Determination of cefadroxil by sequential injection with spectrophotometric detector.

A sequential injection analysis (SIA) spectrophotometric procedure for cefadroxil determination has been developed. The SIA instrumentation was modified to achieve the desired function and operations by using the software developed to interface the PC with the conventional SIA system. The method is based on the measurement of a red, water-soluble product formed by the reaction between cefadroxil and 4-aminoantipyrine in the presence of alkaline potassium hexacyanoferrate(III) at 510 nm. Optimum conditions for determining the drug were investigated. Beer's law was obeyed over the concentration ranges of 1 - 10 mg L(-1) and 10 - 50 mg L(-1) with a detection limit (3 sigma) of 0.17 mg L(-1) and a limit of quantification (10 sigma) of 0.56 mg L(-1). The relative standard deviations of 1.98% and 1.93% for 5 mg L(-1) and 30 mg L(-1) of the drug, respectively (n = 11) are obtained. The proposed method has been applied satisfactorily to the determination of cefadroxil in commercial pharmaceutical formulations with a sampling rate of 100 h(-1). Results obtained were in good agreement with those obtained by the official HPLC method at the 95% confidence level.     

Solid-phase reactors in sequential injection analysis. Determination of manganese (II) in tap water and effluent streams using a solid-phase lead(IV) dioxide reactor in a sequential injection system

The determination of manganese(II) in tap water and effluent streams, using a solid-phase reactor incorporated into a sequential injection system was investigated. Mn2+-ions in samples injected into a carrier stream, were oxidised by solid lead(IV) dioxide suspended on silica gel beads to form MnO4- -ions which were detected spectrophotometrically at 526 nm. The linear range of the system is from 1 to 7 mg L(-1) with a detection limit of 0.62 mg L(-1). The proposed system is suitable for the determination of manganese(II) in tap and effluent streams at a rate of approximately 50 samples per hour with a relative standard deviation of better than 3%. Statistical comparison between the proposed sequential injection system and a standard ICP method revealed that there is no significant difference between the two methods at the 95% confidence level for effluent streams and at 99.9% for tap water.     

Determination of bromide ions in seawater using flow system with chemiluminescence detection

A simple flow-based procedure with chemiluminescence (CL) detection is proposed for bromide ion determination in seawater. The procedure was based on the oxidation of bromide to bromine by chloramine-T followed by the reaction of bromine with luminol resulting in CL emission. Since no significant reaction within chloramine-T and luminol was observed, the detection was carried out without bromine extraction from the oxidant medium. The proposed flow system had a sampling rate of 40 determinations per hour, reagents consumption of 100 μg luminol and 60 μg chloramine-T per determination, a limit of detection of 0.5 mg l⁻¹ bromide ions, a linear concentration range (r = 0.999 and n = 7) between 0 and 100 mg l⁻¹, and a coefficient of variance better than 2.5% (for 10 measurements of a 10 mg l⁻¹ Br⁻ solution) were achieved. The analytical system was applied for the determination of bromide in seawater and estuarine-water samples, obtaining an analyte recovery ranging from 94 to 102% and comparing the results with a reference spectrophotometric method no significant difference was observed in 95% confidence level.     

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.     

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.     

Determination of boron as boric acid in eye lotions using a sequential injection system

A simple and reliable sequential injection analysis (SIA) system is described for the determination of boron as boric acid in eye lotions. This method is based on the complexation reaction between d-sorbitol and boric acid followed by the acid-base reaction with methyl orange (MO). The colour change reaction is monitored at 520 nm. The system is able to monitor boron at a frequency of 30 samples per h with a relative standard deviation of less than 0.6%. The calibration graph is linear up to 12-mg l(-1). The system has a detection limit of 0.06-mg l(-1). No significant differences (at 95% probability level) were found between the proposed SIA method and the reference method.     

