Determination of Chlorine and Chlorine Dioxide in Air with Semiconductor Sensors

The parameters of sensors for the determination of chlorine and chlorine dioxide in air in static and kinetic measurement modes were studied. A photocolorimeter was used for sensor calibration. It was show that the photocolorimeter can be calibrated for chlorine dioxide trace concentrations in air below 4 mg/m³.     

Solid-phase fluorometric determination of Al(III), Be(II), and Ga(III) using dynamic preconcentration on reagent cellulose matrix

A fluorimeter is developed, which provides sample pretreatment, preconcentration of analytes from natural waters on the surface of indicator cellulose matrices, and the simultaneous measurement of their fluorescence. The device employs a L-711UVC ultraviolet light diode and a Digital color sensor S9706 photodiode, which registers simultaneously in the red (615 nm), green (540 nm), and blue (465 nm) spectrum regions. The opportunities of the application of this fluorimeter have been shown by an example of determination of 1–100 μg/L Al(III) and 0.1–10 μg/L Be(II) and Ga(III).     

Comparison of analytical potentials of detection versions in chromaticity rapid analysis using portable instruments

The analytical possibilities of portable photocolorimeter, reflectometer and scanner have been compared by the example of different test systems, involving Co(II) and Fe(III) complexes with thiocyanate and nitrite ions adsorbed onto polyurethane foams. The performance characteristics of Co(II), Fe(III) and nitrite ion determination in water using portable instruments have been determined. The reproducibility and the area of possible application of the instruments have been assessed.     

钛-(口底)唑-CTMAB体系及其用于测定钛的探讨

(口底)唑是一种灵敏的显色剂,为此本文对钛-(口底)唑-阳离子表面活性剂的三元体系进行了研究,结果表明:钛、(口底)唑和所研究的几种阳离子表面活性剂均可形成三元胶束络合物,而其中以CTMAB为最佳,其摩尔吸光系数可达1.1×10⁵。所拟定的方法用于测定水中痕量钛,结果较满意。     

A portable pulsed cavity ring-down transmissometer for measurement of the optical extinction of the atmospheric aerosol

A small portable system is described which is used to directly determine the optical extinction of the atmospheric aerosol. The requisite highly sensitive measurement of the optical extinction is accomplished simultaneously at two wavelengths in the near-infrared (1064 nm) and visible (532 nm), using the pulsed cavity ring-down (CRD) approach. The measurement at the two wavelengths can aid in separating the scattering and absorption components of the optical extinction. Rayleigh equivalent optical extinction of approximately 10 x 10(-6) m(-1) from particulate matter in the atmospherically important 0.1-2.5 pm diameter size range (fine particle accumulation mode) can be readily observed with short (<5 s) integration times. Optical extinction is inversely related to the visual range, and so the instrument provides a direct measurement of this particulate-related air quality indicator. The instrument can also provide particle size range-selected multiwavelength optical property measurements, which can be inverted to provide valuable information about the extant airborne particulate distribution.     

Test Determination of Lead and Zinc in Water with the Use of Xylenol Orange Immobilized on Silica

Xylenol Orange immobilized on silica as a complex of iron(III) was used for the test determination of lead(II) and zinc(II) in drinking water over concentration ranges of 10–100 and 13–130 g/L, respectively. The maximum distribution coefficients were found to be 7.50 × 10³ mL/g for Pb and 3.75 × 10³ mL/g for Zn. The macro main trace components of water at a level of their maximum permissible concentrations caused no interference. Al(III), Fe(III), and Zn(II) in the presence of NH₄F did not interfere with the determination of Pb(II), whereas lead in the presence of acetate caused no interference with the determination of Zn(II).     

