Determination of N-Nitrososarcosine (NSAR) in tobacco

Transcription

1 JTI-Ökolab Vienna, Austria Determination of N-Nitrososarcosine (NSAR) in tobacco Madeleine Werneth, Jutta Pani, Bernhard Mayer-Helm 2014 CORESTA CONGRESS - ST46 Québec City, Canada October 2014

2 Background What is N-Nitrososarcosine (NSAR)? sarcosine nitrite N-Nitrosamine non-volatile nitrosamino acid formed by nitrosation of amino acid sarcosine listed on a draft list by the FDA for harmful and potentially harmful constituents in tobacco products and tobacco smoke IARC 2B: possibly carcinogenic to humans present in smokeless tobacco (ng/g range) Determination of NSAR in tobacco 2

3 Background What is N-Nitrososarcosine (NSAR)? exists as two stereoisomers partial double bonds restrict rotation solid state: Z-configuration in solution: isomerization to E-configuration with an isomeric ratio of about 1:1 at equilibrium [Chow et al., Organ. Magn. Reson. 1981, 15, 200] Determination of NSAR in tobacco 3

4 Background What is N-Nitrososarcosine (NSAR)? exists as two stereoisomers partial double bonds restrict rotation solid state: Z-configuration in solution: isomerization to E-configuration with an isomeric ratio of about 1:1 at equilibrium [Chow et al., Organ. Magn. Reson. 1981, 15, 200] Determination of NSAR in tobacco 4

5 Background Options for NSAR analysis regarding separation gas chromatography: necessity of time-consuming derivatization liquid chromatography: high polarity impedes retardation on conventional reversed phase columns regarding detection TEA: low selectivity ESI-MS impedes addition of ion pairing reagents low m/z range is susceptible to high noise LC-ESI-MS/MS using a suitable stationary phase? Determination of NSAR in tobacco 5

6 Method development Liquid chromatography Reversed phase conventional C18 no retardation C18 + ion pairing reagent triethylamine hampered ionization HILIC Hydrophilic Interaction Liquid Chromatography different stationary phases tested best results with Obelisc N from SIELC Final mobile phase 5 mm ammonium formate and 0.1% formic acid in 95/5 (5/95) water/acetonitrile Internal standard NSAR-D ng/ml NSAR standard solution 4.4 Determination of NSAR in tobacco 6

7 Method development Sample preparation 2 g sample spiking with internal standard NSAR-D 3 extraction with 25 ml of 2% aqueous formic acid for 45 min under agitation 10 ml of supernatant loaded onto solid supported liquid extraction cartridge elution with 2 20 ml of ethyl formate based on [Wu et al., Anal. Methods 2012, 4, 3448] evaporation to dryness under nitrogen at 50 C reconstitution with 1 ml of mobile phase B for subsequent LC-MS/MS analysis Determination of NSAR in tobacco 7

8 Method development Liquid chromatography CRP3 extract NSAR Matrix peaks well separated 2 optimized MRM transitions required Quantifier for quantification Qualifier for identity confirmation Determination of NSAR in tobacco 8

9 Method development Mass spectrometry negative electrospray ionization multiple reaction monitoring mode 7 tested transitions Precursor ion Product ion Relative intensity (%) Quantifier transition used for quantification Determination of NSAR in tobacco 9

10 Method development Mass spectrometry CRP3 extract NSAR Precursor ion Product ion Relative intensity (%) Qualifier transition used for 1. identification (relative intensities) 2. determination of LOQ/LOD Determination of NSAR in tobacco 10

11 Method development Stability of stock solutions Stock solutions in acetone Storage at -20 C? Why does peak area increase with the age of the standard? NSAR isomers! Determination of NSAR in tobacco 11

12 Method development Isomer separation co-elution: 30 min of re-equilibration separation: 5 min of re-equilibration Determination of NSAR in tobacco 12

13 Intensity (cps) Method development Isomeric ratio investigations 0 h Retention time (min) Determination of NSAR in tobacco 13