β-环糊精增敏亚甲基蓝荧光法测定左氧氟沙星

提出了一种增敏亚甲蓝荧光法测定左氧氟沙星新方法。左氧氟沙星(LVFX)与Br2发生加成反应,剩余的Br2能氧化亚甲蓝(MB)使其荧光降低,通过测定亚甲蓝的荧光强度间接测定左氧氟沙星(LVFX)的含量,加入适量β-环糊精(β-CD)使其荧光强度上升为原来的近2倍,大大提高其灵敏度。该体系最大激发波长为λex=660 nm,最大发射波长为λem=678 nm,线性范围为0.002～1.6 mg/L,检出限为0.0008 mg/L,相对标准偏差为0.13%。本方法可作为痕量左氧氟沙星的分析方法。     

溴离子选择电极法测定有机化工产品中四丁基溴化铵的残留

建立了有机化工产品中四丁基溴化铵残留测定的新方法。该法线性范围为0.01~0.10 g/L,检出限为0.4 mg/L,相对标准偏差为2.4%(0.05 g/L,n=11),相关系数为0.998,用于实际样品测定,结果令人满意。     

Simultaneous detection of S and R captopril using sequential injection analysis

A simultaneous detection sequential injection analysis (SIA) system is proposed for the determination of S and R captopril using a potentiometric, enantioselective membrane electrode based on maltodextrin (DE=14-17) for the assay of S-captopril and an amperometric biosensor for the assay of R-captopril. The proposed SIA system can be utilized reliably for the on-line simultaneous detection of the enantiomers in the synthesis process at a rate of 38 samples per hour in the following linear concentration ranges: 100-1000 nmol/l (R-captopril) and 1-1000 mumol/l (S-captopril) with a RSD better than 0.009% (n=10).     

Flow injection photoinduced chemiluminescence determination of imazalil in water samples

In this work, a fast, simple and economic method is proposed for the determination of imazalil in water samples by flow injection photoinduced chemiluminescence. In this method, imazalil degrades in basic media through the use of a photoreactor, and the resulting photofragments react with ferricyanide and generate the direct chemiluminescence signal. To the authors' knowledge, this is the first time that a chemiluminescence method has been proposed for the determination of this fungicide. All physical and chemical parameters in the flow injection chemiluminescence system were optimized in the experimental setting. In the absence of preconcentration, the linear dynamic range for imazalil was 0.75-5 mg L(-1) and the detection limit was 0.171 mg L(-1). The application of solid-phase extraction with C18 cartridges allowed the elimination of interference ions, the reduction of the linear dynamic range to 15-100 μg L(-1), and a detection limit of 3.4 μg L(-1). This detection limit is below the maximum concentration level established by the Regulations of the Hydraulic Public Domain for pesticide dumping. The sample throughput after solid-phase extraction of the analyte was 12 samples h(-1). The intraday and interday coefficients of variation were below 9.9% in all cases. This method was applied to the analysis of environmental water samples, and recoveries of between 95.7 and 110% were obtained.     

Potentiometric flow-injection determination of trace hydrogen peroxide based on its induced reaction in iron(III)-iron(II) potential buffer containing bromide and molybdenum(VI)

A rapid and highly sensitive potentiometric flow-injection method for the determination of trace hydrogen peroxide was developed by use of an Fe(III)-Fe(II) potential buffer solution containing bromide and Mo(VI). The analytical method was based on a linear relationship between a concentration of hydrogen peroxide and a largely transient potential change of an oxidation-reduction potential electrode due to bromine generated by the reaction of hydrogen peroxide with the potential buffer solution. The oxidation of bromide to bromine by hydrogen peroxide occurred very rapidly with the assistance of Mo(VI) when Fe(II) existed in the potential buffer solution. It was estimated by batchwise experiments that hydroxyl radical, OH., was generated by the reaction of hydrogen peroxide with Fe(II) as an intermediate, and subsequently oxidized bromide to bromine. In a flow system, analytical sensitivities to hydrogen peroxide obtained by the detection of the transient change of potential were enhanced about 75 fold compared with those obtained by using the potential change caused by the reaction of hydrogen peroxide with the potential buffer solution without bromide and Mo(VI). Sensitivities increased with decreasing concentration of the Fe(III)-Fe(II) buffer in the reagent solution. The detection limit (S/N = 3) of 4 x 10(-7) M (13.6 ppb) was achieved by using the 1 x 10(-4) M Fe(III)-Fe(II) buffer containing 0.4 M NaBr, 1.0 M H(2)SO(4) and 0.5% (NH(4))(6)Mo(7)O(24). Analytical throughput was approximately 40 h(-1) and the RSD (n = 6) was 0.6% for measurement of 4 x 10(-6) M hydrogen peroxide. The proposed method was applied to the determination of hydrogen peroxide in real rainwater samples, and was found to provide a good recovery for H(2)O(2) added to rainwater samples.     