Simultaneous determination of six components in commercial Roukou Wuwei pills using ultra‐high‐performance liquid chromatography with diode‐array detector

An efficient ultra‐performance liquid chromatography with diode‐array detector method was established for simultaneous determination of six active components in Roukou Wuwei pills, namely gallic acid, piperine, costundide, dehydrocostus lactone, isoalantolactone and alantolactone. Chromatographic separation of six components was successfully achieved on an Waters BEH C₁₈ column (50 × 2.1 mm, 1.7 μm) with a mobile phase composed of acetonitrile and water using a gradient elution. Gallic acid and piperine were detected at 270 nm and 343 nm, respectively; while costundide, dehydrocostus lactone, isoalantolactone and alantolactone were simultaneously measured at 225 nm. All six calibration curves showed good linearity (R² ≥ 0.9994) between the peak area of each component and corresponding concentration. Relative standard deviations for inter‐ and intra‐day precisions were <0.45 and 0.77%, respectively. The mean recovery rates ranged from 96.72 to 102.2% with relative standard deviations <2.07%. The developed method was validated in terms of linearity, precision and accuracy and then successfully applied for the quality control of commercial Roukou Wuwei samples.     

Fast simultaneous spectrophotometric determination of naphazoline nitrate and methylparaben by sequential injection chromatography

Fast simultaneous determination of naphazoline nitrate and methylparaben in pharmaceuticals using separation method based on a novel reversed-phase sequential injection chromatography (SIC) is described in this contribution as an alternative to classical HPLC. A Chromolith™ Flash RP-18e (25 mm × 4.6 mm) column (Merck^®, Germany) and a FIAlab^® 3000 system (USA) with a six-port selection valve and 5.0 ml syringe pump were used for sequential injection chromatographic separations in our study. The mobile phase used was methanol/water (40:65, v/v), pH 5.2 adjusted with triethylamine 0.8 μl ml⁻¹ and acetic acid, at flow rate 0.9 ml min⁻¹. UV detection provided by DAD detector and two wavelengths were simultaneously monitored for increasing sensitivity of determination. Detector was set up at 220 nm for naphazoline nitrate and 256 nm for methylparaben and ethylparaben (IS). There is no necessity to use pre-adjustment of sample of nasal drops (only dilution with mobile phase) so the time of the whole analysis is very short. The validation parameters have shown good results: linearity of determination for both components (naphazoline nitrate and methylparaben), correlation coefficient >0.999; repeatability of determination (R.S.D.) in the range 0.5-1.6% at three different concentration levels, detection limits 0.02 μg ml⁻¹ (naphazoline nitrate) and 0.20 μg ml⁻¹ (methylparaben and ethylparaben), and recovery from the pharmaceutical preparations in the range 100.06-102.55%. The chromatographic resolution between peaks of compounds was more than 4.0 and analysis time was less than 4 min under the optimal conditions. The advantages and drawbacks of SIC against classical HPLC are discussed showing that SIC can be an advantageous alternative in many cases.     

Simultaneous kinetic determination of sulfite and sulfide using artificial neural networks

Artificial neural networks (ANNs) are proposed for the determination of sulfite and sulfide simultaneously. The method is based on the reaction between Brilliant Green (BG) as a colored reagent and sulfite and/or sulfide in buffered solution (pH 7.0) and monitoring the changes of absorbance at maximum wavelength of 628 nm. Experimental conditions such as pH, reagents concentrations, and temperature were optimized and training the network was performed using principal components (PCs) of the original data. The network architecture (number of input, hidden and output nodes), and some parameters such as learning rate (η) and momentum (α) were also optimized for getting satisfactory results with minimum errors. The measuring range was 0.05-3.6 μg ml⁻¹ for both analytes. The proposed method has been successfully applied to the quantification of the sulfite and sulfide in different water samples.     

