Optimizing Splitless GC Injections

Author(s): Linx Waclaski
Restek Corporation

Published By: LCGC’s The Column

Issue: Volume 8, Issue 14

Year of Publication: 2018

Link: www.chromatographyonline.com/optimizing-splitless-gc-injections-0

Abstract: Splitless injections are sometimes necessary for trace analyses, where the analyst hopes to recover 100% of the analytes that are injected. Unfortunately, splitless injections can be challenging, and using an imperfect method can lead to loss of analytes and poor peak shapes. The choice of inlet liner can have an impact on the data and one must consider the effects of geometry, packing, deactivation, and volume on introduction of analytes into the system. Other important inlet parameters to consider include inlet temperature, splitless hold time, and initial oven temperature.

Liquid Chromatography’s Complementary Role to Gas Chromatography in Cannabis Testing

Authors: Justin Steimling, Ty Kahler

Restek Corporation

Published By: Supplement to LCGC North America

Year of Publication:  June 2018

Volume, Number: Volume 36, Number s6

Link: http://files.pharmtech.com/alfresco_images/pharma/2018/06/13/f119cb54-ce43-4628-95f8-af1aa07bb6ff/LCGC_NAmerica_June2018Supp.pdf

Abstract: The absence of consensus methods for cannabis testing is a challenging, but refreshing opportunity for analytical chemists in the field because it enables the incorporation of the newest technologies and best practices without the restrictions imposed by legacy approaches that often impede method development in other industries. Liquid chromatography (LC) is proving to be a valuable complementary technique to gas chromatography (GC) in cannabis testing for the analysis of cannabinoids, mycotoxins, and pesticides. The industry is emerging during a time when superficially porous particles (SPPs) and ultrahigh-pressure liquid chromatography (UHPLC) have become market standards. This article discusses the adoption of LC technology and its role in cannabis testing.

A Simple Way to Reduce Analysis Time in GC

Author: Jaap de Zeeuw

Published By: Restek Corporation

Year of Publication: 2018

Link: https://www.labcompare.com/10-Featured-Articles/350677-A-Simple-Way-to-Reduce-Analysis-Time-in-GC/

Abstract:

There are several ways to decrease analysis time in GC. Reducing analysis time depends on the separations between the peaks of interest. In the case of enough separation, some efficiency can be traded for speed by:

  1. Using a shorter column length
  2. Operating the column at a higher flow rate or using flow programming to elute late-eluting compounds.

If the same efficiency is required, options are to:

  1. Use a faster carrier gas, i.e., hydrogen instead of helium
  2. Use a shorter capillary with a smaller bore—this produces similar efficiency with shorter run times.

In all of the above situations, analysis time is also limited by the maximum temperature programming that is allowed for the instrument used.

Instrumentation Used for Terpene Analysis

Author: Tim Herring

Restek Corporation

Published By: Cannabis Industry Journal

Year of Publication: 2017

Link: https://www.cannabisindustryjournal.com/column/instrumentation-used-for-terpene-analysis/

Abstract:

Because terpenes are somewhat volatile, the Restek team recommends using gas chromatography and advises against using HPLC for terpene analysis.

Many customers ask technical service which instrumentation is best, GC or HPLC, for analysis of terpenes. Terpenes are most amenable to GC, due to their inherent volatility. HPLC is generally not recommended; since terpenes have very low UV or MS sensitivity; the cannabinoids (which are present in percent levels) will often interfere or coelute with many of the terpenes.

Accurate Detection of Residual Solvents in Cannabis Concentrates

Author: Chris English

Restek Corporation

Published By: Cannabis Industry Journal

Year of Publication: 2017

Link: https://www.cannabisindustryjournal.com/category/the-practical-chemist/

Abstract:

Edibles and vape pens are rapidly becoming a sizable portion of the cannabis industry as various methods of consumption popularize beyond just smoking dried flower. These products are produced using cannabis concentrates, which come in the form of oils, waxes, or shatter. Once the cannabinoids and terpenes are removed from the plant material using solvents, the solvent is evaporated leaving behind the product. Extraction solvents are difficult to remove in the low percent range, so the final product is tested to ensure leftover solvents are at safe levels. While carbon dioxide and butane are most commonly used, consumer concern over other more toxic residual solvents has led to regulation of acceptable limits.

