Flow-injection determination of amine contaminants in cyclamate samples based on temperature for controlling selectivity

This paper describes a flow-injection (FI) method for the simultaneous determination of aniline and cyclohexylamine impurities in cyclamate products. The method consists of the derivatization of amines with 1,2-naphthoquinone-4-sulfonate under selective and non-selective conditions. Here, the selectivity is achieved by working at 20 degree C, at which only aniline reacts, whilst higher temperatures (80 degree C) lead to a non-selective reaction of the two analytes. The FI manifold is composed of two flow cells for the spectrophotometric detection of derivatives at 480 nm. Experimental conditions have been optimized by factorial design and multicriteria making approach. Quantification is accomplished by differential analysis of the analyte contributions in the double peaks generated when the sample reaches cell 1 and cell 2. Results obtained with the proposed method are in satisfactory agreement with those provided by the standard method for the analysis of cyclamate samples.     

Simultaneous determination of aniline and cyclohexylamine by principal component artificial neural networks.

A specterophotometric method for simultaneous determination of aniline and cyclohexylamine using principal component artificial neural networks is proposed. This method is based on the reactions involving aniline and/or cyclohexylamine, with bis(acetylacetoneethylendiamine)tributylphosphine cobalt(III) perchlorate as a complexing reagent. A nonionic surfactant, Triton X-100, was used for dissolving the complexes and intensifying the signals. The absorption data were based on the spectra registered in the range of 350 - 550 nm. An artificial neural network consisting of three layers of nodes was trained by applying a back-propagation learning rule. Sigmoid transfer functions were used in the hidden and output layers to facilitate nonlinear calibration. The predictive ability of artificial neural networks was examined for the determination of aniline and cyclohexylamine in synthetic mixtures.     

FLOW - Injection Determination of Traces of Sulfide by the Brilliant Green - Sulfide Reaction with Spectrophotometry Detection

Abstract

A flow injection system is proposed for the rapid and sensitive determination of trace amounts of sulfide based on the addition reaction of sulfide with Brilliant Green at pH 7 and 25 C°. The effect of important parameters, such as reagent concentration, pH, reagent flow rate, sample volume, temperature and length of the reaction coil are reported. Sulfide in the range of 40 - 2000 ng·ml^?1 can be determined at a rate of 40 ± 5 samples per hour. The limit of detection was obtained as 2.0 ng of sulfide. The relative standard deviation for the determination of 100 ng·ml^?1 of sulfide is 0.8%. A system is proposed for elimination of potential interferences. The method was applied to the determination of sulfide in synthetic samples and in spring water.     

流动注射膜分离测定水中的苯胺

本文提出了用硅橡胶膜在线分离的流动注射紫外度法测定水样中的苯胺。该方法的检出限为１ｍｇ／Ｌ，苯胺含量在２－２００ｍｇ／Ｌ范围内呈良好的线性，对５０ｍｇ／Ｌ试样１２次测定的相对标准偏差为１．２％，１ｈ能测３５个样品。用本方法测定了几种水样中苯胺的含量，回收率均达９０％以上。     

流动注射光度法直接测定海水中的微量苯胺

基于苯胺与亚硝酸盐的重氮化反应及反应产物与甲萘酚的显色,借助流动分析技术,实现了海水中苯胺含量的分析测定。体系以30.9g/L的NaCl做载液、人工海水配制标准样品,对各个影响因素进行了优化。苯胺浓度在0.01～1.0mg/L范围内与相对峰高呈线性关系,线性方程ΔH(mV)=200.53ρ+1.0728(n=8,ρ为苯胺浓度mg/L),相关系数R2=0.9982。方法的检出限(3σ)为0.005mg/L,相对标准偏差(RSD)为4.8%(n=11)。考察了共存离子、不同盐度样品对分析测定的影响。用于实际海水样品的分析,回收率为95.8%～106.6%。     

Liquid chromatographic determination of aniline in table-top sweeteners based on pre-column derivatization with 1,2-naphthoquinone-4-sulfonate