反相液相色谱法测定α-甲氧基萘的含量

用反相液相色谱法分析了α-甲氧基萘的含量和其中的有害杂质。色谱条件：色谱柱Nucleosil－C18;流动相V（甲醇）：V（水）=90：10;紫外检测器,面积归一化法定量。方法的变异系数为0．29％。     

Simultaneous determination of six perylenequinones in Shiraia sp. Slf14 by HPLC

The aim of the study was to develop a rapid and sensitive analytical method for simultaneous determination of the hypocrellin A, hypocrellin B, hypocrellin C, elsinochrome A, elsinochrome B, and elsinochrome C content in the Huperzia serrata endophytic fungus Shiraia sp. Slf14. Separation was performed by high-performance liquid chromatography (HPLC) with an YMC-Triart C18 column (4.6?mm?×?250?mm, 5?µm), elution with acetonitrile and triple-distilled water (volume ratio 70:30) as the mobile phase, a detection wavelength of 460?nm, and a flow rate of 1.0?mL/min. All six pigments were successfully determined with good linear correlations and a precision relative standard deviation <2.3%. The methodology was applied to simultaneously measure the concentration of perylenequinones and their derivatives during submerged fermentation and proved adequate for analysis of the biosynthesis of perylenequinones.     

Development and validation of chemometrics-assisted spectrophotometry and liquid chromatography methods for the simultaneous determination of the active ingredients in two multicomponent mixtures containing chlorpheniramine maleate and phenylpropanolamine hydrochloride

Multivariate spectrophotometric calibration and liquid chromatography (LC) methods were used for the simultaneous determination of the active ingredients in 2 multicomponent mixtures containing chlorpheniramine maleate and phenylpropanolamine hydrochloride with ibuprofen and caffeine (mixture 1) or with propyphenazone (mixture 2). For the multivariate spectrophotometric calibration methods, principal component regression (PCR) and partial least squares (PLS-1), a calibration set of the mixtures consisting of the components of each mixture was prepared in distilled water. A leave-1-out cross-validation procedure was used to find the optimum numbers of latent variables. Analytical parameters such as sensitivity, selectivity, analytical sensitivity, limit of quantitation, and limit of detection were determined for both PLS-1 and PCR. The LC method depends on the use of a cyanopropyl column with the mobile phase acetonitrile-12 mM ammonium acetate, pH 5.0 (25 + 75, v/v), for mixture 1 or acetonitrile-10 mM potassium dihydrogen phosphate, pH 4.7 (45 + 55, v/v), for mixture 2; the UV detector was set at 212 nm. In spite of the presence of a high degree of spectral overlap of these components, they were rapidly and simultaneously determined with high accuracy and precision, with no interference from the matrix excipients. The proposed methods were successfully applied to the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the 2 multicomponent combinations.     

Near infrared emission photometer for measuring the oxidative stability of edible oils

Near infrared emission spectroscopy (NIRES) allows the determination of the induction time (IT) of edible oils in accelerated oxidation experiments by monitoring the emissivity of a band at 2900 nm, which corresponds to the formation of hydroperoxides. In this work, a new near infrared emission photometer dedicated to the determination of oxidative stability is described. The photometer presents several advantages compared to the previously reported NIRES instrument, such as lower cost and extreme simplicity of design and maintenance. The results obtained in the evaluation of the proposed instrument were compared with the official Rancimat method and instrument. The significant advantages include: faster analysis, lower sample consumption and operational simplicity. It is demonstrated that the procedure for determination of oxidative stability of oils can be significantly simplified and performed by measuring the sample emission at only one spectral region centered at 2900 nm. Also, the proposed instrument and method present precision equivalent to the Rancimat method (coefficient of variation = 5.0%). A significant correlation between the methods has been found (R² = 0.81).     

2-(5-Nitro-2-Pyridylazo)-5-(N-Propyl-N-Sulfopropylamino)Phenol as a new analytical reagent for flow-injection spectrophotometric determination of trace vanadium(V)

