苯酚,马尿酸和甲基马尿酸的反相高效液相色谱分析

本文提出了人体内苯、甲苯和二甲苯的代谢产物苯酚、马尿酸和甲基马尿酸的反应高效液相色谱分析法，讨论了其保留机制和样品预处理技术，以ＯＤＳ为固定相，甲醇－水－醋酸为流动相时可实现良好分离，方法回收率为９７．３％；相对标准偏差为１．０２％。提出的方法可用于尿样分析，适用于临床与职业防治的监测分析。     

毛细管电泳-紫外检测法同时测定人尿中马尿酸和甲基马尿酸

建立了人尿中马尿酸和甲基马尿酸的毛细管电泳同时测定方法。尿样经乙酸乙酯提取,N2流挥干,硼砂-乙腈缓冲液溶解后毛细管电泳法分析。熔融石英毛细管(50 cm×50μm,有效长度41 cm,未涂层)为分离柱;20 mmol/L的硼砂+20%乙腈(pH 9.3)为运行缓冲液,紫外检测波长为230 nm,电泳分离温度为20℃,分离电压为20kV,重力进样高度20 cm,进样时间为10s。在优化的条件下,马尿酸和甲基马尿酸质量浓度在2～50 mg/L范围内具有良好的线性关系,线性相关系数分别为0.9998和0.9994,检出限分别为0.26和0.20 mg/L,加标回收率分别为100.7%～115.5%及93.3%～116.7%。本法适合于尿中马尿酸和甲基马尿酸的同时快速测定。     

马尿酸分子印迹电化学传感器的制备及应用

采用超声法制备g-C3N4/NiO复合催化材料,将其滴涂在玻碳电极(GCE)表面构建g-C3N4/NiO/GCE催化电极。采用电聚合方法,以马尿酸为模板分子,邻苯二胺为功能单体构建M IP/g-C3N4/NiO/GCE传感器。采用时间-电流法对传感器制备条件优化。结果表明,复合催化材料对H2O2具有良好的催化效果。分子印迹传感器对马尿酸具有良好的选择性。在优化条件下,马尿酸质量浓度在0.05~2 mg/L范围内,电极电流响应与浓度呈良好的线性关系,检出限为7.1μg/L。将电极用于尿液中马尿酸的检测,回收率在87.3%~95.3%之间。     

马尿酸及乙酰苯胺燃烧能的测定

设计并建立一台精密转动弹热量计,能在恒温和绝热两种模式下操作.测量数据的采集由在线微机自动完成,测量结果通过适当的程序计算.用量热标准物质NBS39i苯甲酸标定其能当量,偏差约为±0.006%.马尿酸及乙酰苯胺的燃烧能测定值分别为-(23542.7±0.9)J/g和-(31245.8±2.4)J/g(平均值和标准偏差).不确定度为总标准偏差的2倍,分别为±4.5J/g和±7.5J/g.结果与推荐值一致.还讨论了这两个化合物作为低含氮量量热参考物质的性质.     

从牛尿中制取苯甲酸和马尿酸

原理:用新鲜的牛尿(成尿、羊尿均可,凡是食草动物的尿)可以制得马尿酸,如果让尿自行发酵,则尿中的马尿酸就水解,有苯甲酸生成,所以采用发酵的尿,就可制得苯甲酸。苯甲酸构造式为:-COOH,白色片状或针状结晶熔点为121—122℃,能溶于醇、醚、氯仿、苯等有机溶剂中。苯甲酸最初由安息香胶升华而得,故又名安息香酸。现今工业上制造苯甲酸,多以甲苯为原料,     

