在线裂解气相色谱-质谱法研究单琥珀酸薄荷酯的裂解行为

采用在线裂解气相色谱-质谱联用技术对单琥珀酸薄荷酯的裂解行为进行了研究。在氦气氛围中,分别在300、400、500、600、700、800和900℃下对单琥珀酸薄荷酯进行热裂解,并通过毛细管气相色谱-质谱对裂解产物进行了定性和半定量分析。共鉴定出薄荷醇、p-薄荷-3-烯和琥珀酸等75种裂解产物。结果表明,单琥珀酸薄荷酯在700℃以下裂解出薄荷醇、p-薄荷-3-烯和3-甲基-6-异丙基环己烯等具有致香和清凉作用的物质;而700℃以上没有释放出致香物质。随着裂解温度的升高,裂解产物越来越复杂,有害物质如苯、甲苯、蒽和荧蒽等的含量也逐渐增加。此方法可直接进样,重现性好(相对标准偏差≤2.01%)。根据裂解产物的种类及相对含量变化规律,探讨了裂解成分的形成机理。     

液相色谱-电喷雾离子阱串联质谱分析烟草水提取物中的尼古丁

用液相色谱-电喷雾线性离子阱串联/质谱(LC-ESI-ITMS/MS)在正离子模式下对烟草水提取物中的尼古丁进行了分析:定性分析了尼古丁MS/MS图谱中碎片的可能结构;用尼古丁标准溶液对质谱检测条件进行优化后,在SRM扫描模式下对尼古丁进行定量分析。最低检出限(LOD)可达0.21μg/L;回收率为99%-105%。测试3个不同浓度样品得到的RSD为0.64%-0.72%。实验选用高效的短色谱柱达到了快速定量的目的,适用于对大量样品的分析。     

镧对烟草RuBPcase活性影响的研究

研究了Ｌａ对烟草体内ＲｕＢＰｃａｓｅ总活性和初活性的影响。Ｌａ在０－８０μｍｏｌ．Ｌ＾－１的浓度范围内增强它的活性,酶初活性提高幅度高于总活性,表明Ｌａ可以活性烟草体内ＲｕＢＰｃａｓｅ,但当Ｌａ浓度超过８０μｍｏｌ．Ｌ＾－１时,活化作用下降甚至抑制酶活性。在ＲｕＢＰｃａｓｅ的催化体系中,Ｌａ,Ｃｅ在一定浓度范围内能够取代该酶的激活剂Ｍｇ而激活酶活性,对纯化酶海的激活效果要高于粗酶液。     

全扫描-选择离子数据采集技术应用于烟草中生物碱的快速测定

建立了应用气相色谱-质谱(GC-MS)全扫描-选择离子监测(Scan-SIM)数据采集方式同时测定烟草中8种含量相差较大的生物碱的方法,采用Scan模式分析烟碱、降烟碱、新烟碱、去氢新烟碱,同时采用SIM模式分析麦斯明、二烯烟碱、2,3′-联吡啶、可铁宁。结果表明,烟草中各生物碱的回收率为94.8%～98.8%,5次测定的相对标准偏差均小于6%。该方法具有简单、快速、准确的特点,应用于烟草样品测定,结果令人满意。     

全二维气相色谱-飞行时间质谱法测定烟草的中性化学成分

建立了采用全二维气相色谱-飞行时间质谱(GC×GC-TOFMS)分析烟草的中性化学成分的方法。以DB-Petro(50 m×200 μm×0.5 μm) 为第一维色谱柱,DB-1701(2.3 m×100 μm×0.1 μm)为第二维色谱柱;调制周期为8 s;柱头压力为550 kPa;采用程序升温方式,初始温度分别为80 ℃和85 ℃。采用所建立的方法对不同部位的烟叶、不同品种烟草中的25种中性香味成分含量进行了测定和对比。结果表明：云南楚雄产云烟85的中性香味成分(不包括新植二烯)的总量以中部叶最高,其次是上部叶,下部叶最少;国内外不同品种的烤烟中中性香味成分的含量高低顺序为：巴西烤烟最高,其次是津巴布韦烤烟、云烟85、中烟101、NC89、K326;4类烟草中中性香味成分含量最高的是香料烟,其次是白肋烟、烤烟、马里兰烟。     

Characterization of Tobacco Leaves by Near-Infrared Reflectance Spectroscopy and Electronic Nose with Support Vector Machine

The determination of different regions of tobacco leaves is vital in the tobacco industry. Different parts of tobacco leaves produce varying flavors due to the different chemical compositions. Here, near infrared spectroscopy and electronic nose were combined with support vector machine to predict the parts of tobacco leaves. Comparing to the single data model as near infrared spectroscopy with support vector machine or electronic nose with support vector machine, near infrared spectroscopy and electronic nose with support vector machine model show higher accuracy. The accuracy of near infrared spectroscopy and electronic nose with support vector machine model is 95.31%, while the accuracy of leave-one-out cross-validation is 79.69%. The optimal model was then applied to 60 unknown tobacco samples from different parts of tobacco leaves to test its accuracy, which is 81.67%.     

Efficient synthesis of benzimidazolyl-phenoxyacetic acid O-acetylxylopyranosyl and O-acetylgalactopyranosyl esters and their antiviral activity

Six benzimidazolylphenoxyacetic acid O-acetylxylopyranosyl and O-acetylgalactopyranosyl esters were synthesized through esterification reactions at room temperature using 4-dimethylaminopyridine as a catalyst and triethylamine as a deacidification reagent. Their structure was confirmed by IR, ¹H NMR spectra, MS, and elemental analysis. The synthesized compounds are all of β-configuration. The results show that DMAP is an effective catalyst; the yields can reach 63.6%. The above esters showed improved antiviral activity against tobacco mosaic virus. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 832–837, June, 2006.     

Vibrational Circular Dichroism and Theoretical Study of the Conformational Equilibrium in (−)‐S‐Nicotine

We report an extensive study of the molecular and electronic structure of (?)‐S‐nicotine, to deduce the phenomenon that controls its conformational equilibrium and to solve its solution‐state conformer population. Density functional theory, ab initio, and molecular mechanics calculations were used together with vibrational circular dichroism (VCD) and Fourier transform infrared spectroscopies. Calculations and experiments in solution show that the structure and the conformational energy profile of (?)‐S‐nicotine are not strongly dependent on the medium, thus suggesting that the conformational equilibrium is dominated by hyperconjugative interactions rather than repulsive electronic effects. The analysis of the first recorded VCD spectra of (?)‐S‐nicotine confirmed the presence of two main conformers at room temperature. Our results provide further evidence of the hypersensitivity of vibrational optical activity spectroscopies to the three‐dimensional structure of chiral samples and prove their suitability for the elucidation of solution‐state conformer distribution.     

超临界CO2萃取-气相色谱\质谱分析烟丝化学成分

采用超临界CO2流体萃取(SFE)和气相色谱\质谱联用提取测定了烟丝中的挥发性成分.对超临界萃取过程中的影响因素包括萃取压力、温度、萃取夹带剂等条件结合萃取物测定得到的气相色谱-质谱图进行综合考察,确定了适宜的萃取条件.与传统的蒸馏萃取法比较,超临界CO2流体萃取提取物中含较多的松油醇、烷烃、烟碱等物质.