@article {2129,
	title = {Correction of H3+ contributions in hydrogen isotope ratio monitoring mass spectrometry},
	journal = {Anal Chem},
	volume = {73},
	year = {2001},
	note = {Sessions, A LBurgoyne, T W
Hayes, J M
eng
2001/02/24 12:00
Anal Chem. 2001 Jan 15;73(2):192-9.
},
	month = {Jan 15},
	pages = {192-9},
	abstract = {Two fundamentally different approaches, termed "pointwise" and "peakwise," are currently used to correct hydrogen isotope ratio monitoring data for the presence of H3+ ion contributions. Consideration of the underlying assumptions shows that the peakwise approach is valid only for peaks with the same functional shape and only when background signals do not vary. The pointwise correction is much more versatile and can be used even when peak shapes and sizes, as well as background signals, vary significantly. It is not exact and is limited in accuracy by (1) the signal-broadening effects of electronic time constants, (2) the analog-to-digital conversion frequency, and (3) the highest frequency of the sample signal. To minimize errors for typical gas chromatographic signals, time constants of <500 ms and analog-to-digital sampling intervals of < or =250 ms are needed. Errors are further minimized by matching sample and standard peaks in both amplitude and D/H ratio. Using the pointwise algorithm, we demonstrate that a series of 14 homologous n-alkanes varying in concentration over a 5-fold range can be analyzed with a mean precision of 2.3 per thousand and no systematic errors.},
	isbn = {0003-2700 (Print)0003-2700 (Linking)},
	doi = {10.1021/ac000489e},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/11199965},
	author = {Sessions, A. L. and Burgoyne, T. W. and Hayes, J. M.}
}
@article {2128,
	title = {Determination of the the H3 factor in hydrogen isotope ratio monitoring mass spectrometry},
	journal = {Anal Chem},
	volume = {73},
	year = {2001},
	note = {Sessions, A LBurgoyne, T W
Hayes, J M
eng
2001/02/24 12:00
Anal Chem. 2001 Jan 15;73(2):200-7.
},
	month = {Jan 15},
	pages = {200-7},
	abstract = {The H3 factor, K, is a parameter required in high-precision, mass spectrometric analyses of hydrogen isotopic abundances. When H2 is used as the sample gas, R* = R - Ki2, where R* is the true HD/H2 ratio, R is the observed (mass 3)/(mass 2) ion-current ratio, and i2 is the ion current at mass 2. Four different methods for the determination of K were defined and tested under conditions characteristic of isotope ratio monitoring systems. Three of these were peak-based. The fourth employed steady flows of H2 from a conventional inlet system. Results obtained using the latter method were more precise (standard deviation of K = 0.1 versus approximately 0.6 ppm mV(-1) for the peak-based methods). However, use of the resulting values of K for correction of isotope ratio monitoring GC/MS results led to systematic errors as large as 9 per thousand, whereas use of the peak-based values led to no systematic errors. Values of K were only weakly dependent on the pressure of He, declining approximately 5\% for each 10-fold increase in P(He). Small variations in partial pressures of H2O and CH4, potential contaminants under isotope ratio monitoring conditions, had no significant effect on values of K.},
	isbn = {0003-2700 (Print)0003-2700 (Linking)},
	doi = {10.1021/ac000488m},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/11199966},
	author = {Sessions, A. L. and Burgoyne, T. W. and Hayes, J. M.}
}
@article {811,
	title = {Fractionation of hydrogen isotopes in lipid biosynthesis},
	journal = {Organic Geochemistry},
	volume = {30},
	year = {1999},
	note = {254efTimes Cited:281Cited References Count:26},
	pages = {1193-1200},
	abstract = {Isotopic compositions of carbon-bound hydrogen in individual compounds from eight different organisms were measured using isotope-ratio-monitoring gas chromatography-mass spectrometry. This technique is capable of measuring D/H ratios at natural abundance in individual lipids yielding as little as 20 nmol of H-2, and is applicable to a wide range of compounds including hydrocarbons, sterols, and fatty acids. The hydrogen isotopic compositions of lipids are controlled by three factors: isotopic compositions of biosynthetic precursors, fractionation and exchange accompanying biosynthesis, and hydrogenation during biosynthesis. delta D values of lipids from the eight organisms examined here suggest that all three processes are important for controlling natural variations in isotopic abundance. n-Alkyl lipids are depleted in D relative to growth water by 113-262 parts per thousand, while polyisoprenoid lipids are depleted in D relative to growth water by 142-376 parts per thousand. Isotopic variations within compound classes (e.g., n-alkanes) are usually less than similar to 50 parts per thousand, but variations as large as 150 parts per thousand are observed among isoprenoid lipids from a single organism. Phytol is consistently depleted in D by up to 50 parts per thousand relative to other isoprenoid lipids. Inferred isotopic fractionations between cellular water and lipids are greater than those indicated by previous studies. (C) 1999 Elsevier Science Ltd. All rights reserved.},
	issn = {0146-6380},
	doi = {10.1016/S0146-6380(99)00094-7},
	author = {Sessions, A. L. and Burgoyne, T. W. and Schimmelmann, A. and Hayes, J. M.}
}
