Moldoveanu S.,RJ Reynolds Tobacco Co. |
David V.,University of Bucharest
Essentials in Modern HPLC Separations | Year: 2013
Essentials in Modern HPLC Separations discusses the role of separation in high performance liquid chromatography (HPLC). This up-to-date reference systematically covers new developments in types and characteristics of stationary phases, mobile phases, and other factors of this technique that influence separation of compounds being analyzed. The volume also considers the selection process for stationary and mobile phases in relation to the molecules being separated and examined, as well as their matrices. The book includes a section on the contemporary applications of HPLC, particularly the analysis of pharmaceutical and biological samples, food and beverages, environmental samples, and more. Discusses key parameters in HPLC separation Describes interrelation between various HPLC features (solvent pressure, separation, detection) Includes a large number of references. © 2013 Elsevier Inc. All rights reserved.
Moldoveanu S.,R.J. Reynolds Tobacco Co. |
David V.,University of Bucharest
Journal of Chromatography A | Year: 2015
Phase ratio Φ for an HPLC column is a common parameter being defined as the ratio between the volume of the stationary phase Vst and the void volume of the column V0. Although apparently simple, the evaluation of phase ratio presents difficulties because there is no sharp boundary between the mobile phase and the stationary phase, and different mobile phases lead to different "effective" phase ratios. A considerable number of studies have been dedicated to the evaluation of Vst and V0 with the goal of obtaining the value for Φ. However, the parameter is seldom reported for common commercially available columns and key information for its calculation (e.g. the weight of column packing) is not typically reported by the vendors. Present study describes a novel procedure for the evaluation of phase ratio for a chromatographic column when used with a given mobile phase. The procedure allows the calculation of Φ only from the measurements of retention factors k' for two hydrocarbons i and j, for which the octanol/water partition coefficients log Kow are known. A theoretical support for this procedure based on solvophobic theory of interactions in solution is presented, and several experimental results reported in the literature are used to demonstrate the validity of the procedure. © 2015 Elsevier B.V.
Moldoveanu S.C.,R. J. Reynolds Tobacco Co |
David V.,University of Bucharest
Journal of Separation Science | Year: 2013
The direct calculation of free energy of interactions between a solute j and two immiscible liquids shows a linear dependence between the (logarithm of) the distribution constant in liquid-liquid partition equilibrium log K j and the van der Waals surface area of the solute. The study provides a thermodynamic proof for the formula log KBA,j = c 1 log KBC,j + c2 that describes the linear dependence between (the logarithm of) the distribution constant for a solute j in a solvent system (B/A) and (the logarithm of) the distribution constant for the same solute in a different solvent system (B/C). This relation has been well proven by various experimental studies and it is frequently used in liquid chromatographic separations as well as in liquid-liquid extractions, but was not explained previously based on thermodynamic results. The theory was verified using the prediction of octanol/water distribution constants log Kow for a wide range of molecules, including hydrocarbons and compounds with a variety of functional groups. The results have also been verified for the distribution constants in other solvent systems. The expression for the distribution constant obtained in this study also gives a theoretical base for the additive fragment methodology used for the prediction of log Kow. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Davis M.F.,University of North Carolina at Chapel Hill |
Davis M.F.,R.J. Reynolds Tobacco Co. |
Vigil D.,University of North Carolina at Chapel Hill |
Vigil D.,Vanderbilt University |
Campbell S.L.,University of North Carolina at Chapel Hill
Free Radical Biology and Medicine | Year: 2011
Ras GTPases have been a subject of intense investigation since the early 1980s, when single point mutations in Ras were shown to cause deregulated cell growth control. Subsequently, Ras was identified as the most prevalent oncogene found in human cancer. Ras proteins regulate a host of pathways involved in cell growth, differentiation, and apoptosis by cycling between inactive GDP-bound and active GTP-bound states. Regulation of Ras activity is controlled by cellular factors that alter guanine nucleotide cycling. Oncogenic mutations prevent protein regulatory factors from down-regulating Ras activity, thereby maintaining Ras in a chronically activated state. The central dogma in the field is that protein modulatory factors are the primary regulators of Ras activity. Since the mid-1990s, however, evidence has accumulated that small molecule reactive nitrogen species (RNS) can also influence Ras guanine nucleotide cycling. Herein, we review the basic chemistry behind RNS formation and discuss the mechanism through which various RNS enhance nucleotide exchange in Ras proteins. In addition, we present studies that demonstrate the physiological relevance of RNS-mediated Ras activation within the context of immune system function, brain function, and cancer development. We also highlight future directions and experimental methods that may enhance our ability to detect RNS-mediated activation in cell cultures and in vivo. The development of such methods may ultimately pave new directions for detecting and elucidating how Ras proteins are regulated by redox species, as well as for targeting redox-activated Ras in cancer and other disease states. © 2011 Elsevier Inc. All rights reserved.
