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Summary Glucose and selected phosphate buffers have been reacted employing systematic variations in reaction temperature and time (150–160 °C for 60–90 min) to optimize the yield of acetol. This mixture was reacted further with NH4OH, systematically varying reaction conditions and reagent ratios to optimize pyrazine yield. The highest yield of pyrazine was obtained when 1 g of glucose was reacted with 25 mL of buffer at 150–160 °C for 60 min, which in turn was reacted with 1 mL of concentrated aqueous NH4OH at 120–130 °C for 17–18 h. Higher temperatures and higher concentrations of glucose caused a decrease in the yield of pyrazines. The addition of hydrolyzed tobacco-derived F1 protein as a secondary source of nitrogen increased the yield of pyrazines by 2–10% depending on F1 protein concentration. Furthermore, the addition of any α-hydroxyketone, similar in structure to acetol, as a pure reagent to the reaction mixture not only increased the yields of pyrazine by ranging from 25–100 % depending on the reagent concentration, but also significantly altered the qualitative and quantitative distribution of the pyrazines. With all of the reaction parameters examined (reaction time, temperature, reagent ratios, etc.) the most significant impacts on both pyrazine yield and distribution were noted when: 1) glucose was pre-reacted with buffer, 2) hydrolyzed F1 protein was added as a second nitrogen source, and 3) when pure α-hydroxyketones were employed as co-reagents. Use of these reaction parameters was found to dramatically shift the pyrazine distribution toward higher molecular weight resulting in a pyrazine array having more desirable physical and sensory attributes.

Various pyrazines have been synthesized via reaction of selected cellulosic-derived sugars, ammonium hydroxide and amino acids at 110°C for 2 hours. Different methods of sample cleanup such as liquid–liquid extraction (LLE), liquid–solid extraction, column chromatography and distillation were employed to isolate pyrazines from the reaction mixture. Effective LLE of pyrazines from aqueous solution using either hexane, methyl-t-butyl ether (MTBE) or ethyl acetate required multiple extraction steps with fresh solvent each time. When hexane was used as the extraction solvent, no imidazole derivatives were extracted with the pyrazines. However, when MTBE or ethyl acetate was employed, 4-methyl imidazole was co-extracted and further cleanup was required. Passing the organic solvent extracts through a column of silica revealed that the silica retained the undesirable imidazoles, such as 4-methyl imidazole. A mixture of 90/10 hexane/ethyl acetate as eluting solvent provided the desirable pyrazines, but it also provided a desirable separation of pyrazines as a function of total alkyl substituent content. Distillation of the aqueous reaction mixture was also used to isolate the pyrazines, leaving the undesirable imidazoles in the undistilled portion of the reaction. Additional chromatographic methods were used to isolate pyrazines from the aqueous distillate including a column packed with C18-bonded silica.

Summary Employment of 1-hydroxy-acetone as a carbon source and NH4OH as a source of base and nitrogen, has enabled arrays of pyrazines to be synthesized. Reaction conditions such as temperature, time, carbon/nitrogen mole ratios and pH were optimized to maximize the quantity of pyrazines, thereby providing the synthesis of at least 19–20 structurally different pyrazines. Addition of amino acids, selected aldehydes, and hydrolyzed tobacco-derived F1 protein has positively impacted the array of pyrazines from both qualitative and quantitative aspects. Results further showed that by changing the carbon source from 1-hydroxy-acetone to 1-hydroxy-2-butanone and/or 2-hydroxy-3-butanone, control of the type of pyrazines being synthesized could be realized in that the qualitative and quantitative distributions of the pyrazine array were shifted to higher molecular weight derivatives. A relatively large scale reaction (1.5 L) employing optimized parameters yielded > 2 g of a diverse array of pyrazines dominated by multiple dimethylpyrazine derivatives. While systematically varying reaction conditions and reagent mole ratios can predictably alter the distribution and yield of pyrazines, the two most overwhelmingly significant factors governing these two pyrazine product characteristics included the structure of the carbon source and the presence or absence of aldehydes and free amino acids.

Summary Free amino acids have been isolated via optimized enzymatic hydrolysis of F1 tobacco protein using two cationic resins (Amberlite IR120 and Dowex MAC-2). Optimized enzymatic conversions of the protein as a result of systematic variations in conditions (e.g., time, temperature, pH, enzyme type, enzyme concentration, anaerobic/aerobic environments, and protein concentration) employing commercially available enzymes, were consistently higher than 50% with qualitative amino acid arrays that were consistent with the known composition of tobacco F1 protein. Amberlite IR120 was shown to have a much higher efficiency and capacity for isolation of amino acids from standard solutions and from hydrolysate when compared with the results using Dowex MAC-2. Two columns packed with conditioned Amberlite IR120 (120 × 10 mm,12–15 g resin) and (200 × 25.4 mm, 60–65 g resin) were used to isolate two batches (2.5–3.0 mg and 13–15 mg) of free amino acids, respectively. A relatively inexpensive analytical methodology was developed for rapid analysis of the free amino acids contained within the enzyme hydrolysate. Commercially available enzymes, when employed in optimized reaction conditions, are very effective for enzymatic conversion of tobacco F1 protein to free amino acids.

