Simultaneous determination of amino-alpha-carbolines and amino-gamma-carbolines in cigarette smoke condensate by high-performance liquid chromatography

A method for the simultaneous detection of amino-alpha-carbolines (2-amino-alpha-carboline and 2-amino-3-methyl-alpha-carboline) and amino-gamma-carbolines (3-amino-1,4-dimethyl-5H-pyrido [4,3-b]indole and 3-amino-1-methyl-5H-pyrido [4,3-b]indole) by high-performance liquid chromatography has been developed. It consists of a three-step purification using three different columns with fluorometric detection. With this method, we have demonstrated that both amino-alpha-carbolines and amino-gamma-carbolines are present in cigarette smoke condensate. The method may be useful for detecting these carcinogens in various materials.     

Quantitation of mutagenic/carcinogenic heterocyclic aromatic amines in food products.

A method for screening genotoxic heterocyclic aromatic amines in cooked foods using solid-phase extraction and high-performance liquid chromatography with ultraviolet and fluorescence detection is described. Solid-phase extraction includes basic extraction on diatomaceous earth (Extrelut) and subsequent purification on propylsulphonic acid silica gel. This convenient procedure separates the analytes into a polar group and an apolar group. We have identified the following components in the two groups. The polar group contains aminoimidazoazaarenes i.e. 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine, and glutamic acid pyrolysates, i.e. 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole and 2-aminodipyrido[1,2-a:3',2'-d]-imidazole. The apolar group consists of five carbolines: 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, 3-amino-1-methyl-5H-pyrido[4,3-b]indole, 2-amino-9H-pyrido[2,3-b]indole, 9H-pyrido[3,4-b]indole and 1-methyl-9H-pyrido[3,4-b]indole. The extraction efficiencies range from 45 to 90%, and the detection limits are in the low nanogram per gram range. The method was applied to the analysis of heterocyclic aromatic amines in pan-fried, oven-cooked and barbecued salmon.     

Separation and quantitation of monovalent anionic and cationic species in mainstream cigarette smoke aerosols by high-performance ion chromatography

A simple method has been developed to separate and quantitate monovalent ionic species in mainstream cigarette smoke aerosols based on ion chromatography (IC) with conductivity detection. The method entails collecting the smoke aerosol particulate phase by electrostatic precipitation, dissolving the smoke condensate in methanol (MeOH), and separating the ionic species on either a cation- or anion-exchange column. The method has been applied to the analysis of smoke aerosols from two cigarettes, 1R4F Kentucky Reference cigarettes and a new cigarette that heats but does not burn tobacco. The predominant cations in smoke aerosols from 1R4F Kentucky Reference and the new cigarettes are sodium (Na+), ammonium (NH4+), and potassium (K+) ions; the predominant anions are acetate (AcO-) and formate (HCOO-). Trace amounts of chloride (Cl-), nitrite (NO2-), and nitrate (NO3-) ions are also present.     

固相萃取-高效液相色谱法同时测定羊肉制品中9种杂环胺

建立了同时测定羊肉制品中9种杂环胺的固相萃取-高效液相色谱(SPE-HPLC)分析方法。样品经2 mol/L NaOH超声提取、80 mL二氯甲烷液-液萃取,利用阳离子交换柱(MCX柱)净化和富集后进行HPLC分析。采用反相C18色谱柱,以乙腈和0.01 mol/L磷酸溶液(用三乙胺调整pH 3.6)为流动相对杂环胺进行梯度洗脱,使用二极管阵列检测器(DAD)分别在228 nm(2-氨基-9H-吡啶并［2,3-b］吲哚(AaC)、2-氨基-3-甲基-9H-吡啶并［2,3-b］吲哚(MeAaC))、253 nm(2-氨基-3-甲基咪唑并［4,5-f］喹啉(IQ)、1-甲基-9H-吡啶并［3,4-b］吲哚(Harman)、2-9H-吡啶并［3,4-b］吲哚(Norharman))、263 nm(2-氨基-3,8-二甲基咪唑并［4,5-f］喹喔啉(MeIQx)、2-氨基-3,4,8-三甲基咪唑并［4,5-f］喹喔啉(4,8-DiMeIQx)、3-氨基-1-甲基-5H-吡啶并［4,3-b］吲哚(Trp-p-2))、321 nm(2-氨基-1-甲基-6-苯基咪唑并［4,5-b］吡啶(PhIP))处进行检测。实验结果表明,9种杂环胺分离效果良好,回收率为50.27%～94.77%(n=6),相对标准偏差为0.08%～4.42%;通过全波长扫描,确定检出限(以信噪比(S/N)=3计)为1.6～41.0 μg/L。该方法操作简单,结果准确,重现性好,可用于同时检测羊肉制品中9种杂环胺的含量。     

