Differential pulse polarographic determinations of iodate, bromate and periodate

Summary The application of differential pulse polarography for quantitative trace determination of iodate, periodate and bromate has been investigated. Optimum conditions were found (pulse amplitude 100 mV, scan rate 2 mV s^–1, drop time 2 s). The detection limit for IO ₃ ^– , BrO ₃ ^– and IO ₄ ^– is ca. 2.4×10^–6M at pH 3 whereas at pH 9.3 the reduction of IO ₃ ^– and IO ₄ ^– gave concentration sensitive peak heights down to 9.9 ×10^–7M. A differential pulse polarographic method has been developed for the simultaneous determination of iodate-bromate or periodate-bromate.

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Bestimmung von Iodat, Bromat und Periodat durch Differential-Pulse-Polarographie

Zusammenfassung Optimale Bedingungen zur Bestimmung dieser Ionen im Spurenbereich wurden ausgearbeitet (Pulsamplitude 100 mV, Scangeschwindigkeit 2 mV s^–1, Tropfzeit 2 s). Die Nachweisgrenze für die drei Ionen liegt bei 2,4 · 10^–6 M für pH 3. Bei pH 9,3 ergaben sich für Iodat und Periodat konzentrationsabhängige Peakhöhen bis herab zu 9,9 · 10^–7 M. Da der Bromatpeak bei wesentlich negativerem Potential auftritt als der Iodat bzw. Periodatpeak konnten Iodat und Bromat bzw. Periodat und Bromat nebeneinander bestimmt werden.

     

Simultaneous spectrophotometric determination of Bi(III) and Sb(III) based on their complexes with iodide in acidic media using the H-point standard addition method and first-derivative spectrophotometry.

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of Bi(III) and Sb(III). This method is based on the difference in the absorbance of complexes of Bi(III) and Sb(III) with iodide in acidic media in different wavelength pairs. The results showed that Bi(III) and Sb(III) can be determined simultaneously with concentration ratios of 15:1 to 1:20. First-derivative spectrophotometry was also used for the simultaneous determination of Bi(III) and Sb(III) based on their complexes with iodide. The proposed methods were successfully applied to the simultaneous determination of Bi(III) and Sb(III) in synthetic samples.     

分光光度法同时测定两个干扰组份的研究 I.多波长数据线性回归法及其应用于同时测定微量锰和锌的探讨

In this paper, a linear regression method of multiwavelength data is proposed. The method, based on the difference of molar absorptivity between two coloured chelates at murti-wavelengths, can be applied to simultaneous spectrophotometric determination of two-interfering-component systems in the visible region. As an example, the availability as well as the optimum condition for simultaneous determination of Mn and Zn with 5-Br-PADAP in the presence of nonionic surfactant Triton X-100 have been studied. Measure the absorbance at 15 wavelengths over the range of 540-584 nm and treat the data with the suggested method, the linear correlation coefficients (γ) are found to be 0.998 in the synthetic mixtures containing microamounts of Mn and Zn with the concentration ratio from 1:10 to 10:1. The recoveries of both elements are 95-120% with the relative standard deviations (N=5) less than 17%. the method has been successfully used for direct determination of Mn and Zn in tap water. The new method proposed in this work is simple, fast and can be used for the analysis of two-interfering-component systems.     

H-point standard addition method for the selective simultaneous determination of nickel and copper using 1-(2-pyridylazo)-2-naphthol in Tween 80 micellar media.

The H-point standard addition method (HPSAM) has been applied for the simultaneous determination of nickel and copper in trace levels, using 1-(2-pyridylazo)-2-naphthol (PAN) as a chromogenic reagent in aqueous Tween 80 micellar media. Under the optimum condition, the simultaneous determinations of nickel and copper by HPSAM were performed. The absorbances at one pair of wavelengths, 548 and 579 nm, were monitored with the addition of standard solutions of copper. The method is able to accurately determine copper-to-nickel ratios of 15:1 to 1:10 (Wt/Wt). The effects of diverse ions on the determination of nickel and copper to investigate the selectivity of the method were also studied. The recommended procedure was successfully applied to some water and alloy samples.     

