HS-SPME-GC-MS Analyses of Volatiles in Plant Populations-Quantitating Compound × Individual Matrix Effects.

Elizabeth A Burzynski-Chang,Imelda Ryona,Bruce I Reisch,James J Giovannoni,Itay Gonda,Gavin L Sacks,Majid R Foolad

doi:10.3390/molecules23102436

Abstract

Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography–mass spectrometry (GC-MS) is widely employed for volatile analyses of plants, including mapping populations used in plant breeding research. Studies often employ a single internal surrogate standard, even when multiple analytes are measured, with the assumption that any relative changes in matrix effects among individuals would be similar for all compounds, i.e., matrix effects do not show Compound × Individual interactions. We tested this assumption using individuals from two plant populations: an interspecific grape (Vitis spp.) mapping population (n = 140) and a tomato (Solanum spp.) recombinant inbred line (RIL) population (n = 148). Individual plants from the two populations were spiked with a cocktail of internal standards (n = 6, 9, respectively) prior to HS-SPME-GC-MS. Variation in the relative responses of internal standards indicated that Compound × Individual interactions exist but were different between the two populations. For the grape population, relative responses among pairs of internal standards varied considerably among individuals, with a maximum of 249% relative standard deviation (RSD) for the pair of [U13C]hexanal and [U13C]hexanol. However, in the tomato population, relative responses of internal standard pairs varied much less, with pairwise RSDs ranging from 8% to 56%. The approach described in this paper could be used to evaluate the suitability of using surrogate standards for HS-SPME-GC-MS studies in other plant populations.

Highlights

Headspace solid-phase microextraction (HS-SPME) is widely employed to isolate and pre-concentrate volatiles prior to gas chromatography–mass spectrometry (GC-MS) analysis [1,2,3,4].SPME has several advantages over other sample preparation techniques, including its avoidance of solvents, ease of automation, and small sample size requirements [5]
We describe our approach, and use it to evaluate the extent of Compound × Individual matrix effects in a grape mapping population and a tomato recombinant inbred line (RIL) population
As we were studying plant populations, these standards were either isotopic analogues of plant-derived odorants, or non-labeled surrogate standards previously reported for use in plant volatile profiling

Summary

Introduction

SPME has several advantages over other sample preparation techniques (e.g., solid-phase extraction or liquid–liquid extraction), including its avoidance of solvents, ease of automation, and small sample size requirements [5] These features make SPME well suited for studies that require analysis of a large number of samples, e.g., when evaluating plant populations used by breeders in investigating the genetic underpinnings of traits [6,7]. The preferred choice for an internal standard is a stable isotope-labeled analogue of the target analyte, i.e., stable isotope dilution analysis (SIDA) [20] This technique has been employed in grape mapping populations to identify candidate genes associated with monoterpene production (“muscat” aroma) [12] following a solid-phase extraction, and in basmati rice grains for phenotype 2-acetyl-1-pyrroline (“nutty” aroma) following SPME [21]. It is common for SPME-based volatile phenotyping studies to use a single surrogate standard or to normalize responses to the total ion count

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