Determination of amine-containing phosphonic acids and amino acids as dansyl derivatives

Conditions are selected for the analytical separation of (N-phosphonomethyl glycine), products of its microbiological conversion, glutamic acid, and alanine as dansyl derivatives using reversed-phase HPLC: column (250 × 4.6 mm) ReproSil-PAH EPA; mobile phase, methanol + 20 mM CH₃COONa (pH 5.1) (20: 80); rate of mobile phase, 1 mL/min; working detector wavelength, 330 nm. The duration of separation is 35 min. The lower limits of the analytical range (in ng) for dansyl derivatives are as follows: glyphosate, 8.2; aminomethyl phosphonic acid, 24.2; glutamic acid, 9.4; alanine, 12.6: glycine, 17.7; and sarcosine, 19.3. The TLC study of dansyl derivatives of amino acids was performed on sorbfil plates PTSH-P-V using two-dimensional chromatography in the systems ethyl acetate-isopropanol-24% aqueous ammonia (45: 35: 20) in the first direction and chloroform-methanol-acetic acid (25: 5: 1) in the second one. For determining phosphonic acids (glyphosate and aminomethyl phosphonic acid), a version of one-dimensional chromatography with the sequential use of two systems, chloroform-methanol-acetic acid (25: 5: 0.2) and ethanol-24% aqueous ammonia (7: 3), was proposed.     

Isolation of gentamicin C compounds from culture filtrates of Micromonospora purpurea

A liquid chromatographic method was developed for the isolation of gentamicin C compounds from commercial fermentation products in order to monitor health hazards (oto- and nephrotoxicity). Chromatography was carried out on silica gel 60 (15-40 microns) with a medium-pressure chromatographic system, employing methanol-25% ammonia solution (85:15, v/v) and methanol-chloroform-25% ammonia solution (20:10:5, v/v) as mobile phases. The eluted fractions were neutralized with 1.0 M hydrochloric acid, concentrated in vacuo and desalted by gel filtration. It was possible to demonstrate by 1H NMR spectroscopy and high-performance liquid and thin-layer chromatography that the separated fractions contained components C1, C1a and C2 in purities of more than 95%.     

Determination of glyphosate and its biodegradation products by chromatographic methods

Conditions were selected for the separation of the herbicide glyphosate (N-(phosphonomethyl)glycine) and products of its microbiological utilization as N-acylated derivatives by ion-exchange liquid chromatography. The order of the elution of compounds on a Repro-Gel H column with UV detection correlates with their structures. The detection limits of the derivatives (wavelength 210 nm) are as follows (ng): glyphosate, 30; glycine and sarcosine, 20 and 43, respectively; aminomethylphosphonic acid, 45. The detection limit of methylphosphonic acid is 14 μg. Glyphosate and its biodegradation products were separated by thin-layer chromatography on plates with silica gel in the system isopropanol-5% aqueous ammonia solution (1: 1).     

Extraction of Mercaptans from Light Hydrocarbon Mixtures with Aqueous Ammonia

Results of laboratory studies of the extraction of light mercaptans (methyl, ethyl, and propyl mercaptans) from hydrocarbons mixtures with a 25% aqueous solution of ammonia (caustic ammonia) are presented and discussed. It is shown that aqueous ammonia can in principle be used for controlled demercaptanization of light hydrocarbon fractions and liquefied hydrocarbon gases containing hydrogen sulfide and lower mercaptans. The advantage of this demercaptanization method over the conventional processes of alkali treatment is that there is no stage of oxidative catalytic regeneration of a spent alkali and there are no its highly toxic wastes, sulfurousalkaline waste waters. The regeneration of a spent (saturated with sulfurous compounds) aqueous ammonia can be comparatively easily performed by its heating (boiling), which leads to a hydrolytic decomposition of ammonium sulfides and mercaptides to release their constituent gases: hydrogen sulfide, mercaptans, and ammonia. Ammonia is recycled into the process as freshly prepared (regenerated) caustic ammonia.