Simultaneous spectrophotometric determination of hydrazine and phenylhydrazine based on their condensation reactions with different aromatic aldehydes in micellar media using H-point standard addition method

H-point standard addition method (HPSAM) was applied to the simultaneous determination of hydrazine and phenylhydrazine. The method is based on the hydrazone formation reactions of hydrazine and phenylhydrazine in the presence of micellar sodium dodecyl sulfate (SDS). Mixed reagents of p-(dimethylamino)benzaldehyde (DAB) and p-nitrobenzaldehyde (NB) was used as selective chromogenic reagents for hydrazine and phenylhydrazine. Hydrazine and phenylhydrazine can be determined simultaneously in the range 0.020-0.50 and 0.20-10.0 μg ml⁻¹, respectively. The results allowed that simultaneous determination could be performed with the ratio 1:500 to 1:10 hydrazine-phenylhydrazine. Under working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and phenylhydrazine in several synthetic mixtures and plasma and water samples.     

Simultaneous kinetic determination of beryllium and aluminium by spectrophotometric H-point standard addition method.

The H-point standard addition method (HPSAM), based on spectrophotometric measurements for simultaneous determination of beryllium and aluminium, is described. This method is based on the difference between their rates of reactions with Chrome Azurol S (CAS) in cetyltrimethylammonium bromide (CTAB) micellar media. The results showed that beryllium and aluminium could be determined simultaneously in the ranges of 10-200 and 10-300 ng mL(-1), respectively. Under working conditions, the proposed method was successfully applied to the simultaneous determination of beryllium and aluminium in environmental, geochemical and alloy samples.     

Pretreatment of corn stover by soaking in aqueous ammonia at moderate temperatures

Soaking in aqueous ammonia at moderate temperatures was investigated as a method of pretreatment for enzymatic hydrolysis as well as simultaneous saccharification and cofermentation (SSCF) of corn stover. The method involves batch treatment of the feedstock with aqueous ammonia (15-30 wt%) at 40-90 degrees C for 6-24 h. The optimum treatment conditions were found to be 15 wt% of NH(3), 60 degrees C, 1:6 of solid-to-liquid ratio, and 12 h of treatment time. The treated corn stover retained 100% glucan and 85% of xylan, but removed 62% of lignin. The enzymatic digestibility of the glucan content increased from 17 to 85% with 15 FPU/g-glucan enzyme loading, whereas the digestibility of the xylan content increased to 78%. The treated corn stover was also subjected to SSCF test using Spezyme-CP and recombinant Escherichia coli (KO11). The SSCF of the soaking in aqueous ammonia treated corn stover resulted in an ethanol concentration of 19.2 g/L from 3% (w/v) glucan loading, which corresponds to 77% of the maximum theoretical yield based on glucan and xylan.     

Simultaneous kinetic-spectrophotometric determination of hydrazine and acetylhydrazine in micellar media using the H-point standard addition method.

The H-point standard addition method (HPSAM), based on a spectrophotometric measurement for the simultaneous determination of hydrazine and acetylhydrazine, is described. This method is based on the difference between the rates of their reactions with N,N-dimethylaminobenzaldehyde (DAB) in the presence of sodium dodecyl sulfate (SDS) in acidic media. The results showed that hydrazine and acetylhydrazine could be determined simultaneously in the range of 0.020 - 0.70 and 0.20 - 5.0 mg L(-1), respectively. Under the working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and acetylhydrazine in several synthetic mixtures and plasma and water samples.     

气相色谱-串联质谱检测烟草中15种苯氧羧酸类除草剂残留

建立了气相色谱-串联质谱技术对烟草中15种苯氧羧酸类除草剂农药残留量的分析方法。样品采用乙腈提取、Carbon TPT固相萃取柱净化、三甲基硅烷化重氮甲烷衍生化,采用气相色谱-串联质谱对15种苯氧羧酸类除草剂进行测定,通过保留时间、选择离子及相对丰度定性,外标法定量。结果表明,15种苯氧羧酸类除草剂在20~1 000μg/L浓度范围内均呈良好线性关系,相关系数大于0.992,检出限为0.9~3.3μg/kg,定量下限为3.2~10.8μg/kg。在20,100,200μg/kg 3个加标水平下的平均回收率为71.5%~105.6%,相对标准偏差(RSD)为4.5%~14.9%。该方法简便、快速、灵敏,适用于烟草中15种苯氧羧酸类除草剂的同时检测。     

Automated headspace-solid-phase micro extraction-retention time locked-isotope dilution gas chromatography-mass spectrometry for the analysis of organotin compounds in water and sediment samples

An automated method for the simultaneous determination of six important organotin compounds namely monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT) in water and sediment samples is described. The method is based on derivatization with sodium tetraethylborate followed by automated headspace-solid-phase micro extraction (SPME) combined with GC-MS under retention time locked (RTL) conditions. Home-synthesized deuterated organotin analogues were used as internal standards. Two high abundant fragment ions corresponding to the main tin isotopes Sn118 and Sn120 were chosen; one for quantification and one as qualifier ion. The method was validated and excellent figures of merit were obtained. Limits of quantification (LOQs) are from 1.3 to 15 ng l(-1) (ppt) for water samples and from 1.0 to 6.3 microg kg(-1) (ppb) for sediment samples. Accuracy for sediment samples was tested on spiked real-life sediment samples and on a reference PACS-2 marine harbor sediment. The developed method was used in a case-study at the harbor of Antwerp where sediment samples in different areas were taken and subsequently screened for TBT contamination. Concentrations ranged from 15 microg kg(-1) in the port of Antwerp up to 43 mg kg(-1) near a ship repair unit.     

