Identification of Africanized honeybees

Gas chromatography and pattern recognition methods were used to develop a potential method for differentiating European honeybees from Africanized honeybees. The test data consisted of 237 gas chromatograms of hydrocarbon extracts obtained from the wax glands, cuticle, and exocrine glands of European and Africanized honeybees. Each gas chromatogram contained 65 peaks corresponding to a set of standardized retention time windows. A genetic algorithm (GA) for pattern recognition was used to identify features in the gas chromatograms characteristic of the genotype. The pattern recognition GA searched for features in the chromatograms that optimized the separation of the European and Africanized honeybees in a plot of the two or three largest principal components of the data. Because the largest principal components capture the bulk of the variance in the data, the peaks identified by the pattern recognition GA primarily contained information about differences between gas chromatograms of European and Africanized honeybees. The principal component analysis routine embedded in the fitness function of the pattern recognition GA acted as an information filter, significantly reducing the size of the search space since it restricted the search to feature sets whose principal component plots showed clustering on the basis of the bees' genotype. In addition, the algorithm focused on those classes and/or samples that were difficult to classify as it trained using a form of boosting. Samples that consistently classify correctly are not as heavily weighted as samples that are difficult to classify. Over time, the algorithm learns its optimal parameters in a manner similar to a neural network. The pattern recognition GA integrates aspects of artificial intelligence and evolutionary computations to yield a "smart" one-pass procedure for feature selection and classification.     

Machine learning based pattern recognition applied to microarray data

Motivation: Microarrays have allowed the expression level of thousands of genes or proteins to be measured simultaneously. Data sets generated by these arrays consist of a small number of observations (e.g., 20-100 samples) on a very large number of variables (e.g., 10,000 genes or proteins). The observations in these data sets often have other attributes associated with them such as a class label denoting the pathology of the subject. Finding the genes or proteins that are correlated to these attributes is often a difficult task since most of the variables do not contain information about the pathology and as such can mask the identity of the relevant features. We describe a genetic algorithm (GA) that employs both supervised and unsupervised learning to mine gene expression and proteomic data. The pattern recognition GA selects features that increase clustering, while simultaneously searching for features that optimize the separation of the classes in a plot of the two or three largest principal components of the data. Because the largest principal components capture the bulk of the variance in the data, the features chosen by the GA contain information primarily about differences between classes in the data set. The principal component analysis routine embedded in the fitness function of the GA acts as an information filter, significantly reducing the size of the search space since it restricts the search to feature sets whose principal component plots show clustering on the basis of class. The algorithm integrates aspects of artificial intelligence and evolutionary computations to yield a smart one pass procedure for feature selection, clustering, classification, and prediction.     

Spurenbestimmung von Vergaser- und Dieselkraftstoffen im Wasser mittels Capillar-Gas-Chromatographie/automatischer Mustererkennung

Summary A method for trace analysis determination of carburetor and diesel fuels in water is described. The isolation and concentration of fuel traces is carried out by microextraction with n-hexane using a suitable micro-separator. After their separation by capillary gas chromatography fuels provide typically structured chromatographic patterns and, therefore, a chromatogram (sample pattern) of the extract is generated. The sample pattern is searched for fuel patterns by comparing the chromatogram with reference chromatograms of these fuels in a library. An automatic pattern recognition algorithm is applied, using elements of the fuzzy set theory. As preliminary interpretation the computer delivers a list of identification proposals which have to be assessed and submitted to a final interpretation by the analyst.     

Graphitized carbons for solid-phase extraction

The objective of this review is to provide updated information about the most important features of graphitized carbonaceous sorbents used for solid-phase extraction (SPE) of organic compounds from liquid natural matrices or extracts. The surface characteristics of graphitized carbon blacks and porous graphitic carbons are described which are responsible for the various types interactions (hydrophobic, electronic and ion-exchange) with analytes. The method development is given which is based on the prediction from liquid chromatographic retention data obtained using porous graphitic carbon. Emphasis is placed on their capability for trapping very polar and water-soluble analytes from aqueous samples. Comparison is made between carbon-based SPE sorbents and other reversed-phase materials such as octadecyl silicas and highly cross-linked copolymers. Especially, the difficulty encountered for the desorption of some strongly retained analytes is explained by LC data and solutions are given for optimizing the composition and volume of the desorption solution. Many examples illustrate the various common features of graphitized carbons which are the extraction of very polar analytes and multiresidue extractions. Some applications are specific to graphitized carbon black due to the presence of surface functional groups. They include the extraction of anionic compounds such as benzene and naphthalene sulfonates or acidic pesticides. Other applications are specific to porous graphitic carbon due to its flat and homogeneous surface. One example is the trace extraction of coplanar polychlorinated biphenyls (PCBs), dibenzo-p-dioxins and dibenzofurans from other PCB congeners.     

