Permethrin Drug Impurity Analysis with GC-MS with Cold EI and the Road to Failure in Such Analysis by GC-MS with Standard EI

Aviv Amirav, Tel Aviv University and Aviv Analytical

Abstract

A Permethrin impurity was successfully analyzed by GC-MS with Cold EI after it failed to be analyzed by GC-MS with standard EI. In this application note we demonstrate and discuss the ways GC-MS with standard EI analysis of relatively large compounds gradually becomes more difficult as the sample compound size is increased due to reduced total ion count signal, reduced molecular ion relative abundance and increased noise. Accordingly, as the analyzed sample compound becomes larger its GC-MS analysis becomes harder in a gradual fashion until it fails. In contrast, GC-MS with Cold EI can analyze twice larger compounds and thus significantly extends the range of compounds amenable for GC-MS analysis.    

Lipids in Human Serum Analysis by the 5975-SMB GC-MS with Cold EI

Aviv Amirav and Svetlana Tsizin, Tel Aviv University and Aviv Analytical, Tel Aviv Israel. 

Gabi Shefer, Ichilov hospital Tel Aviv Israel 

Introduction 

Cholesterol and triglycerides analysis in human blood is among the most widely used chemical medical diagnostics tests. Some estimate the number of such analysis at 1 Billion/year with cost of about $30 for each analysis (three analyses of cholesterol LDL, HDL and triglycerides at $10 each). Thus, the total lipids in blood analysis market is about $30 Billion/year. However, current analysis brings limited information and mass spectrometry can provide far better and more detailed lipids in blood information if an appropriate instrument for such analysis will be available. We used our GC-MS with Cold EI and demonstrated as below the analysis of large range of lipids in blood. Each analysis provided information on the amount of several free fatty acids, cholestadiene, cholesterol, vitamins E and 25 Hydroxy vitamin D3 and many diglycerides, cholesteryl esters and triglycerides. Notably, we can clearly distinguish differences among samples from different people. Each analysis took only 10 min via the use of column flow programing. Our results yielded extensive lipidomics information that may include new diagnostic tools. We feel that this new and advantageous assay for lipids profiling in blood is worthy of further investigation and evaluation.  

Impurities Analysis in Active Pharmaceutical Ingredients Comparison of Cold EI with Standard EI

Aviv Amirav, Tel Aviv University and Aviv Analytical, Tel Aviv Israel.

Introduction

Active pharmaceutical ingredients (APIs) in drug formulations need to have impurity levels < 0.1% according to the FDA or else the impurities need to be characterized via lengthy and expensive clinical toxicology procedures. Current impurities in APIs are typically analyzed by LC-MS. However, such LC-MS analysis is confronted by ion suppression effects for impurities that elute near the API, non-polar impurities are not ionized, those impurities that are discovered exhibit mostly protonated molecular ions without structural information and since Electrospray LC-MS has highly non-uniform ionization yields there is no information on the concentration of the discovered impurities. Thus, those API impurities that are observed need to be fully identified, synthesized and follow compound specific concentration calibration.

GC-MS with Cold EI is ideal for analysis of API impurities because:

• It has uniform compound independent response, thus detected impurity concentrations can be assessed, and those below 0.1% can be neglected 
• It often provides EI-based library identification, which is usually improved by the presence of an enhanced molecular in Cold EI plus structural information from the full display of fragment ions 
• Cold EI ionizes non-polar as well as polar analytes 
• It does not suffer from any ion suppression effects 
• Total ion mass chromatograms in Cold EI often provides greater sensitivity than ESI-LC-MS 
• Cold EI has much greater range of compounds amenable for analysis than any other GC-MS. 

Thus, Cold EI seems ideal for API impurities analysis.