高效液相色谱法测定血管紧张素转化酶抑制剂的活性

建立了体外直接测定血管紧张素转化酶抑制剂活性的高效液相色谱分析方法。以马尿酰-组氨酰-亮氨酸为反应底物,血管紧张素转化酶为催化剂,反应所生成的马尿酸为测定指标,未加酶抑制剂的反应为空白对照。使用ZORBAX SB-C18色谱柱(4.6 mm i.d.×150 mm,填料粒径5　μm),柱温25 ℃,流动相为乙腈-超纯水(体积比为25∶75,各含0.05%（体积分数）三氟乙酸及0.1%（体积分数）三乙胺),流速0.5 mL/min,检测波长228 nm。在马尿酸浓度为0.005～1.000 mmol/L时,马尿酸浓度与其峰面积呈良好的线性关系(r＝0.9999),最小检测限为0.50 μmol/L;该方法对马尿酸的回收率为99.48%～105.64%,相对标准偏差(RSD)为2.20%(n＝6)。该方法可适用于血管紧张素转化酶抑制剂活性的体外测定,具有操作简便、精密度和准确性高的特点,为降血压药物的研制提供了方便可靠的检测手段。     

尿中马尿酸及甲基马尿酸的分离和测定

甲苯进入人体首先被氧化成苯甲醇,然后被醇脱氢酶氧化成苯甲醛,再经醛脱氢酶氧化成苯甲酸,后者与甘氨酸结合成马尿酸而从尿中排出。二甲苯进入人体后,二个甲基中的一个被氧化而同甲苯的代谢途径一样,最终生成甲基马尿酸从尿     

键能的研究——马尿酸、哌嗪、氮七环燃烧热的测定

使用精密氧弹量热计测定了下列物质的燃烧热△H^-_o和生成热△H⁰_f(1)马尿酸(c)-1008.30±0.22;(2)哌嗪(c)-707.79±0.27和-9.99±0.27及(3)氮七环(1)-987.03±0.39和-21.35±0.39kcal/mol.利用文献的或我们估计的相变潜热值,得到两个环状化合物的气态生成热.按照键能模式估计了这两个化合物的环张力能,分别为(2)-0.2±1.5和(3)5.6±0.4kcal/mol,并与其它环状化合物的环张力能进行了比较.     

新显色剂对马尿酸偶氮氯膦直接光度法测定土壤中稀土元素总量

拟定了用新合成的显色剂对马尿酸偶氮氯膦直接光度法测定土壤中稀土元素总量的方法。考虑到不同地区的土壤中稀土元素的相互比例变化较大,采用包头混合稀土(轻稀土为主)和龙南混合稀土(重稀土为主)进行试验,选择其“等吸收点”波长(680—685nm)为测定波长并在显色时提高酸度以改善选择性。方法用于分析含量为0.02％(以RExOy计)的试样时变异系数为5.7％。标准加料回收率在93—104％之间,若干对照试样的分析结果与有关单位提供的平均结果相一致。     

对“从牛尿中制取苯甲酸和马尿酸”一文的意见

在“化学通报”1959年第1期“从牛尿中制取苯甲酸和马尿酸”一文里,把废料制成化学原料是有着巨大的经济意义的。但该文中若干问题,尚需研讨,特此提出与原文作者商榷。对该文制造过程的意见:     

顶空直接进样气相色谱法测定黏胶剂中的苯系物

目的建立检测黏胶剂中苯系物的方法。方法用顶空直接进样气相色谱法测定黏胶剂中的苯、甲苯、乙苯、对二甲苯、间二甲苯、邻二甲苯以及苯乙烯7种组分,对气相色谱柱、顶空加热温度以及顶空提取时间进行了讨论。结果对苯乙烯等7种被测组分的检测限均小于5mg/kg,7种组分在毛细管柱中能够很好的分离,回收率范围为81%～94%,RSD为5%～10%,具有操作简单、快速等特点。结论能够满足对黏胶剂中苯系物测定的分析要求。     

Recognition of benzene, toluene and xylene using TGS array integrated with linear and non-linear classifier

Three volatile organic compounds (VOCs): benzene, toluene and xylene were measured with an array of six Taguchi gas sensors in the air with variable humidity content. The recognition of single compounds was performed, based on measurement results. The principal component analysis (PCA) pointed at humidity as the main classification factor in the measurement data set. The linear discriminant analysis (LDA) was applied to overcome this drawback and enforce classification with respect to benzene, toluene or xylene. It was shown that discriminant function analysis (DFA), which is an LDA method allowed for 100% success rate in test samples recognition of benzene. It did not allow for accurate recognition of test samples of toluene or xylene. Following, the non-linear classifier, radial basis function neural network (RBFNN) was applied. A specific configuration of input ‘s was found, which provided for successful recognition of each single compound: benzene, toluene or xylene in air with variable humidity content.     