Moldoveanu S.C.,R.J. Reynolds Tobacco Co. |
Gerardi A.R.,R.J. Reynolds Tobacco Co.
Journal of Chromatographic Science | Year: 2011
A new liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for the analysis of acrylamide in tobacco, alternative tobacco products (wet snuff, snus, orbs, strips, and sticks), and cigarette smoke was developed and evaluated. Besides the LC-MS-MS method, two additional procedures for acrylamide analysis were also developed with the purpose of comparison. A thorough evaluation of the LC-MS-MS technique was performed for typical characteristics of an analytical method such as selectivity, precision, accuracy, range of measurable levels, robustness. The method was found perfectly fit for the analyses of acrylamide in the tobacco, tobacco products, and smoke matrix. Although not essential, the sensitivity of the method was further increased by using a concentration step on a graphitized carbon solid phase cartridge, allowing the measurement of as low as 300 pg/mL and detection of 90 pg/mL acrylamide in solution. Several tobacco samples, alternative tobacco products, and smoke from several cigarettes including commercial cigarettes from the US market, 2R4F, and 3R4F Kentucky reference cigarettes were analyzed. The levels of acrylamide in tobaccos were about 100 ng/g, or lower. The levels found in snus and one brand of wet snuff was also below 100 ng/g. A wintergreen wet snuff had about 180 ng/g, strips had about 126 ng/g and the sticks about 367 ng/g acrylamide. The cigarette smoke had levels of acrylamide around 1 μg/cig or higher. Copyright © 2010 Publishing Technology.
Moldoveanu S.C.,R.J. Reynolds Tobacco Co
Beitrage zur Tabakforschung International/ Contributions to Tobacco Research | Year: 2010
A simple procedure for the collection of vapor phase (VP) of mainstream cigarette smoke for analysis has been developed. This procedure consists of collecting the VP on a commercial charcoal trap (ORBO™-32) followed by dissolution in acetone. The acetone extract can be analyzed by a gas chromatography/mass spectrometry (GC/MS) technique. A qualitative analysis of the collected VP has been performed for 3R4F Kentucky reference cigarette, allowing the identification of 138 compounds, some compounds being present in both VP and in particulate phase (PP) of cigarette smoke. A quantitative analysis method for acrylonitrile and α-methacrylonitrile (2-methyl- 2-propenenitrile) was also developed, and the level of these compounds in 15 different cigarette brands was measured. Acrylonitrile quantitation was selected since this compound in smoke poses significant health related issues. -Methacrylonitrile quantitation was selected due to the similar structure of this compound with acrylonitrile. The analyzed cigarettes were several Kentucky reference cigarettes including 1R5F, 2R4F, 3R4F, 2R1F, and 1R3F, several King Size (KS) commercial cigarettes from the US market including Basic Non Filter (NF), Basic Ultra Lights (UL), Newport, Marlboro (Red), Marlboro Menthol, Camel Filter, Camel Lights, Camel Ultra Lights, and two herbal cigarettes, Ecstasy and Dreams. The results for acrylonitrile were in very good agreement with data reported in the literature for 2R4F and 1R5F cigarettes. The levels of α- methacrylonitrile were not previously reported. The correlation between the levels of acrylonitrile and of α- methacrylonitrile with the (wet) total particulate matter (TPM) was evaluated. Although the levels of acrylonitrile and of α-methacrylonitrile in mainstream smoke depend on the TPM values, the correlation is not very strong, indicat- ing that the nature of the cigarette blend and possible other factors in cigarette construction also influence their levels in smoke. The collection method used in this study allows the subsequent dissolution of VP in a much smaller volume of solvent compared to other methods that use impingers, allows the use of standard GC/MS autosamplers for liquid injection and simple addition of internal standards com- pared to the methods that use gas bags, and allows a simple and immediate collection of VP as it leaves the Cambridge filter pad. These characteristics represent significant advantages versus other methods commonly used for VP analysis.
