Advanced sample pretreatment for the monitoring of polycyclic aromatic hydrocarbons and extractable organic halogens in waste water. Flow based procedures with chromatomembrane cells

Polycyclic aromatic hydrocarbons (PAH) and extractable organic halogens (EOX) pollute industrial waste waters and need to be controlled continuously by automated procedures. Their sample pretreatment requires extraction first from complex matrices containing surfactants, humic acids, urine and electrolytes besides. When using chromatomembrane cells (CMC) for the extraction with pentane or hexane a flow based system can be established which preconcentrates the pollutants up to ratios of 100:1 at the same time. The extracted compounds become supplied to a gas chromatograph (PAH) using the split/splitless injection or to a combustion furnace (EOX), respectively. An aqueous solution later extracts the hydrogen halides from the exhaust gas for their simultaneous detection with an ion-chromatograph. The limits of lowest detection are attainable in the lower μg l⁻¹ range by matrix adjusted calibration. The CMC is a novel device containing a bloc of biporous PTFE which enables the contact of two immiscible phases. Polar liquids fill the macropores whereas the micropores remain available for non-polar liquids or gases.     

On-line collection/concentration of trace amounts of formaldehyde in air with chromatomembrane cell and its sensitive determination by flow injection technique coupled with spectrophotometric and fluorometric detection

A simple, rapid and highly sensitive method for the determination of trace amounts of formaldehyde in air by using flow injection analysis (FIA) system coupled with a three-hole chromatomembrane cell (CMC) was investigated by using a spectrophotometer and a fluorometer. The CMC was applied to on-line collection/concentration of trace amounts of formaldehyde in air into water as an absorbing solution; formaldehyde in the air was found to be quantitatively transferred into the absorbing solution in CMC. The solution, containing absorbed formaldehyde, was introduced into the carrier stream of the FIA system. The amount of formaldehyde in an absorbing solution was measured spectrophotometrically and fluorometrically after the reaction with a mixed reagent of acetylacetone and ammonium acetate at pH 5.6–5.8. The amount of formaldehyde in the absorbing solution, measured by the proposed system, could be converted to the concentration of formaldehyde in the air sample. A calibration graph prepared by a series of standard formaldehyde aqueous solutions was adopted. The formaldehyde in indoor air, determined as exampled by the proposed spectrophotometric FIA, was found to be 5.14 ± 0.08 ppbv for 20 ml of the air sample at the air flow rate of 6 ml min⁻¹, and the relative standard deviation (R.S.D.) was 1.56%. The limit of detections (LODs) of HCHO in an absorbing solution was 2 × 10⁻⁸ M (0.6 ppb) and 8 × 10⁻⁹ M (0.2 ppb), respectively, by the spectrophotometric and the fluorometric FIA, and the LODs of HCHO in air sample of 40 ml were 0.05 and 0.03 ppbv, respectively. The interferences from foreign species were examined; tolerable concentrations of other aldehydes were more than 50-fold of formaldehyde (1 × 10⁻⁶ M).     

电感耦合等离子体原子发射光谱法测定铅锌选矿流程原尾矿中铅锌铜

用5mL氟化氢铵(50g/L)、10mL盐酸、5mL硝酸、5mL高氯酸分解0.1g样品,盐酸(3%,V/V)为测定介质,定容在250mL容量瓶中,直接用电感耦合等离子体原子发射光谱法测定铅锌选矿流程原尾矿中的铅、锌、铜3种元素。根据分析线的选择原则,结合待测元素的检测范围,选择无干扰、峰形对称、灵敏度适中的谱线Pb 220.353nm、Zn 213.856nm、Cu 324.754nm作为分析线。各元素的质量浓度在一定范围内与其发射强度呈线性,校准曲线的线性相关系数均大于0.999 9,方法中各元素检出限为0.066～0.51ng/mL。方法经国家标准物质分析验证,测定值与认定值相符。按照实验方法测定铅锌选矿流程原尾矿中铅、锌、铜,测试结果与火焰原子吸收光谱法测定结果一致。     

On-line sample treatment and FT-IR determination of doxylamine succinate in pharmaceuticals

A low solvent consumption method for Fourier transform infrared spectroscopy (FT-IR) determination of doxylamine succinate in pharmaceuticals has been developed. The analyte was continuous and selectively extracted with a 13% (v/v) ethanol:chloroform solvent mixture, recirculating the solvent through the sample and monitoring the process by FT-IR. Doxylamine succinate was determined by on-line standard addition measuring the peak area in the regions 1730–1710 and 1485–1462 cm⁻¹ corrected with a two-point baseline established between 2000 and 1800 cm⁻¹. This new method implies low volumes of chloroformic solvent mixture, only 2.6 mL per sample, in front of classical batch FT-IR methods, improving analytical efficiency and reducing waste generation. The on-line extraction and standard addition determination of doxylamine succinate allowed a throughput of 10 h⁻¹.     