A liquid chromatographic method for the determination of aniline in cyclamate sweeteners based on a pre-column derivatization with 1,2-naphthoquinone-4-sulfonate (NQS) is proposed. Aniline traces were extracted from the cyclamate samples using dichloromethane. After solvent evaporation, the dry residue was derivatized with NQS at pH 9.5 and 85 degrees C for 1 min. The aniline derivative, which was extracted from the reacting mixture, was redissolved in the eluent solution and injected into the chromatographic system. The separation of aniline derivative from other amine impurities was carried out in a C18 column using a 2% acetic acid-methanol (40:60, v/v) mobile phase. Results from the analysis of aniline in the sweetener samples with the proposed method were compared with those from the standard method. A good concordance between the two methods was observed.     

高效液相色谱法测定废水中苯胺类化合物

应用反相高效液相色谱法,采用ＨｙｐｅｒｓｉｌＢＤＳ色谱柱,以甲醇－水作流动相,梯度洗脱,ＵＶ２５４ｎｍ检测,外标法定量,同时测定苯胺、对硝基苯胺、间硝基苯胺、联苯胺、邻硝基苯胺、２,４－二硝基苯胺及Ｎ,Ｎ－二甲基苯胺的含量。回收率为５１．５７％～１０７．９２％,变异系数为１．８８％～５．９８％。方法快速、准确,是测定废水中苯胺类化合物的有效方法。     

Ascorbate amperometric determination using conducting copolymers from aniline and N-(3-propane sulfonic acid)aniline

The sequential electrochemical polymerization of aniline and N-(3-propane sulfonic acid)aniline (PSA) is proposed to construct a sensor able to detect ascorbate at physiological conditions. Compared to poly(aniline) modified electrode, a device with improved conducting and electrochemical properties at neutral pH is obtained. The electrochemical copolymerization of the same starting materials is also carried out. For a PSA:aniline ratio of 10:90, a polymer with a similar electrochemical behavior to the one grown in the sequential mode is observed.The detection of ascorbate was tested for both configurations at pH 7.2, the modified electrode is able to determine ascorbate at 0 mV versus Ag/AgCl; an optimized sensor constructed by sequential polymerization can easily detect ascorbate concentrations with a detection limit of 2.2 μM. Uric acid and dopamine does not interfere in the ascorbate determination.     

Synthesis of carbazole under conditions for the catalytic dehydrogenation of cyclohexylamine

The dehydrogenation of cyclohexylamine on platinum catalysts is investigated. In addition to aniline and diphenylamine, significant amounts of carbazole are formed. A possible mechanism for its formation is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 617–619, May 1988.     

盐酸吡哆辛在聚对氨基苯磺酸修饰电极上的电化学行为与测定

通过电聚合法制备了聚对氨基苯磺酸(PABSA)修饰玻碳电极(GCE),采用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了盐酸吡哆辛(VB₆)在该修饰电极上的电化学行为。 结果表明,VB₆在该修饰电极上的氧化电流显著增加,为裸电极上的7.5倍。 在pH值3.06.5的醋酸缓冲溶液中,VB₆在PABSA/GCE上的电极反应为吸附控制的一电子两质子的不可逆氧化反应。 在优化条件下,使用DPV对VB₆进行了定量检测,线性范围为0.04100 μmol/L,检出限为0.01 μmol/L,是目前所报道的电化学方法测定VB₆的最低检出限,相对平均偏差为3.1%(n=8)。 采用本方法对维生素B₆片中的VB₆进行检测,回收率为106%~108%。     

Spectrofluorimetric Determination of Methyl Paraben in Pharmaceutical Preparations by Means of its Dansyl Chloride Derivative

 A spectrofluorimetric method for the determination of methyl paraben based on derivatization with the labelling reagent dansyl chloride (DNS-Cl), is presented. The effect of the reaction variables (pH, DNS-Cl concentration, temperature, reaction time) and instrumental parameters, has been examined. A linear calibration graph in the ng/ml range has been established. The limit of detection is 18 ng/ml with relative standard deviation less than 3%. The proposed method has been satisfactorily applied to determination of the paraben in two pharmaceutical preparations. Received May 25, 1999. Revision October 20, 1999.     