     

Identification and structural characterization of major degradation products of tapentadol by using liquid chromatography–tandem mass spectrometry

Tapentadol, a centrally acting analgesic was subjected to hydrolysis (acidic, alkaline, and neutral), oxidation, photolysis, humidity, and thermal stress conditions as per International Conference on Harmonization prescribed guidelines. Tapentadol was found susceptible to oxidative stress that produced two major degradation products DP-I and DP-II. However, it was stable to hydrolysis, photolysis, and thermal stress conditions. A simple, sensitive, and accurate high-performance liquid chromatography stability-indicating assay method (liquid chromatography–mass spectrometer compatible) was developed and validated for identification and characterization of stressed degradation products of Tapentadol. The chromatographic separation of the drug and its degradation products were achieved on Inertsil ODS, C18 (250 × 4.6 mm, i.d., 5 µm) column using a 12.5 mM aqueous ammonium acetate buffer (with 0.2% triethyl amine and final pH of buffer was adjusted to 3.60 with glacial acetic acid): acetonitrile (75:25, v/v) as a mobile phase. The degradation products were characterized by liquid chromatography mass spectrometry and subsequently its fragmentation pathway as well as plausible mechanism for generation of degradation products was also proposed. The stability indicating high-performance liquid chromatographic method was validated with respect to linearity, precision, and accuracy.     

Oxidation of Acyclovir by a Cuprate(III) Periodate Complex in Aqueous Alkaline Media: A Kinetic and Mechanistic Approach

The oxidation of acyclovir by diperiodatocuprate(III) in aqueous alkaline media, at a constant ionic strength of 0.01 mol?dm^?3, was studied spectrophotometrically at 25?°C. The reaction between acyclovir and DPC in alkaline media exhibits 1:4 stoichiometry (acyclovir:diperiodatocuprate(III)). The main oxidation products were identified by a spot test, along with infrared and liquid chromatography mass spectral studies. The oxidation reaction is first order with regard to the diperiodatocuprate(III) concentration, but has less than unit order in the acyclovir concentration and negative fractional orders in the periodate and alkali concentrations. Intervention of free radicals was observed in the reaction. The oxidation reaction in alkaline media was shown to proceed via a diperiodatocuprate(III)?Cacyclovir complex, which decomposes slowly in a rate determining step followed by subsequent fast steps to give the products. A suitable mechanism is proposed for these observations. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism, along with the thermodynamic quantities, were determined and discussed.     

Determination of Diazepam and associated compounds in pharmaceutical preparations

A method for determining Diazepam and its associated compounds in pharmaceutical products by micellar electrokinetic chromatography (MEKC) is described. The separation was carried out at 30 °C and 25 kV, using a 25 mM borate buffer (pH 9.6) and 35 mM sodium dodecylsulfate (SDS) water solution. Under these conditions the analysis was carried out within 12 min with acceptable limits of detection and quantification. The method has been applied for quantifying Diazepam in different commercial formulations when it is the active drug and when it is employed associated with other drugs (Nortriptyline, Pyridoxine hydrochloride and Sulpiride). Received: 30 October 1998 / Revised: 1 February 1999 / Accepted: 3 February 1999     

Pretreatment of wastepaper and pulp mill sludge by aqueous ammonia and hydrogen peroxide

Pretreatment of two different softwood-based lignocellulosic wastes (newsprint and Kraft pulp mill sludge) was investigated. Pretreatment was done by aqueous ammonia and hydrogen peroxide (H₂O₂), two delignifying reagents that are environmentally benign. Three different treatment schemes were employed: aqueous ammonia alone (ammonia recycled percolation [ARP]), mixed stream of aqueous ammonia and H₂O₂ and successive treatment with H₂O₂ and aqueous ammonia. In all cases there was a substantial degree of delignification ranging from 30 to 50%. About half of the hemicellulose sugars were dissolved into the process effluent. Retention of cellulose after pretreatment varied from 85 to 100% for newspaper feedstock and from 77 to 85% for the pulp mill sludge. After treatment with aqueous ammonia alone (ARP), the digestibility of newspaper and the pulp mill sludge was improved only by 5% (from 40 to 45% for the former and from 68 to 73% for the latter), despite a substantial degree of delignification occurring after the ARP process. The lign in content thus did not correlate with the digestibility for these substrates. Simultaneous treatment with H₂O₂ and aqueous ammonia did not bring about any significant improvement in the digestibility over that of the ARP. A succcessive treatment by H₂O₂ and ARP showed the most promise because it improved the digestibility of the newspaper from 41 to 75%, a level comparable to that of α-cellulose.     

Preparative separation of cichoric acid from Echinacea purpurea by pH-zone-refining counter-current chromatography

pH-zone-refining counter-current chromatography was successfully applied to the separation of cichoric acid from Echinacea Purpurea (L.) Moench. A 3.0 g quantity of sample was separated using the following two-phase solvent system: MtBE-CH3CN-water (4:1:5, v/v), 10 mM trifluoroacetic acid in organic stationary phase and 10 mM ammonia in aqueous mobile phase. The obtained fractions were analyzed by high-performance liquid chromatography and negative ion electrospray ionization mass spectrometry. Double separations were performed with the same solvent system yielding 563 mg cichoric acid at 95.6% purity.     