Summary An array of pyrazines have been synthesized using sugars derived from tobacco cellulose (CDS), ammonium hydroxide, and hydrolyzed tobacco F1 protein as a source of free amino acids (isolated amino acids from F1 hydrolysate, from filtered F1 hydrolysate and from non-filtered F1 hydrolysate). All reactions were performed at 120 °C for 60 min using a 40-mL Parr reaction vessel. Results showed that the addition of hydrolyzed F1 protein as free amino acid source increased the number of pyrazines with branched alkyl chains (for example, 2-butyl-3-methyl pyrazine) compared to when no amino acids were added. However, using isolated amino acids from hydrolyzed F1 protein versus just hydrolyzed F1 protein (filtered or not filtered) did not make a difference in yield or type of branched pyrazines. When non-filtered hydrolyzed F1 protein was used, the solution was much more viscous and contained suspended solid material when compared to the use of filtered hydrolyzed F1 protein. Addition of threonine (THR) to the reaction mixture did not increase the yield of pyrazines but did slightly shift the distribution of pyrazines toward those with three and four carbons attached. Similar but not identical arrays of pyrazines were obtained when somewhat resembling reaction conditions were applied on a larger reaction scale (~1.5 L). A significant 50%-decrease in pyrazine yield was observed when the reaction temperature was reduced from 120 to 100 °C. No noticeable difference in the array of pyrazines from these two reactions was observed. In the majority of cases, the presence of free amino acids resulted in an increase in pyrazine yield coupled with a change in the qualitative array of pyrazines. These results clearly illustrate that sugar prepared from tobacco cellulose (glucose) can be used just like high fructose corn syrup to prepare flavor compounds via Amadori and Maillard reactions. The evidence highlights that hydrolyzed amino acids from F1 tobacco protein can be used via Maillard reactions to produce complementary arrays of pyrazine flavor compounds.

Summary In the present work, microwave and Parr reactors were utilized for synthesis of pyrazines from plant-based biomass in the presence of ammonia and different amino acids. Using these techniques led to synthesis of a relatively wide range of pyrazines with sweet odor and chocolate-like smell. The optimum synthetic conditions to have maximum pyrazine yield for both the microwave and Parr reactions were 41 g of fructose/glucose syrup derived from cellulosic biomass, 28 mL NH4OH (30%), and 0.96 g L-threonine, 0.56 g L-valine, 0.5 g L-leucine, and 0.5 g L-isoleucine at 120 °C for 30 min. Quantitative results obtained via gas chromatography-mass spectrometry (GC-MS) using the traditional open-heated oil bath method have been compared with data obtained via microwave and Parr reactors. In these two latter methods, sealed vessels under high pressure and higher temperature were used. The yield of synthesized pyrazines increased dramatically with both microwave and Parr reactors. Surprisingly, the yield of synthesized pyrazines was both reproducible and nearly two times higher via the Parr reactor than that observed with the microwave reactor under comparable conditions.

Lignins from industrial crops could be converted into valuable chemicals in the context of a second generation biorefinery, but prior understanding of their structure is required. This work is focused on the characterization of lignins from stalks and roots of corn, cotton, sugarcane and tobacco. Lignin structure was studied through nitrobenzene oxidation, C-13, P-31, and 2D nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). Lignins were isolated by mild acidolysis with a maximum degree of contamination of 10% (carbohydrates plus ashes). Interpretation and quantification of NMR spectra provided consistent data about typical units and structures, such as syringyl:guaiacyl:p-hydroxyphenyl (S:G:H), frequency of beta-aryl ether linkages (beta-O-4) and non-condensed structures (NCS), total hydroxyl phenolic groups and their distribution on different non-condensed units type, and the presence of p-coumaric and ferulic acids. In general, roots lignin contains fewer beta-O-4 and lower S/G ratio than the respective stalks, while NCS content does not follow a perceptible trend. In spite of the similarity between corn and sugarcane lignins, radar plots promptly demonstrate higher differences between species than between morphological parts, confirming the lignin specificity of each species. These results are discussed in a comparative approach, highlighting for each material the characteristic features of its lignin.

Semi-quantitative characteristics of headspace volatile pyrazines which constituted around 1% by weight of the final product have been previously described. The influence of reactant concentration, reaction temperature, and reaction time on both the yield of total alkyl pyrazines and the distribution pattern of specific identified pyrazines has not been reported.; Results: The optimum synthetic conditions were 5 mol L-1 NH4 OH, 2 mol L-1 rhamnose, 0.5 mol L-1 leucine at 110°C for 2 h. The greatest total amount of pyrazines obtained was 17 280 µg of extracted product which translated into 31% 2,6-dimethyl pyrazine, 17% 2-methyl pyrazine, 15% 2-ethyl-6-methyl pyrazine, and 16% 2-isoamyl-6-methyl pyrazine.; Conclusion: The yield of synthesized pyrazines increased at higher temperatures. Quantitative total and specific pyrazine results as opposed to analysis of only headspace volatiles are more representative of pyrazine synthesis. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

L'objectif de la présente étude était de quantifier les esters éthyliques d'acides gras (FAEE) produits à partir de deux grands lots d'huile de graines de tabac soumis à une transéstérification éthanolique en présence d'un catalyseur d'acide sulfurique. La purification des produits combinés de la réaction des esters éthyliques visait la suppression, autant que faire se peut, de la couleur et de l'odeur du produit final et fut accomplie via une chromatographie sur colonne conventionnelle avec silice sublimée et une élution en tandem de l'hexane, dans un premier temps et de l'alcool éthylique, dans un deuxième temps, en guise de phase mobile. La chromatographie en phase gazeuse fut utilisée afin de quantifier les esters éthyliques des acides gras spécifiques dans la matière purifiée. Le pourcentage d'esters éthyliques d'acides gras purs récupérés dans le lot n°1 s'éleva à près de 87% tandis que le pourcentage d'esters éthyliques d'acides gras purs récupérés dans le lot n°2 fut supérieur à 89% avec des rendements à la préparation supérieurs à 400 g d'esters éthyliques par essai d'estérification. Les esters éthyliques d'acides gras ne possédaient pas d'arome détectable et ne présentaient qu'une légère coloration jaune à l'issue de ce traitement chromatographique. Pour caractériser la pureté de chaque lot d'esters éthyliques d'acides gras produits, une chromatographie en phase supercritique dont la phase mobile était un fluide composé de dioxyde de carbone modifié au méthanol/acétonitrile et une phase fixe composée d'une silice greffée avec groupement fonctionnel octadécyle furent utilisées. Aucune impureté liée au glycérol ou à des acides gras libres ne fut détectée dans le produit transestérifié purifié. Notre article est le premier rapport décrivant la transestérification optimisée de l'huile de graines de tabac à une échelle relativement grande, ladite transestérification fut couplée à une purification et un isolement ultérieurs des esters éthyliques produits. [Beitr. Tabakforsch. Int. 26 (2015) 205-213]

