title: A practical methodology to measure unbiased gas chromatographic retention factor vs. temperature relationships.
abstract: Compound identification continues to be a major challenge. Gas chromatography-mass spectrometry (GC-MS) is a primary tool used for this purpose, but the GC retention information it provides is underutilized because existing retention databases are experimentally restrictive and unreliable. A methodology called "retention projection" has the potential to overcome these limitations, but it requires the retention factor (k) vs. T relationship of a compound to calculate its retention time. Direct methods of measuring k vs. T relationships from a series of isothermal runs are tedious and time-consuming. Instead, a series of temperature programs can be used to quickly measure the k vs. T relationships, but they are generally not as accurate when measured this way because they are strongly biased by non-ideal behavior of the GC system in each of the runs. In this work, we overcome that problem by using the retention times of 25 n-alkanes to back-calculate the effective temperature profile and hold-up time vs. T profiles produced in each of the six temperature programs. When the profiles were measured this way and taken into account, the k vs. T relationships measured from each of two different GC-MS instruments were nearly as accurate as the ones measured isothermally, showing less than two-fold more error. Furthermore, temperature-programmed retention times calculated in five other laboratories from the new k vs. T relationships had the same distribution of error as when they were calculated from k vs. T relationships measured isothermally. Free software was developed to make the methodology easy to use. The new methodology potentially provides a relatively fast and easy way to measure unbiased k vs. T relationships.
authors.affiliation: Department of Horticultural Science, University of Minnesota, 1970 Folwell Avenue, St. Paul, Minnesota 55108, USA. Electronic address: pengx107@umn.edu.
authors.forename: Baijie
authors.initials: B
authors.lastname: Peng
authors.affiliation: Department of Horticultural Science, University of Minnesota, 1970 Folwell Avenue, St. Paul, Minnesota 55108, USA. Electronic address: kuoxx110@umn.edu.
authors.forename: Mei-Yi
authors.initials: MY
authors.lastname: Kuo
authors.affiliation: Department of Horticultural Science, University of Minnesota, 1970 Folwell Avenue, St. Paul, Minnesota 55108, USA. Electronic address: yangp@carleton.edu.
authors.forename: Panhia
authors.initials: P
authors.lastname: Yang
authors.affiliation: Department of Horticultural Science, University of Minnesota, 1970 Folwell Avenue, St. Paul, Minnesota 55108, USA. Electronic address: hewi0041@umn.edu.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Hewitt
authors.affiliation: Department of Horticultural Science, University of Minnesota, 1970 Folwell Avenue, St. Paul, Minnesota 55108, USA. Electronic address: boswell@umn.edu.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Boswell
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D012985:Software Design; D013696:Temperature; D013997:Time Factors
keywords: Gas chromatography–mass spectrometry; Retention database.; Retention library; Retention prediction; Retention projection