Surface electrochemistry of the oxidation reactions of α- and β-alanine at a platinum electrode

The electrochemical oxidation reactions of α- and β-alanine at a Pt electrode were investigated in aqueous solutions at pH 1, 7, and 13 using steady-state current-potential measurements, cyclic voltammetry, and open circuit potential decay. The capacitance behaviour and the high Tafel slopes suggest the production of free radicals at the surface of the electrode accompanied by a second reaction involving loss of CO₂ which is the rate determining step. In the surface electro-oxidation of α-alanine, it appears that the adsorbed intermediate species is either hydrolyzed anodically to acetaldehyde and ammonia, or is oxidized to a carbonium ion which is subsequently hydrolyzed to acetaldehyde and ammonia in solution, analogous to the behaviour observed for glycine [D.G. Marangoni, R.S. Smith and S.G. Roscoe, Can. J. Chem., 67 (1989) 921]. The mechanisms for β-alanine would be similar except carbonium ion formation would probably be accompanied by a hydride transfer to form acetaldehyde. No dimerized products were detected by gas chromatography. These mechanisms differ from the dimerization process typical of the radical reactions associated with the Kolbe mechanism.     

Direct determination of tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate by HPLC and GC methods

The high performance liquid chromatography and gas chromatography methods were investigated for their applicability in determining micro-level concentrations of tri-n-butyl phosphate (TBP). A high performance liquid chromatograph (HPLC) equipped with refractive index detector was used in determining TBP up to 2 ppm concentration level in the aqueous nitric acid solutions. The gas chromatography incorporated with Thermionic Detector (NPD) and Flame Photometric Detector (FPD) were examined for their potential in analyzing TBP in organic phase up to sub-ppm level. The results indicated that HPLC-RI technique is well suited for direct analysis of aqueous phase. For organic phase analysis, gas chromatographic methods with the TID and FPD were suitable but performance of detectors deteriorated often due to fouling.     

Hydrolyzabilities of Different Corn Stover Fractions After Aqueous Ammonia Pretreatment

The effect of aqueous ammonia pretreatment on the hydrolysis of different corn stover fractions (rind, husk, leaf, and pith) by xylanase (XYL) with cellulases (CELs) was evaluated. The aqueous ammonia pretreatment had excellent delignification ability (above 66 %) for different corn stover fractions. The corn rind exhibited the lowest susceptibility to aqueous ammonia pretreatment. The pretreated rind showed the lowest hydrolyzability by CEL and XYL, which was supported by a high content of crystalline cellulose in the hydrolyzed residues of rind, as confirmed by X-ray diffraction (XRD). With the addition of 1 mg XYL/g dry matter, a high glucose yield (above 90 %) could be obtained from the pretreated rind by CEL. The results revealed that a high hydrolyzate yield of corn rind after aqueous ammonia pretreatment could be obtained with 1 mg xylanase/g dry matter, showing that aqueous ammonia pretreatment and xylanase addition to cellulases have great potential for the efficient hydrolysis of corn stover without previous fractionation.     

由2-烷基蒽醌一步法制备2-烷基蒽(英文)

本文报道了以2-烷基蒽醌为原料,结晶硫酸铜为催化剂,锌粉为还原剂于浓氨水(25%～28%)中一步法制备2-烷基蒽.产物通过硅胶柱层析,收率范围:55%～90%.文中从取代基的电子效应和空间位阻角度分析了产率的变化规律.同时考察了其它几种无机盐用作催化剂的催化作用.     

Purification of Food Color Red No. 106 (acid red) using pH-zone-refining counter-current chromatography

pH-Zone-refining counter-current chromatography was successfully applied to the separation of the main components of Food Color Red No. 106 (R-106, acid red, Color Index No. 45100). A 300-mg quantity of sample was separated using the following two-phase solvent system: n-butanol-water, 40 mM sulfuric acid in organic stationary phase and 30 mM ammonia in aqueous mobile phase. The obtained fractions were analyzed by high-performance liquid chromatography and fast atom bombardment mass spectrometry. The separation yielded 261.9 mg of main component of acid red with purity of 99.9%.     

Direct fluorescence detection of non-steroidal anti-inflammatory agents separated by TLC with 9-isothiocyanatoacridine derivatives

Summary Non-steroidal anti-inflammatory agents were separated by thin-layer chromatography, utilizing precoated plates with silica gel R as the stationary phase and chloroform:methanol:25% ammonia (80∶15∶5), as the mobile phase. The spots were visualized by spraying with 0.1% solution of 9-isothiocyantoacridine derivatives in methylene chloride or benzene and irradiating with UV at 254 and 366nm. The visual detection limit of a spot was 0.1μg.     