Among the more than 5000 chemicals reported in cigarette smoke condensate (CSC), heterocyclic aromatic amines (HAAs) are considered to be a contributor to observed biological activity. HAAs are non-volatile and are reported at ppb levels in CSC. A new method for HAA analysis at the trace level is reported here. N, O-Bis(trimethylsilyl) trifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane was employed to derivatize amino groups by heating the reagent containing a sample of CSC at 80 °C for 30 min followed by analysis employing gas chromatography-mass spectroscopy (GC-MS) in the selected-ion-monitoring (SIM) mode. This derivatization method afforded symmetrical peak shapes on a ZB-50 stationary phase and achieved instrumental limits of quantification (LOQ) at 10:1 S/N from -1 ng/mL for AαC to120 ng/mL for Glu-P-1. The chemical identity of each derivative was confirmed by comparison of retention time and mass spectra of standards. The latter were characterized by the following ions: M·+ or [M-1]+, [M-15]+, and m/z 73 (i.e., trimethylsilyl). CSC and its base sub-fractions were studied using the GC-MS method. Ten HAAs were screened and five were quantified in cigarette smoke condensate, while 2-5 HAAs were quantified in each of three base sub-fractions. Values obtained with the new procedure agree well with values reported in the literature and with results obtained from a commercial laboratory via a different analytical method. The potential contribution of each HAA to the overall mutagenic activity observed for CSC and its base fractions is discussed. When considered together, HAAs account for only a small portion (-7.8%) of the observed mutagenicity of the CSC.

Four different Nicotiana flowers (Nicotiana alata (alata), Nicotiana sylvestris (Sy), Nicotiana suaveolens (Su), and Nicotiana tabacum cv. Flue-Cured (FC)) from farms in Virginia and North Carolina were harvested and promptly quenched with liquid nitrogen and hand-ground prior to analysis. Each Nicotiana flower was pre-extracted with hexane to remove unbound volatiles. Fifteen standard compounds that were thought to be in the pre-extract were employed to aid in GC-MS identification and quantification. Glucosides were then chromatographically isolated and next hydrolyzed via 2 M sulfuric acid for 24 h at 75 °C. For each flower, the products of hydrolysis were extracted in tandem with hexane and dichloromethane (DCM) prior to analysis by GC-MS. The mixture of hexane and DCM extracts of the flowers after hydrolysis were then analyzed for each of 15 external standards via GC-MS to determine the concentration of any isolated flower-derived aglycone. Quantitative results for each of the possible 15 free volatile compounds extracted before and after hydrolysis were compared. Benzyl alcohol, phenethyl alcohol, and cis-3-hexenol were found in all Nicotiana both before and after acid hydrolysis. Enormous increases in the mass of benzyl alcohol and phenethyl alcohol were obtained with all flowers as a result of acid hydrolysis. With selected Nicotiana flowers, significant increases were observed for eugenol and cinnamaldehyde. The significant increases observed in cinnamaldehyde and eugenol upon mild acid hydrolysis strongly indicate that this approach could be a viable alternative process for the production scale isolation of these important natural flavor compounds.

L'ampleur de la degradation du melange de glycerol dans une cigarette en train de se consumer pour former de l'acroleine et de l'acetone a ete quantifiee par l'addition de glycerol- 13 C 3 aux trois sortes de cigarettes d'une marque leader sur le marche. Plusieurs tampons Cambridge imbibes d'une solution de 2,4-dinitrophenylhydrazine (DNPH) ont ete employes pour pieger des derives d'hydrazone de composes de carbonyle de faible poids moleculaire dans la fumee principale et la fumee laterale. La chromatographie liquide a haute performance en tandem avec la spectrometrie de masse des ions negatifs a ete employee pour isoler les derives DNPH des produits carbonyles volatiles de combustion et pour etablir leur concentration. Acroleine, acetone et propionaldehyde ont ete les principaux composes etudies. Les derives DNPH de l'acroleine- 13 C 3 et de l'acetone- 13 C 3 ont ete synthetises independamment et ils ont servi de normes externes pour la quantification absolue. Le cout du propionaldehyde entierement marque exclut son utilisation dans cette etude. Les sortes de cigarettes de marque selectionnees pour l'etude presentent les caracteristiques de conception des cigarettes actuellement les plus courantes sur le marche americain et offrent une gamme de taux de «goudron » standardisee representative (14, 10 et 5 mg/cig respectivement selon la methode de filtre Cambridge). Les sortes de cigarettes de la marque etudiees ici font partie d'une famille de cigarettes de marque commercialisees qui ne contiennent pas d'additifs au melange de tabac, y compris le glycerol. La fumee principale a ete generee par une machine a fumer automatique utilisant un regime de fumage standard pour le filtre Cambridge et un regime plus intense exigeant des bouffees plus grandes et plus frequentes et obstruction des orifices a 100%, ce qui est specifie par le gouvernement federal canadien a des fins de regulation. La recherche a indique que seule une faible fraction du glycerol ajoute (∼0,25% a 0,30%, p/p) a ete convertie dans les deux composes etudies, la majeur partie ayant generalement ete observee dans la fumee laterale. Moins de 0,1 % du glycerol ajoute a ete converti en acroleine dans la fumee principale pour toutes les conceptions de cigarettes et les regimes de tumage etudies.