Triglycerides in Oils Analysis by the 5975-SMB GC-MS with Cold EI

Aviv Amirav, Tel Aviv University and Aviv Analytical, Tel Aviv Israel.
Hans-Gerd Janssen, Unilever R&D Vlaardingen and University of Amsterdam, Amsterdam The Netherland

Introduction 

Triglycerides analysis is challenging since these large compounds do not elute from standard GC columns under the conditions used in GC-MS and furthermore their standard EI mass spectra do not exhibit any molecular ion, as shown in the NIST library. In addition, their analysis by LC-MS is also challenging in view of their poor proton affinity. Thus, and in view of the importance of triglycerides analysis we decided to analyze three oil samples that were previously analyzed by GC-FID in order to evaluate these oils analysis by GC-MS with Cold EI. The challenge was to properly elute these large compounds and demonstrate the availability of abundant molecular ions plus useful and informative high mass fragments. Triglycerides analysis is very important for the food industry and such analysis can also be potentially important for human medical diagnostics in the form of cholesterol and triglycerides analysis in blood. Currently triglycerides are hydrolyzed and methylated to form FAMEs (fatty acid methyl esters) that are analyzed by GC-MS. However, in such analysis vital information is lost on the actual structure and concentration of the various parent triglycerides and GC-MS with Cold EI is challenged to exhibit such information.     

Explosives Analysis with the 5975-SMB GC-MS with Cold EI

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director - Aviv Analytical Ltd, December 4, 2013.

Introduction

Effective explosives analysis is very important for homeland security and forensic applications. However, explosives analysis is challenging and the number of explosive compounds that require monitoring is growing with time. Furthermore, the growing use by terrorists of peroxide explosive compounds such TATP (triacetone triperoxide, C9H18O6) and HMTD (Hexamethylene triperoxide diamine, C6H12N2O6) implies that modern analytical techniques of explosive analysis must be as effective with peroxide explosive as with the traditional poly nitro explosives. In fact, there is no limit to the desirable LOD and selectivity of explosives analysis but these features must be combined with an analytical system that enables the analysis of the entire explosives family used by terrorists. We note that the actual system sensitivity and selectivity should be measured by its performance with the most difficult to analyze explosives such as the peroxide explosives and not with TNT and alike. 

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI uniquely enables the sensitive analysis of the full range of explosive compounds including TATP, HMTD, R-Salt, TNT, ETN, PETN, RDX, Tetril, HMX and Urea Nitrate while providing abundant molecular ions or high mass fragments that improve the detection selectivity and identification capability of these labile compounds.

Pesticide Analysis by Pulsed Flow Modulation GCxGC-MS with Cold EI – An Alternative to GC-MS-MS

Uri Keshet (1), Tal Alon (1), Paulina Goldshlag (2) and Aviv Amirav (1)

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

2. Israel Plant Protection and Inspection Services, Beit Dagan, Israel.

3. Aviv Analytical LTD, Tel Aviv, Israel.   

Introduction 

Pesticide analysis in agricultural products is an application area of growing importance which is usually addressed by GC-MS and LC-MS. However, pesticide analysis is confronted by the dominance of matrix interference which severely restricts the achievable limits of detection. As a result, several methods were developed and used for the reduction of matrix interference and the most widely used is MS-MS. While in LC-MS, MS-MS is practically a must in view of absence of libraries and consistent fragments in the mass spectra, in GC-MS the use of full scan possesses a few advantages of unambiguous library identification and its applicability to unlimited number of GC-MS amenable pesticides, provides however that the problem of matrix interference can be properly addressed. In addition to MS-MS at least three other techniques can be used to reduce matrix interference while enabling the use of full scan namely: a) high resolution mass spectrometry; b) GC-MS with Cold EI in which the enhanced molecular ions suppress matrix interference as described in another article in this blog. c) GCxGC-MS with its improved GC separation that can be used for the reduction of matrix interference as described in a few papers with thermal modulation and as discussed in this article.  

