10–15 min. The optimum pH range is 3.5 to 5.5 and the system adheres to Beer's law between 0.2 and 16.8 p.p.m. of palladium. The average and maximum relative standard deviations were 0.60% and 1.40% respectively. Interferences due to other platinum metals were studied and a procedure is suggested for the simultaneous determination of rhodium and palladium.     

New computational approach for the simultaneous photometric determination of catalysts and activators

A new method for the simultaneous kinetic determination of catalysts and activators was developed on the basis of a mathematical model. The parameters and variables are optimized from experimental data obtained by application of a multiple standard-addition method and use of the Gauss-Newton and Simplex method, both of which provide identical results. The proposed method was applied to the simultaneous photometric determination of Mn(II) and Pb(II) on the basis of their catalytic and activating effects, respectively, on the oxidation of Tiron by hydrogen peroxide. Data were both acquired and processed with the aid of software developed by the authors. The linear determination range achieved was 1.00-5.00 ng/ml Mn(II) and 200-800 ng/ml Pb(II). Experimental readings were made at 450 nm with a fibre optics detector. The most serious interference with the method was posed by Cr(III).     

Simultaneous measurements of As, Mo, Sb, V and W using a ferrihydrite diffusive gradients in thin films (DGT) device

The ferrihydrite-backed DGT (diffusive gradients in thin films), recently developed for arsenic and phosphate measurements was, for the first time, characterized with respect to molybdate, antimonate, vanadate and tungstate determination. Arsenate was included in the characterization to allow comparison with literature data and thus provide quality control of the measurements. In addition to laboratory experiments, field measurements were carried out in a natural stream in northern Sweden affected by mine drainage. It was shown that ferrihydrite-DGT is suitable for simultaneous determination of labile arsenic, molybdate, antimonate, vanadate and tungstate over a wide pH range. Diffusion coefficients were estimated using two different methods; diffusion cell and direct uptake to DGT devices in synthetic solutions. Estimations of the coefficients using the direct uptake method were performed between pH 4 and 8. The results from the two methods agreed well irrespective of pH, except for molybdate and antimonate that showed decreased values at pH 8. Adsorption of the analytes to ferrihydrite gel-discs was rapid at all pH values. However, there was a tendency toward lower adsorption affinity for antimonate compared to the other anions. 100% recovery of accumulated analytes was achieved through complete dissolution of the ferrihydrite adsorbent using 1.4 molL(-1) HNO(3) with 0.1 molL(-1) HF. From field sampling it was concluded that the opportunities for accurate antimonate and molybdate determination decrease at pH≥8.7. DGT-labile concentrations were generally lower than dissolved concentrations. Relatively lower DGT concentrations, compared to dissolved (<0.45 μm), were observed under a period when ferric oxide precipitations were detected on the DGT protective filter.     

停流流动注射-诱导动力学光度法同时测定微量铁和锑

依据诱导反应的基本原理, 提出了一种同时测定多元素的方法; 研究了Fe(II)、Sb(III)诱导的Cr(VI)-I^-氧化还原反应体系, 并据此建立了停流-诱导动力学光度法同时测定微量铁和锑的工作条件。线性范围分别为0~1.2μg.mL^-1Fe(II)和0~2.0μg.mL^-1Sb(III); 检测限为0.012μg/mL^-1Fe(II)和0.014μg.mL^-1Sb(III)。除Ti(III)、V(IV)及As(III)外, 其余共存离子不影响测定。用本法测定了锌标准物及模拟样品中的铁和锑含量, 结果满意。     

Simultaneous spectrophotometric determination of paracetamol and salicylamide in human serum and pharmaceutical formulations by a differential kinetic method

A rapid, simple, and sensitive differential kinetic method is presented for the determinations of acetaminophen (also known as paracetamol) and salicylamide. The method is based on their oxidation reaction by Fe3+ ion in the presence of 1, 10-phenanthroline as indicator. The reactions can be monitored spectrophotometrically by measuring the increase in the absorbance of the solution at 510 nm. Two times were selected one in which only paracetamol is oxidized by Fe3+ ion and the other in which both drugs are oxidized by Fe3+ ion. The data were evaluated by the proportional equations method. The method allowed the simultaneous determination of paracetamol and salicylamide at concentrations between 0.5-20 and 1-40 microg/mL with relative standard deviations of 3.47 and 2.58%, respectively. The method was applied to the simultaneous determination of paracetamol and salicylamide in human serum and pharmaceutical formulations.     