Plusieurs approches ont ete explorees pour developper une procedure a haute performance pour la determination relative de 14 radicaux libres centres sur le carbone, de type a la fois acyle et alkyle aminocarbonyle, dans la fumee de cigarette. Deux procedes de piegeage utilisant le 3-cyano-2,2,5,5-tetramethyl-1-pyrrolidinyloxy, ou le radical 3-cyanoproxyl (3-CNP) ont ete concus pour cette etude: a) le piegeage dans une solution et b) le piegeage sur un support solide a savoir un tampon-filtre Cambridge. La totalite de la fumee fraiche et la fumee en phase vapeur de la fumee principale des cigarettes de reference Kentucky 2R4F, telles que separees par un tampon-filtre Cambridge non modifie ont ete transferees a un systeme de piegeage lors d'experiences distinctes. L'approche avec le filtre Cambridge enduit de 3-CNP s'est averee superieure a la procedure avec impacteur telle que decrite dans cette etude. La chromatographie en phase gazeuse avec detection selective de masse (GC-MS) a ete employee pour la premiere fois comme methode alternative de detection de plusieurs adduits radicaux de concentration relativement elevee. La chromatologie phase liquide couplee a la spectrometrie de masse en tandem (LC-MS/MS) avec un controle des ions precurseurs et un controle des ions selectionnes (SIM) a ete utilisee pour detecter une large gamme de radicaux, dont plusieurs qui n'avaient pas ete reportes au prealable: formyl, crotonyl, acroleine, aminocarbonyl, et des radicaux anilinocarbonyl. Une quantification relative a ete realisee en utilisant des normes de calibration externes de 4-(1-pyrrolidino)benzaldehyde et de nicotine. Il a ete determine que le taux de radicaux libres centres sur le carbone dans la cigarette de reference 2R4F etait approximativement de 265 nmoles/cigarette dans des conditions de duree de fumage de 35 cm 3 par bouffee/60 sec. a intervalle de 2 sec.

Isolation, fractionation, and identification of sucrose esters from aged oriental tobacco employing supercritical fluids have been completed. Underivatized sucrose ester-rich extracts were obtained using supercritical CO2 at densities greater than 0.73 g/mL. Lower density CO2 provided extracts with notable amounts of tobacco derived material; yet, no detectable sucrose ester content. Preparative supercritical fluid chromatography (SFC) provided for an additional purification of the sucrose ester-enriched fraction after column optimization. Structural assignments of the SFC fractions were facilitated using gas chromatography/mass spectrometry (GC/MS) accompanied by N, O-bis(trimethylsilyl)trifluoroacetamide-dimethylformamide (BSTFA-DMF) derivatization of the free hydroxyl groups and high performance-liquid chromatography/mass spectrometry (HPLC/MS). From a relative quantitative perspective regardless of tobacco type, sucrose esters having an acetyl group on C6 of the glucose function (Group III) were in higher concentration compared to both the concentration observed for sucrose ester of Group I (acetyl group on C3 of fructose) and sucrose ester of Group II (no acetyl group on either glucose or fructose). Saturated fatty acid constituents were found to range from a maximum total of 18 carbons to a minimum total of 13 carbons. Unsaturated and isomeric fatty acid homologues were detected within the Group II sucrose ester.

The chemical nature of davanone isolated from natural davana oil via packed column preparative supercritical fluid chromatography with a carbon dioxide-based mobile phase has been defined. Analyses used to characterize davanone included nuclear magnetic resonance spectroscopy, optical rotation, mass spectrometry, headspace solid-phase microextraction, enantiomeric purity via gas chromatography (GC), and GC-coupled olfactometry. For comparison, natural davana oil was subjected to the same types of measurements. The enriched davanone sample was nearly 100% optically pure. This indicates that fractionation of the davana oil with supercritical fluids at near room temperature had little effect on the optical integrity of the sample.

For the first time, relative distributions of optical and geometrical isomers in selected propylene glycol acetals are determined. Resolution of the four acetal isomers possible through the reaction of racemic propylene glycol (PG) with selected aldehydes is demonstrated. The four isomers are ascribed to the presence of syn and anti geometrical isomers for each optically active PG acetal enantiomer. Thus, the (+) and well as (-) enantiomer are found to have a pair of syn and anti geometrical isomers. The ratio of the (+) and (-) isomers in the product remains at an approximate 50:50 ratio, as expected. However, somewhat unexpectedly, the syn/anti geometrical isomer ratio systematically varies with the nature of the substituent comprising the side chain of the aldehyde. Mechanisms involving electronic and minimal steric effects are advanced as possible reasons for the change in the syn/anti PG acetal ratios.

Gas chromatography-mass spectrometry (GC-MS) and reversed-phase liquid chromatography-mass spectrometry (LC-MS) were used to compare and quantify sucrose esters (SE) in five different tobaccos. The concentration of SE varied from 340 to 950 µg/g. In order to quantify the SE in each tobacco, the trimethylsilane (TMS) derivative of each sample was analyzed via GC-MS. It appeared that in the five tobaccos, the intensities of the five chosen SE-derived molecular masses increased in the order m/z 622 < 636 < 678 < 650 < 664 for samples 1-3, but for samples 4 and 5, the m/z 678 and 650 were reversed. In order to qualitatively characterize the various SE chromatographic fractions LC-MS was used. It was determined that the lowest parent SE m/z in which acetyl was attached to glucose was detected at m/z 566 (10 carbons), and the highest m/z was found at 692 (19 carbons). Some m/z values showed more than one peak which indicated the presence of isomers. All samples showed the presence of at least five different SE peaks wherein acetyl was attached to fructose (i.e. m/z 205). Also, acyl unsaturation was observed in selected fractions.

Des esters tetra-acyle de saccharose (SE) dans des extraits de tabac turc ont ete separes et identifies par chromatographie liquide-spectrometrie de masse (LC-MS). Une fraction enrichie de SE obtenue par chromatographie liquide en phase normale semi-preparatoire de l'extrait de chlorure de methylene a ete choisie pour etre caracterise. Plusieurs types de SE ont ete observes differant par la localisation de la fonction de l'acyl dans les fractions de glucose ou de fructose. En plus de l'acetyl, les trois autres schemas de substitution de l'acetyl ont ete commandes par la presence de substituants butyl, pentyl et hexyl alkyl. Dans chaque type de SE plusieurs homologues ont ete observes ayant un groupement methylene different. Dans chacun des homologues, un nombre de composants isomeriques ont ete trouve. La presence de substituants acyl alkyl non sature a induit une autre serie homologue avec des isomeres ayant la meme masse ont ete decouverts. Les informations sur le schema de substitution de SE obtenues par cette nouvelle approche LC-MS est semblable a celles obtenues auparavant par chromatographie en phase gazeuse-spectrometrie de masse (GC-MS) des SE derivatises dans des echantillons de tabac.