We developed Pulsed Flow Modulation (PFM) for obtaining GCxGC-MS with supersonic molecular beams (SMB) (also named Cold EI) based on a low cost single 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 and analyzed with it twelve pesticides in two agricultural matrices. PFM-GCxGC-MS with Cold EI combines the improved separation of GCxGC with the features of Cold EI of enhanced molecular ions and isotope information for the provision of ultimate sample identification information. Unique to PFM-GCxGC-MS with Cold EI is that in contrast to thermal modulation with standard GC-MS the second dimension elution time does not suffer from any ion source peak tailing and/or second column saturation effects and thus it is ideally suitable for pesticide analysis in complex matrices.   

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI enables effective pesticide analysis in agricultural matrices while using improved PFM-GCxGC separation for obtaining a major reduction of matrix interference by an average measured factor of 32. As a result, the road is open for PFM-GCxGC-MS with Cold EI to serve as an alternative to GC-MS-MS while enabling the use of full scan which is applicable to unlimited number of GC-MS amenable pesticides with improved library identification and the novel use of isotopomer ratios for pesticides identity confirmation

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. 

Organo-Iodine Compounds Analysis by the 5975-SMB GC-MS with Cold EI

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director - Aviv Analytical

Larisa Panz Ph.D., Ksenia Kulbitski and Professor Mark Gendelman, Schulich Faculty of Chemistry at the Technion Haifa Israel. 

Introduction

Organo-iodine compounds are used in several applications, mostly as intermediates in organic synthesis because of the easy formation and cleavage of the C–I bond. The analysis of organo-iodine compounds is highly challenging since most of them are not compatible with LC-MS and electrospray ionization while in GC-MS their analysis is hampered via their possible decomposition at the GC injector, column and ion source since the iodine-carbon bond is by far the weakest among all halogen-carbon bonds. Furthermore, even if the organo-iodine compounds elute from the GC column their standard EI mass spectra are often void of any molecular ions and as a result their identification becomes impossible. Motivated by the above challenges we explored the analysis of novel synthetic organo-iodine compounds with the Aviv Analytical 5975-SMB GC-MS with Cold EI, developed a method for its successful analysis and compared the results with that obtained with GC-MS with standard EI.

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI uniquely enables the effective analysis of synthetic organo-iodine compounds and provides unambiguous identification of all the synthetic organo-iodine reaction mixture compounds and as a result helps optimizing the synthesis reaction conditions and yields.

Free Fatty Acids Analysis by GC-MS - Cold EI Versus Standard EI

Aviv Amirav (1)  and David Benanou (2) 

1. Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical 

2. Veolia Environment Recherche and Innovation 

Gas Chromatography Mass Spectrometry (GC-MS) is known to be limited in the analysis of polar organic compounds such as free acids and bases which require derivatization for their proper analysis. The problem in free acids analysis emerges from extended peak tailing at the GC separation column (and liner) as well as peak tailing and sample compound degradation at the metallic surfaces of the ion source. Recently, a few of the major column vendors introduced new brands of inert columns and liners that alleviates and significantly reduces column related peak tailing by polar compounds. However, the problem of ion source activity remained unsolved and it is currently the main reason why free fatty acids and other polar organic compounds cannot be properly analyzed by standard GC-MS and require derivatization. While derivatization enables the GC-MS analysis of polar compounds such as fatty acids, it requires another step in the sample preparation. Furthermore, derivatization is not always practical since for a large variety of sample types the presence of compounds that require derivatization is not known hence they are analyze without derivatization and in such cases important sample information on such polar compounds is lost.

In this Advanced GC-MS Blog post we describe the analysis of an anti foam agent which in this case is hydrocarbon based oil that also contains free fatty acids. However, the presence of these free fatty acids was not initially known.            

                  

Keep reading to find out how the 5975-SMB GC-MS with Cold EI uniquely enables the analysis of free underivatized fatty acids which could not be properly analyzed by standard GC-MS.  

