Evaluation of needle trap micro extraction and solid phase micro extraction: obtaining comprehensive information on volatile emissions from in vitro cultures.
Volatile organic compounds (VOCs) emitted from in vitro cultures may reveal information on species and metabolism. Due to low nmol L-1 concentration ranges, pre-concentration techniques are required for gas-chromatography mass-spectrometry (GC-MS) based analyses. This study was intended to compare the efficiency of established micro-extraction techniques - solid-phase micro-extraction (SPME) and needle-trap micro-extraction (NTME) - for the analysis of complex VOC patterns. For SPME, a 75 μm Carboxen®/Polydimethylsiloxane fibre was used. NTME needle was packed with Divinylbenzene, Carbopack X, and Carboxen 1000. Headspace was sampled bi-directionally. Seventy-two VOCs were calibrated by reference standard mixtures in the range of 0.041 to 62.24 nmol L-1 by means of GC-MS. Both pre-concentration methods were applied to profile VOCs from cultures of Mycobacterium avium ssp. paratuberculosis (MAP). Limits of detection ranged from 0.004 to 3.93 nmol L-1 (median = 0.030 nmol L-1 ) for NTME and 0.001 to 5.684 nmol L-1 (median = 0.043 nmol L-1 ) for SPME. NTME showed advantages in assessing polar compounds such as alcohols. SPME showed advantages in reproducibility but disadvantages in sensitivity for N-containing compounds. Micro extraction techniques such as SPME and NTME are well suited for trace VOC profiling over cultures if limitations of each technique is taken into account.
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