Using a non-equilibrated solid-phase microextraction/gas chromatography/mass spectrometry technique, differentiation between a wide variety of types and examples of artificial flavors has been demonstrated. Addition of an internal standard to the samples, as received, allowed for the calculation of yields on a µg g−1 basis for the majority of headspace volatiles. The relative standard deviation values expressed as percentages were between 3 and 5%. The precise nature of the approach coupled with the compound identification capacity of the mass spectrometer afforded the capability to easily differentiate between multiple sources of artificial flavors. With a total analysis time of approximately 30 min and the absence of solvent, this approach has the capability of detecting and quantifying the presence of the low-molecular-weight solvents often used in the preparation of artificial flavors. Such a capability represents a distinct advantage over more conventional methods of solvent dilution. Results from conventional gas chromatography/mass selective detector analyses are contrasted and compared with the results obtained from the headspace SPME approach. Copyright © 2005 Society of Chemical Industry

The amount and type of selected sugars and selected amino acids have been shown to significantly impact the structure of headspace-volatile pyrazines produced in aqueous microwave heat-treated formulations. Selection of sugar and amino acid can dictate the structure, yield and distribution of headspace-volatile pyrazines. Under the same reaction conditions and sugar to ammonium hydroxide ratios, rhamnose was found to produce more pyrazines than did high-fructose corn syrup (HFCS). With rhamnose, the yield of pyrazines approached 4500 µg mL−1. Formulations selectively enriched in ethyldimethylpyrazines can be prepared by stepwise substitution of HFCS with rhamnose. Formulations preferably enriched in methyl- and dimethyl-(3-methylbutyl)- as well as methyl- and dimethyl-(2-methylpropyl)pyrazines were prepared through selective combinations of rhamnose/HFCS and amino acids. Stepwise substitution of HFCS with rhamnose coupled with the use of selected amino acids allowed for the control of the yield, structure and distribution of volatile pyrazines in microwave heat-treated aqueous formulations. Reaction temperature was also found to significantly influence pyrazine yield and distribution. Statistical modeling of the reaction yields as functions of reaction variables produced surfaces with acceptable modeling coefficients. Mechanisms were postulated to account for the increased yields and selected distributions pyrazines when rhamnose was employed. Copyright © 2005 Society of Chemical Industry

The undesirable top notes or off-notes found in mint, clary sage, and cedarwood oils could be quantitatively determined using a non-equilibrated solid phase microextraction/gas chromatography/selected ion monitoring/mass spectrometry (SPME/GC/SIM-MS) technique. Using the low threshold components, dimethyl sulfide, 2-methylpropanal, 2-methylbutanal, and 3-methylbutanal, which are associated with the off-notes of these oils, their levels could be reproducibly quantitatively determined. The highest level of off-notes was found in a sample of Scotch spearmint oil where the levels of the four constituents were, dimethyl sulfide (238 µg g−1), 2-methylpropanal (286 µg g−1), 2-methylbutanal (1048 µg g−1) and 3-methylbutanal (1489 µg g−1). These quantitative results in combination with sensory evaluations could provide for a powerful overall assessment of essential oil quality. Copyright © 2004 Society of Chemical Industry

Microwave-assisted extraction (MAE) has been shown to be an easy, rapid, accurate, quantitative, and precise component of an overall method for the quantitative analysis of flavor components formulated into high-density polyethylene (HDPE) pellets. Under optimized extraction conditions, MAE can be perform extraction of flavors from pellets within 1/2 h with flavor recoveries ranging from approximately 90% to 100%. The variability in the data expressed as percent relative standard deviation from gas chromatographic-mass selective detector analysis of targeted flavor components is always less than 5%, indicating a precise method. In addition, the major components identified in the flavor formulation prior to formulation into the HDPE pellets are the major components detected in the extraction, indicating an accurate determination. Thus, MAE can be readily recommended as an essential component of a high-volume approach to the quantitative determination of flavors formulated into HDPE pellets.

Mint essential oils are produced by the steam distillation of dried or partially dried harvested plant material. In the United States, harvesting is done mechanically so that any weeds found in the field are concomitantly harvested. Steam distillation of contaminated plant material leads to off-notes in the oil, which are currently determined by a sensory panel. Furthermore, nonoptimized distillation conditions can lead to the thermal degradation of carbohydrates and proteins resulting also in the formation of very volatile off top-notes. As a result, the use of a nonequilibrated solid-phase microextraction (SPME) procedure to determine the off-notes is evaluated. The results of this evaluation include a combination of semiquantitative data, odor threshold data, and mathematical data manipulation to ascertain the capabilities of a SPME approach. The results are correlated with sensory panel data to yield a relatively rapid analytical methodology that can be used either in place of or in support of sensory analyses. The main advantage of the technique described is to provide some semiquantitative data in support of the odor-panel screening of mint oils for off-notes. Based on the data presented in this report, it is believed that this has been successfully demonstrated.

Experiments were conducted to independently determine the mainstream smoke transfer efficiency of d-nicotine and l-nicotine. Two types of cigarettes (University of Kentucky 2R1 reference cigarette and a cigarette prepared from reconstituted sheet material, TS1) were employed in the study. A chiral-gas chromatography-selected ion monitoring-mass selective detection analysis was used to separate and determine d- and l-nicotine. The two types of cigarettes were injected with varying levels of d- or l-nicotine (0-20 mg). The tobacco was removed from the nicotine-injected cigarettes and analyzed for total nicotine and d- and l-nicotine. The cigarettes were smoked under FTC (Federal Trade Commission) conditions, and the Cambridge pad extracts were analyzed for total nicotine and d- and l-nicotine. The total nicotine transfer efficiency and the transfer efficiencies of d- and l-nicotine were determined. Nicotine transfer efficiency is dependent on the type of tobacco employed in a blend and the configuration of the cigarette. As a result, the total nicotine transfer efficiency for the 2R1 cigarettes was different than for the TS1 cigarettes. Likewise, the independently measured transfer efficiencies for d- and l-nicotine were different between the two cigarettes. The transfer efficiencies of d- and l-nicotine were not found to be different within a cigarette type. The average transfer efficiency for d-nicotine in a 2R1 cigarette was determined to be 19.25%. The average transfer efficiency for l-nicotine in a 2R1 cigarette was 16.05%. The average transfer efficiency for d-nicotine in a TS1 cigarette was 10.15% and 10.65% for l-nicotine. These differences between d- and l-nicotine were determined not to be statistically significant and are of no practical consequence.