Does this Pill Contain its Claimed Active Ingredients? Finasteride in Male Baldness Treatment Pills

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director - Aviv Analytical

Introduction

Finasteride (C23H36N2O2, MW = 372.2777, structure at right) is an approved drug for the treatment of male baldness. It acts as an inhibitor of the enzyme that converts testosterone to dehydrotestosterone. Finasteride pills are available by Merck and other companies but at a high price. They are also available from a relatively unknown Indian company at over three times lower price. Thus, a colleague friend approached us with a request to analyze a Finasteride pill from the Indian company to ensure the presence (or absence) of this active pharmaceutical ingredient and determine if it is a major or minor constituent in their pills. In fact, the topic of fake drugs is serious and requires attention thus we bring our advanced GC-MS experience with it into this post.

Keep reading how the 5975-SMB GC-MS with Cold EI enables Finasteride in male baldness treatment pills.
          

Isomer Distribution Analysis – A New Tool for Organic Geochemistry Analysis

Aviv Amirav, Prof of Chemistry at Tel Aviv University and Director - Aviv Analytical 

Saturated hydrocarbons constitute the majority of oils and fuels and they are distributed among a large number of isomers whose number grows in a combinatorial series with size. However, natural synthesis prefers only a small fraction of all possible isomers.

The isomeric content and distribution affects all the major physical and chemical properties of oils and fuels, including: combustion efficiency, octane number, flash point, viscosity, lubrication properties, solubility and solvation power, boiling points and melting points. However, since current instrumentation can not be properly used for isomer distribution analysis this important subject is being ignored, as discussed in another post in this blog.

As a result, organic geochemists currently attempt to characterize oils and lead oil explorations based on information gathered from ppm range biomarker compounds such as hopanes and stearanes instead of using the information content in the majority hydrocarbon isomers.

The Aviv Analytical 5975-SMB GC-MS with Cold EI provides, for the first time, a unique opportunity to explore isomer abundance distributions in order to correlate between them and other various oils and fuels features. In this post we measure and attempt to evaluate the importance of isomer distribution (abundance) analysis in organic geochemistry samples.

For further information on GC-MS with Cold EI and on the possible use of isomer abundance analysis for fuel characterization please refer to the paper "Hydrocarbons and Fuel Analysis with the Supersonic GC-MS - The Novel Concept of Isomer Abundance Analysis", Alexander B. Fialkov and Aviv Amirav. J. Chromatogr. A. 1195, 127-135 (2008).

The main features of the Aviv Analytical 5975-SMB GC-MS with Cold EI include enhanced molecular ions which are observed and can be abundant for all isomers, combined with isomer related structurally informative fragments mass spectral peaks. In addition, extended range of compounds are amenable for analysis to include low volatility and thermally labile compounds that cannot be analyzed by standard GC-MS and unlike ESI-LC-MS it provides uniform response to all compounds for improved quantitative analysis.

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI enables a new type of oil characterization and analysis for improved organic geochemical information and oil exploration.

Extraterrestrial Allende Meteorite Analysis by the Aviv Analytical ChromatoProbe and 5975-SMB GC-MS with Cold EI

Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical 

The Allende meteorite is the largest carbonaceous chondrite ever found on Earth. It fell on February 8, 1969, near the village of Pueblito de Allende in the state of Chihuahua Mexico. The original stone is believed to have been approximately the size of an automobile traveling towards the Earth at more than 10 miles per second. After breaking up in the atmosphere, it produced thousands of fusion crusted individuals and an extensive search for pieces was conducted which led into what is often described as "the best-studied meteorite in history". The Allende meteorite contains about 4% carbonaceous chondrites. The subject or organic compounds in meteorites was investigated by several authors [1-3] and for example the organic compounds of the Allende meteorite were analyzed by photoionization combined with TOF-MS and some PAHs compounds such as phenanthrene and pyrene were found [3]. 