模式识别法用于反相液相色谱等度分离条件优化

以分离条件参数为特征变量构筑模式空间，串行指标ＨＣＲＦ为目标划分样本类别，通过主成分分析揭示模式空间的可视优化区，再由低维优化点回复到高维原始空洞，获得了最佳分离条件，此方法用于７种水溶性维生素分离，取得满意结果。     

Recent developments in polymer-based sorbents for solid-phase extraction

A review with 136 references on the principles and recent developments in the solid-phase extraction based on polymer sorbents is presented. New polymer-based materials, chromatographic modes, experimental configurations are described and their advantages for a rapid sample preparation of certain classes of compounds with different functional groups are discussed and compared to silica-based sorbents.     

全二维气相色谱-质谱分析煤油基吸热型碳氢燃料烃族组成

采用全二维气相色谱-质谱联用（GC×GC-MS）考察了色谱柱系统、程序升温条件和调制周期3个主要因素对样品组分分离结果的影响,建立了煤油基吸热型碳氢燃料烃族组成的定性分析方法,并利用GC×GC-FID通过有效碳数校正因子对烃族组成进行定量。对选取的9种燃料的分析结果表明,该方法对链烷烃和环烷烃的定量结果与标准方法ASTM D2425的结果高度一致,相对误差基本均在±10%以内。利用该方法计算的碳含量结果与元素分析法相比误差均在0.5%以下。该方法无需复杂的前处理,稀释后可直接进样分析,操作简单,而且可直观地看出不同样品之间的差异,为改进燃料的性能提供了必要的分析手段。     

Analytical-numerical solution for turbulent jet diffusion flames of hydrogen

The hydrogen fuel seems to be a good candidate to replace the energy obtained from some fossil fuels. Therefore this work explains the process of obtaining a two-step reduced chemical kinetic mechanism for the hydrogen combustion. The development of a reduced mechanism consists in eliminating reactions that produce negligible influence on the combustion process. Moreover, for this mechanism, we obtain an analytical-numerical solution for a turbulent jet diffusion flame. To quantify the intermediate species, the mixture fraction is decomposed into three parts, each part directly related to the mass fraction of a species. The governing equations are discretized using the second order finite-difference approach and are integrated in time using the second order simplified three-step Runge-Kutta scheme. Obtained results compare favorably with data in the literature for a 50/50 % volume H ₂?N ₂ jet diffusion flame. The main advantage of this strategy is the decrease of the work needed to solve the system of governing equations, by one order of magnitude for the hydrogen.     

Retention properties of a cyanopropylsiloxane-bonded silica-based sorbent for solid-phase extraction

The characteristic kinetic and retention properties of a silica-based cyanopropylsiloxane-bonded sorbent for solid-phase extraction are described. Abraham′s solvation parameter model is used to characterize the contribution of individual intermolecular interactions to retention under liquid chromatographic and sample processing conditions with aqueous methanol mixtures as the mobile phase. The main features governing retention by the sorbent are the solute's size and hydrogen-bond basicity; interactions of a dipole type are not significant when aqueous methanol solutions are employed as the mobile phase. Compared to typical silica-based octadecylsioxane-bonded sorbents the greater difficulty of forming a cavity in the solvated cyanopropylsiloxane-bonded sorbent more than offsets the more favorable dipole-type and solute hydrogenbond base interactions of the cyanopropylsiloxane-bonded sorbent. It is shown that there are no practical circumstances for which a cyanopropylsiloxane-bonded sorbent would be more useful than a typical ODS sorbent for the isolation of organic non-electrolytes from water by solid-phase extraction.     

