On-line speciation of bromine and bromide using sequential injection analysis with spectrophotometric detection

An on-line procedure for the simultaneous determination of bromine and total bromine (bromine+bromide oxidised to bromine) is proposed, which lead to the determination of bromide by subtraction. Phenol red was used as chromogenic reagent for bromine and total bromine after bromide was oxidised to bromine by Chloramine T. The linear range found is 1-10 mg L(-1) with a detection limit of 0.6 mg L(-1) for bromine, and a linear range of 0.8-15 mg L(-1) with a detection limit of 0.4 mg L(-1) for total bromine. The calculated RSD for bromine is less than 0.8% and for total bromine less than 0.7%. The system is fully computerised and able to run 30 samples per hour with an automated rinsing step that eliminates sample carry-over. The results for both bromine and bromide from the proposed sequential injection analysis (SIA) system compare favourably with standard manual methods and statistical evaluation proves no significant difference between the results of the proposed SIA system and the standard method at the 95% confidence level. The presence of other halides was found not to interfere.     

Determination of zinc in pharmaceutical products by use of a sequential injection analysis system

A sequential injection analysis (SIA) system is proposed for the determination of zinc in pharmaceutical samples. The method is based on the spectrophotometric detection of zinc using xylenol orange as a colour reagent at 568 nm. The system can be used to monitor zinc at a frequency of 30 samples h(-1) with an average recovery of +/-98.5% and a relative standard deviation of less than 1%. A linear relationship between peak height and zinc concentration is obtained between 10 and 60 mg L(-1). The results obtained are in good agreement with those obtained by use of a standard method.     

Spectrophotometric Determination of Cefadroxil in Drug Formulations using flow Injection Analysis

ABSTRACT

A flow injection analysis method for the determination of cefadroxil is proposed. The method is based on the hydrolysis of cefadroxil in sodium hydroxide solution followed by treatment with 1,4-phenylenediamine and Fe(III) in sulphuric acid solution to produce a violet color which has a maximum absorption at 600 nm. Variables such as acidity, reagent concentrations, flow rate of reagents and other FI parameters were optimized to produce the most sensitive and reproducible results. The calibration graph is linear between 80 - 320 mg/l. The detection limit is 40 mg/l with a relative standard deviation, RSD (n=6) of 1.8%. The proposed method, combining the advantages of speed and accuracy was applied to the determination of cefadroxil in pharmaceutical preparations. The results have been compared with those obtained using HPLC method (USP-procedure). Excellent agreement between the results of the proposed method and the HPLC method was observed.     

Permanganate-based chemiluminescence analysis of cefadroxil monohydrate in pharmaceutical samples and biological fluids using flow injection

A chemiluminescent method using flow injection is described for the determination of cefadroxil monohydrate. The method is based on the chemiluminescence reaction of cefadroxil with potassium permanganate in sulphuric acid, sensitized by quinine. The proposed procedure allows the determination of cefadroxil over the concentration range 0.1-30 mug ml(-1) with a detection limit of 0.05 mug ml(-1) and a sample measurement frequency of 150 samples h(-1). The method was successfully applied to the determination of cefadroxil in pharmaceutical preparations and biological fluids.     

A simple flow injection spectrophotometric procedure for the determination of diazepam in pharmaceutical formulation.

A single-channel flow injection (FI) manifold with spectrophotometric detection has been designed and fabricated for diazepam determination. A 100 microl sample and/or standard solution containing diazepam was injected into a flowing stream of 0.1 mol L(-1) hydrochloric acid with the optimum flow rate of 6.8 mL min(-1). As soon as the sample reached the detector, the FI signal as a peak was recorded at 360 nm. The optimum conditions for microg amounts of diazepam were achieved. A linear calibration graph over the range of 2-110 mg L(-1) diazepam was obtained with the regression equation Y = 0.2926X + 0.5896 (r2 = 0.9929). The method was very sensitive, since as little as 0.60 mg L(-1) could be detected; very reproducible with an RSD of 3.3% (n=11); and very rapid with a sampling rate of 100 h(-1). The limit of quantitation (10 sigma) was 2.0 mg L(-1). The proposed FI procedure has been satisfactorily applied to the quantitation of diazepam in commercial pharmaceutical formulations. The obtained results were in excellent agreement with those obtained by the conventional spectrophotometric method, verified by the student t-test at the 95% confidence level.     