Absorption, concentration and determination of trace amounts of air pollutants by flow injection method coupled with a chromatomembrane cell system: application to nitrogen dioxide determination

The concentration distribution of an analyte in a chromatomembrane cell (CMC) was examined by using various air samples of different air pollutant (NO₂) concentrations and volumes, and the results obtained could be explained by a proposed principle of the concentration distribution of the analyte in the CMC. This principle was for the first time proved experimentally in the present study. On-line preconcentration and continuous determination of the air pollutant (NO₂) in air samples were realized by coupling a three-hole CMC with a flow injection analysis (FIA) system, where a triethanolamine (TEA) aqueous solution (2 g l⁻¹) was used as an absorbing solution for NO₂ in the air samples. A calibration method with standard nitrite aqueous solutions was developed for the determination of NO₂ in the air samples. Concentrations of NO₂ in indoor air and its diluted air samples were determined by the proposed CMC/FIA method. The volume of air sample necessary for the measurement was decreased to only 5 ml. The measuring time for one sample was about 5–6 min even when a 20 ml air sample was used.     

氨基酸铜螯合率测定光度新方法的研究

研究了新试剂对羧基偶氮安替比林的合成及其与铜的显色反应,建立测定氨基酸铜螯合率的光度方法。在乙酸介质中,Cu2 与对羧基偶氮安替比林反应形成组成比为2∶1的蓝色配合物,配合物的最大吸收峰位于622nm,表观摩尔吸光系数达3.03×104L·mol-1·cm-1,Cu2 的质量浓度在0～0.80μg/mL符合比耳定律。此外,显色体系有很高的选择性,大多数金属离子允许量在mg级以上。氨基酸铜螯合率的测定包括结合态和游离态铜的分析,由于在氨基酸铜的水溶液中加入对羧基偶氮安替比林试剂时,氨基酸铜被试剂立即分解并转化为稳定的对羧基偶氮安替比林铜配合物,因此,总铜量的测定不需消化样品而直接进行。游离态的铜经葡聚糖凝胶(G-15)吸附后,用稀HCl洗脱后按上述方法测定。     

A flow injection method for biamperometric determination of dipyrone in pharmaceuticals

A flow-injection method for determination of dipyrone (novalgin, metamizol) in pharmaceutical tablets with biamperometric detection is described. Flow-parameters such as flow rate, coil length and sample injection volume were optimized. The calibration graph was linear (r=0.9997) within the range of 10-50 mg l⁻¹ in a 1-mmol l⁻¹ HCl carrier solution for an applied potential of 100 mV between the two platinum wire electrodes. Two indicating redox systems were studied, namely Fe(III)/Fe(II) and I₂/I⁻. The former proved to be well suited as a selective and sensitive biamperometric indicating system for dipyrone in the presence of ingredients commonly accompanying the drug. The developed method was successfully applied to the determination of dipyrone in several commercial pharmaceutical preparations. The sampling rate was 71 samples per hour with a rsd of 1.6% (eight injections of a 14-mg l⁻¹ dipyrone solution). Recoveries close to 100% demonstrated the reliability of the proposed method.     

Kinetic spectrophotometric method for the determination of ranitidine and nizatidine in pharmaceuticals

An accurate and simple kinetic method is described for the determination of ranitidine and nizatidine in pure form and in pharmaceuticals. The method is based on the reaction of the compounds with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole in pH 7.4 borate buffer at 60 degrees C for a fixed time of 25 min for both compounds. The absorbance of the reaction product is measured at 495 nm for ranitidine and nizatidine. Calibration graphs were linear over the concentration range of 2-20 microg/mL, with limits of detection of 0.13 (3.7 x 10(-7) M) and 0.25 microg/mL (7.5 x 10(-7) M) for ranitidine and nizatidine, respectively. The proposed method was applied successfully to the determination of ranitidine in tablets and ampoules with average recoveries of 100.26+/-0.69 and 100.29+/-0.59%, respectively, and to the determination of nizatidine in capsules with an average recovery of 104.26+/-0.44%. The results obtained are in good agreement with those obtained by the other methods used for comparison. A proposal of the reaction pathway is also presented.     

