Rapid spectrophotometric determination of fosfestrol following on-line hydrolysis by alkaline phosphatase using flow injection and chasing zones

A new flow injection (FI) method is reported for the spectrophotometric determination of fosfestrol (diethyl-stilbestrol (DES) diphosphate) in pharmaceutical formulations. The proposed method is based on the on-line hydrolysis of the analyte by alkaline phosphatase (Al-Pase) using a “chasing zones” FI manifold. The orthophosphate ions, thus, generated are determined spectrophotometrically (λ_max=690 nm) using the molybdenum blue approach. The chemical and FI variables affecting the enzymatic reaction were investigated. The proposed method is very precise (s_r=1.1% at 1×10⁻⁴ mol l⁻¹ fosfestrol, n=12), fast (allowing up to 40 samples h⁻¹ to be analyzed) and has a determination range of 2×10⁻⁵ to 2×10⁻⁴ mol l⁻¹, with a satisfactory 3σ detection limit of 5×10⁻⁶ mol l⁻¹. The method was shown to provide accurate determinations of the fosfestrol concentration in a pharmaceutical formulation, giving relative errors, e_r, of +0.6 and −0.5% compared to the value stated by the supplier (Asta Medica Inc.) and the concentration derived using a method recommended by the United States Pharmacopoeia XXI, respectively. In addition, the average recoveries of known amounts of the analyte ranged between 99.2 and 101.2%.     

Chemiluminescence sequential injection immunoassay for vitellogenin using magnetic microbeads

A rapid and sensitive immunoassay for the determination of carp vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a samarium-cobalt magnet. An anti-Vg monoclonal antibody, immobilized on magnetic beads, was used as a solid support for the immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by a samarium-cobalt magnet and the flow of the carrier solution. The immunoassay was based on a sandwich immunoreaction of anti-Vg monoclonal antibody (primary antibody) on the magnetic beads, Vg, and the anti-Vg antibody labeled with horseradish peroxidase (HRP) (secondary antibody), and was based on a subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The magnetic beads to which the primary antibody was immobilized were prepared by coupling the primary antibody with the magnetic beads after an agarose-layer on the surface of the magnetic beads was epoxidized. The primary antibody-immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the samarium-cobalt magnet, a Vg sample solution, an HRP-labeled secondary antibody solution and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photomultiplier located at the upper side of the flow cell. The optimal incubation times both for the first and second immunoreactions were determined to be 20 min. A concave calibration curve was obtained between Vg concentration and chemiluminescence intensity when various concentrations of standard Vg samples (2–100 ng mL⁻¹) were applied to the SIA system under optimal conditions. In spite of a narrow working range, the lower detection limit of the immunoassay was about 2 ng mL⁻¹.     

Flow injection fluorescence determination of dopamine using a photo induced electron transfer (PET) boronic acid derivative

An automated flow injection analysis system was developed for the fluorometric determination of dopamine in pharmaceutical injections. The method is based on the quenching effect of dopamine on m-dansylaminophenyl boronic acid (DAPB) fluorescence due to the reverse photo induced electron transfer (PET) mechanism. Effects of pH and interfering species on the determination of dopamine were examined. Calibration for dopamine, based on quenching data, was linear in the concentration range of 1.0 × 10⁻⁵ to 1.0 × 10⁻⁴ M. Detection limit (3 s) of the method was found to be 3.7 × 10⁻⁶ M. Relative standard deviation of 1.2% (n = 10) was obtained with 1.0 × 10⁻⁵ M dopamine standard solution. The proposed method was applied successfully for the determination of dopamine in pharmaceutical injection sample. The sampling rate was determined as 24 samples per hour.     

测定驱油体系中碱度的流动注射分光光度法

采用流动注射分析技术，以酸碱指示剂－－间硝基酚溶液作载流，实现了三元复合驱油体系中碱的测定；该法可测定10－600mg/L NaOH(强碱），20－1400mg/L Na2CO3(弱碱）；方法的检出限为0．5mg/L NaOH,1mg/L,Na2CO3；对含量为200mg/L的样品测定6次的相对标准偏差为0.6%(NaOH),0.5%(Na2CO3);测定速率每小时达94个样；该法也适用于其它无机碱、有机碱的测定。     

Flow-injection fluorimetric determination of menadione using on-line photo-reduction in micellar media

A very sensitive fluorimetric method for the determination of menadione using a flow injection system is proposed. The method is based on the on-line reduction of menadione in dodecylsulphate micelles upon irradiation with UV light. The strong fluorescence of the reduced menadione in micellar medium is measured at 410 nm with excitation at 340 nm. The method shows a linear range between 2.42 and 245 ng ml⁻¹ and a limit of detection of 0.18 ng ml⁻¹. The sample throughput was 90 injections per hour. The applicability of the assay was demonstrated by analysing this vitamin in commercial pharmaceutical preparations.     