Determination of salbutamol using on-line solid-phase extraction and sequential injection analysis. Comparison of chemiluminescence and fluorescence detection

Determination of salbutamol using sequential injection analysis (SIA) with chemiluminescence and fluorescence detection has been devised. The chemiluminescence signal was emitted during the oxidation of salbutamol by potassium permanganate in sulfuric acid medium. Sodium polyphosphate was used as chemiluminescence enhancer. The fluorescence signal (excitation wavelength 230 nm) was also measured in sulfuric acid medium. Both detection techniques were compared with respect to the application of the methods to the determination of salbutamol in biological materials. The sample pre-treatment takes place directly in the SIA system, when salbutamol is adsorbed on the solid-phase (Baker-carboxylic acid) microcolumn integrated into the system. Sulfuric acid serves both as the reagent and the eluent. The lab-made SIA system consisted of a 2.5-mL Cavro syringe pump, ten-port Vici Valco selection valve and Spectra-Physics FS 970 fluorescence detector, which was lab-modified for chemiluminescence detection. The system was controlled by a PC using originally compiled LabVIEW-supported software. Concentrations, volumes of reagents and flow rates were optimised by a simplex method. Salbutamol was determined in the linear range 0.05-10 microg mL(-1) (RSD 1.53%), with the detection limit (3 sigma) 0.03 microg mL(-1) and sample throughput of 42 samples per hour with chemiluminescence detection in standard solutions. The fluorescence detection enabled the determination of salbutamol in standard solutions in the linear range 0.5-100 microg mL(-1) (RSD 2.69%), with the detection limit 0.2 microg mL(-1) and sample throughput of 24 h(-1). The proposed methods were applied to the determination of salbutamol in human serum and urine. However, serum is a very complicated matrix and the SIA-SPE analysis did not provide satisfactory results. It was possible to determine salbutamol in human urine using this technique. Better recovery was achieved with fluorescence detection.     

Development and validation of a flow-injection assay for dissolution studies of the anti-depressant drug venlafaxine.

The first flow-injection method has been developed, optimized and validated for the determination of venlafaxine, an antidepressant drug. The method is based on a direct measurement of the absorbance of the analyte in an acidic medium, at 274 nm. Flow-injection parameters, such as sample injection volume and flow rate, were studied and optimized. The proposed method was validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. Linearity was obeyed in the range 30 - 150 mg L(-1) of venlafaxine, while the detection limit (1.5 mg L(-1)) and repeatability (sr < 1.0%, n = 12) were satisfactory. The sampling rate was 30 h(-1). The results of dissolution studies of venlafaxine tablets obtained by the proposed method were in good agreement with those by high-performance liquid chromatography.     

Simultaneous determination of N,N-dimethylaniline and phenol in wastewater by high-performance liquid chromatography with chemiluminescence detection.

A method using HPLC-CL linkage was developed for simultaneous determination of N,N-dimethylaniline and phenol in wastewater, based on the strong sensitive chemiluminescence of the luminol-K3Fe(CN)6 systems in alkaline medium. The separation was carried out on a Hypersil ODS column with a mobile phase of ethanol-0.01% triethylamine (2:1, v/v). The linear ranges for N,N-dimethylaniline determinations were 2.0 x 10(-7) - 2.5 x 10(-5) g/mL and 4.0 x 10(-5) - 1.5 x 10(-4) g/mL with a detection limit (3sigma) of 1.20 x 10(-8) g/mL; the relative standard deviation (3sigma) for 5.0 x 10(-6) g/mL N,N-dimethylaniline was 1.4% (n = 6). The range for phenol was from 5.1 x 10(-7) to 1.3 x 10(-4) g/mL, and a detection limit (3sigma) of 2.5 x 10(-8) g/mL could be obtained. The method can be useful for the determination of N,N-dimethylaniline and phenol in some environmental samples.     

