Evaluation of needle trap micro‐extraction and solid‐phase micro‐extraction: Obtaining comprehensive information on volatile emissions from in vitro cultures

Abstract

Volatile organic compounds (VOCs) emitted from in vitro cultures may reveal information on species and metabolism. Owing to low nmol L 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 fiber was used. The NTME needle was packed with divinylbenzene, Carbopack X and Carboxen 1000. The headspace was sampled bi-directionally. Seventy-two VOCs were calibrated by reference standard mixtures in the range of 0.041-62.24 nmol L by means of GC-MS. Both pre-concentration methods were applied to profile VOCs from cultures of Mycobacterium avium ssp. paratuberculosis. Limits of detection ranged from 0.004 to 3.93 nmol L (median = 0.030 nmol L ) for NTME and from 0.001 to 5.684 nmol L (median = 0.043 nmol L ) 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 the limitations of each technique is taken into account.

Core profile of volatile organic compounds related to growth of Mycobacterium avium subspecies paratuberculosis – A comparative extract of three independent studies

“…Different techniques of pre-concentration were used in the three studies (Table 2). The limit of detection of several substances was shown to depend on the pre-concentration technique [26, 27]. Therefore, some alkanes such as Methyl-cyclo-pentane could not be detected in Study 1.…”

“…Therefore, some alkanes such as Methyl-cyclo-pentane could not be detected in Study 1. Other substances, which were assigned to the MAP-indicative profile in at least one of the studies were not detectable via SPME at all [27], i. e. alcohols (3-Octanol), 2-Methyl-2-butenal, Heptanal, Benzene, 3-Methylfuran and 2-Butanone, others were not captured by NTME, for example Methyl-acetate and 2-Methylfuran [27]. In addition, the concentration levels of individual substances varied amongst the three studies.…”

Non-Invasive O-Toluidine Monitoring during Regional Anaesthesia with Prilocaine and Detection of Accidental Intravenous Injection in an Animal Model

“…Preconcentration was performed by means of Carboxen/polydimethylsiloxane (CAR/PDMS)-SPME-fibres (75 µm, SIGMA, Bellefonte, PA, USA) using a CombiPAL autosampler (CTC analytics AG, Zwingen, Switzerland) with 3 min equilibration time at 42 • C and 7 min adsorption time. For the separation and detection of o-toluidine desorbed from the SPME fibre, a GC-MS system (Agilent 7980A/5975C inert XL MSD, Santa Clara, CA, USA) was used as described before [27]. Quantification was performed via 5-point calibration in the range of 66.3 to 1060.5 ppbV (0.32-5.07 ug/mL).…”

“…data (in counts per second) from breath measurements were processed by means of a custom made Matlab-based algorithm [14]. Needle trap micro extraction coupled with GC-MS was applied as previously described to verify the presence of o-toluidine in exhaled breath [27,29]. O-toluidine in exhaled breath was quantified via 4-point calibration with pure reference substance in the range of 1-100 ppbV.…”

Volatile Organic Compounds, Bacterial Airway Microbiome, Spirometry and Exercise Performance of Patients after Surgical Repair of Congenital Diaphragmatic Hernia

“…For that purpose, a mixture of gaseous standards (Gas-MIX, Ionicon Analytik GmbH, Innsbruck, Austria) and aqueous solutions of pure reference substances (Sigma Aldrich, Darmstadt, Germany) were evaporated by means of a liquid calibration unit (LCU, Ionicon Analytik GmbH, Innsbruck, Austria). Concentration levels of the gas standards were prepared from 1 ppb to 500 ppb by diluting the standards with nitrogen and water with a matrix adapted humidity of 25 g/m 3 as previously described [32,33]. Evaporated standard gas was pre-concentrated onto NTDs and analyzed by GC-MS.…”