固相萃取-高效液相色谱法同时测定传统禽肉制品中的9种杂环胺类化合物

建立了固相萃取-高效液相色谱同时测定传统禽肉制品中9种杂环胺类化合物(HAAs)(包括2-氨基-3-甲基咪唑并［4,5-f］喹啉、2-氨基-3,4-二甲基咪唑并［4,5-f］喹啉、2-氨基-3,8-二甲基咪唑并［4,5-f］喹喔啉、2-氨基-3,4,8-三甲基咪唑并［4,5-f］喹喔啉、2-氨基-1-甲基-6-苯基-咪唑并［4,5-b］吡啶、3-氨基-1-甲基-5H-吡啶并［4,3-b］吲哚、3-氨基-1,4-二甲基-5H-吡啶并［4,3-b］吲哚、9H-吡啶并［4,3-b］吲哚、1-甲基-9H-吡啶并［4,3-b］吲哚)含量的分析方法。经过条件优化,肉样选用乙酸乙酯进行提取,提取液经丙基磺酸(PRS)和C18固相萃取小柱净化,采用TSK-gel ODS-80TM色谱柱,以乙腈和0.05 mol/L醋酸-醋酸铵缓冲液(pH 3.4)为流动相进行梯度洗脱分离,紫外-荧光检测器串联方式对目标化合物进行检测。通过波长扫描,确定紫外检测波长为263 nm,荧光激发波长/发射波长随时间切换程序为: 0～21 min, 300 nm/440 nm; 21～23.8 min, 315 nm/410 nm; 23.8～35 min, 265 nm/410 nm。在上述条件下,9种HAAs在35 min内实现基线分离。3个加标水平的平均回收率为60.47%～90.55%(n=6),相对标准偏差(RSD)为0.49%～9.74%(n=6),检出限(以信噪比为3计)为0.1～3.6 μg/kg。该方法简便快速、结果准确、灵敏度高,可作为测定传统禽肉制品中多种杂环胺类化合物的有效方法。     

Determination of heterocyclic aromatic amines by capillary high-performance liquid chromatography with diode array detection in ready-to-eat cooked ham treated with electron-beam irradiation

Heterocyclic aromatic amines (HAs) are a group of mutagenic and carcinogenic substances present in significant amounts in cooked meat and fish that can potentially be formed during food processing operations. This paper proposes a capillary liquid chromatography method with diode array detection for the trace-level determination of three HAs, namely, MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline), norharman (9H-pyrido[3,4-b]indole) and harman (1-methyl-9H-pyrido[3,4-b]indole), in ready-to-eat (RTE) cooked ham processed by electron-beam (accelerated electrons) irradiation to eliminate pathogenic microorganisms and to extend its shelf-life. The HAs selected have frequently been detected and quantified in a wide range of food and could be potential markers to indicate the presence of these toxic compounds. The method is based on the separation in an Inertsil C(8) capillary column (150 mm x 0.3-mm internal diameter, 3 microm) by gradient elution mode using a mixture of acetonitrile and 30 mM ammonium acetate pH 4.5 buffer as the mobile phase. Detection was at 250 and 265 nm and, to improve sensitivity, large injection volumes (20 microL) and on-column focusing techniques based on the injection of HA samples in low organic solvent strength solutions were employed. A simple and short solid-phase extraction and purification procedure was also optimized for sample preparation. Nonirradiated and irradiated RTE cooked ham samples at doses between 1 and 8 kGy were analyzed. HAs were not detected in any of the samples analyzed; so both types of samples were spiked at concentration levels in the range 5-25 ng g(-1), which may be found in meat products. The quality parameters of the method developed in the food matrix were established, and detection limits around 0.3 ng g(-1) were obtained. Spiked recoveries between 70 and 79% (n = 3 for each spiked level) relative standard deviations between 1 and 5% were also obtained, showing the effectiveness of the proposed method.     

Photodegradation of environmental mutagens by visible irradiation in the presence of xanthene dyes as photosensitizers

The photodegradation of environmental mutagens, such as 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAαC), and 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), was investigated by visible irradiation in the presence of xanthene dyes as photosensitizers. Although the environmental mutagens themselves were very stable during visible irradiation under the conditions in this study, they were effectively photodegraded in the presence of the xanthene dyes (erythrosine, rose bengal, and phloxine). Moreover, photodegradation of the mutagens was further enhanced for xanthene dyes loaded onto a water-soluble diethylaminoethyl (DEAE)-dextran anion-exchanger via ionic interactions (xanthene-dyeDEX). Photodegradation was inhibited by O2 removal from the reaction solution. In ESR spin-trapping experiments using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a trapping reagent, signals characteristic of DMPO-?OH (hydroxyl radical) were observed in the presence of xanthene-dyeDEX. These results suggest that reactive oxygen species derived from O2, such as singlet molecular oxygen (?1O2) and/or ?OH, were active participants in photodegradation of the mutagens in the presence of xanthene dyes or xanthene-dyeDEX.     

