Highly selective catalytic determination of ultra trace amounts of rhodium by linear sweep voltammetry

A highly selective and sensitive method is proposed for the determination of rhodium, based on the catalytic effect on the oxidation of Nile blue by periodate. The reaction rate is monitored by measuring the current of Nile blue at –0.37 V vs. Ag/AgCl reference electrode. The linear working range is 5 to 100 ng/mL with a limit of detection of 0.1 ng/mL. The interference effects of more than forty ions were studied. The method was used for the determination of Rh (III) in synthetic samples with satisfactory results.     

Highly selective catalytic determination of ultra trace amounts of rhodium by linear sweep voltammetry

A highly selective and sensitive method is proposed for the determination of rhodium, based on the catalytic effect on the oxidation of Nile blue by periodate. The reaction rate is monitored by measuring the current of Nile blue at –0.37 V vs. Ag/AgCl reference electrode. The linear working range is 5 to 100 ng/mL with a limit of detection of 0.1 ng/mL. The interference effects of more than forty ions were studied. The method was used for the determination of Rh (III) in synthetic samples with satisfactory results. Received: 2 July 1997 / Revised: 23 September 1997 / Accepted: 24 September 1997     

催化动力学分光光度法测定微量铁的研究

在 Na2 HPO4介质中 ,研究了 Fe( )催化 H2 O2 氧化甲基百里酚蓝褪色指示反应及其动力学条件 ,建立了测定痕量铁的新方法。方法的线性范围为 0 .0 2～ 0 .2 5μg/2 5m L,检出限为 0 .0 1 2 μg/2 5m L。用以测定过氧化碳酸钠 ( 2 Na2 CO3· 3H2 O2 )中的铁 ,结果令人满意。     

硫胺素-亚硝酸根体系的荧光性质研究及应用

研究了在碱性溶液中硫胺素（VB1）与亚硝酸根的荧光反应,建立了荧光光度法测定硫胺素的新方法。方法线性范围为1．28－324ng/mL,检出限0．52ng/mL,对15个浓度为100ng/mL的硫胺素溶液进行测定,相对标准偏差为1．4％。应用于药物中硫胺素的测定,回收率在96．5％－101．8％之间。     

Flow-Injection Catalytic Spectrophotometric Determination of Trace Amounts of Nitrite

ABSTRACT

A flow-injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on potassium bromate oxidation of acridine orange in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of acridine orange at 491.5 nm coupling with the stopped-flow technique. The calibration curve was linear between 3.4 and 65 ng/mL, and the detection limit was 2.2 ng/mL. Up to 30 samples can be analyzed per hour with a relative precision of ca. 1.9%. The proposed method was successfully applied to the determination of nitrite in waters and food samples with satisfactory results.     

催化反应-示波极谱测定痕量亚硝酸根——NO2——MR-BrO3-催化体系

基于在0.016mol/LH₂SO₄中及加热条件下,NO₂^-对BrO₃^-氧化甲基红有强烈的催化作用,籍自来水冷却中止反应,以NaOH作示波极谱测量指示组分甲基红(E_p=-0.56V,vs.SCE)的支持电解质,建立了NO₂^-的第一个催化反应-示波极谱分析法。该法检出限为0.035ng/mL,测定范围为0.1～50ng/mL。     

Kinetic Spectrophotometric Method for the Determination of Rhodium by Its Catalytic Effect on the Oxidation of O-Toluidine Blue by Periodate in Micellar Media

A simple kinetic spectrophotometric method was developed for the determination of ultra trace amounts of Rh(III). The method is based on the catalytic effect of rhodium(III) on the oxidation of o-Toluidine blue by periodate in micellar media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of o-Toluidine blue at 628 nm with a fixed-time method. The decrease in the absorbance of o-Toluidine blue is proportional to the concentration of Rh(III) in the concentration range 1.0–400.0 ng/mL, with a fixed time of 0.5–4.5 min from initiation of the reaction. The limit of detection is 0.2 ng/mL Rh(III). The relative standard deviation for the determination of 0.020 and 0.100 g/mL Rh(III) was 2.2 and 1.5%, respectively. The method was applied to the determination of rhodium in water.     