H-point standard additions method for simultaneous determination of sulfamethoxazole and trimethoprim in pharmaceutical formulations and biological fluids with simultaneous addition of two analytes

The applicability of H-point standard additions method (HPSAM) to the resolving of overlapping spectra corresponding to the sulfamethoxazole and trimethoprim is verified by UV-vis spectrophotometry. The results show that the H-point standard additions method with simultaneous addition of both analytes is suitable for the simultaneous determination of sulfamethoxazole and trimethoprim in aqueous media. The results of applying the H-point standard additions method showed that the two drugs could be determined simultaneously with the concentration ratios of sulfamethoxazole to trimethoprim varying from 1:18 to 16:1 in the mixed samples. Also, the limits of detections were 0.58 and 0.37 μmol L(-1) for sulfamethoxazole and trimethoprim, respectively. In addition the means of the calculated RSD (%) were 1.63 and 2.01 for SMX and TMP, respectively in synthetic mixtures. The proposed method has been successfully applied to the simultaneous determination of sulfamethoxazole and trimethoprim in some synthetic, pharmaceutical formulation and biological fluid samples.     

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.     

A sensitive high-throughput HPLC assay for simultaneous determination of everolimus and clobetasol propionate

A novel sensitive high-throughput high-performance liquid chromatography assay is developed and validated for the simultaneous determination of everolimus and clobetasol propionate in pharmaceutical formulations. The chromatographic separation is achieved on a Zorbax Eclipse XDB-C18 reversed-phase column using a gradient elution, with solvent A: ammonium acetate (pH 6.8; 0.01 M) and solvent B: acetonitrile. The mean recovery ranges from 95.1% to 100.0% for clobetasol propionate and from 97.9% to 103.7% for everolimus. The limit of quantitation for each analyte is 0.02 microg/mL. The percent relative standard deviations are less than 3% for intra- and inter-day analyses. The proposed method can be used for the routine quality control of everolimus and clobetasol propionate in complex pharmaceutical formulations, especially the drug-delivery systems with a low total drug-load.     

Simple regression model using an optode for the simultaneous determination of zinc and cadmium mixtures in aqueous samples.

An optical-fiber chemical sensor (optode) is described for the simultaneous determination of Zn2+ and Cd2+ mixtures using 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol immobilized onto XAD-4 (Br-PADAP/XAD-4). A simultaneous analysis was achieved by using a single-wavelength kinetic approach coupled with a regression model. Here, the regression model was derived for the slope response of Br-PADAP/XAD-4 to binary mixtures of the metal ions, Zn2+ and Cd2+, at pH 8. The model was used then to predict the concentration of one metal ion while the other was kept constant. This was found to be reasonably successful for Zn2+ and Cd2+, with deviations of 3% and 10%, respectively. The sensor was also found to provide excellent sensitivity for both metal ions with excellent LODs (< 0.1 ppm) and very short analysis times (< 30 s).     

溶剂去乳化-悬浮固化分散液液微萃取-气相色谱-质谱联用测定水中的有机氯农药

建立了溶剂去乳化-悬浮固化分散液液微萃取技术结合气相色谱-质谱联用技术同时测定水样中8种有机氯农药的方法。以正十六烷作为萃取剂,将其与分散剂丙酮混合后,快速注入水样,获得乳化体系并完成萃取;然后加入丙酮作为去乳化剂破坏乳化体系,不需要经过离心即能使两相分层;经冰浴冷冻使其固化后,取出上层凝固的有机相(正十六烷)在室温下融化,取上清液进行GC-MS分析。考察了萃取剂、分散剂、去乳化剂的种类和体积,水样盐浓度和pH值对萃取效率的影响。结果表明,8种有机氯农药在0.025~2.00 μg/L范围内有良好的线性关系(r=0.9995~0.9999), 8种有机氯农药的检出限为0.012~0.024 μg/L,精密度为3.15%~4.53%,富集倍数为96~101。将该方法应用于农田池塘水的测定,加标回收率为96.77%~102.93%,精密度为2.68%~4.86%。方法快速灵敏,有机溶剂消耗少,对环境友好,操作简便,适用于水中有机氯农药的批量分析,并为实现其样品前处理的自动化提供了技术和方法学的支持。     

Simultaneous determination of ampicillin and tetracycline in milk by using a stopped-flow/T-format spectrofluorimeter

A fast and simple fluorimetric method is described for the simultaneous determination of ampicillin and tetracycline in milk by combining the stopped-flow mixing technique with a T-format spectrofluorimeter. Ampicillin determination is based on its hydrolysis with penicillinase and reaction with mercuric chloride, while the intramolecular energy transfer from tetracycline to europium ions in the presence of thenoyltrifluoracetone is used for tetracycline determination. The similar excitation wavelengths of both systems and the separation between the corresponding emission wavelengths allow the direct determination of both analytes by measuring simultaneously the initial rate of the ampicillin system and the equilibrium signal of the tetracycline system. The relative standard deviations were lower than 2%. The proposed method was applied to the determination of these antibiotics in different milk samples with a recovery of 95.0-103.3% for ampicillin and 93.3-103.3% for tetracycline.     