Reactions of o-bromoacetylacylphenones with several primary amines

o-Monobromoacetylacylphenones, 3a and 3b reacted with hydroxylamine or hydrazine hydrate to produce heterocycles, 2,3-benzoxazine or phthalazine derivatives. The reaction of bromoacetyl group of 3a and 3b with several thioamides afforded thiazole derivatives in high yields. Whereas o-dibromoacetyl-benzophenoe 2a reacted with aniline or cyclohexylamine to produce non-heterocycles, 2-substituted-iminophenylindanones and the mechanism for the formation of these non-heterocycles is proposed.     

液相色谱-串联质谱法测定水中14种苯胺类化合物

通过优化色谱和质谱条件,建立了直接进样-液相色谱-串联四极杆质谱法同时快速检测水中14种苯胺类化合物的分析方法。水样经0.45 μm聚醚砜(PES)滤膜过滤后,采用Shim-pack FC-ODS柱(75 mm×4.6 mm, 3 μm)进行分离,以甲醇-0.1%(v/v)甲酸(35:65, v/v)梯度洗脱,流速0.3 mL/min,柱温35 ℃,串联四极杆质谱的多反应监测模式进行检测。在优化的分析条件下,14种苯胺类化合物可在12 min内分析完毕,而且线性关系良好(r>0.999),方法检出限在0.03~4.19 μg/L之间。对加标3个质量浓度(0.5、5.0、20.0 μg/L)的地表水样品平行测定6次,14种苯胺类化合物的相对标准偏差在0.4%~9.4%范围内。该方法抗干扰能力强、分析速度快、灵敏度高,已应用于实际样品的分析,样品加标回收率在68.0%~130%之间。     

Spectrofluorimetric Evaluation of Total Aliphatic and Aromatic Amines in Well Waters and Wastewaters

Abstract

A simple and rapid spectrofluorimetric method is described for the determination of aliphatic and aromatic amines on the basis of ammonia and aniline, respectively. Aromatic amines in samples were reacted at pH 5.5 with fluram immoblised on an Octadecylsilane Solid Phase Extraction (ODS-SPE) cartridge. The produced pyrrolinones were adsorbed on SPE and separated from the aliphatic amines. Analysis of these compounds was carried out by elution of SPE with 1 ml Tetrahydrofuran (THF) and determination of fluorescence intensity at excitation wavelength 400 nm and emission wavelength 475 nm. Aliphatic amines after passing from SPE were collected and reacted with fluram at pH 9.2, and extracted into dichloromethane at pH 3 and quantitated fluorimetrically.

Linear dynamic ranges and detection limits (LOD) were 1–20, 0.43 mg 1^?1 and 1-200, 0.39 μg 1^?1 for ammonia and aniline, respectively. The proposed method was successfuly applied for the evaluation of these compounds in local well waters and municipality wastewaters.     

Use of 4-chloro-7-nitrobenzofurazane as a derivative reagent for the determination of amino acids by cathodic stripping square wave voltammetry in biological fluids

The rapid and simple reaction of 4-chloro-7-nitrobenzofurazane with amino acids allows the determination of amino acids in urine using cathodic stripping square wave voltammetry. The obtained compounds are adsorbed on a hanging mercury drop electrode for determination by voltammetric methods using phosphate buffer at pH 2.0 as supporting electrolyte. The proposed method allows determination with an error of 5.68%. A limit of detection (3sigma) of 3.64 nM (0.766 ng ml(-1)) and a limit of determination (10sigma) of 12.12 nM (2.55 ng ml(-1)) are obtained for arginine determination. The proposed method has been applied to the determination of amino acids in urine.     