LC‐MS/MS determination of bakkenolide D in rats plasma and its application in pharmacokinetic studies

A sensitive and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for determination of bakkenolide D (BD), which was further applied to assess the pharmacokinetics of BD. In the LC‐MS/MS method, the multiple reaction monitoring mode was used and columbianadin was chosen as internal standard. The method was validated over the range of 1–800 ng/mL with a determination coefficient >0.999. The lower limit of quantification was 1 ng/mL in plasma. The intra‐ and inter‐day accuracies for BD were 91–113 and 100–104%, respectively, and the inter‐day precision was <15%. After a single oral dose of 10 mg/kg of BD, the mean peak plasma concentration of BD was 10.1 ± 9.8 ng/mL at 2 h. The area under the plasma concentration–time curve (AUC_{0–24 h}) was 72.1 ± 8.59 h ng/mL, and the elimination half‐life (T_1/2) was 11.8 ± 1.9 h. In case of intravenous administration of BD at a dosage of 1 mg/kg, the AUC_{0–24 h} was 281 ± 98.4 h?ng/mL, and the T_1/2 was 8.79 ± 0.63 h. Based on these results, the oral bioavailability of BD in rats at 10 mg/kg is 2.57%. Copyright © 2013 John Wiley & Sons, Ltd.     

The use of thermal lensing for the determination of pyrogens

Based on the optimized spectrophotometric determination of pyrogens (of various classes ( p-aminophenol and endotoxins), thermal lensing was applied to the determination of these substances at the submicrogram level. The limit of detection of p-aminophenol, a pyrogenic impurity in pharmaceutical formulations of paracetamol, by reaction with resorcinol in alkaline solutions is 100 ng mL(-1). Phloroglucinol was considered as an analog of resorcinol as a reagent in this reaction. The conditions of spectrophotometric determination of pyrogenic lipopolysaccharides (endotoxins) by ion-pair formation with methylene blue (the limit of detection is 100 ng mL(-1)), by ion-pair formation with Stains-All (1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl]naphtho[1,2-d]thiazolium bromide) (the limit of detection is 500 ng mL(-1)), and by reaction of 2-keto-3-deoxyoctonic acid with thiobarbituric acid (the limit of detection is 800 ng mL(-1)) were proposed. The optimized procedure for 2-keto-3-deoxyoctonic acid was applied for thermal lensing that provided a decrease in the limit of detection to 70 ng mL(-1) and was also used for lipopolysaccharide determination in the endotoxin standard from E. coli.     

Kinetic spectrophotometric method for the determination of selenium(IV) by its catalytic effect on the reduction of spadns by sulphide in micellar media

A simple kinetic spectrophotometric method was developed for the determination of ultratrace amounts of Se(IV). The method is based on the reduction of spadns by sulphide in micellar media. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of spadns at 515 nm with a fixed-time method. The decrease in the absorbance of spadns is proportional to the concentration of Se(IV) in the range 0.5–100 ng/mL with a fixed time of 2.5–7.0 min from the initiation of the reaction. The limit of detection is 0.3 ng/mL Se(IV). The relative standard deviation for the determination of 0.02 and 0.10 μg/mL Se(IV) was 2.10 and 1.95%, respectively. The method was applied to the determination of Se(IV) in water. The text was submitted by the authors in English.     