Rapid Solvent Extraction of Tin(IV) with High Molecular Weight Amine from Hydrochloric Acid Solution

A novel method has been developed for the solvent extraction of tin(IV) from 8 M hydrochloric acid with 4% N‐n‐octylaniline. Tin(IV) from the organic phase was determined spectrophotometrically with pyrocatechol violet at 550 nm. Extraction was found to be quantitative in the range of 7–10 M hydrochloric acid. When the concentration of N‐n‐octylaniline was varied from 0.05–20% in xylene, it showed that optimum concentration was > 3%. Amongst diluents like benzene and xylene, toluene was found to be an effective diluent. Effect of shaking time, concentration of metal ion, and salting out agents was studied. Tolerance limits of various diverse ions were determined by masking interfering cations. Tin(IV) was separated from associated elements in its binary mixture with Se(IV), Sb(III), Bi(III), Pb(II), Au(III), Cu(II) and Zn(II) and from its ternary mixtures with Sb(III), Bi(III) and Cu(II), Au(III). The proposed method was applied for separation and determination of tin(IV) in tin bearing alloys and foodstuffs.     

Adsorption studies of acetic acid dimers on activated charcoal from organic solvents

Acetic acid exists as dimers in organic solvents like benzene, toluene and xylene. Adsorption of dimeric acetic acid on activated charcoal (AC) at various temperatures from benzene, toluene and xylene solutions have been studied. The system obeys Langmuir isotherm, thus signifying a monolayer adsorption of dimers. Corrections on AC-solvent pore volume fillings, molecular cross sectional surface area of acetic acid dimers, the adsorption equilibrium constants, the free energy change and the enthalpy change values are computed at different temperatures for the three solvents. The adsorption process has been found to be physisorption type. The FTIR measurements show that the adsorbed acetic acid dimer seems to retain the cyclic structure against the open chain non-cyclic structure.     

Simultaneous determination of benzene,toluene, ethylbenzene,and xylene metabolites in human urine using electromembrane extraction combined with liquid chromatography and tandem mass spectrometry

For the first time, electromembrane extraction combined with liquid chromatography and tandem mass spectrometry was applied for the determination of urinary benzene, toluene, ethylbenzene, and xylene metabolites. S‐Phenylmercapturic acid, hippuric acid, phenylglyoxylic acid, and methylhippuric acid isomers were extracted from human urine through a supported liquid membrane consisting of 1‐octanol into an alkaline acceptor solution filling the inside of a hollow fiber by application of an electric field. Various extraction factors were investigated and optimized using response surface methodology, the statistical method. The optimum conditions were established to be 300 V applied voltage, 15 min extraction time, 1500 rpm stirring speed, and 5 mM ammonium acetate (pH 10.2) acceptor solution. The method was validated with respect to selectivity, linearity, accuracy, precision, limit of detection, limit of quantification, recovery, and reproducibility. The results showed good linearity (r² > 0.995), precision, and accuracy. The extract recoveries were 52.8–79.0%. Finally, we applied this method to real samples and successfully measured benzene, toluene, ethylbenzene, and xylene metabolites.     

Quantitative analysis of trace‐level benzene,toluene, ethylbenzene,and xylene in cellulose acetate tow using headspace heart‐cutting multidimensional gas chromatography with mass spectrometry

This study describes a method for the quantification of trace‐level benzene, toluene, ethylbenzene, and xylene in cellulose acetate tow by heart‐cutting multidimensional gas chromatography with mass spectrometry in selected ion monitoring mode. As the major volatile component in cellulose acetate tow samples, acetone would be overloaded when attempting to perform a high‐resolution separation to analyze trace benzene, toluene, ethylbenzene, and xylene. With heart‐cutting technology, a larger volume injection was achieved and acetone was easily cut off by employing a capillary column with inner diameter of 0.32 mm in the primary gas chromatography. Only benzene, toluene, ethylbenzene, and xylene were directed to the secondary column to result in an effective separation. The matrix interference was minimized and the peak shapes were greatly improved. Finally, quantitative analysis of benzene, toluene, ethylbenzene, and xylene was performed using an isotopically labeled internal standard. The headspace multidimensional gas chromatography mass spectrometry system was proved to be a powerful tool for analyzing trace volatile organic compounds in complex samples.     