胶束电动色谱-激光诱导荧光检测法测定肌松弛药巴氯芬

以4-氯-7-硝基苯并-2-氧杂-1,3-二唑(NBD-Cl)为柱前衍生试剂,建立了胶束电动色谱-激光诱导荧光检测法测定肌松弛药巴氯芬(BAL)的新方法。经过实验条件的优化,采用15 mmol/L硼砂、20 mmol/L十二烷基硫酸钠、10%(v/v)乙腈、pH 9.75的缓冲体系,在分离电压为17.5 kV、柱温为25 ℃的条件下,压力进样3.45 kPa(0.5 psi)×3 s,巴氯芬及其内标物的衍生产物在7 min内实现较好的基线分离,线性范围为0.025～25 mg/L,相关系数为0.9999,检出限(S/N=3)和定量限(S/N=10)分别为0.90 μg/L和6.25 μg/L。该方法被应用于巴氯芬制剂及加入巴氯芬对照品的尿液样品分析,回收率范围分别为101.6%～107.9%和107.0%～109.6%。该方法有望应用于巴氯芬药物制剂的质量监控以及为巴氯芬药物代谢的研究提供辅助手段。     

Development of sequential injection spectrophotometric method for determination of mercury (II) using pyrogallol red

A sequential injection analysis (SIA) spectrophotometric method for the determination of trace amount of mercury (II) with pyrogallol red (PGR) was described. The method was based on the measurement of absorbance of the mercury (II)–PGR complex, yielding a light yellow-coloured product at pH 9.0 with absorption maximum at 370 nm. The SIA parameters affecting the signal response were optimised in order to obtain the better sensitivity and minimum reagent consumption. The linear range for determination of mercury (II) was over the range of 0.1–2.0 mg L^?1. The limit of detection and limit of quantification, calculated following IUPAC were 0.06 and 0.10 mg L^?1, respectively. The repeatability was 1.25% (n = 10) for 0.5 mg L^?1 of mercury (II). The proposed method was successfully applied to determine the mercury (II) in commercial cosmetics, local Thai traditional medicines and water samples with a sampling rate of 40 h^?1. Results obtained were in justifiable agreement with those obtained by the official ICP-MS method at the 95% confidence level.     

Flow-injection chemical vapor-generating procedure for the determination of Au by atomic absorption spectrometry

Volatile Au species in an acidified medium were generated at room temperature by reduction with NaBH4 in acidified aqueous medium using a flow-injection chemical vapor-generation atomic absorption spectrometric (FI-CVG-AAS) system in the presence of micro amounts of sodium diethyldithiocarbamate (DDTC). Precision of 2.0% RSD (n = 11, 2.0 mg L(-1) level) was obtained at a sample throughput of 180 h(-1). A detection limit of 24 ng mL(-1) (3sigma) was obtained with 300 microL sample solution. The method was used for the determination of gold in ore sample digests, and the results obtained agreed well with those obtained by flame AAS.     

Ultrasound-enhanced flow injection chemiluminescence for determination of hydrogen peroxide

A novel ultrasonic flow injection chemiluminescence (FI-CL) manifold for determining hydrogen peroxide (H2O2) has been designed and evaluated. Chemiluminescence obtained from the luminol-H2O2-cobalt(II) reaction was enhanced by applying 120 W of ultrasound for a period of 4 s to the reaction coil in the FI-CL system and this enhancement was verified by comparison with an identical manifold without ultrasound. The system was developed for determining ultra-trace levels of H2O2 and a calibration curve was obtained with a linear portion over the range of 10-200 nmol L(-1) H2O2 (correlation coefficient 0.9945). The detection limit (3sigma) and the quantification limit (LOQ) were found to be 1 x 10(-9) and 3.3 x 10(-9) mol L(-1) respectively and the relative standard deviation was 1.37% for 2 x 10(-7) mol L(-1) H2O2 (n = 10). The method was applied to the determination of trace amounts of H2O2 in purified water and natural water samples without any special pre-treatments.     