液相色谱–原子荧光光谱法检测水产品中汞形态

建立了液相色谱–原子荧光光谱联用测定水产品中无机汞和甲基汞含量的方法。对影响测定结果的分析条件,如流动相组成、载流、还原剂、氧化剂、载气和屏蔽气进行了研究和优化,同时考察了该方法的有效性。结果表明:无机汞和甲基汞在质量浓度1~20 ng/m L范围内线性关系良好,相关系数分别为0.999 4,0.999 1;检出限分别为0.19,0.17 ng/m L;色谱峰面积的相对标准偏差分别为3.16%,2.16%(n=7);加标回收率分别为74%~100%,71%~91%。该方法可用于水产品中汞元素的形态分析。     

Determination of the antibacterial drug sulfamethoxazole in pharmaceutical preparations containing trimethoprim by spectrofluorimetry after derivatization with fluorescamine

An analytical method was developed for the determination of sulfamethoxazole (SMZ) in the presence of trimethoprim (TMP) by normal fluorescence. When both analytes are present a selective derivatization with fluorescamine of SMZ gives an intense fluorescent derivative with no interference from the other compound. The reaction was optimized to obtain the best analytical performance. The detection limit and the lower limit of quantitation of SMZ in the reaction medium was 5.2 ng/mL. The intra-day precision (relative standard deviation) was 1.51% for a 100 ng/mL SMZ standard solution and the inter-day precision over 7 days for a 100 ng/mL solution in the presence of 20 ng/mL TMP solution was 2.5%. The method has been applied to three pharmaceutical preparations containing both compounds, without any separation steps required.     

A sensitive flow-injection method for determination of trace amounts of nitrite

A new sensitive colour reaction for nitrite determination is presented. In acidic medium, nitrite was reacted with safranine to form a diazonium salt which caused the reddish-orange dye colour of the solution to change to blue. The carrier stream, into which the sample solution was injected, was doubly distilled water. The reagent solution stream, which contained safranine dye, hydrochloric acid and potassium chloride, was mixed with the carrier in a 3-m length of silicon tubing (bore 0.5 mm) maintained at 30°C in a thermostatic bath. The absorbance intensity was measured at 520 nm. The detection limit was 20 ng ml⁻¹ and the RSD% of 20 injections of 1 μg ml⁻¹ of nitrite was 0.65%. Analysis can be done at a rate of up to 30 h⁻¹. Under the optimum conditions in the concentration range of 30–4000 ng ml⁻¹ of nitrite ion, a linear calibration graph was obtained (r=0.9999). The method was applied successfully to the determination of nitrite in sausages.     

A sensitive LC–MS/MS‐based bioanalytical method for quantification of salviaflaside and rosmarinic acid in rat plasma and its application in a pharmacokinetic study

A selective and sensitive liquid chromatography tandem mass spectrometry method was developed for the simultaneous determination of salviaflaside and rosmarinic acid in rat plasma. Sample preparation was carried out through liquid–liquid extraction with ethyl acetate using curculigoside as internal standard (IS). The analytes were determined by selected reaction monitoring operated in the positive ESI mode. Chromatographic separation was performed on an Agilent Eclipse Plus C₁₈ column (100 × 4.6 mm, 1.8 μm) with a mobile phase consisting of methanol–water–formic acid (50:50:0.1, v/v/v) at a flow rate of 0.3 mL/min. The run time was 1.9 min per sample and the injection volume was 5 μL. The method had an LLOQ of 1.6 ng/mL for salviaflaside and 0.94 ng/mL for rosmarinic acid in plasma. The linear calibration curves were fitted over the range of 1.6–320 ng/mL for salviaflaside and 0.94–188 ng/mL for rosmarinic acid in plasma with correlation coefficients (r²) >0.99. Intra‐ and inter‐day precisions (relative standard deviation) were < 13.5%, and accuracies (relative error) were between −8.6% and 14.5% for all quality control samples. The method was validated and applied to the pharmacokinetics of salviaflaside and rosmarinic acid in plasma after oral administration of Prunella vulgaris extract to rats.     