Catalytic determination of ultra trace amounts of tellurium by 2.5-order differential oscillopolarography

A highly sensitive and selective catalytic method with 2.5-order differential oscillopolarographic detection is described for the determination of tellurium, based on its activation effect on the slow Pd(II)-catalyzed reaction of sodium hypophosphite and methyl red in hydrochloric acid medium at 100 degrees C. Methyl red exhibited a sensitive 2.5-order differential polarographic wave at -0.35 V (vs. SCE) in the supporting electrolyte of pH 5.0 acetate buffer solution and was chosen as the indicating component for the indirect determination of tellurium. A calibration curve of tellurium in the range of 0.02-2.0 ng mL(-1) was obtained by the fixed-time procedure. The detection limit was 0.007 ng mL(-1). Possible interferences by co-existing substances were examined. The new method has been used to analyze trace tellurium in organs of white mice with satisfactory results. RSD was 0.54% to 2.10%, recovery 98.4% to 95.7%. The mechanism is also discussed.     

气相色谱-氮化学发光检测法分析催化汽油中含氮化合物类型的分布

建立了催化汽油馏分中各种含氮化合物类型分布的气相色谱-氮化学发光检测分析方法,考察了各种色谱条件对含氮化合物分离的影响。采用化学预处理的方法浓缩了催化汽油中的含氮化合物,并结合气相色谱-质谱检测以及部分含氮化合物标准样品,对某催化汽油中的20多个含氮化合物进行了定性(或归类)。催化汽油中几种主要含氮化合物(苯胺、2-甲基苯胺、二甲基苯胺)含量测定值的相对标准偏差(RSD)均不大于2.5%。当信噪比(S/N)为3时,苯胺氮的检出限为1.0 mg/L。该方法可用于不同来源和不同加工工艺的汽油馏分中各种含氮化合物类型分布的研究。     

丹磺酰氯柱前衍生-超高效液相色谱-串联质谱法测定人体尿样中的环己胺

建立丹磺酰氯柱前衍生-超高效液相色谱-串联质谱法测定人体尿样中环己胺的方法。冷冻样品经解冻、离心后,用丹磺酰氯衍生,固相萃取小柱净化。目标化合物采用 Waters ACQUITY CSHTM C18色谱柱(50 mm×2.1 mm,1.7μm)分离,以甲醇和0.002 mol/L乙酸铵溶液为流动相梯度洗脱,采用电喷雾离子源电离、正离子多反应监测模式质谱检测。环己胺在2.5~200μg/L浓度范围内有较好的线性关系,相关系数大于0.999,回收率为98.7%~102.3%,精密度为3.1%~5.2%,检出限和定量限分别为1.0和3.0μg/L。结果表明,本方法操作简单、准确可靠,可适用于人体尿液中环己胺的定量分析。应用本方法测定200份学生尿液样品,环己胺检出率为34.5%。     

Synthesis of 1,5-bis(4,6-dichloro-1,3,5-triazinylamino)naphthalene and its application to spectrofluorimetric determination of aniline

A new fluorescent reagent 1,5-bis(4,6-dichloro-1,3,5-triazinylamino)naphthalene (DTAN) was synthesized. The optimum conditions of fluorescent reaction of this reagent with aniline (PA) were also investigated. Based on this reaction, a new spectrofluorimetric method was developed for the determination of aniline. The fluorescent intensity was directly proportional to the concentration of aniline in the ranges 0.05-2.0 microg mL(-1) and 2.0-50 microg mL(-1) with the detection limits of 34 ng mL(-1) and 90 ng mL(-1). This method is simple, practical and can afford good precision and accuracy and can be successfully applied to assess aniline in water samples. A possible mechanism of the change of fluorescence intensity introduced by putting the aniline into the system is also discussed.     

Al2O3-SiO2催化环己胺氧化制备环己酮肟

以Al2O3-SiO2为催化剂,用双氧水氧化环己胺制备了环己酮肟。考察了溶剂用量、催化剂用量、反应时间和反应温度等因素对催化性能的影响。结果表明,在溶剂乙腈与环己胺体积比为3∶1,催化剂质量分数31.0%,75℃反应5 h后的环己胺转化率为100%,环己酮肟选择性可达83.6%。并对环己胺催化氧化的反应机理作了初步的探讨。