A flow injection method using 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol-(Nitro-PAPS) as a new chromogenic reagent is presented for sensitive and rapid determination of vanadium. Nitro-PAPS reacts with vanadium(V) in weakly acidic medium to form a water soluble complex of molar absorptivity of 8.0 × 10⁴L mol^–1 cm^–1 at 592 nm (maximum absorption wavelength), which permits the straightforward application of a flow injection system to the sensitive determination of vanadium. Under the optimum conditions established, a linear calibration graph was obtained in the range 1–120 ng mL^–1. The relative standard deviation for 60 ng mL^–1 vanadium was 2.2% (n = 5) and the limit of detection was 1 ng mL^–1. The sample throughput is about 40 h^–1. Most inorganic and organic anions examined did not interfere even at concentrations of 3000–6000 times of vanadium. Interference from cobalt(II), copper(II) and nickel(II) at 200ng mL^–1 levels can be overcome by the addition of N-(dithio-carboxy)sarcosine. The recoveries for each 20 and 10 ng mL^–1 vanadium added to the river water were 98 and 97%, respectively.The authors express their thanks to Miss Miho Suzuki and Miss Hiroyo Yamada for their experimental assistance in part.     

Fluorometric Determination of Trace Amounts of Fluoride Ion Using an Expanded Porphyrin

A highly selective and sensitive method of fluorometry is described for determination of the fluoride ion at the parts per billion level via the ion-pair complex formation of the fluoride ion with an expanded prophyrin [2,23-diethyl-8,17-bis(2-ethoxycarbonylethyl)-3,7,12,13,18,22-hexamethylsapphyrin (H₃sap)]. The ion-pair complex gives out an enhanced fluorescence intensity at 680 nm on excitation at 450 nm. Since the present method is based on a direct reaction of the fluoride ion with the sappyrin, a 200-fold amount of the aluminum (III) ion [10⁻⁴M (M = mol dm⁻³)] and a 2000-fold amount of the iron(III) ion (10⁻³M) over the fluoride ion did not interfere with determination of the fluoride ion at concentrations as low as 5 × 10⁻⁷M in the presence of 1,2-diaminocyclohexane-N,N,N′,N′-teraacetic acid. The proposed method was applied to determination of the fluoride ion in various water samples (tap water, river water, rain water, underground water, and hot spring water) and satisfactory results were obtained.     

Evaluation of feed-forward back propagation and radial basis function neural networks in simultaneous kinetic spectrophotometric determination of nitroaniline isomers

Mixtures of 2-, 3-, and 4-nitoroanilines, are simultaneously analyzed with spectrophotometry, based on their different kinetic properties. These nitroanilines react differentially with 1,2-naphtoquinone-4-sulphonate (NQS) at pH 7 in micellar medium to produce colored product. The differential kinetic spectra were monitored and recorded at 500 nm, and the data obtained from the experiments were processed by chemometric approaches, such as back-propagation neural networks (BPNNs), radial basis function neural networks (RBFNNs), and partial least squares (PLS). Experimental conditions were optimized and training the network was performed using principal components (PCs) of the original data. A set of synthetic mixtures of nitroanilines was evaluated and the results obtained by the application of these chemometric approaches were discussed and compared. The analytical performance of the models was characterized by relative standard errors. It was found that the artificial neural networks model affords relatively better results than PLS. The proposed method was applied to the determination of considered nitroanilines in water samples.     

Preconcentration of uranium(VI) on a chelating adsorbent followed by photometric determination with 2,3,4-trihydroxy-3′-nitro-4′-sulfoazobenzene

The complexation of uranium(VI) with 2,3,4-trihydroxy-3′-nitro-4′-sulfoazobenzene was studied. A complex was formed with the molar ratio of the components 1: 2, the maximum of light absorption at 435 nm, and the molar absorption coefficient 1.00 × 10⁴. A new adsorbent bearing carboxyl groups was synthesized. The batch adsorption capacity of the adsorbent with respect to K⁺ ions was found, and the ionization constants of the ionogenic groups were determined by potentiometric titration. An adsorption isotherm of uranium was measured and the optimal conditions for preconcentration were found. Under the optimal conditions, the recovery of U(VI) ions was more than 95%. The detection limit was 14.2 ng/mL (3σ, n = 20). A procedure was developed for the adsorption-photometric determination of uranium(VI) in water.     