High-speed simultaneous ion-exclusion/cation-exchange chromatography of anions and cations on a weakly acidic cation-exchange resin column

The simultaneous ion-exclusion/cation-exchange separation column packed with a polymethacrylate-based weakly acidic cation-exchange resin of 3 microm particle size was used to achieve the simultaneous high-speed separation of anions and cations (Cl(-), NO3(-), SO4(2-), Na(+), K(+), NH4(+), Ca(2+) and Mg(2+)) commonly found in environmental samples. The high-speed simultaneous separation is based on a combination of the ion-exclusion mechanism for the anions and the cation-exchange mechanism for cations. The complete separation of the anions and cations was achieved in 5 min by elution with 15 mM tartaric acid-2.5 mM 18-crown-6 at a flow-rate of 1.5 ml/min. Detection limits at S/N=3 ranged from 0.36 to 0.68 microM for anions and 0.63-0.99 microM for cations. This method has been applied to the simultaneous determination of anions and cations in several environmental waters with satisfactory results.     

Simultaneous Kinetic Determination of Phosphate and Silicate by Spectrophotometric H‐Point Standard Addition Method

The H‐point standard addition method (HPSAM), based on spectrophotometric measurements for simultaneous determination of phosphate and silicate, has been established. The method is based on the difference between their reactions rates with molybdenum in the presence of ascorbic acid. The results revealed that phosphate and silicate could be determined simultaneously with the concentration ratios of phosphate to silicate varying from 1:10 to 12:1 in the binary mixtures. The effects of chelating agent nature, time, interferents and experimental variables are also investigated. Under working conditions, the proposed method was successfully applied to the simultaneous determination of phosphate and silicate in synthetic detergents.     

Simultaneous multianalysis for tumor markers by antibody fragments microarray system

It is often necessary to measure a spectrum of tumor markers in oncology. We have developed a simultaneous multiplexing immunoassay method to determine six tumor markers: -fetoprotein (AFP), carcinoma embryonic antigen (CEA), beta-human chorionic gonadotropin (β-HCG), carbohydrate antigen 125 (CA 125), carbohydrate antigen 19-9 (CA 19-9) and carbohydrate antigen 15-3 (CA 15-3). F(ab′)₂ fragments of six capture antibodies were prepared and printed as microarrays on silylated slides to perform sandwich immunoassays with the use of an avidin–biotin system for amplified fluorescence signals. Each antigen with different concentrations was detected to assemble its calibration curve, and combinations of different markers were determined to examine the specificity of simultaneous detection based on the F(ab′)₂ microarrays. Some clinical samples were analyzed to compare with results obtained with the use of immunoradiometric assay (IRMA) method. Wide range calibration curve and its R-value were obtained for each analyte. Calibration curves concentrations were 0–640 μg/l for CEA, AFP and β-HCG, and 0–1280 kU/l for CA 125, CA 19-9 and CA 15-3. The antibody fragments microarray system bears comparison with conventional immunoassays and may find feasible application in measurement of series markers in oncology and other areas of medicine.     

Sample stacking with matrix removal for the determination of paraquat, diquat and difenzoquat in water by capillary electrophoresis

Conditions for the simultaneous determination of paraquat, diquat and difenzoquat by capillary zone electrophoresis using a stacking technique in a chemically modified capillary have been established. To apply the stacking method with sample matrix removal for the analysis of cations, an anodic electroosmotic flow is mandatory. For quats, 50 mM acetic acid-ammonium acetate (pH 4.0) with 5% (v/v) methanol as electrophoretic buffer and the addition of 0.8 mM cetyltrimethylammonium bromide as wall capillary organic modifier was proposed. Field polarity reversal time was optimised for several sample matrices. Detection was carried out at 220 and 255 nm. Detection limits, based on a signal-to-noise ratio of 3:1, were lower than 15 microg l(-1) for standards in Milli-Q water and two to ten times higher for drinking water samples. Run-to-run and day-to-day reproducibility have been established. The method was successfully applied to the determination of the three herbicides in spiked drinking water.     

