顶空-气相色谱法测定烟用胶粘剂中的挥发性有机物

采用顶空-气相色谱法对烟用胶粘剂中的挥发性有机物(甲醇、丙酮、乙酸甲酯、叔丁醇、乙酸乙烯酯、乙酸乙酯)进行分析,讨论了气相色谱柱的升温方式、顶空平衡温度、平衡时间、胶粘剂加入量对分析结果的影响,从而获得优化的检测工艺参数。该检测方法对上述6种挥发性有机物的线性范围分别为甲醇40～400μg/g,丙酮4～40μg/g,乙酸甲酯9.2～92μg/g,叔丁醇3.2～32μg/g,乙酸乙烯酯7.5～75μg/g,乙酸乙酯4.5～45μg/g,测定结果的相对标准偏差为0.6%～2.7%,样品的回收率为90.8%～104.2%。该方法可用于烟用胶粘剂中挥发性有机物的分析,方法简便、快速、重现性好。     

MSPD-GC测定水稻土壤、糙米和秸秆中唑草酮残留

[方法]采用基质固相分散技术从3种基质(土壤、糙米、秸秆)中提取、净化除草剂唑草酮,用气相色谱法进行检测.方法以N-丙基-乙二胺(PSA)为吸附剂,以正己烷-丙酮(体积比6∶4)混合溶剂为洗脱溶剂,实现了样品快速制备.利用所建立的方法进行0.005、0.05、0.1 mg/kg三个水平的加标回收试验.[结果]唑草酮的回收率在84.9％～96.7％之间,相对标准偏差1.5％～3.0％,检出限为3×10-14 g.[结论]均符合农药残留分析方法的技术要求.     

气相色谱-串联质谱法测定生姜中的黄樟素

建立了固相萃取净化结合气相色谱-质谱联用仪测定生姜中的黄樟素的分析方法。实验优化了样品前处理条件和色谱质谱条件。样品经乙腈提取,高速离心后,采用Carb-NH_2固相小柱富集净化,洗脱液经旋转蒸发仪浓缩。采用气相色谱分离,多反应离子监测模式(MRM)进行黄樟素质谱检测。以基质匹配标准溶液外标法定量测定。实验结果表明,黄樟素在0.005～0.5μg/mL范围内呈良好的线性关系,相关系数(R~2)大于0.999,方法检出限(S/N=3)为0.42μg/kg,定量限(S/N=10)为1.41μg/kg,在5、25、50μg/kg 3个添加水平下,样品中黄樟素的平均回收率为107.7%～111.9%,相对标准偏差为2.02%～2.32%。该方法具有灵敏度高、富集效果好、回收率高等优点,为生姜及其生姜制品中的黄樟素筛查提供技术支持。用本研究建立的方法检测151个生姜样品,发现部分生姜样品中有微量黄樟素检出,浓度范围为0.45～1.3μg/kg。     

顶空-GC/MS法同时测定废水中16种挥发性酮、醇、酯、腈类化合物

为了准确分析挥发性酮、醇、酯、腈类化合物在废水中的残留情况,建立了顶空-气相色谱-质谱法测定废水中16种挥发性酮、醇、酯、腈类化合物的方法,选用DB-624（30 m×0.32 mm×1.8 μm）毛细管柱,在柱流速1.5 mL/min条件下,采用电子轰击电离源,全扫描定性,选择离子进行外标法定量。结果表明16种化合物线性良好,相关系数r>0.995。当废水取样量为10.0 L时,方法检出限为0.04~0.95 mg/L,在3个不同加标水平下,实际废水样品中16种化合物的相对标准偏差为0.32%~7.61%,加标平均回收率为89.2%~118%。本方法可快速、准确测定废水样品中的16种挥发性酮、醇、酯、腈类化合物。     

(Z)-9-Nonacosene—Major Component of the Contact Sex Pheromone of the Beetle Megacyllene caryae

Male Megacyllene caryae (Gahan) (Coleoptera: Cerambycidae) respond to females only after touching them with their antennae, indicating that mate recognition is mediated by a contact sex pheromone. Gas chromatography-mass spectrometry analyses of whole-body solvent extracts of male and female M. caryae revealed substantial differences in hydrocarbon profiles, with nearly half of the compounds in the extracts from females being absent from those of males. Biological activities of fractions of crude extracts of females, and reconstructed blends of the most abundant straight-chain (nC₂₇, nC₂₈, nC₂₉), methyl-branched (2Me-C₂₆, 9Me-C₂₉, 11, 13, 15Me-C₂₉), and unsaturated (Z9:C₂₉, Z13:C₂₉, Z14:C₂₉, Z13:C₃₁, Z14:C₃₁, Z15:C₃₁) compounds in extracts of females were tested in arena bioassays, assessing four steps in the mating behavior sequence of males (orientation, arrestment, body alignment, mounting and attempting to couple the genitalia). Males showed limited response to dead females treated with fractions of the crude extract or blends of synthetic straight-chain and methyl-branched alkanes, but responded strongly to the blend of synthetic monoenes. Further trials determined that the complete sequence of mating behaviors, up to and including coupling the genitalia, was elicited by Z9:C₂₉ alone. Z9:C₂₉ is a homolog of the contact pheromone (Z9:C₂₅) of the congener M. robiniae (Förster). Previous work with M. robiniae suggested that wipe sampling of cuticular hydrocarbons of females by solid phase microextraction yielded a more representative profile of components actually encountered by a male’s antennae, and so provided a more readily interpretable profile of potential semiochemicals present in the wax layer than does solvent extraction. We tested this hypothesis by comparing hydrocarbon profiles of female M. caryae by the two sampling methods. Z9:C₂₉ was the only compound among the dominant hydrocarbons that was present in higher abundance in SPME than in solvent extracts (∼12% vs. ∼8%, respectively), supporting this hypothesis.Electronic supplementary material Supplementary material to this paper is available in electronic form at.     