Determination of bromide by low power surfatron microwave induced plasma after bromine continuous generation

A simple continuous flow generation of volatile bromine is described for the determination of low concentrations of the elements by atmospheric-pressure argon microwave induced plasma (MIP) surfatron. Bromine is continuously generated by mixing the bromide with sulphuric acid and hypochlorite solutions. The bromine vapor is separated from the aqueous phase by a gas-liquid separator and is desiccated by passing it through concentrated sulphuric acid. The detection limit attained was 2 microg/l. and the precision was +/-0.7% (at the 80 microg/l. level). The proposed determination is very selective if oxidizing/reducing agents are absent. The procedure has been tested for bromide determination in two drug preparations. Good agreement between the experimental results and the certified values has been obtained.     

On-line monitoring of nitrite in fertilizer process streams, natural and waste water effluents with sequential injection analysis

A sequential injection system for the online monitoring of nitrite in fertilizer process streams, natural and waste water effluents is proposed. Nitrite is diazotised in the SIA system with N-(1-naphthyl) ethylenediammonium dichloride to form a highly coloured azo dye which is measured at 525 nm. The proposed system is fully computerised and is able to monitor nitrite at a frequency of 49 samples per hour with a relative standard deviation of < 2.7%. The calibration curve is linear up to 5 mg/l. The detection limit is 0.053 mg/l.     

Spectrophotometric flow injection methods for zinc determination in pharmaceutical and biological samples.

Zinc ions form a yellow complex with di-2-pyridyl ketone salicyloylhydrazone (DPKSH). This complex showed maximum absorption at 376 nm, and it was used to develop spectrophotometric flow injection methods for Zn(II) determination in different samples. Two types of flow systems were proposed. In the first system, a linear analytical curve was obtained in a concentration range from 0.217 to 4.60 mg L(-1) Zn(II), with a detection limit of 48.8 microg L(-1). In the second system, a minicolumn packed with an anion exchanger resin was used to concentrate Zn(II) as a chlorocomplex, and a linear analytical curve within a concentration range from 0.0824 to 2.06 mg L(-1) Zn(II) was obtained, having a detection limit of 13.9 microg L(-1). The developed methods were applied to biological and pharmaceutical samples, and a great compliance was observed by comparing the results with ones obtained by an atomic absorption technique.     

Determination of bromine in organic compounds by high-performance liquid chromatography

A method is proposed for the determination of bromine in organic compounds (which may also contain chlorine and iodine) by oxygen-flask combustion of the compound followed by pre-column reaction of bromide with acetanilide and 2-iodosobenzoic acid to form 4-bromoacetanilide which is then chromatographed on an ODS column with a mobile phase of methanol: water, 65:35 v/v, detection at 240 nm, and 4-N-acetylaminotoluene as internal standard. The method is rapid and precise (RSD 相似文献   

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.     

Solid-phase reactors in sequential injection analysis. Determination of manganese(II) in tap water and effluent streams using a solid-phase lead(IV) dioxide reactor in a sequential injection system

The determination of manganese(II) in tap water and effluent streams, using a solid-phase reactor incorporated into a sequential injection system was investigated. Mn²⁺-ions in samples injected into a carrier stream, were oxidised by solid lead(IV) dioxide suspended on silica gel beads to form MnO₄ ^–-ions which were detected spectrophotometrically at 526 nm. The linear range of the system is from 1 to 7 mg L^–1 with a detection limit of 0.62 mg L^–1. The proposed system is suitable for the determination of manganese(II) in tap and effluent streams at a rate of approximately 50 samples per hour with a relative standard deviation of better than 3%. Statistical comparison between the proposed sequential injection system and a standard ICP method revealed that there is no significant difference between the two methods at the 95% confidence level for effluent streams and at 99.9% for tap water.     

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.     

流动注射双安培法测定多巴胺

通过偶合多巴胺在铂电极上的氧化和高锰酸钾在铂电极上的还原,建立了一个不施加电压的条件下的流动注射双安培法直接测定多巴胺的新方法。以0.05 mol/L硫酸为载液,多巴胺的氧化峰电流与其浓度在0.8~160 mg/L范围内呈线性关系,线性回归方程为i(nA)=652.9C-239.2(r=0.9998,n=10),检出限为0.2 mg/L;RSD为2.86%(N=80 mg/L,n=14);进样频率为80次/h。本方法具有很高的选择性和灵敏度,样品处理方法简单快速,适于连续自动测定。用于实际样品的测定,结果满意。     

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.