Determination of trichloroacetate in human serum and urine by ion chromatography

A simple and rapid ion chromatographic method has been developed for the determination of trichloroacetate in human serum and urine. Two short (50 x 5 mm i.d.) low-capacity anion-exchange resin columns in series were used as the analytical column and a mixture of 35 mM sodium hydroxide, 20 mM p-hydroxybenzonitrile and 2% V/V acetonitrile (pH 12.3) as the eluent. The calibration graph was rectilinear from 0.3 to 33 mg l-1 of trichloroacetate at 10 microS with a detection limit (3 sigma) of 0.08 mg l-1. The recovery of trichloroacetate, obtained by analysing spiked serum and urine samples, was in the range 98.2-101% and the coefficient of variation was always less than 3.0%.     

Flow injection spectrophotometric determination of tetracycline in a pharmaceutical preparation by complexation with aluminium(III).

A rapid flow injection (FI) spectrophotometric procedure for tetracycline determination is described. It is based on the injection of a 100 microl sample solution containing tetracycline into merged streams of aluminium(III) chloride (0.01 mol 1(-1)) and Tris-buffer in the presence of KCl (0.06 mol l(-1)), pH 7.0, with the same optimum flow rate of 3.2 ml min(-1). A yellow Al(III)-tetracycline complex was monitored at 376 nm. The flow injection system and the experimental conditions were optimized by means of the univariate method. The procedure was applied to the determination of tetracycline in pharmaceutical preparations with a high sampling rate of at least 165 h(-1). A high precision with a relative standard deviation was obtained less than 0.72 and 0.30% of 5.0 and 10 microg ml(-1) (n=11), respectively. The detection limit (3sigma) and the quantification limit (10sigma) were 0.07 and 0.72 mg l(-1), respectively. There were no interference effects from traditional excipients in the dosage forms when the method was applied to pharmaceutical preparations. The matrix effect could be reduced by the standard addition method.     

Use of 4-chloro-7-nitrobenzofurazane as a derivative reagent for the determination of amino acids by cathodic stripping square wave voltammetry in biological fluids

The rapid and simple reaction of 4-chloro-7-nitrobenzofurazane with amino acids allows the determination of amino acids in urine using cathodic stripping square wave voltammetry. The obtained compounds are adsorbed on a hanging mercury drop electrode for determination by voltammetric methods using phosphate buffer at pH 2.0 as supporting electrolyte. The proposed method allows determination with an error of 5.68%. A limit of detection (3sigma) of 3.64 nM (0.766 ng ml(-1)) and a limit of determination (10sigma) of 12.12 nM (2.55 ng ml(-1)) are obtained for arginine determination. The proposed method has been applied to the determination of amino acids in urine.     

Spectrophotometric Assay of Certain Cephalosporins Based on Formation of Ethylene Blue

Abstract

The hydrolytic degradation of antibiotics is very often used as a preliminary step in the analytical procedures for their determination. Therefore, a procedure was developed for measuring small amounts of cefadroxil and cefotaxime in pure samples as well as in formulations.

The method depends on forming a vis-absorbing compound with N,N-diethyl-p-phenylenediamine sulphate (N,N-DPPD) (ethylene blue dye), after the hydrolysis of cefadroxil and cefotaxime in sodium hydroxide solution to give hydrogen sulphide. The method is selective for cephalosporins, since other β-lactam compounds such as penicillins do not give hydrogen sulphide under alkaline hydrolysis. Variables such as pH, temperature, reagent concentrations and stability of the colour produced have been evaluated to permit selection of the most advantageous technique. Beer's law obeyed over the concentration range 0.5–10 μg/ml and 0.5–7 μg/ml for cefadroxil and cefotaxime, respectively. The detection limit being 0.1 μg/ml and 0.05 μg/ml (defined as the amount of the drug that gave a signal of twice the background noise) for cefadroxil and cefotaxime, respectively. The method has been successfully applied to the analysis of some pharmaceutical formulations.

The results have been statistically compared with those obtained by the official method. The relative standard deviation (for 10 replicates) was 1.12 (9 μg/ml) and 0.49% (5 μg/ml) for cefadroxil and cefotaxime, respectively. Procedural details and data for the effect of operating parameters are presented.     