Transfer of nicotine to mainstream smoke was measured for Reference cigarettes made with the addition of 20 -40 mg of seven different nicotine salts, d- and l-nicotine and N’-formylnornicotine. Regression analysis of the nicotine yields from these cigarettes as a function of the nicotine content of the tobacco rods indicated an average nicotine transfer efficiency (17.5%), similar to that found for a separate series of cigarettes made with single-grade tobacco materials (16.2%). Analysis of the enantiomeric purity of the smoke nicotine from the cigarettes made with added nicotine salts and neat nicotine showed no evidence of conversion between l- and d-nicotine during the smoking process. The cigarette made with added N’-formylnornicotine showed no evidence of additional nicotine transfer attributable to reduction of this compound to nicotine. A third series of cigarettes were made with varying levels of d- and l-nicotine added to a tobacco blend and to reconstituted tobacco to further investigate transfer efficiency of the enantiomers. Regression analysis indicated no statistically significant difference between transfer efficiencies of d- and l-nicotine. These results suggest that nicotine salts and d- and l-nicotine transfer to smoke at the same efficiency. However, transfer efficiency of either compound was lower when applied to reconstituted tobacco (9.7%) than when applied to the Reference tobacco blend (15.3%). The thermal stabilities of nicotine salts have little bearing on efficiency of transfer to smoke or on racemization between d- and l-nicotine. Formation of d-nicotine in mainstream smoke via reduction of N’-formylnornicotine does not appear to occur.

A viable approach for the determination of sources of essential oils based on automatic injection solid-phase microextraction-chiral-gas chromatography-mass selective detection is demonstrated. With no sample preparation, it is shown that the source of essential oils such as peppermint, spearmint, and rosemary can be easily distinguished. Short fiber exposure times of approximately 6 s to the headspace above submicroliter quantities of the selected oils are all that is required to obtain both the required sensitivity and resolution to afford analyses with excellent reproducibilities (relative standard deviation values consistently less than 5.0%).

Confirmation of the proposed mechanisms of Strecker aldehyde involvement in the production of branched-chain alkyl-substituted pyrazines is easily accomplished using an automated solid-phase microextraction-gas chromatography-mass selective detection (AutoSPME-GC-MSD) approach. The method is relatively elementary with minimal sample preparation. Microwave heated aqueous formulations require only the addition of NaCl to salt-out the analytes prior to analysis by AutoSPME-GC-MSD. A 100-μm polydimethylsiloxane fiber with accompanying fiber vibration can extract ample quantities of the compounds of interest in as little as 1 min. Such sensitivity negates the requirements for time and reagent-consuming sample extraction via organic solvents or concentration using heat. This approach, therefore, should find additional expanded applications in establishing reaction pathways.

Employing automated solid-phase microextraction-gas chromatography-selected ion monitoring-mass selective detection, mechanistic information on the formation of volatile components associated with carbonyl-amine chemistries in microwave heat-treated natural products is gathered. Employing 13 C uniformly labeled amino acids and sugars, pathways for the formation of Strecker aldehydes, pyrazines, and furan derivatives are delineated in a heat treated licorice suspension. The results are among the first pieces of information providing unambiguous reaction pathways for the production of these compounds in heated natural products.

A viable approach for the analysis of the enantiomeric distributions of volatile components in essential oils based on automatic injection solid-phase microextraction-chiral-gas chromatography-mass selective detection (AutoSPME-chiral-GC-MSD) is demonstrated. From a selection of polar and non-polar fibers of varying thickness, the relatively non-polar thin-film polydimethylsiloxane fiber is found to be the best fiber for the analysis. Fiber exposure to the headspace above sub-microliter quantities of the oils for approximately 6 s is all that is required to obtain both the required sensitivity and resolution to produce excellent reproducibilities (generally ≤ 5.0%). The findings using this approach are in good agreement with previous findings based on chiral-GC-flame ionization detection analysis of solutions of essential oils. These results clearly establish AutoSPME as a simple, rapid, accurate, and precise method of sample preparation for the qualitative and quantitative analysis of enantiomeric distributions within essential oils. This work will be expanded to include studies directed at determining the purity of additional essential oils as well as experiments directed at determining the production location of essential oils.

Manual solid-phase microextraction (SPME) coupled with gas chromatography-mass selective detection has been shown to be a rapid, precise, and reliable method for testing the origin and purity of menthol samples. Exposure of a 65-μm carboxenpolydimethylsiloxane fiber to the headspace above a menthol sample held at 50°C in a sealed vial provides for excellent signal-to-noise responses for a variety of volatile components. Detection differences in menthol compositions are based on documenting predictable changes in the ratios of identified and/or unknown components adsorbed onto the SPME fiber. Differences in composition can be detected as a function of manufacturing site using this approach. In addition, the presence of added synthetic menthol can be detected in the natural samples employing the same principle, thus assisting in determining the purity of the natural menthol.

Menthol occurs naturally in oils of the Mentha species in the (1 R, 3R, 4S)-(–) form (l-menthol), whereas synthetic menthol is available either in the same form or as a racemic mixture (d- and l-menthol). Quantitative analysis of the presence of the (1S, 3S, 4R)-(+)- form (d-menthol) is achieved by using gas chromatographic analysis on a chiral capillary column with selective ion monitoring detection. Detection of the presence of as little as 0.01 % (d-menthol in the total menthol concentration is possible with relative standard deviation values averaging around 7%. Minimal sample preparation with short sample analysis times of 30 min provide for a rapid sample turn around. This method should be applicable to the speciation of menthol in a wide variety of menthol-containing products, including cigarettes.