14 Intensity (cps) Method development Isomeric ratio investigations 1 h 2 h 3 h 4 h 5 h 7 h 8 h 10 h 12 h 13 h Retention time (min) 17 h 22 h Determination of NSAR in tobacco 14

15 Intensity (cps) Method development Isomeric ratio investigations 27 h 33 h 38 h 43 h 50 h 57 h Retention time (min) 65 h 75 h Determination of NSAR in tobacco 15

16 Intensity (cps) Method development Isomeric ratio investigations isomeric ratio is unstable changes with the age of the standard 84 h peak decreases and peak increases peak increases twice as fast as peak decreases Retention time (min) peak area sum increases isomers have different ESI-MS/MS response! factor of 2 hypothesized Determination of NSAR in tobacco 16

17 Intensity (cps) Method development Isomeric ratio investigation Chromatogram of NSAR at equilibrium 1 H NMR spectrum of NSAR at equilibrium * - CH 3 - CH 2 - Retention time (min) isomers have different ESI-MS/MS response! * measurements performed by Prof. Kählig, University of Vienna factor of 2 confirmed Determination of NSAR in tobacco 17

18 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

19 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

20 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

21 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

22 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

23 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

24 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

25 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

26 ESI-MS/MS behavior of NSAR isomers Why do E- and have different MS response? injection detection LC column ESI Q1 cell Q2 cell Q3 cell

27 Quantification of NSAR Approaches to compensate for different ESI-MS/MS response Correction of the peak areas by the determined factor Adjustment of the isomeric ratio of the calibration standard to that of the real sample separation method is required earlier elution hampered matrix separation and lower sensitivity degree of response difference might be instrument dependent co-elution method can be used better matrix separation and higher sensitivity correction is instrument independent Determination of NSAR in tobacco 27

28 Peak area percentage of (%) Quantification of NSAR Preparation of external calibration standard sample standard at 50 C standard at 60 C external calibration calibration standard heated at 60 C for 90 min Time (min) standard at 25 C internal standard correction NSAR-D 3 behaves similarly Determination of NSAR in tobacco 28

29 Quantification of NSAR Method validation CRP2 CRP3 Intra-day repeatability (% RSD, n = 5) 6 5 Inter-day repeatability (% RSD, n = 7) 8 5 LOD (ng/g) 4 9 LOQ (ng/g) Recovery NSAR (%) 17 9 NSAR-D 3 (%) 18 9 Determination of NSAR in tobacco 29

30 Quantification of NSAR Results Description NSAR (ng/g) CRP1 Swedish-style snus pouch < LOD CRP2 American-style loose moist snuff 36 ± 8 CRP3 American-style loose dry snuff powder 58 ± 9 CRP4 American-style loose-leaf chewing tobacco < LOQ tobacco of 3R4F Kentucky Reference Cigarette < LOQ Determination of NSAR in tobacco 30

31 References Y. L. Chow, J. Polo. The nuclear magnetic resonance spectra of N-nitroso-N-alkyl amino acids. Org. Magn. Reson. 1981, 15, 200. J. Wu, W. S. Rickert, A. Masters, P. Joza. Determination of N-nitrososarcosine in tobacco and smokeless tobacco products using isotope dilution liquid chromatography tandem mass spectrometry. Anal. Methods 2012, 4, M. Werneth, J. Pani, S. Pummer, M.-T. Weber, L. Hofbauer, G. Pour, H. Kählig, B. Mayer-Helm, H. Stepan. Stereospecific mass spectrometric response of N-nitrososarcosine and its impact on quantification in smokeless tobacco products. Submitted to J. Mass Spectrom. Determination of NSAR in tobacco 31

32 I want to thank my team! Madeleine Werneth Bernhard Mayer-Helm Stefan Pummer Special thanks to Hanspeter Kählig, University of Vienna, for NMR measurements Determination of NSAR in tobacco 32

33 Thank you for your attention! Determination of NSAR in tobacco 33