A simple spectrophotometric method for determination of isoxsuprine hydrochloride in pharmaceuticals

A spectrophotometric method has been developed for the determination of isoxsuprine hydrochloride and its dosage forms, based on its coupling reaction with diazotized sulphanilic acid. The yellow chromophore has an absorption maximum at 440 nm. Beer's law holds over the range 0.8-8 mu/ml in the final solution.     

A rapid spectrophotometric method for determination of zinc in milk

1-(2',3'-Dihydroxypyridyl-4'-azo)benzene-4-sulphonic acid and the corresponding 5'-chloro-substituted acid are proposed as sensitive reagents for zinc. Cyanide masking and selective demasking of zinc can be used to deal with the interference of many metal ions, cadmium can be masked with semithiocarbazide, and thiosulphate can be used for masking Hg(II), Pd(II) and Os(VIII). The molar absorptivities are about 1.3 x 10(5) 1.mole(-1).cm(-1). The method has been used for determinating zinc in milk.     

A spectrophotometric method for quantitative determination of lactulose in pharmaceutical preparations

A simple spectrophotometric assay for the quantification of lactulose in pharmaceutical preparations was developed. The method is based on hydrolysis of lactulose under acidic conditions. The hydrolyzed product reacts with resorcinol, giving absorption peaks at 398 and 480 nm. Both absorption wavelengths can be used for the determination of lactulose. The limit of detection of lactulose at 398 nm and 480 nm was 0.075 μg mL⁻¹ and 0.65 μg mL⁻¹, respectively. The calibration was linear in the range of 5–25 μg mL⁻¹. Analytical conditions were optimized, and the method was validated for analysis of pharmaceutical preparations. The determined amount of lactulose was found to be in good agreement with labeled claims in commercial products. The proposed method is economical, convenient, and suitable for the quantification of lactulose in pharmaceutical preparations. The text was submitted by the authors in English.     

‘In situ’ preparation of nitrous acid solutions by photoreduction in a flow assembly for analysis of pharmaceuticals

The solutions of nitrite ion, or nitrous acid, are frequently used as reagent in different analytical procedures and in pharmaceutical analysis. The low stability of the aqueous solutions of this reagent implies the tedious work of freshly prepared solutions every day and being kept in the refrigerator. In this paper, a photoreactor formed by a low pressure mercury lamp and nesting in a continuous-flow manifold is studied, tested, and proposed for the in situ reduction of nitrate solution into nitrite. The conversion into nitrite is reproducible and it has been successfully applied to determination of different drugs, mostly from the sulphonamide family, in an FIA assembly.     

Development of a validated HPLC method for the determination of four penicillin antibiotics in pharmaceuticals and human biological fluids

A quantitative method for the determination of four penicillin antibiotics, amoxicillin (AMO), oxacillin (OXA), cloxacillin (CLO), and dicloxacillin (DICLO), has been developed. Separation was achieved on an Inertsil ODS-3 (250 x 4 mm, 5 microm) column after selective extraction of penicillin drugs from biological matrices by means of SPE. Gradient elution with a mobile phase consisting of 0.1% TFA (pH 1) and ACN, and PDA detection with monitoring at 240 nm was applied. Salicylic acid (5 ng/microL) was used as the internal standard. RP-8 Adsorbex Merck cartridges provided high absolute recoveries (98-101%). The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 8) and between-day precision (n = 8) revealed RSD <10%. Recoveries from biological samples ranged from 91 to 103%. The detection limits were estimated as 3.3 ng for AMO, OXA, and CLO, and 6.6 for DICLO in blood plasma. LOD in whole blood and urine was 6.6 ng. Injection volume was 20 microL. The method was applied to commercially available AMO containing pharmaceuticals and spiked biological matrices. The method was also applied to biological samples after AMO oral administration, where the drug was successfully identified and quantified.     