By combining the results of a review of the 1996 literature with that from a review of the 1994-1995 literature, it is possible to establish trends in the science of gas chromatography (GC). GC is found to embrace a diverse array of chemical interests from thermodynamic property calculations to the speciation of metal ion complexes in marine environments. Advances in speed, sensitivity, automation, computer modeling, detector design, and sample preparation are presented, indicating clearly that GC is a well-established, very healthy, expanding science finding influence in an ever-growing pattern of scientific endeavors.

Aqueous solutions of Maillard reaction products are analyzed using nonpolar and relatively polar solid-phase microextraction (SPME) fibers. The behavior of the polydimethylsiloxane (nonpolar) and carbowaxdivinylbenzene (CWDVB, polar) fibers toward these solutions over a concentration range of 0.005-50 ppm is described. Both fibers demonstrate a marked tendency to selectively adsorb the more highly alkyl-substituted components relative to their comparable proton-substituted counterparts. The CWDVB fiber is found to be more selective for the more polar Maillard reaction products. By employing SPME, gas chromatography, selected ion monitoring (SIM), mass selective detection, and a relatively short exposure time of 10 min, a detection limit in the range of unit parts per billion is established for the fibers. The addition of NaCl to the aqueous solutions significantly increases the amounts of adsorbed components. A linear response between average analyte SIM area counts and analyte concentration over the range of 0.005-0.50 ppm is demonstrated for many of the components.

Aqueous solutions and headspace above volatile and semivolatile compounds associated with the Maillard reaction and sugar thermal degradation are analyzed using solid-phase microextraction. The structure of the model compounds is shown to have a dramatic effect on the rate, equilibration time, and amount of compound adsorbed. Alkyl and alkoxy substitution on the ring of pyrazines, pyridines, thiazoles, and furfurals result in increases in the rates and amounts of compound adsorbed. The presence of multiple components in the aqueous solution results ir a significant competition for adsorption onto the solid-phase microextraction fiber. Increases in the amount and rate of adsorption were found upon addition of NaCl.

Based on the characteristics of a wide range of natural products, a more comprehensive understanding of the role of the Maillard reaction has been developed which describes a molecular basis for the production of a common set of flavourful, volatile aromatic compounds from the reactions between amino acids and sugars at elevated temperature (pressure cooking). By employing a variety of natural products, a clearer knowledge of the common mechanisms for the production of many important flavourants and odourants has been established. Regardless of the starting natural product the same qualitative profile of volatile materials is produced upon ‘pressure cooking’ an aqueous extract of the natural product. The notable differences in aroma arise not from significant differences in the qualitative nature of the materials but from variations in the quantitative distribution of the volatile materials produced.

This article describes a new gas chromatography-based emissions monitoring system for measuring volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). The system is composed of a dual-column gas chromatograph equipped with thermal conductivity detectors, in which separation is optimized for fast chromatography. The system has the necessary valving for stream selection, which allows automatic calibration of the system at predetermined times and successive measurement of individual VOCs before and after a control device. Nine different VOCs (two of which are HAPs), plus methane (CH4) and carbon dioxide (CO2) are separated and quantified every two minutes. The accuracy and precision of this system has been demonstrated to be greater than 95%. The system employs a mass flow measurement device and also calculates and displays processed emission data, such as control device efficiency and total weight emitted during given time periods. Two such systems have been operational for one year in two separate gravure printing facilities; minimal upkeep is required, about one hour per month. One of these systems, used before and after a carbon adsorber, has been approved by the pertinent local permitting authority.

The effect of inorganic ion concentrations and pH on the yields of volatile materials from aqueous pressure-cooked solutions of green coffee beans, green tea leaves, and green peanuts as measured by purge and trap—gas chromatography (P&T—GC) with mass spectrometric (MS) detection and flame-ionization detection (FID) is described. Through the use of an internal standard, quantitative descriptions of the effects of these two parameters on the volatile compounds associated with pressure-cooked aqueous extracts of selected natural products are presented. The magnitude of the effect of ion concentration on the amount of material in the headspace is a function of the inorganic compound employed. The higher molecular weight components in the headspace are found to be the most affected by pH and salt concentration. As the concentration of certain inorganic species increases, more of the higher molecular weight components relative to the internal standard are found in the headspace above, the pressure-cooked aqueous extracts. Variations in the pH produce similar changes. However, the effect is not universal for the extracts as a group. Increasing the pH results in both increases and decreases in the total amount of volatile material as a function of the aqueous extract type. The ability to exercise control over the release of volatile material from these aqueous extracts by varying the ion concentration and pH of the solutions would seem to provide flexibility in the design of aroma formulations.

The characteristics of the aqueous extracts of cashews and two varieties of peanuts in terms of their total and free amino acid profiles are described. When the aqueous extracts of these natural products are «heat-treated» in a sealed reaction vessel, selected types of volatile organic compounds are produced. The various types and yields of compounds produced are described. Additionally, theories based on (1) free and total amino acid pools, (2) Maillard chemistries, and (3) sugar degradation processes are advanced to account for their origin. On the basis of differences in the free amino acid pools of the aqueous extracts of each natural product, quantitative differences in the distribution of volatile materials can be explained

Eight compounds from a Kentucky 1R4F reference cigarette smoke condensate have been determined by selected ion monitoring-mass spectrometry (SIM-MS) to confirm the validity of multidimensional gas chromatography (MDGC) as a quantitative tool in complex mixture analyses. Four electrostatically precipitated smoke condensate samples of 100 cigarettes each are dissolved individually in 25 mL of 2-propanol. The 2-propanol contains two methyl esters (C8 and C14) and seven deuterium-labeled compounds used as internal standards (IS). Analysis of the compounds of interest, pyridine; acetamide; acrylamide; phenol; o-, m-, and p-cresol; and quinoline, is accomplished by using two heartcuts. Heartcut times of the MDGC analysis are selected such that at least one IS is transferred with each group of compounds being analyzed. This study shows that the MDGC technique previously developed and described can be used for quantitative analyses. A comparison is made between the two types of internal standards. The results obtained for both types of internal standards agree within 20% of each other, on the average, with higher standard deviations for approximately 60% of the compounds where methyl esters are used as internal standards.