Determination of the antibacterial drug sulfamethoxazole in pharmaceutical preparations containing trimethoprim by spectrofluorimetry after derivatization with fluorescamine

An analytical method was developed for the determination of sulfamethoxazole (SMZ) in the presence of trimethoprim (TMP) by normal fluorescence. When both analytes are present a selective derivatization with fluorescamine of SMZ gives an intense fluorescent derivative with no interference from the other compound. The reaction was optimized to obtain the best analytical performance. The detection limit and the lower limit of quantitation of SMZ in the reaction medium was 5.2 ng/mL. The intra-day precision (relative standard deviation) was 1.51% for a 100 ng/mL SMZ standard solution and the inter-day precision over 7 days for a 100 ng/mL solution in the presence of 20 ng/mL TMP solution was 2.5%. The method has been applied to three pharmaceutical preparations containing both compounds, without any separation steps required. Received: 28 December 1998 / Revised: 28 April 1999 / Accepted: 30 April 1999     

Sensitive spectrophotometric determination of nitrite in human saliva and rain water and of nitrogen dioxide in the atmosphere

A new simple, sensitive, and selective spectrophotometric method was developed for the determination of nitrite. The method is based on the reaction of nitrite with sulfathiazole in acidic medium to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly stable, violet azo dye. The reaction product has an absorption maximum at 546 nm and obeys Beer's law over a nitrite range of 0.054-0.816 microg/mL. The molar absorptivity of the colored compound is 4.61 x 10(4) L/mol x cm). The detection limit is 12.1 microg/L. The relative standard deviation is 0.85% for 5 determinations of nitrite at 0.27 microg/mL. The reproducibility and validity of the proposed method are discussed in the present paper. The simplicity of the method is demonstrated by the high stability of the azo-dye product as well as the short time required for its complete formation in a reaction at room temperature without pH control or extra extraction. The sensitivity of the method is shown by the successful determination of nitrite in human saliva and rain water, and of nitrogen dioxide in the atmosphere. The results compare favorably with those obtained by the reference method. The selectivity of the method is indicated by its freedom from most interferences, even at high concentrations of nitrate (500 microg/mL).     

Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis.

A new catalytic spectrophotometric method is reported for the simultaneous determination of nitrite and nitrate by flow injection analysis, based on the catalytic effect of nitrite on the redox reaction between pyrogallolsulfonephthalein and potassium bromate in acidic media. Nitrate can also be on-line reduced to nitrite with a modified copper-coated cadmium reduction column. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of pyrogallolsulfonephthalein at 465 nm. Various analytical parameters such as effects of acidity, reagent concentrations, flow rates, sample sizes, lengths of the reaction coil and temperatures were studied and were optimized. Under the optimized conditions, the calibration graph was linear for 2.4 to 160 ng ml(-1) of nitrite and 4.0 to 100 ng ml(-1) of nitrate. The influences of potential interfering cations and anions for nitrite and nitrate determination were studied. The method is successfully applied for food and water samples. Up to ten samples can be analyzed per hour.     

荧光动力学法测定唾液中痕量硫氰根

人体内的SCN-主要分布于人体体液及代谢物中,如唾液、血浆、尿液等。其来源主要有两种途径:一是烟草中氰化物的代谢产物,人体内硫氰酸盐的含量是区别吸烟者和不吸烟者的重要标志[1,2];二是某些食物的代谢产物,如卷心菜等。硫氰酸盐可作为药物用于治疗甲状腺疾病,但体液中SCN-含     

荧光分析法测定痕量亚硝酸根

在硫酸介质中,亚硝酸根能还原吡咯红Y,使其荧光猝灭据此提出了一个测定痕量亚硝酸根的荧光分析法,方法的检出限为2.7ng/mL,线性范围为6.0-88ng/mL,可直接用于电厂废水、自来水、井水中亚硝酸根的测定。     

Kinetic Spectrophotometric Determination of Trace Amounts of Nitrite Ion Using Its Reaction With Neutral Red

Abstract

A rapid, simple, sensetive and selective method for the determination of trace amounts of nitrite ion(30-800 ng/ml) is developed. It depends on the reaction of nitrite with Neutral Red. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance at 530 nm by a fixed time method. The limit of detection is 14 ng/ml. The method is used for the determination of nitrite ion in waste water.