Evaluation of Purge-and-Trap Parameters: Optimization Using a Statistical Design

Abstract

Literature studies emphasize the importance of experimentally optimizing all purge-and-trap parameters to obtain adequate amounts of representative compounds for gas chromatographic analyses. Conventional "one variable at a time" evaluation of method parameters calls for exhaustive experimentation, systematically altering one variable at a time until an optimum point is attained.Response surface methodology was utilized in this study to determine the best combination of sampling parameters that maximized the amounts (with respect to proportion) of compounds isolated from dry pet foods. Purge time, sample size, and their interaction had the greatest effects on response. Quantities of volatile flavors isolated could be optimized and the sampling time could be reduced using response surface methodology.One objective for the quantitative and qualitative analyses of flavors is to correlate sensory data with instrumental results to determine flavor components of organoleptic importance. Volatile flavor compounds occur in foods in defined proportions, and they exhibit their desirable sensory attributes in given concentration ranges. Therefore, the analytical methods used to assay flavors must yield data that are reflective of the original composition of a sample. Unfortunately, the isolation and characterization of flavor compounds is very challenging because flavor compounds have trace level properties, complex nature, and diverse chemical classes.Purge-and-trap, also referred to as dynamic headspace sampling (DHS), is a means of enriching headspace gas prior to GC analyses. DHS with thermal desorption has been shown to be highly sensitive and relatively inert in the analyses of fragrances and food flavors (7-3). Cessna and Kerr (4) commented that the use of purge-and-trap systems for the analysis of aroma compounds has grown in popularity because of greater sensitivity in detecting both volatile and semi-volatile organic compounds. 22

Instrumental Methods of Analysis

“…As Buckholz et al (1980) noted, operating conditions have a strong influence on the composition of the aroma isolate. Sucan et al (1998) used response surface methodology to optimise their purge and trap method for a study of dry dog food aroma. This approach, once optimised, yielded a very good quality aroma isolate.…”