Split Injection GC: Increasing Response Factors for Compounds Prone to Inlet Liner Adsorption by Using Shoot-and-Dilute GC

Author: Jack Cochran

Published By: LCGC Chromatography Online

Issue: Volume 12, Issue 16

Year of Publication: 2016

Link: http://www.chromatographyonline.com/split-injection-gc-increasing-response-factors-compounds-prone-inlet-liner-adsorption-using-shoot–0

 

Abstract:

Hopefully, by now at least, readers who are following this Practical GC series on split injection gas chromatography (GC) (1–3) have been able to take advantage of its benefits in their own laboratories. Chemists analyzing environmental samples, especially those that produce dirty extracts, could have the most to gain from split injection GC given the wide variety of semivolatile organic compounds that are typically determined. Analyte lists include compounds that can react with GC inlet liner surfaces during splitless injection, leading to degradation of those compounds, which prohibits their accurate quantification. In fact, an example was given in my first Practical GC article in The Column (1) for the pesticides endrin and DDT. Sample extracts containing high concentrations of involatile material exacerbate the situation because the nonvolatiles are deposited on the inlet liner wool and bottom seal where they catalyze degradation of sensitive compounds. Buildup of nonvolatile material in the inlet during repeated splitless injections leads to even higher breakdown. Split injection mitigates the degradation potential because the typical inlet flow is 10 times (or more) higher than for splitless injection. The time for unwanted reactions on liner surfaces, including those that have been modified by nonvolatile coextractives, is reduced in split injection.

Split Injection GC: Setting the Split Ratio in Shoot-and-Dilute GC

Author(s): Jack Cochran
Restek Corporation

Published By: LCGC’s The Column

Issue: Volume 12, Issue 8

Year of Publication: 2016

Link: http://www.chromatographyonline.com/split-injection-gc-setting-split-ratio-shoot-and-dilute-gc

For the full issue,visit http://images2.advanstar.com/PixelMags/lctc/digitaledition/May06-2016-us.html#11

Abstract: Jack Cochran’s new column “Practical GC” provides readers with practical advice and new experimental evidence for how to get the best results from their gas chromatography (GC) systems.  This installment looks at understanding and using split ratio for “shoot and dilute” GC.

Analysis of Gases via Gas Chromatography: Part 1: Nitrous Oxide

Author: Jaap de Zeeuw
Restek Corporation

Published By:  J. Sep. Sci.

Year of Publication: 2016

Abstract:

Gas chromatography (GC) is a technique that deals with gas separations. Practically the components to separate must be brought in the gaseous phase to be able to be transported by the carrier gas. In order to do that, the temperature of the sample and column can be increased. Today’s gas chromatographs can be used up to 500 °C, meaning that it is possible to analyse components with boiling points around 700 °C. The component must be thermally stable. This works fine for hydrocarbons but more polar molecules will decompose.

Faster (GC) Tactics: Five ways to speed up gas chromatography analyses using your current system

Author: Jaap de Zeeuw
Restek Corporation

Published By: The Analytical Scientist

Issue: 36

Year of Publication: 2016

Link: https://theanalyticalscientist.com/issues/the-new-dawn-of-precision-medicine/polishing-your-injection-technique

For the full issue, visit: https://theanalyticalscientist.com/fileadmin/tas/pdf-versions/TAS-Issue-0116.pdf

Abstract:

Reducing analysis time is a constant priority. And it’s sensible because it cuts costs per analysis and you get faster results. Here, I’d like to share some clever ways to reduce gas chromatography (GC) analysis time using existing instrumentation in two real-world situations.

Split Injection GC: The Benefits of “Shoot-and-Dilute” GC

Author(s): Jack Cochran
Restek Corporation

Published By: LCGC’s The Column

Issue: Volume 11, Issue 21

Year of Publication: 2015

Link: http://www.chromatographyonline.com/split-injection-gc-benefits-shoot-and-dilute-gc

For the full issue, visit http://images2.advanstar.com/PixelMags/lctc/digitaledition/November23-2015-uk.html

Abstract: Jack Cochran’s new column “Practical GC” aims to provide readers with practical advice and new experimental evidence for how to get the best results from their gas chromatography (GC) systems. The first article in a series on split injection GC focuses on the advantages of using “shoot-and-dilute” GC.