Atomic absorption spectrometric determination of trace amounts of copper and zinc after simultaneous solid-phase extraction and preconcentration onto modified natrolite zeolite.

This work assesses the use of modified natural natrolite zeolite as an adsorptive material for the separation and preconcentration of trace amounts of ions. In this work we investigated the potential of modified natural natrolite zeolite for the simultaneous separation and preconcentration of trace amounts of copper and zinc ions. We have developed a simple, rapid, selective, sensitive and economical method for the simultaneous separation and preconcentration of trace amounts of copper and zinc in an aqueous medium using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as an analytical reagent. The sorption was quantitative in the pH range 7.5 - 9.5, whereas quantitative desorption occurred instantaneously with 5.0 mL of 2 mol L(-1) nitric acid. Linearity was maintained between 0.05 - 6.0 microg mL(-1) for copper and 0.02 - 1.5 microg mL(-1) for zinc in the final solution. Ten replicate determinations of 1.0 microg mL(-1) copper and 0.5 microg mL(-1) zinc in a mixture gave mean absorbances of 0.1687 and 0.2788 with relative standard deviations of +/-1.2% and +/-1.3%, respectively. The detection limits were 0.03 ng mL(-1) for Cu(II) and 0.006 ng mL(-1) for Zn(II) in the original solution (3 sigma(bl)/m). Different parameters, such as the effect of the pH, flow rate, breakthrough volume and interference of a large number of anions and cations, were studied and the proposed method was used for the determination of these metal ions in water as well as standard samples (e.g. Nippon Keikinzoku Kogyo (NKK) CRM, No. 916 and No. 920 aluminum alloy, National Institute for Environment Studies (NIES) No. 1 pepperbush and NIES No. 2 pond sediment). The determination of these metal ions in standard samples showed that the proposed method has good accuracy (recovery > 97%).     

Application of continuous wavelet transformation to the simultaneous kinetic determination of binary mixtures

Wavelet transformation of kinetic profiles as a new and simple method was developed for the simultaneous determination of binary mixtures without prior separation steps. The mathematical explanation of the procedure is illustrated. Daubechies (db), symlet (sym) and discrete meyer wavelet (meyr) from the family of wavelet transforms were selected and applied under the optimal conditions for the resolution of binary mixtures. A model data as well as experimental data were tested. The results from the experimental data relating to the simultaneous spectrophotometric determination of phosphate and silicate based on the formation of phospho- and silico-molybdenum blue complexes in the presence of ascorbic acid, and also simultaneous determination of Co²⁺ and Ni²⁺ based on their complexation reactions with 1-(2-pyridylazo)-2-naphthol (PAN) in micellar media at pH 6.0 were presented as real models. The proposed method was validated by simultaneous determination of phosphate and silicate in detergent and tap water and also Co²⁺ and Ni²⁺ in tap water samples.     

Individual and simultaneous fluorimetric determination of glycine and cysteine by flow injection analysis

A dual-channel flow injection configuration is proposed for individual and simultaneous determinations of glycine and cysteine (based on their reaction with phthaldialdehyde) in the range 1 × 10⁻⁷ – 1.5 × 10⁻⁵ M, with relative standard deviations of ± 1.7 and ± 1.3%, respectively, and a sampling frequency of 75–80 hr⁻¹ for both analytes. The inclusion of a selecting valve in the configuration allows the simultaneous determination of these analytes in the concentration range achieved in their individual determinations. The resolution of mixtures is feasible with average errors of ± 2.2%.     

Simultaneous determination of benserazide and levodopa by capillary electrophoresis-chemiluminescence using an improved interface

A capillary electrophoresis coupling with indirect chemiluminescence detection method for the simultaneous determination of benserazide and levodopa has been developed. The detection interface was improved to simplify the capillary electrophoresis-chemiluminescence (CE-CL) system and the features of this improved interface were illustrated in this paper. The CE-CL conditions for the simultaneous determination of benserazide and levodopa were optimized. Under the optimal conditions, the CL intensity was linear with concentrations of levodopa in the range of 1.0 to 100.0 microg ml(-1), and benserazide in the range of 10.0 to 1,000 microg ml(-1), respectively. The detection limits (S/N=3) in turn were 1.85 microg ml(-1) for BS and 0.12 microg ml(-1) for L-dopa with relative standard deviations of less than 3%. The proposed method has been successfully applied to the determination of benserazide and levodopa in medopar tablets and spiked urine samples, demonstrating the feasibility and reliability of the proposed method.