Open Probe Fast GC-MS - Real Time Analysis with Separation

Uri Keshet (1), Tal Alon (1,2) , Alexander B. Fialkov (1), and Aviv Amirav (1,2) 

1.   School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.  

2.   Aviv Analytical Ltd, 3 Haarad Street, Tel Aviv 69107, Israel  

Abstract 

An Open Probe inlet was combined with a low thermal mass (LTM) ultra fast gas chromatograph (GC) and a mass spectrometer (MS) of a standard GC-MS for obtaining real time analysis with separation. The Open Probe is based on a vaporization oven that is open to room air with an addition of helium purge flow protection that eliminates air leakage into the oven, column and MS ion source. Sample introduction into the Open Probe is as simple as; touch the sample, insert the sample holder into the open probe oven and have the results in 30 s with under a minute ready for next analysis. 

The Open Probe Fast GC-MS revolutionizes the field of real time analysis as it provides several major benefits in comparison with DART, DESI and other ambient ionization methods or MS probes:

• GC separation,
• Library identification
• Absence of ion suppression effects
• Uniform electron ionization response for improved quantitation
• Uses a low cost quadrupole MS (of GC-MS). 

Watch the short video below and keep reading to find out more about the new Open Probe fast GC-MS which was combined with Agilent 7890B GC and 5977 MS and learn about its several demonstrated application and benefits. 

If the video doesn't show, you can click here to see it on Youtube.

Pulsed Flow Modulation GCxGC-MS with Cold EI – The Emergence of Novel Concept of GCxGCxMS

Aviv Amirav, Tal Alon, Uri Keshet and Alexander Fialkov 

Tel Aviv University and Aviv Analytical

Introduction 

Comprehensive two dimensional GCxGC-MS significantly improves the separation of the GC. However, it suffers from complexity and high cost of purchase and maintenance cooling gases. In addition, with standard electron ionization the molecular ions are often weak or absent, particularly in the analysis of complex hydrocarbon mixtures. 

We developed Pulsed Flow Modulation (PFM) for obtaining GCxGC-MS with supersonic molecular beams (SMB) (also named Cold EI) based on quadrupole mass analyzer and without any added cooling gas. For further information on the concept of Pulsed Flow Modulation GCxGC please read M. Poliak, M. Kochman and A. Amirav, "Pulsed Flow Modulation Comprehensive Two Dimensional Gas Chromatography" J. Chromatogr. A. 1186, 189-195 (2008) (also Israel patent number 176724 and USA patent number 7518103). 

In PFM-GCxGC-MS with Cold EI, sample compounds which elute from the first GC column are temporarily stored in a fused silica transfer line and are pulsed periodically injected by ~25 ml/min He gas pulse into the second column. After the pulse, ~20 ml/min He develops the chromatography in the second column for a few seconds (typically 4s). PFM is simple to construct, does not require any added gas with Cold EI and the injection time can be tuned, hence PFM-GCxGC-MS with Cold EI is enabled with quadrupole MS. The increased PFM second GC column flow rate is seamlessly handled by the Cold EI nozzle vacuum chamber. 

We combined PFM-GCxGC with the Aviv Analytical 5975-SMB GC-MS with Cold EI. PFM-GCxGC-MS with Cold EI combines the improved separation of GCxGC with the features of Cold EI of enhanced molecular ions and extended mass spectral isomer and isotope information for the provision of ultimate sample information. Unique to PFM-GCxGC-MS with Cold EI is that as the second dimension elution time is increased the molecular ion mass is reduced for easier GCxGCxMS like identification. 

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI enables effective PFM-GCxGC-MS with Cold EI and provides ultimate level of information with an example of the analysis of JP8 jet fuel (with some Biodiesel related FAMEs). This article also describes and exposes the emergence of the novel concept of GCxGCxMS. 

Advanced GC-MS Presentations of Aviv Analytical in Pittcon 2013

Aviv Amirav and Tal Alon, Tel Aviv University and Aviv Analytical, Emails: amirav@tau.ac.il and polaris@tau.ac.il

In the 2013 Pittcon meeting (Philadelphia 17-21 March 2013) Prof. Aviv Amirav and Dr. Tal Alon will present six advanced GC-MS presentations performed mostly with the 5975-SMB GC-MS with Cold-EI. Brief abstracts of these presentations are given below (we will be happy to provide the full presentations upon request). 

We will be happy to meet you at our posters (240-11, 1210-6, 2180-3) or at the lecture halls after our oral presentations (1430-3, 2080-4, 2330-5) to discuss your advanced GC-MS needs and challenging applications, or any other topic.

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI brings the next GC-MS revolution and largely improves GC-MS performance for a broad range of applications. 

Dramatically Improved Hydrocarbon Analysis with the 5975-SMB GC-MS with Cold EI

Alexander B. Fialkov and Aviv Amirav, Tel Aviv University and Aviv Analytical

In the 2012 IMSC meeting (15-21 September 2012) Dr. Alexander Fialkov and Prof. Aviv Amirav present, among other things, the dramatically improved petroleum-sample analysis performed with the 5975-SMB GC-MS with Cold-EI. A brief abstract of the presentation is given below and we shall be happy to provide our full power point presentation upon request.

Presentation Number PTu-111, Tuesday 9/18, 11:10-14:40, Event Hall
Title: "Dramatically Improved Hydrocarbon Analysis with the 5975-SMB GC-MS with Cold EI"

The Aviv Analytical 5975-SMB GC-MS with Cold EI provides enhanced molecular ions for all hydrocarbons and thus enables their improved analysis including their isomer distributions. In addition, isomers and structurally related fragments mass spectral peaks are exhibited which enables NIST library identification. Furthermore, extended range of compounds are amenable for analysis with short column and high column flow rates, including low volatility large oil and wax compounds that cannot be analyzed by standard GC-MS. In addition, the 5975-SMB GC-MS enables much shorter analysis time and improved sensitivity that could be up to and over three orders of magnitude better on the molecular ions of large hydrocarbons.

Representative results

The figure above compares Cold EI (upper traces) with Standard EI (bottom traces) in the analysis of a Petroleum related hydrocarbon mixture. (60 m column 1.2 ml/min flow rate in Cold EI). While the TIC mass chromatograms are similar, the Cold EI mass spectral content is dramatically improved. The mass spectra are of the isoprenoid isomer of C18H38 with MW=254.3 and while the molecular ion is not observed in standard EI it is the dominant mass spectral peak in Cold EI. A closer look at the standard EI-MS reveals that its molecular ion relative abundance is 0.12%. Such large (three orders of magnitude) sensitivity gain of Cold EI plus its more uniform response enable isomer distribution analysis which is a novel and effective technique for fuel and oil characterization. 

Isomer Distribution Analysis – An Important yet Currently Neglected Analysis

Isomer distributions affect all the major physical and chemical properties of oils and fuels including: combustion and octane number, flash point, viscosity, lubrication properties, solubility and solvation power, boiling point and melting points. However, since current instrumentation can not be used for isomer distribution analysis this important subject is being ignored. With the 5975-SMB GC-MS with Cold EI such vital information can be obtained as above. A few application notes and a paper can be sent upon request on this topic

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