Analysis of the Volatiles Emitted by Whole Flowers and Isolated Flower Organs of the Carob Tree Using HS-SPME-GC/MS

The volatiles emitted by fresh whole flowers and isolated flower organs of male, female, and hermaphrodite carob trees (Ceratonia siliqua L.; Leguminosae) were analyzed by headspace solid-phase microextraction followed by capillary gas chromatography and mass spectrometry. The headspace of carob flowers is mainly constituted of high amounts of monoterpenes and sesquiterpenes, and more than 25 compounds were identified. The gender and cultivar affected both the qualitative profile and the relative abundances of the volatiles of whole flowers and isolated floral organs. Linalool and its derivatives (cis-linalool furan oxide, 2,2,6-trimethyl-3-keto-6-vinyltetrahydropyran, cis-linalool pyran oxide, and trans-linalool furan oxide), α-pinene, and α-farnesene were the dominant volatiles. Female flowers had a higher diversity of volatile compounds than males and hermaphrodites, but a lower abundance of the major ones. Similarly, the floral scent of female flowers of cv. Mulata had a higher content of volatiles but a lower abundance of the major ones, when compared to cv. Galhosa. In each of the three gender types of flowers, the nectary disks seemed to be the major source of volatiles.     

Industrial trial to evaluate the effect of oxygen concentration on overall quality of refined, bleached, and deodorized soybean oil in PET bottles

Soybean oil, owing to its FA composition, is highly susceptible to deterioration by oxidation. The use of nitrogen gas permits the removal of dissolved oxygen and oxygen in the headspace of tanks and bottles. The objective of this work (an industrial trial) was to evaluate the shelf life of soybean oil packaged in polyethylene terephthalate (PET) bottles with different levels of oxygen in the headspace (<0.3, 5–6.5, 7–9, and >15%). The quality of the oil was evaluated during 6 mon. FFA and moisture increased and the smoke point decreased in all experimental conditions, even though the difference between the experiments was not significant. An increase was observed for peroxide value (PV), anisidine value (AV), and specific extinction, and higher increases in these parameters were observed in higher oxygen concentrations. After 180 d, the difference between the PV and AV was significant. According to sensory analysis, the shelf life of the oil increased from 60 to 90, 120, and 180 d as the initial concentration of oxygen was reduced from >15%, 7–9%, 5–6.5%, and 0–3%, respectively. The results demonstrated that shelf life of soybean oil packaged in PET bottles can be significantly increased by using nitrogen to reduce available oxygen in the headspace.     

多变量统计分析技术在评价燕京啤酒风味质量中的应用

采用静态顶空进样结合高效毛细管气相色谱分析啤酒香味组分的技术 ,对 2 0 0 4年“燕京”纯生啤酒的10种主要香味组分进行了测定。所获数据以多变量统计分析技术的主成分分析法作了统计运行。结果表明 ,“燕京”纯生啤酒具有良好的风味质量一致性。试验同时还测定了“百威”等其他国内外品牌啤酒 ,分析证明了不同啤酒 ,其风味特性存在着或多或少的差异或相似性。研究证明 ,多变量统计技术可有效地应用于啤酒风味质量一致性与均一性的评价。     

Study of volatile compounds of defective virgin olive oils and sensory evaluation: a chemometric approach

It is well known that olive oils are the only foods whose legal control must also involve sensory evaluation, and that a harmonised protocol is used for this purpose: EEC regulation 2568/91 and an IOOC trade norm of the 1990s introduced a standard method among those used to assess the quality of virgin oils, after which a modified method known as the ‘panel test’ was developed and adopted, firstly by the IOOC and later by the EEC. One problem in applying the panel method often depends on the lack of reference standards for training judges, in addition to, in some cases, a lack of exact knowledge of the origin of some defects; for these reasons, several judges have suggested the unification of some defects, even when these originate from different kinds of problems. In this paper we have applied headspace analyses to a number of samples of oils that were also characterised by a panel. Besides the samples, standard defective oils obtained by the IOOC and used for training sensory judges were also analysed, with the aim of obtaining a model for use in method validation. Seventy‐six peaks were detected and most of them identified by gas chromatography/mass spectrometry; their distribution was different in the samples characterised by different defects as assessed by the panel test. The well‐known compounds of virgin olive oils were detected, including the series of C₆ compounds, whose importance in defining positive (‘green’ flavour) and negative (rancid) characteristics of olive oils is well known. No samples classified as extra virgin ever present peaks with magnitudes as great as those found in defective oils. Chemometric data evaluation was carried out and samples were clustered on the basis of the headspace composition; the results were found to agree with those of the panel test, so a number of compounds were related to the presence of particular defects. Copyright © 2005 Society of Chemical Industry     

CO偶联制草酸二乙酯汽液平衡的测定与关联

采用液上气相色谱法测定了CO气相催化偶联制草酸二乙酯产物中有关的六组二元物系的等温汽液平衡数据。选用Wilson、NRTL、UNIQUAC活度系数方程关联了实验数据,计算值与实验值吻合较好