Pretreatment with ammonia water for enzymatic hydrolysis of corn husk, bagasse, and switchgrass

Bagasse, corn husk, and switchgrass were pretreated with ammonia water to enhance enzymatic hydrolysis. The sample (2 g) was mixed with 1–6 mL ammonia water (25–28% ammonia) and autoclaved at 120°C for 20 min. After treatment, the product was vacuum-dried to remove ammonia gas. The dried solid could be used immediately in the enzymatic hydrolysis without washing. The enzymatic hydrolysis was effectively improved with more than 0.5 and 1 mL ammonia water/g for corn husk and bagasse, respectively. In bagasse, glucose, xylose, and xylobiose were the main products. The adsorption of CMCase and xylanase was related to the initial rate of enzymatic hydrolysis. In corn husks, arabinoxylan extracted by pretreatment was substantially unhydrolyzed because of the high ratio of arabinose to xylose (0.6). The carbohydrate yields from cellulose and hemicellulose were 72.9% and 82.4% in bagasse, and 86.2% and 91.9% in corn husk, respectively. The ammonia/water pretreatment also benefited from switchgrass (Miscanthus sinensis and Solidago altissima L.) hydrolysis.     

反相高效液相色谱法测定血浆中的单硝酸异山梨酯

建立了反相高效液相色谱测定血浆中单硝酸异山梨酯浓度的方法。样品在碱性条件下经二氯甲烷提取后,用C18柱进行分离,以H2O(用0.03 mol/L氨水调pH至7.8)-乙腈(体积比为80∶20)为流动相,对乙酰氨基酚为内标,于230 nm处测定。结果表明,单硝酸异山梨酯的质量浓度为20~1000 μg/L时其峰面积与内标峰面积之比与单硝酸异山梨酯浓度有良好的线性关系。方法的最低检测质量浓度为12 μg/L,平均回收率为(97.11±2.45)％~(104.34±2.17)%,日内测定的相对标准偏差(RSD)≤2.52%,日间测定的RSD≤5.21%。     

Composition of reaction mixtures formed by ethanolamine detoxication of yperite

The reaction mixture from detoxication of technical-grade yperite with monoethanolamine was fractionated, and its composition was determined. The structures of the free thiomorpholine bases formed in the process were determined by gas chromatography—mass spectrometry.     

气相色谱法测定费托合成水相产物中的低碳醇、醛、酮化合物

建立了铁基催化剂费托合成反应水相产物中低碳(C₁~C₈)醇、醛、酮的气相色谱测定方法.对色谱分离条件进行了优化,确立了以乙醇为基准物质并结合各组分校正因子的定量方法;考察了方法的精密度和准确度,并对费托合成反应水相产物样品进行了测定.结果表明,乙醇在不同的含量范围内呈现良好的线性关系,相关系数均大于0.99.费托合成水相产物中的加标回收率在93.4%~109.6%之间,准确性可以满足实际分析的需要.实际费托合成水相产物的分析结果表明,费托合成水相产物中主要的低碳醇、醛、酮的总质量分数约为3%~12%,乙醇含量最高(约为1.7%~7.3%),且正构醇、异构醇和醛酮类化合物所占的总比率依次降低.该方法简单、快速,对费托合成水相产物中重要组分的分析有重要意义.     

同位素内标-多反应监测同步在线质谱全扫描确证火锅料中罂粟壳成分

建立了高效液相色谱-三重四极杆线性离子阱质谱测定火锅料中吗啡、可待因、蒂巴因、罂粟碱、那可丁等5种生物碱残留的确证方法。样品采用稀盐酸加热提取,正己烷除脂,阳离子混合机理固相萃取柱净化,5%氨化乙酸乙酯-甲醇洗脱,PAK ST色谱柱分离,5 mmol/L乙酸铵甲醇溶液-10 mmol/L乙酸铵水溶液(pH 3.6)作为流动相洗脱,电喷雾正离子模式下多反应监测同步增强子离子在线全扫描(EPI)。在该实验条件下,5种生物碱的LOD在0.05~0.5 μg/kg之间,增强型子离子全扫描水平限和LOQ在0.2~2 μg/kg之间,方法回收率为64.2%~110.6%, RSD为4.2%~12.5%。阳性样品的定性确证需采用其子离子全扫描质谱图与标准图库中子离子质谱图检索匹配。经测定多种火锅料,表明本方法操作简单、测定结果准确,可用于火锅料中5种生物碱残留的阳性结果确证分析。