Puff-by-puff resolved characterisation of cigarette mainstream smoke by single photon ionisation (SPI)-time-of-flight mass spectrometry (TOFMS): comparison of the 2R4F research cigarette and pure Burley, Virginia, Oriental and Maryland tobacco cigarettes

Soft single photon ionisation (SPI)-time-of-flight mass spectrometry (TOFMS) is applied for the characterisation and comparison of puff-by-puff resolved and total yields of cigarette mainstream smoke from single tobacco type cigarettes (Virginia, Oriental, Burley, and Maryland) and the 2R4F University of Kentucky research cigarette. Puff-by-puff characteristics of various smoke components within one cigarette type as well as between different cigarette types can differ tremendously. This is demonstrated by means of a few selected compounds. Puff yields vary between 15 and 106 μm for acetaldehyde, 6 and 57 μm for NO, and between 1 and 8 μm for butadiene. Thereby, cigarettes containing 100% Oriental and Burley tobacco exhibit a very unique behaviour for the first and last puff. Different cultivation and processing methods as well as burning characteristics are most likely responsible for this. Since the 2R4F cigarette contains all four tobacco types it combines features of all of them. However, for some smoke constituents, smoking of the 2R4F reference cigarette results in exceptionally high yields which might not be attributable to the four pure tobacco types, but to other factors. In addition, comparison of the different cigarettes was also carried out by normalising the yields to puff resolved particulate matter. This procedure minimises effects caused by unequal smoke formation and represents another approach in evaluating the data.     

An investigation of nitrogen- and sulfur-containing heterocycles

The reaction of 3-amino-6-chloro-2-mercaptopyridine with ortho-substituted phenacyl halides has been investigated. Two types of intermediate compounds have been isolated: 3-amino-6-chloro-2-(phenacylthio)pyridines and 2-aryl-2-hydroxy-1,2-dihydro-3H-pyrido[2,3-b][1,4]thiazines. Boiling 3-amino-6-chloro-2-mercaptopyridine with ortho-substituted phenacyl halides in ethanol has given 2-aryl-3H-pyrido[2,3-b][1,4]thiazines.For Communication XXVII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1262–1265, September, 1973. Original article submitted March 15, 1972,     

Methyl trifluoropyruvate in the Pictet-Spengler reaction

Condensation of methyl trifluoropyruvate with 2-(3,4-dimethoxyphenyl)ethylamine, tryptamine, and (D, L)-tryptophan yielded 1-methoxycarbonyl-1-trifluoromethyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline, 1-methoxycarbonyl-1-trifluoromethyl-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole, and Z-1-methoxycarbonyl-1-trifluoromethyl-3-carboxy-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole, respectively. The Z configuration of the latter was determined by x-ray structural analysis.A. N. Nesmayanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow, Russia. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1831–1836, August, 1992.     

Real-time assessment of cigarette smoke particle deposition in vitro

ABSTRACT: BACKGROUND: Recently there has been a rapid increase in approaches to assess the effects of cigarette smoke in vitro. Despite a range of gravimetric and chemical methods, there is a requirement to identify simpler and more reliable methods to quantify in vitro whole smoke dose, to support extrapolation and comparisons to human/in vivo dose. We have previously characterised an in vitro exposure system using a Borgwaldt RM20S smoking machine and a chamber exposing cellular cultures to whole smoke at the air-liquid interface. In this study we demonstrate the utility of a quartz crystal microbalance (QCM), using this exposure system, to assess real-time cigarette smoke particulate deposition during a 30 minute smoke exposure. Smoke was generated at various dilutions (1:5--1:400, smoke:air) using two cigarette products, 3R4F Kentucky reference and 1 mg commercially available cigarettes. The QCM, integrated into the chamber, assessed particulate deposition and data generated was compared to traditional chemical spectrofluorometric analysis. RESULTS: The QCM chamber was able to detect mass differences between the different products within the nanogram range. 3R4F reference cigarette smoke deposition ranged from 25.75 [PLUS-MINUS SIGN]2.30 mug/cm2 (1:5) to 0.22 [PLUS-MINUS SIGN]0.03 mug/cm2 (1:400). 1 mg cigarette smoke deposition was less and ranged from 1.42 [PLUS-MINUS SIGN]0.26 mug/cm2 (1:5), to 0.13 [PLUS-MINUS SIGN]0.02 mug/cm2 (1:100). Spectrofluorometric analysis demonstrated statistically significant correlation of particulate deposition with the QCM (p < 0.05), and regression R2 value were 97.4 %. The fitted equation for the linear model which describes the relationship is: QCM = [MINUS SIGN]0.6796 + 0.9744 chemical spectrofluorescence CONCLUSIONS: We suggest the QCM is a reliable, effective and simple tool that can be used to quantify smoke particulate deposition in real-time, in vitro and can be used to quantify other aerosols delivered to our chamber for assessment.     