高效液相色谱-质谱法及模式识别法用于鉴别普洱生茶与熟茶

采用高效液相色谱-质谱联用技术及高效液相色谱法对生熟普洱茶中的主要成分进行定性和定量分析。鉴定出普洱茶水溶液中8种主要成分,分别为没食子酸(GA)、没食子酸儿茶素(GC)、表没食子酸儿茶素(EGC)、儿茶素(C)、咖啡因(CAF)、表儿茶素(EC)、表没食子酸儿茶素没食子酸酯(EGCG)和表儿茶素没食子酸酯(ECG)。以这8种成分的含量为指标,对普洱生茶和熟茶各20批进行主成分分析、聚类分析和判别分析,能准确地区分普洱生茶与熟茶。     

Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques

Gas chromatographic (GC) profiles of cuticular hydrocarbon extracts obtained from individual and pooled ant samples were analyzed using pattern recognition techniques. Clustering according to the biological variables of social caste and colony were observed. Pooling individual extracts enhanced the recognition of patterns in the GC profile data characteristic of colony. Evidently, the contribution of the ant's individual pattern to the overall hydrocarbon profile pattern can obscure information about colony in the GC traces of cuticular hydrocarbon extracts obtained from red fire ants. Re-analysis of temporal caste and time period data on the cuticular hydrocarbon patterns demonstrates that sampling time and social caste must be taken into account to avoid unnecessary variability and possible confounding. This and the fact that foragers could not be separated from reserves and brood-tenders in all five laboratory colonies studied suggests that cuticular hydrocarbons as a class of sociochemicals cannot model every facet of nestmate recognition in Solenopsis invicta which in turn suggests a potential role for other compounds in the discrimination of alien conspecifics from nestmates.     

Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques

Gas chromatographic (GC) profiles of cuticular hydrocarbon extracts obtained from individual and pooled ant samples were analyzed using pattern recognition techniques. Clustering according to the biological variables of social caste and colony were observed. Pooling individual extracts enhanced the recognition of patterns in the GC profile data characteristic of colony. Evidently, the contribution of the ant's individual pattern to the overall hydrocarbon profile pattern can obscure information about colony in the GC traces of cuticular hydrocarbon extracts obtained from red fire ants. Re-analysis of temporal caste and time period data on the cuticular hydrocarbon patterns demonstrates that sampling time and social caste must be taken into account to avoid unnecessary variability and possible confounding. This and the fact that foragers could not be separated from reserves and brood-tenders in all five laboratory colonies studied suggests that cuticular hydrocarbons as a class of sociochemicals cannot model every facet of nestmate recognition in Solenopsis invicta which in turn suggests a potential role for other compounds in the discrimination of alien conspecifics from nestmates.     

基于挥发性组分的气相色谱指纹图谱评价沉香化气片质量

建立了沉香化气片的气相色谱指纹图谱,并结合化学模式识别评价20批沉香化气片的质量。乙醇超声提取20批沉香化气片的挥发性成分,以正十八烷为内标,分析了3个主要组分的含量,且以内标计算其他各组分的相对峰面积,建立了沉香化气片的气相色谱指纹图谱,确定了11个共有峰,得到了各批次样品的相似度,并通过气相色谱-质谱法和对照品比对对10个共有峰进行了指认。将获得的峰面积指纹图谱采用系统聚类分析和主成分分析进行化学模式识别研究,实现了不同批次沉香化气片的区分,发现了造成不同批次样品差异的主要标记物。该方法有效且综合性强,为科学评价与有效控制沉香化气片的质量提供了可靠的参考。     

Determination of Zy 17617B in plasma by solid-phase extraction and liquid chromatography with automated pre-column exchange.

An automated chromatographic system, combining solid-phase extraction and automated pre-column exchange, is described for the routine determination of Zy 17617B at the pmol/ml level in human plasma. The sample extraction and elution onto the analytical column were performed automatically and concomitantly using a conventional liquid chromatographic apparatus equipped with a Merck OSP-2 on-line sample preparator. Validation data demonstrate the reliability of the method.     

Characterization of the volatile fraction emitted by phloems of four pinus species by solid-phase microextraction and gas chromatography-mass spectrometry

Pine forests constitute some of the most important renewable resources supplying timber, paper and chemical industries, among other functions. Characterization of the volatiles emitted by different Pinus species has proven to be an important tool to decode the process of host tree selection by herbivore insects, some of which cause serious economic damage to pines. Variations in the relative composition of the bouquet of semiochemicals are responsible for the outcome of different biological processes, such as mate finding, egg-laying site recognition and host selection. The volatiles present in phloem samples of four pine species, P. halepensis, P. sylvestris, P. pinaster and P. pinea, were identified and characterized with the aim of finding possible host-plant attractants for native pests, such as the bark beetle Tomicus piniperda. The volatile compounds emitted by phloem samples of pines were extracted by headspace solid-phase micro extraction, using a 2cm 50/30mm divinylbenzene/carboxen/polydimethylsiloxane table flex solid-phase microextraction fiber and its contents analyzed by high-resolution gas chromatography, using flame ionization and a non polar and chiral column phases. The components of the volatile fraction emitted by the phloem samples were identified by mass spectrometry using time-of-flight and quadrupole mass analyzers. The estimated relative composition was used to perform a discriminant analysis among pine species, by means of cluster and principal component analysis. It can be concluded that it is possible to discriminate pine species based on the monoterpenes emissions of phloem samples.     