New methodologies for qualitative and semi-quantitative determination of carbon-centered free radicals in cigarette smoke using liquid chromatography-tandem mass spectrometry and gas chromatography-mass selective detection
Gerardi A.R.,R.J. Reynolds Tobacco Co |
Coleman III W.M.,R.J. Reynolds Tobacco Co
Beitrage zur Tabakforschung International/ Contributions to Tobacco Research | Year: 2010
Several approaches were explored to develop a high throughput procedure for relative determination of 14 different carbon-centered free radicals, both acyl and alkylaminocarbonyl type, in cigarette smoke. Two trapping procedures using 3-cyano-2,2,5,5-tetramethyl-1- pyrrolidinyloxy, or 3-cyanoproxyl radical (3-CNP) were designed for this study: a) trapping in solution and b) trapping on a solid support which was a Cambridge filter pad. Fresh whole smoke and vapor phase smoke from mainstream cigarette smoke from Kentucky Reference Cigarettes 2R4F, as partitioned via an unadulterated Cambridge filter pad, were transferred into each trapping system in separate experiments. The 3-CNP coated Cambridge filter pad approach was shown to be superior to the impinger procedure as described in this study. Gas chromatography coupled with mass selective detection (GC-MS) was employed for the first time as an alternate means of detecting several relatively highly concentrated radical adducts. Liquid chromatography tandem mass spectrometry (LC-MS/MS) with precursor ion monitoring and selected ion monitoring (SIM) was used for detecting the large array of radicals, including several not previously reported: formyl, crotonyl, acrolein, aminocarbonyl, and anilinocarbonyl radicals. Relative quantitation was achieved using as external calibration standards of 4-(1- pyrrolidino)benzaldehyde and nicotine. It was determined that the yield of carbon-centered free radicals by reference cigarette 2R4F was approximately 265 nmoles/cigarette at 35 mL puff/60 sec interval/2 sec duration smoking conditions.
Moldoveanu S.C.,R. J. Reynolds Tobacco Co. |
Chang Y.,R. J. Reynolds Tobacco Co.
Journal of Agricultural and Food Chemistry | Year: 2011
A number of reference oils, two commercial oils, and several oil extracts from seeds of Nicotiana species were analyzed for the fatty acid content and also for triglyceride composition. The seed oils were obtained using an accelerated solvent extraction procedure, which was proven to be very efficient and reproducible. The fatty acids were analyzed after the hydrolysis of the oils, using trimethylsilylation and gas chromatography/mass spectrometry (GC/MS) analysis. The levels of sixteen molecular species of triglycerides in the oils were measured after GC separation using MS for identification and flame ionization detection (FID) for quantitation. The results for the fatty acids and those for triglycerides were combined to generate uniform information regarding the composition of the analyzed oils. For a number of oils, the individual triglyceride quantitation and mass spectra were reported for the first time. The study showed that in some cases, oils with similar fatty acid content do not have the same triglycerides profile. The fatty acids and triglycerides profile for selected Nicotiana species were described for the first time in the literature. © 2011 American Chemical Society.
Moldoveanu S.C.,R.J. Reynolds Tobacco Co.
Beitrage zur Tabakforschung International/ Contributions to Tobacco Research | Year: 2013
The chiral separation of minor alkaloids from tobacco is of interest because R and S isomers of these compounds have differences in their physiological activity. This difference is also reflected in the physiological properties of tobaccospecific N'-nitrosamines (TSNAs), in particular that of N'- nitrosonornicotine. This compound results mainly from nornicotine nitrosation. The previously reported analytical techniques for the enantiomer separation of minor alkaloids have various shortcomings, such as the need for bidimensional chromatography or poor enantiomer separation. A new method for the analysis of nornicotine, anabasine and anatabine has been developed, based on an original derivatization and a simple gas chromatography/mass spectrometry (GC/MS) analysis. The method allows separate quantitation of S-nornicotine and Rnornicotine, and the analysis of anabasine and anatabine (without isomer separation). It was found that the proportion of S-nornicotine in the total nornicotine present in tobacco varies, depending on the tobacco type, between 52.6% for a flue-cured tobacco to 91.4% for a Burley. Green tobaccos (freeze dried) showed lower levels of minor alkaloids and S-nornicotine accounted for between 31.6% to 43.8% of the total nornicotine (in the analyzed samples).
Moldoveanu S.C.,R.J. Reynolds Tobacco Co |
Scott W.A.,R.J. Reynolds Tobacco Co
Journal of Separation Science | Year: 2016
Several pentacyclic triterpenoid acids including betulinic, oleanolic, and ursolic acids were reported to have health beneficial properties such as antiviral and anti-inflammatory properties, as well as the capability to inhibit "in vitro" the development of various cancer cell types. For this reason betulinic, oleanolic, and ursolic acids are used as neutraceuticals. For the analysis of the pentacyclic triterpenoid acids in complex plant materials, an improved scheme was developed, involving a qualitative screening using silylation and gas chromatography with mass spectrometry analysis, followed by quantitation using a novel liquid chromatography with tandem mass spectrometry procedure. The use of the two methods provides more reliable information regarding the plant materials with unknown composition. Besides betulinic, oleanolic, and ursolic acids that were analyzed, by this procedure a fourth pentacyclic triterpenoid acid was identified and quantitated that was not previously reported to be present in plants. This acid has been identified as 3β-3-hydroxy-lupa-18,20(29)-dien-28-oic acid. The newly identified acid has a structure as a derivative of lupane, although lupane with a double bond in the 18-position was not previously reported as present in plants. The new liquid chromatography with tandem mass spectrometry procedure developed for this study offers a very low limit of quantitation, excellent precision, and robustness. Rosemary was found to contain the largest levels of pentacyclic triterpenoid acids among all the analyzed botanicals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.