Hyphenated gas chromatography (GC) refers to not only the coupling of a GC to information-rich detectors but also the coupling of the gas chromatograph to automated sample preparation techniques. Examples of information-rich detectors include mass and infrared spectrometers, whereas automated sample preparation techniques include solid-phase microextraction (SPME), large-volume injection (LVI), purge and trap (PT), headspace (HS), and gas chromatographic approaches. The gas chromatographic approach involves the wedding of two gas chromatographs and is commonly referred to as multidimensional gas chromatography (MDGC). The union of the automated sample preparation techniques with MDGC and information-rich detectors affords the capability for quantitative and qualitative analysis of a wide variety of sample matrices for analytes at parts per billion (ppb) concentrations. However, not every hyphenated configuration is worth considering, and careful matching of the hyphenated approaches is essential to obtain the maximum analytical benefits.

Matrix-isolated (MI) Fourier transform infrared spectra have been collected on a series of aliphatic ketones. The values for the carbonyl absorptions maxima are intermediate between vapor-phase (VP) and solid-state solution (SS) phases. The data reveal a stereochemical influence on the position of the ketone carbonyl absorption when the carbons that are in the alpha position with respect to the carbonyl group contain alkyl snbstituents vs. protons. Steric bulk causes the frequency of the absorption to decrease. The position of the ketone carbonyl absorption was also shown to decrease as the carbonyl group migrated toward the center of a long straight-chain hydrocarbon backbone. Stereochemical influences due to ring strain were also documented. Unsaturation, located in the alpha position with respect to the carbonyl, was shown to reduce the absorption frequency. The trends found in this MI study are comparable to those previously documented from VP and SS studies. In two cases wherein very bulky substituents were located in the alpha position with respect to the carbonyl, a splitting of the carbonyl absorption was observed. Studies are underway to test for a general trend in and to uncover an explanation for this phenomenon.

The characteristics of the OH stretching absorptions in a series of catechols, resorcinols, hydroquinones, and diols have been documented with the use of matrix isolation Fourier transform infrared spectroscopy. Steric and electronic effects were described and found to agree with published results on the vapor-phase studies on the same compounds. The positions of the OH absorptions were shown to fall within a window set on the high energy side by the vapor-phase results and on the lower energy side by solid-state/solution results. The very low full width at half-height values unique to the matrix experiment allowed for the observance of absorption bands not yet seen before in the vapor-phase or solid-state studies. These new bands confirm the presence of intramolecular interactions not previously documented. The data as a whole do indicate that extensive intermolecular interactions do occur at very low loadings on the cryogenic disk (10 ng) for compounds containing polar substituents.

Matrix isolation Fourier transform infrared information has been presented on a series of aliphatic amines, anilines, and amides. The absorptions associated with NH stretches are found at essentially the same energies in both the vapor phase (VP) and matrix isolation (MI) phase. Both the VP and MI values are found at higher energy than the solid state (SS) phase. The similarity of the values for the MI and VP phases is a departure from results found previously for other types of organic compounds. The carbonyl absorptions for the amides (MI) were found to be intermediate between the VP (high) and SS (low) values. This is consistent with established trends for other carbonyl containing compounds. The absorptions for carbonyl groups for the majority of the compounds appear as split absorptions on the order of 20 cm−1 peak to peak. These split absorptions were ascribed to intramolecular hydrogen bonding and rotational conformer isolations. Minor aggregation effects were found to occur as band broadening effects when the ratio of matrix gas (argon) to analyte dropped below 1000:1.

MI/FT-IR spectral data have been collected on selected types of organic compounds containing the carbonyl group. By the varying of the ratio of the matrix gas to the compound ( M/E) as well as the matrix gas (Ar vs. Xe), the observed splitting of the carbonyl absorption band was attributed to both conformer isolation and aggregation in the matrix. The splitting of the carbonyl group of methyl acetate was attributed to aggregation, while conformer isolation was found to exist for phenyl acetate and trimethylacetaldehyde. The magnitude of the splittings found in this study, 3–30 cm−1, is within the range of values found for other organic compounds. Band splitting was shown by (1) compounds that are linear and contain ≤5 carbons or (2) compounds that are branched and contain 5 carbons displayed only band broadening. Varying M/E ratios has been found to be a reasonable method by which to distinguish between conformer and aggregation. These data confirm the influence of sample phase and indicate that extreme care must be taken in the use of MI/FT-IR spectra as physical probes for structure determination.

Data are presented that describe the IR spectra of organic compounds obtained under matrix isolation conditions. Among the types of compounds examined are amides, lactones, lactams, esters, acids, alcohols, and phenols. Trends, as a function of structure, established in vapor-phase IR are shown to exist under MI conditions. The frequency (cm−1) of the stretching absorption for hydroxyl groups and carbonyl groups associated with the types of compounds listed above under MI conditions is shown to be intermediate between the vapor-phase position (highest energy) and the solid-solution position (lowest energy). In some cases the three phases differ by as much as 300 cm−1 (OH group in carboxylic acids) and by as little as 15 cm−1 (carbonyl group in carboxylic acid esters).

Information concerning the matrix isolation Fourier transform infrared spectra of a series of alkanes, esters, lactones, lactams, phenols, alcohols, amides, alkenes, and ketones is presented. A comparison between the characteristics of the spectra in two matrices (argon and xenon) as well as in the absence of any matrix (bare gold disk) is drawn. The impact of these matrices on the characteristics of the IR spectra is compared with the impact observed when spectra are gathered in the vapor phase as well as the condensed phase/solid state. For the majority of compounds studied, the major absorption bands of each class of compound fall between higher values for the vapor phase and lower values for the condensed phase when either argon or xenon is used as the matrix gas. The few exceptions are discussed. The absorption bands found in the xenon matrix are usually at a lower energy than are comparable bands in the argon matrix. In most all cases, the values of absorptions for compounds on the bare disk were lower than the comparable values found in the argon matrix. These results represent the first extensive study at 10 K of the effect of different matrix gas hosts and document the proposal that preconceptions of noble gases as inert hosts for the examination of FT-IR spectra at low temperature are not valid.