Structural studies of bacterial cellulose through the solid-phase nitration and acetylation by CP/MAS <Superscript>13</Superscript>C NMR spectroscopy

The solid-phase nitration and acetylation processes of bacterial cellulose have been investigated mainly by CP/MAS ¹³C NMR spectroscopy to clarify the features of these reactions in relation to the characterization of the disordered component included in the microfibrils. CP/MAS ¹³C NMR spectra of bacterial and Valonia cellulose samples are markedly changed as the nitration progresses, in a similar way to the case of cotton linters previously reported; and the relative reactivity of the OH groups in the glucose residues is found to decrease in the order of O(6)H>O(2)H>O(3)H. Moreover, the nitration rate and mode greatly depend on the concentration of nitric acid in the reaction media. At dilute and medium concentrations, the O(6)H groups in the crystalline and disordered components are subjected to nitration at nearly the same rate, indicating that these two components are distributed almost at random in the entire region of each microfibril. The preferential penetration of nitric acid into each microfibril also occurs prior to nitration at the medium concentration, resulting in an increase in the mole fraction of the disordered component. In contrast, all OH groups undergo nitration very rapidly at the higher concentration, although nitration levels off to a certain extent for O(3)H groups. In solid-phase acetylation, no regio-selective reactivity is observed among the three kinds of OH groups, which may be due to the characteristic reaction that proceeds in a very thin layer between the acetylated and nonacetylated regions in each microfibril. The almost random distribution of the disordered component in the entire region of the microfibrils is also confirmed in this solid-phase acetylation. On the basis of these results, the mechanism of the solid-phase reactions and the microfibril structure are discussed.     

Estimation of individual ultraviolet spectra in incomplete two-component separations by high-performance liquid chromatography

A method is described for the estimation of spectral features in a two-component chromatographic peak by means of a u.v. diode-array detector. The calculation relies on the assumption that the front of a fused chromatographic peak contains a single pure component. The spectrum of this component is used in calculating the concentration profile of the other component, thus allowing the determination of a solution band for the spectrum of the second component. The boundaries of the solution band are based on non-negativity restrictions of chromatographic and spectral features. The method does not require the use of principal components analysis.     

Headspace solid-phase microextraction gas chromatography/mass spectrometry in the analysis of the aroma constituents of 'Cannonau of Jerzu' wine

"Cannonau of Jerzu" wine is a typical Sardinian product, obtained from only one particular grape variety. Its aroma profile is highly characteristic from the organoleptic point of view but, until now, no analytical investigation of the aroma components has been reported. This aspect has been studied by headspace solid-phase microextraction coupled with gas chromatography/mass spectrometry (GC/MS). Using this approach, 76 abundant aroma components were identified. The results thus obtained show on one hand that the terpene profile is, as expected, dependent on the quality of the grapes (in terms of selection before vintage), and, on the other, that some components are strongly dependent on the production and ageing method.     

Disengaging solutes in shale- and petroleum-derived jet fuels by altering GC programmed temperature rates

Overlapping chromatographic peaks of components from different hydrocarbon classes can be disengaged by exploiting their shifts in relative retention behavior with changes in linear rates of programmed temperature. Many co-eluting species in complex chromatograms of shale- and petroleum-derived jet fuels can be resolved without varying stationary phase, column length, or initial column temperature. Retention indices were simultaneously determined on two bonded-phase, fused silica capillary columns of slightly different polarities at three different linear programmed temperature rates. For certain hydrocarbon types, no change in index values was observed with an alteration in programming rate. However, the indices of other hydrocarbon classes shifted uniformly with programmed temperature rates on each of the two stationary phases. When applied, this phenomenon could help resolve coeluting members of different or even the same hydrocarbon type and elucidate their probable structure. The overall precision of the retention indices, i.e., the mean standard deviation at the 95% confidence levels, was less than ±0.13 for either column at any of the three programming rates. Since the above technique is automated, it could also be a useful screening tool to search for specific hydrocarbons in a myriad of unknown components of a complex hydrocarbon mixture.