Interaction of aliphatic polyamines with Nessler reagent

It was found that products of the interaction of Nessler reagent with ethylenediamine and other aliphatic polyamines are insoluble complexes of different composition and soluble colored complexes. The latter are formed only in the presence of ammonia and can be used for the determination of polyamines in water with a detection limit of ～1 × 10^?6 M.     

纳氏试剂测定水中氨氮影响因素的探讨

对国家生活饮用水标准检验方法"GB/T5750—2006"中涉及到的水中氨氮的检测条件进行了探讨,讨论了样品的采集与保存,影响显色、空白值的各项因素,并提出相应的解决办法。对国家标准物质以及实际样品的验证表明,方法的相对误差为0.03%~1.5%,相对标准偏差RSD为0.55%~5.3%,准确度也能满足分析要求,对国家标准方法进行了补充与细化,在实际工作中有参考价值。     

Mercurous nitrate as a reductimetric reagent : The determination of hydroxylamine and nitrates

Hydroxylamine can be determined indirectly using standard mercurous nitráte, by treating the test solution with an excess of standard ferric alum, and back titrating the excess.The same procedure cannot be recommended for the determination of hydrazine and hydroquinone. The results with hydrazine were irregular and generally low. With hydroquinone, the brown colour of the oxidation product masked the endpoint.An attempt was made to determine nitrate after reduction with ferrous ammonium sulphate, but the high acidity required is unfavourable for mercurous nitrate titration, and results are only accurate to about 1 per cent.     

近红外分光光度法测定高氯酸羟胺中的水含量

建立近红外分光光度法测定高氯酸羟胺中的水含量.以四氢呋喃水溶液为标准溶液,以四氢呋喃为参比溶液,测定系列标准溶液于波长1920 nm处的校正吸光度,标准曲线线性方程为y=113.76x+0.0065,相关系数为0.9996.样品重复性测定相对标准偏差小于2％(n=5),样品加标回收率为98.06％～99.92％.该方法操作简便.     

Determination of hydroxylamine using a carbon paste electrode modified with graphene oxide nano sheets

A carbon paste electrode that was chemically modified with 3-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4-AA) was used as a selective electrochemical sensor for the detection of hydroxylamine. Cyclic voltammetry (CV), choronoamperometry (CHA) and square wave voltammetry (SWV) were used to investigate oxidation of hydroxylamine in aqueous solution. Under optimized concentration the electrocatalytic oxidation current peak for hydroxylamine increased linearly with concentration in the range of 0.025–10.0 μM. The detection limits for hydroxylamine was 0.012 μM. Finally, the modified electrode was applied to detection hydroxylamine in water samples.     

Determination of immobilized digitonin with the aid of an anthrone reagent

A colorimetric method using an anthrone reagent has been developed for the direct quantitative determination of digitonin oxidized with NaIO₄ in solution and after immobilization on Aminosilochrome. The amounts of immobilized digitonin found agree with the results obtained by the sorption of cholesterol from blood serum.M. V. Lomonosov Moscow State University. N. I. Pirogov Second Moscow State Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 453–457, July–August, 1981. Original article submitted January 14, 1981.     

Determination of water by flow-injection analysis with the karl fischer reagent

A method for the determination of water in organic solvents by flow-injection analysis (f.i.a.) is described. The method, which is based on the reaction between water and the Karl Fischer reagent, is capable of 120 determinations per hour. The concentration range 0.01–5% (v/v) of water can be covered by using a single Karl Fischer reagent solution. The results obtained with a specially constructed potentiometric detector showed a relative standard deviation of less than 0.5% (v/v). This value was about 3 times less than that obtained with a spectrophotometric detector. The f.i.a. technique is shown to offer some unique possibilities in minimizing interferences associated with the standard Karl Fischer batch titration method.     

纳氏试剂分光光度法测定铝灰渣浸出液中的氨氮含量

随着水土资源环境日益恶化,监测氨氮量对水土的污染程度也备受关注。为了准确测定铝灰渣浸出液中的氨氮量,实验对振荡方法、振荡时间、固液比、试液过滤方式、纳氏试剂加入量以及测定干扰因素进行了研究。确定了以翻转振荡为前处理方式,最佳振荡时间为14 h,固液比为1:10,最佳纳氏试剂加入量为1.0 mL,通过改善过滤方式,降低了空白值。由实验结果可知：在试验范围内,F^-对氨氮量的测定不产生干扰;对于浸出液中Cl^-、Al³⁺和Ca²⁺浓度高的样品,可通过移取稀释液2.00 mL,加入1.0 mL酒石酸钾钠溶液(500 g/L),即可消除其干扰。运用纳氏试剂分光光度法测定铝灰渣浸出液中的氨氮量,得到氨氮标准曲线线性相关系数为0.9998,方法检出限为0.39 mg.L^-1,RSD(n=6)<5%,回收率在94.7%～105%之间。本方法简单快速,精密度高,且具有较低的检出限,适用于大批量铝灰铝渣等固体废物浸出液中氨氮量的测定。     

Reactions of benzoylheteroaroylmethanes with hydroxylamine hydrochloride

Benzoyl-2-furoylmethane reacts with hydroxylamine hydrochloride to give predominantly 5-(2-furyl)-3-phenylisoxazole and not as reported in the literature 3-(2-furyl)-5-phenylisoxazole. Benzoyl-2-thenoylmethane and benzoylpicolinoylmethane afforded 3-phenyl-5-(2-thienyl)isoxazole and 5-phenyl-3-(2-pyridyl)isoxazole respectively.     