    

Allende Meteorite sample was provided to Prof. Aviv Amirav by Prof. Richard Zare from Stanford University during the Isranalytica 2010 meeting in Tel Aviv in January 2010. The meteorite small stone was broken with a clean tweezers into small (about 1 mm diameter) stones and it was analyzed via the use of ChromatoProbe sample introduction device for intra injector thermal extraction followed by 5975-SMB GC-MS with Cold EI analysis. 

Keep reading how the Aviv Analytical 5975-SMB GC-MS with Cold EI helps in extraterrestrial matter analysis and provides new data and unique insight into the extraterrestrial matter composition and possible origin.       

The Discovery of New Ant Head Compounds via ChromatoProbe Sampling and 5975-SMB GC-MS with Cold EI

Aviv Amirav (1), Raya Seltzer (2), and Abraham Hefetz (3), 

1. Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical 

2. Graduate student at the department of Zoology at Tel Aviv University 

3. Professor of Zoology at Tel Aviv University   

Introduction

Ants represent an interesting example of social insects and thus the chemical composition of their epicuticle is widely explored including in order to learn about the way they communicate. Much of the chemical ecology research of ants is focused on their wax hydrocarbons structure. In a previous post we described the results of our study of Ants Communication Exploration via their Wax Analysis by GC-MS with Cold EI – The Unique Role of Hydrocarbon Isomer Distributions.

As often the case, when new and powerful equipment is being used new discovery are being found as described in this post. We followed our exploration of the chemical structure of Cataglyphis ant waxes with the Aviv Analytical 5975-SMB GC-MS with Cold EI via sampling with the CPAV7980 ChromatoProbe sample introduction device. The ChromatoProbe allowed us to introduced ants body parts and glands without any sample preparation for their intra injector thermal extraction combined with GC-MS with Cold EI analysis with its features of having significantly enhanced molecular ion abundances, amplified isomer structural mass spectral effects and the ability to have tail free GC-MS analysis of underivatized free fatty acids. 

Keep reading how the 5975-SMB GC-MS with Cold EI in combination with the CPAV7890 ChromatoProbe brings new, untapped and important chemical information about ants wax composition.       

C-4 Explosives Characterization by the 5975-SMB GC-MS with Cold EI

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical 

Introduction 

C-4 is a widely used family of plastic explosives. It is composed of explosives, plastic binder, plasticizers and sometimes a marker taggant chemical. The explosive compound in C-4 is RDX, which makes up around 91% of C-4 by mass. The plasticizer is diethylhexyl or dioctyl sebacate and the binder is usually polyisobutylene. Another plasticizer used is dioctyl adipate (DOA). A small amount of SAE 10 non-detergent motor oil is also added. C-4 material is an off-white solid with a texture similar to modeling clay. In view of possible use of C-4 and other related type of plastic explosives (such as PE4 and Semtex) by terrorists there is an important need to have an improved method and instruments for the C-4 source identification. The various C-4 explosives can be correlated to their source in a few ways including: a) Main explosive type such as RDX with or without few percents of co-produced HMX; b) The type of taggant compound added; c) Plasticizer used; d) Oil used and its composition. However, taggant compounds are not always found, particularly in terrorist used C-4, HMX is not always found (co-produced) and while oil characterization is possible, its characterization via isomer abundance analysis although possible with Cold EI it is not sensitive enough in view of the large variety of compounds in the oil and its small concentration. Thus, we selected C-4 characterization via its plasticizers types, their isomer distributions, homologous compounds and major plasticizer related impurities. While for effective C-4 source identification one needs to build a library of C-4 explosives mass chromatograms our goal is to demonstrate the effectiveness of C-4 source characterization method via its plasticizers analysis by the 5975-SMB GC-MS with Cold EI.       

Keep reading to find out how the 5975-SMB GC-MS with Cold EI helps in C-4 source characterization for its identification via the fingerprinting of its plasticizers type, isomers and homologous compounds.