Development of an impurity‐profiling method for source identification of spilled benzene series compounds by gas chromatography with mass spectrometry: Toluene as a case study

In this study, an impurity profiling method was established for the source identification of spilled benzene series compounds. Toluene was used as a case study to demonstrate the feasibility of this approach. Gas chromatography with mass spectrometry was applied for identification and quantification of the impurities including ethyl benzene, p‐xylene, m‐xylene, and o‐xylene in toluene. Impurities in toluene were detected at very low levels by applying mass spectrometry in selected‐ion monitoring mode. Eight authentic toluene samples collected from different manufacturers were analyzed by the developed gas chromatography with mass spectrometry method to construct the characteristic impurity profiling of toluene. Then, combined with scatter distribution, similarity analysis and t‐test, a suite of diagnostic ratios based on the impurity distribution was used for the differentiation of toluene from different sources. Results indicated that scatter distribution method can discriminate the original toluene samples from different manufacturers. Similarity calculation and t‐test methods can identify effectively the weathered toluene samples. The proposed impurity profiling method was useful for discrimination between toluene samples from different sources. Statistical analysis of these impurity profiles demonstrated the potential to investigate whether two questioned spilled toluene samples encountered in forensic casework are from the same source.     

Study on adsorption kinetic of aromatic hydrocarbons onto activated carbon in gaseous flow method

The adsorption behavior of benzene, toluene, o-xylene, m-xylene, and p-xylene onto activated carbon was investigated using the flow method. The removal efficiency of aromatic hydrocarbons in the gaseous phase was estimated based on the adsorption kinetic constants and the saturated amount of aromatic hydrocarbons adsorbed on the activated carbon. The saturated amount of benzene and toluene adsorbed was greater than that of xylene adsorbed because the molecular sizes of benzene and toluene are smaller than that of xylene. The adsorption kinetic constant increased in the order of xylene, toluene, and benzene. Those of the three xylene isomers were similar. These results indicated that the adsorption rate of benzene by the activated carbon was the fastest and the kinetic constant depended upon the different between the boiling point and the melting point and the molecular size of the aromatic hydrocarbons.     

The alkylation reaction of benzene with methanol to produce toluene: Y-C and Y-CCs catalyst

The secondary reaction of toluene is difficult to be suppressed in benzene alkylation with methanol over conventional acidic zeolite catalysts. Moreover, the formation of coke yet remains a challenging problem. In this study, Na-Y zeolites were modified with ammonium carbonate (AC), citric acid (CA) and caesium nitrate(CN) to evaluate the alkylation of benzene with methanol, which was also characterized by XRD, SEM, FT-IR, N₂ adsorption and Py-IR. For the Na-Y treated with AC-CA-CN, not only the catalytic selectivity for the alkylation of benzene with methanol was improved (the total selectivity of toluene and xylene was 97.9% and toluene selectivity was 86.4%), but also the quantity of coke was greatly decreased.     

DFC-1氢型丝光沸石的吸附热与甲苯歧化催化活性的研究

在工业生产条件下对催化剂和催化作用的动态研究已经引起重视。吸附热能反映催化剂表面能量状况和吸附分子间的相互作用,是表征催化剂表面性质的重要参量。对于国产甲苯歧化催化剂DFC-1氢型丝光沸石(简称HMDFC-1)的吸附热和催化活性之间关系的报道还不多。在用吸附差热方法考察HMDFC-1的表面酸性时发现,在动态条件下HMDFC-1存在着对NH_3可逆和不可逆两种吸附,而对吡啶则只有不可逆吸附。本文利用脉冲色谱法分别测定了苯、甲苯、二甲苯在HMDFC-1上以及在被NH_3中毒的HM吸附热,和甲苯在被吡啶中毒的HMDFC-1上的吸附热,并以吸附热的差别区别了两类DFC-1上的酸中心,找出了催化活性随甲苯吸附热的变化曲线。