Optimization strategies of in-tube extraction (ITEX) methods

Abstract

Microextraction techniques, especially dynamic techniques like in-tube extraction (ITEX), can require an extensive method optimization procedure. This work summarizes the experiences from several methods and gives recommendations for the setting of proper extraction conditions to minimize experimental effort. Therefore, the governing parameters of the extraction and injection stages are discussed. This includes the relative extraction efficiencies of 11 kinds of sorbent tubes, either commercially available or custom made, regarding 53 analytes from different classes of compounds. They cover aromatics, heterocyclic aromatics, halogenated hydrocarbons, fuel oxygenates, alcohols, esters, and aldehydes. The number of extraction strokes and the corresponding extraction flow, also in dependence of the expected analyte concentrations, are discussed as well as the interactions between sample and extraction phase temperature. The injection parameters cover two different injection methods. The first is intended for the analysis of highly volatile analytes and the second either for the analysis of lower volatile analytes or when the analytes can be re-focused by a cold trap. The desorption volume, the desorption temperature, and the desorption flow are compared, together with the suitability of both methods for analytes of varying volatilities. The results are summarized in a flow chart, which can be used to select favorable starting conditions for further method optimization.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-015-8854-4) contains supplementary material, which is available to authorized users.

Investigation of carbon-based nanomaterials as sorbents for headspace in-tube extraction of polycyclic aromatic hydrocarbons

“…According to the high F values and low p values in Table 4, the number of strokes and the extraction temperature are the two parameters with the highest influence on the extraction yield [32,33]. In comparison, the extraction flow and desorption temperature are less decisive for the extraction yield.…”

“…A combination of a high number of strokes (e.g., 80 strokes) with a slow extraction flow (e.g., 30 μL s −1 ) results in long sampling time [32], which is not favorable for prompt/practical applications. A decrease in the extraction yield is reported [32], when a high extraction flow (e.g., 100 μL s −1 ) is applied. Thus, a suitable extraction flow for initial trials would be 50 μL s −1 .…”

“…After the samples were placed on the TrayCooler, the vials were transported to the SMM, where the samples were heated and stirred at 500 rpm for 15 min [32,33]. For the optimization of the extraction and desorption procedure, four factors (i.e., extraction temperature, extraction strokes, extraction flow, and desorption temperature) at three levels where set Table 1 displays the codification of the factors and levels.…”

Polymerization Inhibitors and Promoters for Unsaturated Polyester Resins; Use of Solid Phase MicroExtraction and Gas Chromatography Coupled to Mass Spectrometry for the Determination of 4-tert-Butyl Catechol and Acetylacetone

“…Sample preparation remains one of the more time-consuming and error-prone aspects of analytical chemistry. To overcome drawbacks of conventional extraction techniques, alternative miniaturized methods have been proposed both as solid phase microextraction, as Solid Phase MicroExtraction (SPME) [7][8][9], MicroExctraction by Packed Sorbent (MEPS) [10], Stir Bar Sorptive Extraction (Twister, SBSE) [11], Solid Phase Dynamic Extraction (Magic Needle, SPDE) [12], In-Tube Extraction (ITEX) [13] and liquid phase microextraction like Single-Drop MicroExtraction (SDME) [14], Hollow Fiber LiquidPhase Microextraction (HF-LPME) [15,16], Dispersive Liquid-Liquid Microextraction (DLLME) [17], Solvent Bar MicroExtraction (SBME) [18]. On-sample derivatizations applied in miniaturized extraction systems and their simultaneous GC and liquid chromatography analysis has been described for the determination of analytes in aqueous matrices [19,20].…”

Sorbent material characterization using in‐tube extraction needles as inverse gas chromatography column

“…Recently, Laaks et al. published a guideline about optimization strategies for a successful analysis with ITEX . To save time and costs, it was shown that design of experiment can be used to determine optimal extraction parameters .…”