利用混合线性分析分光光度法同时测定微量铜、锌、镍

研究以5 Br PADAP为显色剂,用混合线性分析分光光度法同时测定铜、锌、镍。在pH8.2的硼砂 盐酸缓冲溶液中,Cu2 、Zn2 、Ni2 分别与5 Br PADAP形成稳定的配合物,其吸收光谱相互重叠。用一种新的数学模型,即混合线性分析进行光谱分辨,各组分的纯光谱则用最小二乘法求得。讨论了反应条件、测量波长的选择等因素的影响。铜、锌、镍的标准回收率分别为95.0%～102.5%、94.2%～101.3%和96.2%～104.2%。应用于铝合金中铜、锌、镍的同时测定。     

Continuous spectrophotometric determination of copper, nickel and zinc in copper-base alloys by flow-injection analysis

Flow-injection methods have been developed for the determination of copper, nickel and zinc in copper-base alloys, including several types of brasses, deoxidized copper, beryllium copper and German silver. The system for copper and nickel involves the measurement of the absorbance of the copper(II) and nickel(II) aquo-complexes at 805 and 410 nm, respectively, after simple dissolution of the sample in a nitric acid-phosphoric acid mixture. The system needs no further reagents and the sample solutions can be analysed at rates of up to 280 /hr for copper (or nickel in German silver) without any carry-over. The system for zinc consists of automatic dilution of the injected sample with a thiosulphate-acetate buffer solution and the subsequent measurement of the absorbance of the zinc-Xylenol Orange complex at 568 nm. This system permits analysis rates of up to 90/hr for zinc solutions, with no carry-over. The procedures have been applied to standard copper-base alloys. The results agreed satisfactorily with the certified values. The precision ranges are 0.2-0.7% for copper and nickel and 0.5-0.8% for zinc.     

New method for the spectrophotometric determination of ultramicro amounts of copper

A deep yellow colour is formed by the reaction with phenol and chloramine-T in the presence of copper, and this reaction is used for the photometric determination of copper. An aqueous solution of copper and the reagents at pH 11.5-11.6 is heated. The molar absorptivity at 410 mmu, is 2.32 x 10(6). The method has been used satisfactorily to determine ultram amounts of copper in high-purity silicon.     

An extractive spectrophotometric method for the determination of tetramisole hydrochloride in pharmaceutical preparations

A simple extractive photometric method for the determination of tetramisole hydrochloride in pharmaceutical preparations is described. The method uses the formation of coloured complexes of the drug with reagents such as Solochrome Dark Blue, Solochrome Black T, Bromocresol Purple, Bromothymol Blue, Bromophenol Blue and Bromocresol Green in an acidic buffer. The ion-pair complexes formed are quantitatively extracted into chloroform under the experimental conditions.     

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.     

Application of a poly(dithiocarbamate) resin to the determination of trace copper,iron and zinc in natural waters

A chelating poly(dithiocarbamate) resin with macroreticular support is shown to be effective for the preconcentration of copper, iron and zinc in natural waters. The retained ions can be eluted efficiently in 5 ml of 8M nitric acid from 1–20-cm columns of resin.This poly(dithiocarbamate) resin is used for the preconcentration and determination of copper, iron and zinc by flame atomic absorption spectrophoto-metry. Common ions present in natural waters do not interfere. The detection limits were 0.50, 0.21 and 0.04 g 1^–1 for Cu, Fe and Zn respectively.     

A Kinetic spectrophotometric method for determination of amlodipine and Nifedipine in pharmaceutical preparations

A simple, accurate, sensitive and economical procedure for the estimation of amlodipine besylate and nifedipine, both in pure and dosage forms, has been developed. The method is based on the reduction of iron(III) by the studied drugs and subsequent interaction of iron(II) with ferricyanide to form Prussian blue. The reaction develops through a slow kinetics and completes in about 10 min. Both initial slope and fixed time methods were used to derive calibration graphs. The resulted calibration equations were linear in the concentration ranges of 1.0-20.0 and 3.0-19.0 μg ml^-1 for AML and NIF, and the detection limits were 0.10 and 0.19 μg ml^-1, respectively. Seven replicate analyses of solutions containing three different levels of each drug resulted in very low relative error of prediction (less than 1.6%) and relative standard deviation (less than 4%) confirming accuracy and precision of the proposed method. The proposed method was applied to the determination of these drugs in pharmaceutical formulations and excellent recoveries were obtained.