On-line organoselenium interference removal for inorganic selenium species by flow injection coprecipitation preconcentration coupled with hydride generation atomic fluorescence spectrometry

The existence of dimethylselenium (DMSe) and dimethyldiselenium (DMDSe) in some environmental samples can cause serious interference on Se(IV) determination by hydride generation atomic fluorescence spectrometry (HG-AFS) due to their contribution on HG-response. A flow injection separation and preconcentration system coupled to HG-AFS was therefore developed by on-line coprecipitation in a knotted reactor (KR) for eliminating interference subjected from organoselenium. The sample, spiked with lanthanum nitrate, was merged with an ammonium buffer solution (pH 8.8), which promoted coprecipitation of Se(IV) and quantitative collection by 150 cm PTFE KR. DMSe and DMDSe, however, were unretained and expelled from the KR. An air flow was introduced to remove the residual solution from the KR, then a 1.2 mol l⁻¹ HCl was pumped to dissolve the precipitates and merge with KBH₄ solution for HG-AFS detection. The interference of DMSe and DMDSe on the Se(IV) determination by conventional HG-AFS and its elimination by the developed separation and preconcentration system were evaluated. With optimal experimental conditions and with a sample consumption of 12.0 ml, an enhancement factor of 18 was obtained at a sample frequency of 24 h⁻¹. The limit of detection was 0.014 μg l⁻¹ and the precision (R.S.D.) for 11 replicate measurements of 1.0 μg l⁻¹ Se(IV) was 2.5%. The developed method was successfully applied to the determination of inorganic selenium species in a variety of natural water samples.     

A Novel Potentiometric Membrane Sensor Based on Aryl Palladium Complex for Selective Determination of Thiocyanate in the Saliva and Urine of Cigarette Smokers

A highly selective potentiometric sensor for thiocyanate ion based on the use of a newly synthesized organo‐palladium ion exchanger complex dispersed in a plasticized poly(vinyl chloride) membrane is described. The sensor displays a Nernstian response (?57.8±0.2 mV decade^?1) over a wide linear concentration range of thiocyanate (1.0×10^?6–1.0×10^?1 mol L^?1 ), low detection limit (6.3×10^?7 mol L^?1), fast response (20 s), stable potential readings (±0.4 mV), good reproducibility (±0.9%), long term stability (8 weeks), high precision (±0.7%) and applicability over a wide pH range (4–10). Negligible interferences are caused by F^?, Cl^?, I^?, Br^?, NO₃^?, NO₂^?, CN^?, SO₄^2?, S₂O₃^2?, PO₄^3?, citrate, acetate and oxalate ions. Under hydrodynamic mode of operation (FIA), the calibration slope is ?51.1±0.1 mV decade^?1, the linear response range is 1.0×10^?5–1.0×10^?1 mol L^?1 SCN^? and the sample throughput is 40–45 per hour. The sensor is satisfactory used for manual and flow injection potentiometric determination of SCN^? in the saliva and urine of cigarette smokers and non smokers. The data agree fairly well with results obtained by the standard spectrophotometric technique. Direct potentiometry and potentiometric titration of SCN^? with Ag⁺ are also monitored with the sensor.     

Greener analytical method for the determination of copper(II) in wastewater by micro flow system with optical sensor

Greener analytical method using micro flow system for the determination of Cu(II) in wastewater samples was designed and investigated. The micro flow system consisted of a planar glass chip with poly(dimethylsiloxane) (PDMS) top plate and fixed with fiber optic probe as optical sensor for monitoring of Cu(II) that reacted with 2-carboxy-2′-hydroxy-5′-sulfoformazyl benzene (zincon) on the chip at 605 nm. This design gave a satisfied sensitivity with a linear calibration graph over the range of 0.1-3.0 μg mL⁻¹ of Cu(II) and correlation coefficient 0.9991. The percentage relative standard deviation was 2.5 for 10-replicate measurements and the limit of detection (LOD) was 0.1 μg mL⁻¹. This system has been successfully applied to the determination of Cu(II) in wastewaters from electroplating industry with less reagents and samples consumption and diminutive waste generation.     

痕量锰的停流反相流动注射分析——Mn~(2+)-NaH_2PO_2-KIO_4-NTA催化体系

本文提出了一种新的停流流动注射分析技术-阀停流技术.基于以氨三乙酸(NTA)作助催剂Mn2+对KIO4,氧化NaH2PO2的催化作用,建立了痕量锰的停流反相流动注射分析。在0-5.0μg/L Mn2+呈线性,可测浓度y10.05Vg/L.X3.Opg/L Mn1` 10次测定的相对标准偏差为_3.0%.选择性很高,用于自来水、污水及井水中痕量锰的侧定,获得满意结果.     

Spectrophotometric determination of magnesium in pharmaceutical preparations by cost-effective sequential injection analysis

A simple and rapid, inexpensive spectrophotometric method was proposed for magnesium assay in pharmaceutical preparations by sequential injection analysis (SIA). The method is based on the reaction between o-cresolphthalein complexone (CPC) and Mg(II) in alkaline media, yielding a pink colored complex with absorption maximum at 570 nm. Since the formation constant between Ca-CPC and Mg-CPC is similar, initially a sample/standard solution was aspirated into the holding coil followed by a mixture of masking-buffer solutions. This was done because masking of calcium should be accomplished before Mg-CPC complexation. Then the reagent was introduced into the reaction coil to produce a colored complex, which is measured spectrophotometrically at 570 nm. In this way the interference of calcium was reduced. Furthermore, all the parameters that affect the reaction were evaluated. The calibration curve is linear over a range of 0-20 mg l⁻¹ of Mg(II) with a detection limit of 0.24 mg l⁻¹. A sample throughput of 80 samples per hour and relative standard deviation <2.0% were achieved. The proposed method was successfully applied for the assay of magnesium in three different compositions of pharmaceutical preparations (tablets). The results were found to be in good agreement with the manual flame atomic absorption spectrophotometry (FAAS) and UV-Vis spectrophotometry methods and with the claimed values by the manufactures. The t-test shows no significant difference at 95% confidence level.