Keywords: Programmed Temperature Vaporizers, PTV, Split/Splitless Inlet, Septumless Sample Introduction, Oxidative Decomposition, Thermal Degradation
The benefits of using a Programmed Temperature Vaporizer (PTV) type inlets instead of hot split/splitless (S/SL) inlets for the liquid and headspace (HS) measurements of volatile compounds are shown. The use of a PTV (GERSTEL CIS 4) for Solid Phase MicroExtraction (SPME) measurements has an advantage due to the use of a septumless head (SLH) instead of a septum for sealing the inlet. The significant accumulation of septum material inside the liner by SPME injections is demonstrated. This will lead to higher chromatographic background, restrictions in the flow through the inlet and in worst case to the loss of the fiber. This problem does not appear when using septumless sample introduction systems.
Keywords: Pesticide Analysis, Matrix Effects, QuEChERS, Automated Liner Exchange, ALEX, Cooled Injection System, CIS, PTV
Fruit and vegetable extracts that are produced following the well established QuEChERS method typically contain a significant amount of nonvolatile matrix material. After several injections of such extracts into the GC, sufficient matrix residue will be present in the GC inlet liner to lower or sometimes even increase the response of certain pesticide compounds affecting the accuracy of the analysis. The performance can be restored by exchanging the GC inlet liner. Normally this has to be done manually which means stopping the analysis sequence. The GERSTEL Automated Liner Exchange system (ALEX) provides an automated solution. As this study shows, automated liner exchange restores the original performance of the GC system and is therefore generally useful for the analysis of extracts that contain nonvolatile matrix residue.
Keywords: Thermal Desorption, Air Analysis, VOC, JHAP
System performance of the GERSTEL TDS in conjunction with an Agilent GC/MSD system was tested using a 43 component gas calibration mixture which was developed for the Japanese Hazardous Air Pollutants (JHAP) monitoring method. A five point calibration curve was obtained for each compound (2-20 ppb@1L) with an average correlation coefficient of 0.996. Twelve replicate analyses of the mixture, where each component was present at 20 ppb@1L, gave an average percent relative standard deviation (%RSD) of 4.6.
Keywords: Thermal Desorption, PTV, Inlet liner, Sample Introduction
PTV inlets are often used for cryo-focussing and trapping of analytes for large volume, headspace, and thermal desorption applications. Selecting and optimizing trapping conditions for thermal desorption applications can be challenging, since often a wide variety of analytes spanning a broad boiling point range are present in each sample. For efficient, high fl ow thermal desorption systems such as the GERSTEL TDS, a variety of inlet liner configurations with different trapping characteristics are available. This study was conducted to qualify the best type of liner for the determination of alkanes, aromatics and oxygenated compounds by thermal desorption GC. Inlet liners packed with materials of different trapping strengths ranging from glass wool to adsorbents (Carbotrap™ or Tenax TA™) to special purpose multi-bed liners were used to cryo-focus test mixtures of alkanes, aromatics and oxygenates thermally desorbed from air sampling adsorbent tubes. The parameters trapping temperature and desorption fl ow were optimized for the best trapping efficiency. Guidelines are given for choosing appropriate trapping conditions for these analyte classes.
Keywords: Gas Chromatography, Injector, PTV, Automated Liner Exchange, Sample Preparation, Sample Clean-up, Large Volume Injection, LVI
Sample clean-up steps, which are needed in order to prepare for example environmental or food samples for pesticide analysis, are time-consuming and a potential source of errors. Simplification or elimination of such procedures is often the motivation behind the development of new analytical methods and new instrumentation. Unfortunately, analytical instruments normally do not tolerate introduction of “dirty” samples or even “dirty” extracts. For example, extracts containing suspended matter or high molecular weight compounds contaminate a GC inlet within a few injections, causing peak broadening or even loss of sensitive compounds. Reducing or eliminating clean-up steps will result in “dirty” extracts and daily – or even hourly - maintenance of the GC system.
Keywords: Cooled Injection System, CIS, PTV
Below is a list of publications on CIS/PTV inlets for your reference. These cannot be downloaded due to Copyright protection.
Optimization of a preparative capillary gas chromatography-mass spectrometry system for the isolation and harvesting of individual polycyclic aromatic hydrocarbons. Mandalakis, M.; Gustafsson, O. ;J. Chromatogr. A. 2003, 996, 163-172.
Stir bar sorptive extraction and large volume injection gas chromatography to determine a group of endocrine disrupters in water samples. Penalver, A. et al. ;J. Chromatogr. A. 2003, 1007, 1-9.
Large-volume injection in capillary gas chromatography using a programmed-temperature vaporizing injector in the on-column or solvent-vent injection mode Jeroen C. Bosboom, Hans-Gerd Janssen, Hans G.J. Mol, Carel A. Cramers Journal of Chromatography A, 724 (1996) 384-391
Headspace GC-SCD monitoring of low volatile sulfur compounds during fermentation and in wine D. Rauhut, H. Kürbel, K. MacNamara, M. Grossman Analusis, 1998, 26, 142-145
GC Analysis of Trichloroacetic Acid in Water Samples by Large-Volume Injection and Thermal Decarboxylation in a Programmed-Temperature Vaporizer D. Drechsel, K. Dettmer, W. Engewald, Th. Bittner, J. Efer Chromatographia 2001, 54, August (No. ¾) 151-154
The Loss of Volatile Esters from Cookies S. Heiderich, Gary Reineccius Perfumer & Flavorist. Vol. 26, November/December 2001
SPME: An Interesting Sampling Technique for Occupational Measurements W. Nyiry, S. Springer, N. Winker Symposium on Capillary Chromatography and Electrophoresis -Riva del Garda, Italy (2002)
Influence on Recovery of Stir Bar Sorptive Extraction (SBSE) of Water/PDMS Phase Ratio, Volume of PDMS Coated onto the Stir Bar and Sampling Temperature C. Bicchi, C. Cordero, C. Iori, P. Rubiolo, P. Sandra Symposium on Capillary Chromatography and Electrophoresis-Riva del Garda, Italy (2002)
Large-Volume PTV Injection: Comparison of Direct Water Injection and In-Vial Extraction for GC Analysis of Triazines J. Teske, J. Efer, W. Engewald Chromatographia Vol. 47, No. ½. January 1998
Thermal Degradation Observed with Different Injection Techniques: Quantitative Estimation by the use of Thermolabile Carbamate Pesticides Hans-Martin Müller, Hans-Jürgen Stan Journal of High Resolution Chromatography, 1990, 759
Large-Volume PTV Injection: New Results on Direct Injection of Water Samples in GC Analysis J. Teske, J. Efer, W. Engewald Chromatographia Vol. 46, No. 11/12, December 1997
Design, Performance and Applicability of a Newly Developed Sample Introduction System for Use with Stir Bar Sorptive Extraction (SBSE) A. Hoffman, B. Kolaghar, C. Heinz, S. Funke, B. Rose Symposium on Capillary Chromatography and Electrophoresis-Riva del Garda, Italy (2002)
Programmed temperature vaporiser-based injection in capillary gas chromatography W. Engewald, J. Teske, J. Efer Journal of Chromatography A, 856 (1991) 259-278