         

Drug Impurities Analysis by the Aviv Analytical 5975-SMB GC-MS with Cold EI

Aviv Amirav, School of Chemistry, Tel Aviv University and Director – Aviv Analytical 

Drugs are typically analyzed by LC-MS. When active pharmaceutical ingredients (API) are analyzed for the presence of impurities, the general requirements are that every impurity found should be at concentration below 0.1% of the API or it must be either cleaned or identified and toxicologically characterized which is a time consuming and expensive procedure. However, the ionization yields of Electrospray and/or APCI in LC-MS are highly non-uniform and compound dependent, and as a result when an impurity is found in a given LC-MS mass chromatogram its actual concentration is not known. Consequently, regardless of its actual concentration that can be well below 0.1% every impurity that is found must be isolated, fully identified, synthesized (or obtained) and serve for the provision of a calibration curve in order to measure the actual concentration of that small impurity peak. In addition, several types of impurities such as non-polar compounds are not properly ionized and are not detected by LC-MS. Thus, clearly drug impurity analysis represents an unmet analytical challenge.  

Alternatively, GC-MS with its standard electron ionization (EI) can be used and has, for volatile compounds, approximately uniform, semi-quantitative ionization yield. However, GC-MS with standard EI is compatible only with a limited range of thermally stable drugs and it provides useful molecular ions only for a portion of the analyzed compounds. Furthermore, ion source degradation and peak tailing severely erode the standard EI response uniformity for semi-volatile compounds. 

We used the Aviv Analytical 5975-SMB GC-MS with Cold EI for the analysis of drug impurities. Cold EI is the electron ionization of cold molecules in supersonic molecular beams (SMB). The technology of GC-MS with Cold EI is reviewed by A. Amirav, A. Gordin, M. Poliak, and A. B. Fialkov, J. Mass Spectrom., 43, 141-163. (2008). The later is available upon request. 

GC-MS with Cold EI as implemented with the Aviv Analytical 5975-SMB uniquely extends the range of drugs that are amenable for GC-MS analysis, including thermally labile drugs that are not compatible with standard GC-MS analysis. Furthermore, it is characterized by having uniform response to all compounds due to its contact-free fly-through ion source that eliminates any ion source peak tailing or losses. In addition, it provides trustworthy enhanced molecular ions that can be converted with the Tal-Aviv Molecule Identifier software into elemental formulae. Thus, the high sensitivity and uniform response of Cold EI uniquely enables the detection, identification and quantitation of low level impurities in drugs without lengthy calibration procedures. 

In order to evaluated the above attributes of the 5975-SMB we analyzed impurities in two Active Pharmaceutical Ingredient (API) samples (powder form) of Haloperidol and Ramelteon (Structures are given below).   

      

 

Keep reading to find our how the Aviv Analytical 5975-SMB GC-MS with Cold EI uniquely enables quantitative drug impurities analysis and helps in their identification. 

A Universal Method for Pesticide Analysis with the 5975-SMB GC-MS with Cold EI

 Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical

Introduction 

An estimated 2000 chemicals are being used as pesticides worldwide, including banned pesticides and other hazardous chemicals. In view of international food trade this large number implies that pesticide analysis should not be treated as target compounds analysis. Thus, current mass spectrometry instrument development is challenged to provide a one system and method that will be capable of analyzing as many pesticides as possible in full scan mode, in the needed instrumental sensitivity and selectivity in complex agricultural matrices, and in a short amount of time for effective (and lower cost) pesticides screening.   

In order to advance towards meeting the above challenges, a GC-MS with Cold EI (EI of Cold Molecules in Supersonic Molecular Beams) was evaluated in the past with pesticide analysis in agricultural products as described in M. Kochman, A. Gordin, P. Goldshlag, S. J. Lehotay and A. Amirav "Fast, High Sensitivity, Multi-Pesticide Analysis of Complex Mixtures with the Supersonic GC-MS" J. Chromatogr. A. 974, 185-212 (2002). Recently, we further evaluated pesticide analysis with the Aviv Analytical 5975-SMB GC-MS with Cold EI (GC-MS with supersonic molecular beam (SMB) interface and its fly through ion source) and developed a method to meet the above challenges. 