Electrothermal atomic absorption spectrometric determination of cobalt in biological samples and natural waters using a flow injection system with on-line preconcentration by ion-pair adsorption in a knotted reactor

An on-line flow injection preconcentration-ETAAS method is developed for trace determination of cobalt in biological materials and natural samples by ion-pair sorption on the inner walls of a PTFE knotted reactor. The ion-pair is formed between the negatively charged cobalt-nitroso-R-salt complex and the tetrabutylammonium counter-ion. An enhancement factor of 15, a sampling frequency of 17 and a concentration efficiency of 4 are obtained for a preconcentration time of 60 s and a sample loading flow rate of 5 mL min(-1). The detection limit (3sigma) is 5 ng L(-1). The relative standard deviation at the 0.2 microg L(-1) level is 2.3%. The analytical results obtained for standard reference materials are in good agreement with the certified or indicated values and satisfactory recoveries of spiked cobalt in tap water are obtained.     

Separation and preconcentration of chromium species by selective absorption on Lemna minor and determination by slurry atomisation electrothermal atomic absorption spectrometry

A novel method for the separation and preconcentration of Cr(III)/Cr(VI) with Lemna minor and determination by slurry atomization electrothermal atomic absorption spectrometry (ETAAS) was developed. A sample solution was added to a polyethylene beaker containing 10 mg of 160 mesh pre-treated Lemna minor, adjusted to pH 1.0, stirred for 8 min for selective absorption of Cr(III) and then centrifuged. The upper layer of solution was transferred into another polyethylene beaker containing 10 mg of 160 mesh pre-treated Lemna minor, adjusted to pH 5.0, stirred for 12 min for adsorption of the residual Cr(VI) and centrifuged. The two residues in two centrifuge tubes were washed twice with water, 2 ml of agar solution added, stirred for 2 min, then two slurries were prepared and used for the determination of Cr(III) and Cr(VI) by ETAAS. Detection limits (3sigma) of 0.01 microg L(-1) for Cr(III) and 0.03 microg L(-1) for Cr(VI) were obtained. The relative standard deviation was 2.8% for Cr(III) and 3.3% for Cr(VI) at the 1 microg L(-1) level. The method was applied to the determination of Cr(III)/Cr(VI) in water samples. The analytical recoveries of Cr(III) and Cr(VI) added to samples were 97-102 and 96-103%, respectively.     

Simultaneous square-wave voltammetric determination of aspartame and cyclamate using a boron-doped diamond electrode

A simple and highly selective electrochemical method was developed for the simultaneous determination of aspartame and cyclamate in dietary products at a boron-doped diamond (BDD) electrode. In square-wave voltammetric (SWV) measurements, the BDD electrode was able to separate the oxidation peak potentials of aspartame and cyclamate present in binary mixtures by about 400 mV. The detection limit for aspartame in the presence of 3.0x10(-4) mol L(-1) cyclamate was 4.7x10(-7) mol L(-1), and the detection limit for cyclamate in the presence of 1.0x10(-4) mol L(-1) aspartame was 4.2x10(-6) mol L(-1). When simultaneously changing the concentration of both aspartame and cyclamate in a 0.5 mol L(-1) sulfuric acid solution, the corresponding detection limits were 3.5x10(-7) and 4.5x10(-6) mol L(-1), respectively. The relative standard deviation (R.S.D.) obtained was 1.3% for the 1.0x10(-4) mol L(-1) aspartame solution (n=5) and 1.1% for the 3.0x10(-3) mol L(-1) cyclamate solution. The proposed method was successfully applied in the determination of aspartame in several dietary products with results similar to those obtained using an HPLC method at 95% confidence level.     

Determination of manganese in feedstuffs by flow injection spectrophotometry based on rapid formation of permanganate at room temperature

A simple and rapid flow injection spectrophotometric procedure was developed for determination of manganese. In the presence of pyrophosphate and acetate, manganese was immediately oxidized to permanganate by periodate at room temperature in slightly alkaline medium. Under optimized conditions, the determination was made with a sampling rate of 120/h, a linear range of 0-30 mg/L Mn(II), a detection limit (S/N = 3) of 0.08 mg/L, and a relative standard deviation of 0.6% (n = 11) at 10 mg/L Mn(II). The proposed method was used to determine manganese in trace mineral premixes and feedstuffs. Results agreed well with those obtained by the standard atomic absorption spectroscopy method.