Isotope dilution gas chromatography-mass spectrometry in the determination of benzene, toluene, styrene and acrylonitrile in mainstream cigarette smoke

A cryogenic trapping method with isotope dilution gas chromatography-mass spectrometry analysis has been developed for the determination of benzene, toluene, styrene and acrylonitrile in mainstream vapor phase cigarette smoke. The method is simple, direct, and quantitative. Vapor phase samples are collected cryogenically in a series of four traps following removal of the particulate phase with a Cambridge filter pad. For all four analytes, 75-85% of the total amounts recovered were found in the initial trap and less than 1% in the final trap. Assessment of instrumental precision by multiple injections of a sample gave relative standard deviations of less than 2%. Linear calibration for all analytes over the analysis range gave an r2 value greater than 0.99 with average relative standard deviations at the mean ranging from 1.4 to 8.2%. The cigarettes analyzed include a reference cigarette (Kentucky 1R4F), a commercial ultra-low "tar" mentholated cigarette, and two cigarettes that heat but do not burn tobacco. The values determined for the four analytes in the 1R4F samples are comparable to reported values of similar cigarettes. The cigarettes which heat rather than burn tobacco yield less of all four analytes compared to the other cigarettes in the study.     

Quantitative determination of selected compounds in a Kentucky 1R4F reference cigarette smoke by multidimensional gas chromatography and selected ion monitoring-mass spectrometry

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.     

1,1-Disubstituted-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indolecarboxylic acid esters and ketones. The base catalyzed transformation of 1-(2′,3′,4′,9′-tetrahydrospiro[cyclohexane-1,1′-[1H]pyrido[3,4-b]indol]-2-yl)alkanones into 2-(4,9-dihydro-3H-pyrido[3,4-b]indol-1-yl)-1 -alkylcyclohexanols

Condensation of 1H-indole-3-ethanamines 1 with cyclic β-keto esters 2 under azeotropic conditions followed by acid-catalyzed ring closure of the resulting enamines 3 gave 2′,3′,4′,9′-tetrahydrospiro[piperidine-3,1′,-[1H]pyrido[3,4-b]indole] -4-carboxylic acid alkyl esters 4 . Condensation of 1 with 2-acylcycloalkanones 8 gave two types of enamines, 10 and 11 , respectively. Enamines 10 on treatment with acid gave 1-(2′,3′,4′,9′-tetrahydro-3H-pyrido[3,4-b]indol-1-yl)-1-alkylcyclohexanols 17 . Compounds 17 were further dehydrated to give cycloalkane derivatives 19.     

An efficient synthesis of 4-(phenylsulfonyl)-4H-furo[3,4-b]indoles

The fused heterocycle 4-(phenylsulfonyl)-4H-furo[3,4-b]indole, which is an indole-2,3-quinodimethane synthetic analogue, is prepared in five steps from indole in 46% yield. A similar sequence is used to synthesize C-3 derivatives (3-methyl, 3-phenyl, and 3-heptyl). Thus, indole-3-carbaldehyde (1) is protected as the N-phenylsulfonyl derivative 2 and converted to the ethylene acetal 6. Lithiation at C-2 followed by treatment with an aldehyde affords the expected hydroxy acetals 7 and 8. Exposure to acid effects cyclization to the furoindoles 5 and 9. Furthermore, C-1 lithiation of furo[3,4-b]indole 9c followed by treatment with methyl iodide affords disubstituted furo[3,4-b]indole 10.     