Keep reading to find out how the Aviv Analytical 5975-SMB GC-MS with Cold EI enables a truly universal method of pesticide analysis in agricultural matrices with improved range of compounds amenable for analysis, reduced matrix interference, lower LOD particularly for difficult to analyze pesticides, improved pesticide identification and shorter analysis time.   

Ants Communication Exploration via their Wax Analysis by GC-MS with Cold EI – The Unique Role of Hydrocarbon Isomer Distributions

Aviv Amirav (1), Raya Seltzer (2), and Abraham Hefetz (3), 
1. Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical 
2. Graduate student at the department of Zoology at Tel Aviv University 
3. Professor of Zoology at Tel Aviv University

Introduction 

Ants are social insects and thus the exploration of their ways of communication is an interesting research area. For example, nestmate recognition is essential for ants for the defense against exploitation of nest resources, and such recognition is largely mediated by chemical signals. When two individuals meet they match the label, the chemical signal it carries on the epicuticle and represents the colony odor, with a postulated neural template present in the brain. If the label matches the template amicable interactions between the individual ensue, (photo in the graphical abstract) otherwise they engage in aggressive interaction. Since the ant wax is composed mostly from saturated hydrocarbons, both linear chain and their branched isomers, we decided to explore the chemical structure of ant waxes with the Aviv Analytical 5975-SMB GC-MS with Cold EI which significantly enhances the molecular ion abundances and amplifies isomer structural mass spectral effects. We studies Cataglyphis ants from 17 different nests in various locations in Israel and found that although morphologically they are practically indistinguishable, isomer distribution analysis found significant differences between cryptic ant species or ants from different nests. Thus, the data strongly supports the hypothesis that ant communication is based on branched hydrocarbon abundances as a recognition fingerprint. 

Keep reading how the 5975-SMB GC-MS with Cold EI helps in ant communication research and to view the important role of isomer distribution analysis in our findings.  
    

Flies Wax Analysis by GC-MS with Cold EI and its Comparison with Standard EI

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director – Aviv Analytical, 

Joanne Yew, Temasek Life Sciences Laboratory and National University of Singapore, Department of Biological Sciences, Singapore. 

Introduction 

Insects such as flies, ants and mosquitoes express species-specific blends of cuticular hydrocarbons (CHCs) on their surface that serve as pheromones and play an important role in their behavior and communication. In view of growing interest and importance of this research area recently several advanced tools were developed for improved CHCs analysis. However, one major limitation of these methods and instrumentations is that alkanes cannot be properly detected via some of the atmospheric pressure ionization ion sources while in standard electron ionization as used with GC-MS the molecular ion is often very weak or altogether missing thereby proper identification is hindered. Furthermore, standard GC-MS is limited to relatively small compounds up to about C40-C44. Thus, we explored the chemical structure of fly and mosquito waxes with the Aviv Analytical 5975-SMB GC-MS with Cold EI which significantly enhances the molecular ion abundances, amplifies and exposes isomer structural mass spectral effects and enables the elution of much larger hydrocarbons via the use of short columns with high column flow rates. In addition, it provides uniform response for accurate quantification of the waxes compounds which is superior to standard EI and in contrast to API ionization methods (APCI, DART MALDI etc). For further information on GC-MS with Cold EI please read the review article A. Amirav, A. Gordin, M. Poliak, T. Alon and A. B. Fialkov "Gas Chromatography Mass Spectrometry with Supersonic Molecular Beams" J. Mass. Spectrom. 43, 141-163 (2008)., which is available on request. In this post we report on the analysis of two fly samples. A) Male Drosophila melanogaster, and B) Male Drosophila mojavensis. 