Determination of small amounts of water with coulometrically generated Karl Fischer reagent

A coulometric method for the determination of small amounts of water described in a previous report has been further developed. Improved electronic circuitry and a redesigned electrolysis cell have extended the range of determination and decreased the time of analysis. By means of a movable oven specially adapted to the cell, water in solids has also been determined. The method presented is applicable with high accuracy in the range 0.005–5 mg of water in a large variety of substances.     

Ammonium Determination in Water Samples by Using Opa-Nac Reagent: A Comparative Study with Nessler and Ammonium Selective Electrode Methods

A selective and sensitive method based on the ammonium derivatisation with o -phthaldialdehyde (OPA) and N -acetyl-cysteine (NAC) has been developed for ammonium determination in real water samples. The proposed procedure has been compared with ammonium reference methods such as Nessler reagent method and ammonium selective electrode. All procedures have been chemometrically tested and compared in terms of the main analytical properties. These procedures have been used to determine ammonium in unknown water samples. The OPA-NAC reagent method does not present any systematic error (proportional or constant), while Nessler reagent presents both of them for some samples assayed. The ammonium selective electrode is free of corrigible systematic errors, however presents amine interference. The OPA-NAC ammonium method is able to achieve a detection limit (LOD) of 0.07 mg/L in the sample, with a linear dynamic range up to 1.4 mg/L of ammonium.     

Selectivity of the bulky proton-containing reagent N-methyl-N,O-bis(trimethylsilyl)hydroxylamine in the formation of nitrones.

Silicon reagent Me₃SiN(ME)OSiMe₃ contains bulky protons (i.e. Me₃Si⁺). This reagent was found to possess regio- and chemoselectivities in the formation of nitrones from carbonyl compounds.     

Selective deacylation of enol esters with hydroxylamine

An effective procedure for selectively cleaving enol esters in the presence of normal ester functions has been developed, involving hydroxylaminolysis to the oxime of the parent ketone.     

Reaction of substituted benzylideneacetylacetones with hydroxylamine hydrochloride

The reaction of α,β-unsaturated β-diketones, such as 3-(o-chloro, m-nitro, and o-nitrobenzylidene)acetylacetones (I, II, and III) with hydroxylamine hydrochloride was carried out. Among them, compound I and II in acetonitrile, methanol, and acetic acid afforded 4-(α-hydroxy, methoxy, acetoxy, and chlorobenzyl)-3,5-dimethylisoxazoles (IV-XI) in fairly good yield. On the other hand, III yielded 3-(3′,5′-dimethylpyrazolo)-5-chloroanthranil (XV) under the almost same conditions by the participation of o-nitro group.     

Reactions of α-pentafluorophenylpyrylium salts with hydroxylamine

The reactions of α-pentafluorophenylpyrylium salts with hydroxylamine in ethanol afford isoxazoline derivatives and/or pyridine N-oxides depending on the steric characteristics of the substituent in the second α position. The structure of 2-hydroxy-2-pentafluorophenyl-4-phenyl-2,3,5,6,7,8-hexahydroquinoline 1-oxide, which was synthesized by the reaction of 2-pentafluorophenyl-4-phenyl-5,6,7,8-tetrahydrobenzopyrylium perchlorate with NH₂OH, was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 402–407, February, 2008.     

N-amination of amino acids and its derivatives using N-Boc-O-tosyl hydroxylamine as an efficient NH-Boc transfer reagent: electrophilic amination

Terminal tert-butyloxycarbonyl (Boc) protected hydrazino acids, useful intermediates for modified peptides and biologically active heterocyclic derivatives, were synthesized by electrophilic amination methodology using N-Boc-O-tosyl hydroxylamine as an efficient NH-Boc transfer reagent. Also, we have demonstrated the conversion of other amino acid derivatives such as amino esters and amino alcohols into β-Boc-hydrazino derivatives using this reagent.     

Determination of ketotifen by using calcein as chemiluminescence reagent

Chemiluminescence (CL) was observed when potassium hexacyanoferrate(III) reacted with the mixture of calcein and ketotifen. Interestingly, the CL intensity would be enhanced by trace amounts of Mg²⁺ and the CL intensity was strongly dependent on ketotifen concentration. Based on this phenomenon, a flow injection CL method was established for the determination of ketotifen. The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction, CL spectrum, ultraviolet (UV) spectra and fluorescent spectra. The CL intensity was correlated linearly with concentration of ketotifen over the range of 6.0 × 10⁻⁹ to 2.0 × 10⁻⁷ g mL⁻¹ and the detection limit was 3 × 10⁻⁹ g mL⁻¹. The relative standard deviation was 1.8% for 2.0 × 10⁻⁸ g mL⁻¹ ketotifen (n = 11). This method was applied to the determination of ketotifen in the tablets successfully.     

Variamine blue as a gravimetric reagent Determination of tungsten

Tungsten can be precipitated by a solution of Variamine Blue at pH 5. The precipitate is ignited to constant weight at a temperature above 600 degrees and weighed as tungsten trioxide. The method can be used for the determination of tungsten in alloy steels.     

Magnesia-supported hydroxylamine hydrochloride in the presence of sodium carbonate as an efficient reagent for the synthesis of 1,2,4-oxadiazoles from nitriles

An efficient one-pot method has been developed for the synthesis of 1,2,4-oxadiazoles through a one-pot reaction of nitriles with hydroxylamine hydrochloride in the presence of magnesia-supported sodium carbonate followed by reaction with acyl halides under solvent-free conditions using microwave irradiation. This method is easy, rapid and good yielding.