Determination of bisphenols A and F and their diglycidyl ethers in wastewater and river water by coacervative extraction and liquid chromatography-fluorimetry

A simple, rapid and sensitive analytical method was developed for the simultaneous determination of bisphenol A (BPA), bisphenol F (BPF) and their corresponding diglycidyl ethers (BADGE and BFDGE) in wastewater and river water, in order to have a useful tool for evaluating their fate and distribution in aquatic environments. It was based on their extraction with coacervates made up of decanoic acid reverse micelles and subsequent determination by liquid chromatography-fluorimetry. The procedure involved the extraction of 10.8 mL of water sample for 5 min, its centrifugation for 10 min to accelerate phase separation and then the chromatographic analysis of the target compounds. Clean-up or solvent evaporation steps were not necessary to get the required sensitivity and selectivity. Extraction efficiencies and concentration factors mainly depended on the amount of decanoic acid and tetrahydrofuran making up the coacervate. A general equation for the prediction of the volume of the coacervate as a function of its components has been proposed and fitted by nonlinear regression. This equation permits to know a priori the maximum concentration factors that can be achieved under given experimental conditions. Extractions were independent of salt addition (up to 1 M), the temperature (up to 60 °C) and the pH (below 4) rendering the method robust. Recoveries in samples ranged between about 80 and 92% and the actual concentrations factors were between 87 and 102, which resulted in practical detection limits around 30-35 ng L⁻¹. The method was successfully applied to the determination of the target pollutants in raw and treated sewage from four mechanical-biological treatment plants and three rivers. Bisphenols and their diglycidyl ethers were present in wastewater influents at concentrations in the range 0.96 to 1.6 μg L⁻¹. The biological treatment at the wastewater treatment plants (WWTP_s) studied reduced the concentration of BPA and BPF in a percentage above 75%, while diglycidyl ethers were not detected in most of the effluents investigated. Only BPA was detected in surface waters.     

Portable Fibre Optic Oxygen Sensor Based on Room-Temperature Phosphor escence Lifetime

 A portable fibre optic instrument for oxygen sensing based on luminescence lifetime is presented. The instrument is based on measurement of the quenching by oxygen of the room temperature phosphorescence (RTP) emitted by aluminium tris(8-hydroxy-7-iodo-5-quinolinesulfonic acid) chelate incorporated in an inorganic matrix by sol–gel technology. The comparatively long RTP lifetime of this sensing material (450 μs) and the large singlet–triplet splitting (λ_exc 390 nm, λ_em 590 nm) allow the use of simple opto-electronic circuits and low-cost processing electronics. Standard electronic components have been applied in development of the low-cost lifetime-measurement instrumentation presented here. Two optical sensor configurations, “flow-through cell” and “probe”, have been designed and evaluated for the determination of very low levels of oxygen, in gaseous argon streams and in waters. The basic technology, design parameters and performance characteristics of the optical sensors are discussed. Applications to determination of dissolved oxygen in river, tap and sewage waters are described. The advantages of luminescence lifetime measurements over conventional RTP intensity measurements for oxygen sensing are discussed. Received April 1, 1999. Revision November 4, 1999.     

固相萃取-亲水相互作用液相色谱法同时测定环境水样中3种酰胺类化合物

基于亲水相互作用液相色谱(Hydrophilic Interaction Liquid Chromatography,HILIC)技术,建立了同时测定环境水样中丙烯酰胺、N,N-二甲基甲酰胺和N,N-二甲基乙酰胺的液相色谱分析方法.水样采用石墨化碳黑固相萃取柱净化,上样1.0 mL,并最终用1.0 mL乙腈洗脱,洗脱液进样色谱分析.选择Waters HILIC色谱柱,以乙腈/水作为流动相,等度洗脱,二极管阵列检测器200 nm条件下检测.在优化的分析条件下,3种酰胺类化合物在11 min内实现基线分离.所有目标化合物浓度在0.05～ 100 mg/L范围内线性良好,相关系数均大于0.9999;检出限达0.01 mg/L.加标回收率为84.1％～106％;相对标准偏差1.8％～10.4％.本方法具有简便快捷、灵敏准确等特点,能够满足环境水样中痕量酰胺类污染物检测的要求.