Keep reading how the 5975-SMB GC-MS with Cold EI drastically improves flies cuticular hydrocarbons analysis and bring novel tools for its characterization. 

               

Pistol Oil Analysis by the Aviv Analytical 5975-SMB GC-MS with Cold EI – A New Forensic Method for the Verification of Pistol Holding

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director - Aviv Analytical 

Introduction: 

There is an established forensic need to link between a given pistol (or any other firearm) and a suspect, who often denies ownership of that pistol, or claims that it was never touched. Pistols and other firearms are sometimes linked to their holders via their Iron print (induced by iron reaction with human sweat), which can be developed on the suspect's holding hand by special chemicals. However, there is a growing need for alternative forensic methods as some pistols or firearms have chromium coated or plastic based handles which are incompatible with the Iron print technique. In addition, the Iron print method is performed on the human suspect hand, and an alternative method based on field sample collection followed by laboratory analysis would be advantageous. 

The Novel Pistol Oil Analysis Idea: 

Every pistol and fire arm is lubricated by special oil for its improved maintenance and unhindered operation. This oil unavoidably touches the holding hand and consequently must leave its deposit on the holding hand. The oils used typically consist of a range of hydrocarbons, often aliphatic hydrocarbons that are distributed in a range of isomers. Thus, pistol oil analysis on a human hand can serve as an effective new method for linking between a given pistol and/or fire arm to the hand that held it, given that a suitable method and instrument will be found for obtaining a unique pistol oil characterization finger print.       

Keep reading how the Aviv Analytical 5975-SMB GC-MS with Cold EI enables the verification of pistol holding.

Approaching a Step Forward Towards the CSI Vision - Cannabis Seeds Identification with the 5975-SMB GC-MS and Cold EI

Aviv Amirav, Professor of Chemistry at Tel Aviv University and Director - Aviv Analytical

Ehud (Udi) Wolf (Ph.D.), head of the Analytical Lab, DIFS (division of Identification and Forensic Science), Israel police HQ, Jerusalem, Israel

Introduction 

In the popular Crime Scene Investigation (CSI) TV series (Las Vegas, New York and Miami) a common scene involves the injection of an unknown material into a GC-MS while obtaining an answer in a minute or so about what is the material. However, current GC-MS abilities are far away from such a vision, in both the time needed for analysis and particularly in the fact that GC-MS produces mass chromatograms that require data analysis. Furthermore, GC-MS data analysis generates compounds identification and not any material identification since each material is composed from many compounds and no "material library" exists. Thus, it is a major analytical and forensic chemistry challenge to advance into material identification. 

Motivated by the Israeli police request we were given Cannabis seeds with the goal of finding a new method, based on GC-MS with Cold EI, to characterize, distinguish and identify them as Cannabis seeds and not any other type of seeds. 

Initial search in the literature revealed that Cannabis seeds are claimed to have "more Omega 3 and Omega 6 fatty acids than virtually any other source, including fish" and that a highly abundant fatty acid in Cannabis seeds is the doubly unsaturated linoleic acid. In addition, Cannabis seeds are claimed to contain Vitamin E. 

We used the Aviv Analytical 5975-SMB GC-MS with Cold EI for the analysis and identification of the Cannabis seeds. Cannabis seeds appear as small, ~2-3 mm brown elongated balls, with somewhat hard shell and softer inside. Sample preparation was very simple and included crashing three seeds inside thin aluminum foil, moving the crashed seeds into a one ml glass vial with about 400 µL Dichloromethane (DCM) followed by ~3 min of sonication and injection of the DCM "extract" as is. We used such a simple form of sample preparation since the 5975-SMB GC-MS with Cold EI can uniquely elute all the sample compounds that are vaporized by the GC injector at 270ºC and enter the column, including the late eluters triglycerides. 

    

Keep reading to learn how the 5975-SMB GC-MS with Cold EI enables Cannabis seeds identification.