Fluorimetric differential-kinetic determination of silicate and phosphate in waters by flow-injection analysis

A flow-injection analysis (FIA) method for simultaneous determination of silicate and phosphate, based on the different rates of formation of their molybdate heteropoly acids is suggested. The fluorimetrically monitored product is thiochrome, formed by oxidation of thiamine by the heteropoly acid. The FIA configurations designed allow performance of two measurements at different times on each sample injected. The method permits the determination of these anions in the range 30-600 ng ml in ratios from 1:10 to 10:1 and can be applied to samples of running and bottled water with good results. The sampling frequency achievable is 60 hr .     

Simultaneous determination of calcium and magnesium by derivative spectrophotometry in pharmaceutical products

First- and second-derivative spectrophotometric methods for the simultaneous determination of calcium and magnesium in their mixtures are described. The methods are based on the colored complexes formed by calcium and magnesium with bromopyrogallol red in presence of Tween 80 as a surfactant. The zero-crossing method has been utilized to measure the first- and second-derivative value of the derivative spectrum. Calcium (0.8-4.8microgml(-1)) is determined in the presence of magnesium (0.5-3.5microgml(-1)) at the pH 10 and vice versa at zero-crossing wavelengths of 544.5 and 570nm in the first-derivative procedure and 574 and 531nm in the second-derivative procedure, respectively. The detection limits achieved were 0.0575microgml(-1) of calcium and 0.03microgml(-1) of magnesium. The relative standard deviations were in all instances less than 2%. The proposed method has been applied to the simultaneous determination of calcium and magnesium in different samples: commercial multivitamin, human serum and drinking water where excellent agreement between reported and obtained results was achieved.     

Simultaneous kinetic determination of epinephrine and norepinephrine by the stopped-flow technique.

A stopped-flow method for the simultaneous determination of epinephrine and norepinephrine, two catecholamines with a wide spectrum of biological activity, is proposed. The method is based on the oxidation of these compounds with 1,10-phenanthroline-iron(III) complex, which is monitored by measuring the initial rate of change of the absorbance of the ferroin formed at 510 nm. The difference in kinetic behaviour between the two species was exploited by applying a modified version of the proportional-equation method for the resolution of epinephrine-norepinephrine mixtures at the micrograms ml-1 level over the ratio range 1:10-10:1, with an error of less than 5% and an average precision of about 2.5%. The method was successfully applied to the determination of the two catecholamines in pharmaceuticals.     

Zero-crossing second derivative spectrophotometry for simultaneous determination of palladium and nickel using 1-(2-pyridylazo)-2-naphthol in mixed micellar solutions

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous determination of nickel and palladium at trace levels. PAN complexes of nickel and palladium in the pH 1.98 form red and green colored complexes, respectively, which are soluble in aqueous 4:1 Triton X-100 to sodium dodecylsulfate (SDS) micellar media with total detergent concentration of 3.2%. Under optimum conditions, calibration graphs for the simultaneous determination by second derivative spectrophotometry were obtained. Zero crossing second derivative spectrophotometry at 668 and 572 nm, respectively for palladium and nickel was used for the simultaneous determination. The method is able to determine palladium to nickel ratio 70:1 to 1:6 (Wt/Wt), accurately. Accuracy and reproducibility of the determination method on the known various amounts of palladium and nickel in their binary mixtures were tested. Effects of diverse ions on the determination of palladium and nickel to investigate selectivity of the method also were studied.     

Simultaneous spectrophotometric determination of mercury and palladium with Thio-Michler's Ketone using partial least squares regression and orthogonal signal correction

A simple, novel and sensitive spectrophotometric method was described for simultaneous determination of mercury and palladium. The method is based on the complex formation of mercury and palladium with Thio-Michler's Ketone (TMK) at pH 3.5. All factors affecting on the sensitivity were optimized and the linear dynamic range for determination of mercury and palladium found. The simultaneous determination of mercury and palladium mixtures by using spectrophotometric method is a difficult problem, due to spectral interferences. By multivariate calibration methods such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction (OSC) is a preprocessing technique used for removing the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for PLS calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 360-660 nm range for 25 different mixtures of mercury and palladium. Calibration matrices were containing 0.025-1.60 and 0.05-0.50 microg mL(-1) of mercury and palladium, respectively. The RMSEP for mercury and palladium with OSC and without OSC were 0.013, 0.006 and 0.048, 0.030, respectively. This procedure allows the simultaneous determination of mercury and palladium in synthetic and real matrix samples good reliability of the determination.