卷烟主流烟气中碳中心自由基的自旋标记荧光表征

以自旋标记荧光探针4-((9-acridinecarbonyl)amino)-2,2,6,6-tetramethylpiperidin-1-oxyl(TEMPO-9-AC)研究了卷烟主流烟气中的碳中心自由基。以吸烟机抽吸卷烟,以弱荧光的TEMPO-9-AC作为捕集剂捕集卷烟主流烟气中的碳中心自由基,生成稳定的强荧光的碳中心自由基捕集加合物,以高效液相色谱-三重四极杆串联质谱联用仪(HPLC-MS/MS)对其结构进行了确认,并建立了高效液相色谱-荧光检测(HPLC-FLD)的定量方法。结果表明,方法的检出限为0.318 nmol/cig,相对标准偏差(RSD)为3.5%～9.7%;利用TEMPO-9-AC捕集体系鉴别出了10种碳中心自由基;对5种代表性卷烟烟气中的碳中心自由基进行了定量计算,获得了它们在主流烟气中碳中心自由基的含量数据,并发现碳中心自由基总量与焦油释放量之间具有高度的相关性。本法检出限低,重复性好,适用于卷烟主流烟气中碳中心自由基的结构验证及释放量的检测分析。     

Collection and preparation of sidestream cigarette smoke for trace elemental determinations by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

A novel method for the collection and preparation of sidestream cigarette smoke condensate is described for trace elemental analysis by inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry. The smoke collection method utilizes a specially designed chimney that collects and directs the sidestream smoke (SS) to a 2-stage trapping system consisting of an impaction trap followed by a 0.8 microm mixed cellulose ester filter. The samples are digested with nitric acid in a commercial heating block before analysis. The method limits of detection (LODs) are 1, 0.2, 2, 9, 6, and 7 ng/cigt for As, Cd, Pb, Ni, Se, and Cr, respectively. The SS collected from an industry reference cigarette, 1R4F, produced by the University of Kentucky was analyzed. The concentrations of As, Cd, and Pb in 1R4F were determined to be 27.3+/-2.1, 412+/-14, and 43.8+/-2.0 ng/cigt, respectively, while the concentrations of Ni, Cr, and Se are below the method LOD. Consequently, this novel method successfully addresses contamination, instrumentation, and collection issues for performing trace elemental analysis of sidestream cigarette smoke condensate.     

Nucleophilic substitution reactions in 2-chloropyridines and 2,5-dioxo-1,2,5,7-tetrahydro-1H-furo[3,4-b]pyridines

3-Cyano- and 3-carbamoyl-2-chloropyridines react with hydrazine hydrate to form substituted 3-amino-1H-pyrazolo[3,4-b]pyridines and 3-oxo-2,3-dihydro-1H-pyrazolo[3,4-b]pyridines. Hydrazine hydrate reacts with 3-carbamoyl-2-chloro-5-oxo-5,7-dihydrofuro[3,4-b]pyridine to form substituted 3,5-dioxo-2,3,5,7-tetrahydro-1H-pyrazolo[3,4-b]furo[3,4-e]pyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1218–1222, September, 1992.     

Analysis of aromatic amines in cigarette smoke

A method for the analysis of o-toluidine, o-anisidine, 2-naphthylamine, and 4-aminobiphenyl in cigarette mainstream smoke has been developed, which combines the sensitivity of their pentafluoropropionyl (PFP) derivatives in negative ion chemical ionization (NICI) mode with the selectivity of the gas chromatography/tandem mass spectrometry (GC/MS/MS) technique. The use of four deuterated analogues as internal standards along with the application of the standard addition method results in accurate and precise results; the interday precision for the aromatic amines was 3-10% and the accuracy ranged from 97-100%. This method was applied to two American-blend University of Kentucky reference cigarettes, eight American-blend market cigarettes, a bright (flue-cured) tobacco cigarette, and an electrically heated cigarette smoking system (EHCSS). For the American-blend cigarettes there was a linear correlation between aromatic amine yields and mainstream smoke 'tar' ('tar' = total particulate matter - (nicotine + water)), whereas the bright tobacco cigarette and the EHCSS demonstrated significantly lower aromatic amine yields on an equal 'tar' basis. The results support the hypothesis that the nitrogen content of the tobacco, and above all the cigarette combustion temperature, are determining factors for the yields of aromatic amines in smoke.     

Rapid and sensitive method for the determination of propylene oxide in cigarette mainstream smoke by gas chromatography-mass spectrometry

A rapid method using gas chromatography-mass spectrometry for the analysis of propylene oxide in cigarette mainstream smoke is reported. Validation data show the method, which requires a minimum of sample preparation, to be selective, sensitive, reliable, and robust. Propylene oxide is found in the University of Kentucky Reference Cigarettes 1R4F and 2R4F at concentrations of 0.93 and 0.65 microg/cigarette, respectively, with a quantitation limit of 0.135 microg/cigarette.