title: A retention index calculator simplifies identification of plant volatile organic compounds.
abstract: BACKGROUND
  Plant volatiles (PVOCs) are important targets for studies in natural products, chemotaxonomy and biochemical ecology. The complexity of PVOC profiles often limits research to studies targeting only easily identified compounds. With the availability of mass spectral libraries and recent growth of retention index (RI) libraries, PVOC identification can be achieved using only gas chromatography coupled to mass spectrometry (GCMS). However, RI library searching is not typically automated, and until recently, RI libraries were both limited in scope and costly to obtain.
  
  
  OBJECTIVE
  To automate RI calculation and lookup functions commonly utilised in PVOC analysis.
  
  
  METHODS
  Formulae required for calculating retention indices from retention time data were placed in a spreadsheet along with lookup functions and a retention index library. Retention times obtained from GCMS analysis of alkane standards and Koeberlinia spinosa essential oil were entered into the spreadsheet to determine retention indices. Indices were used in combination with mass spectral analysis to identify compounds contained in Koeberlinia spinosa essential oil.
  
  
  RESULTS
  Eighteen compounds were positively identified. Total oil yield was low, with only 5 ppm in purple berries. The most abundant compounds were octen-3-ol and methyl salicylate. The spreadsheet accurately calculated RIs of the detected compounds.
  
  
  CONCLUSIONS
  The downloadable spreadsheet tool developed for this study provides a calculator and RI library that works in conjuction with GCMS or other analytical techniques to identify PVOCs in plant extracts.
authors.affiliation: USDA, ARS, Jornada Experimental Range, Las Cruces, NM 88003, USA. malucero@nmsu.edu
authors.forename: Mary
authors.initials: M
authors.lastname: Lucero
authors.forename: Rick
authors.initials: R
authors.lastname: Estell
authors.forename: María
authors.initials: M
authors.lastname: Tellez
authors.forename: Ed
authors.initials: E
authors.lastname: Fredrickson
mesh_terms: D000465:Algorithms; D008401:Gas Chromatography-Mass Spectrometry; D005843:Geography; D019684:Magnoliopsida / Q000737:chemistry* / Q000254:growth & development; D013058:Mass Spectrometry; D009516:New Mexico; D009822:Oils, Volatile / Q000032:analysis / Q000302:isolation & purification; D010936:Plant Extracts / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D010938:Plant Oils / Q000032:analysis / Q000302:isolation & purification; D015203:Reproducibility of Results; D052617:Solid Phase Microextraction; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000302:isolation & purification
chemical_list: D009822:Oils, Volatile; D010936:Plant Extracts; D010938:Plant Oils; D055549:Volatile Organic Compounds