<h4>Pre-Installation Checklist</h4><ul><li>Replace oxygen, moisture and hydrocarbon traps as necessary.</li><li>Check gas cylinder pressures to ensure that an adequate supply of carrier, make-up and fuel gases are available. Carrier gases should be of the highest purity.</li><li>Ensure that the injection port is clean and free of sample residues, septum, or capillary debris.</li><li>Check and replace as necessary critical injector components such as seals, liners, and septa.</li><li>Check and replace detector seals as necessary.</li><li>Carefully inspect your column for damage or breakage.</li></ul>Note: It is critical that oxygen and water be removed from the carrier gas by the appropriate use of filters and adsorbents<h4>Injector Installation</h4>Note: GC columns do not have a specific directional flow when received from the manufacturer. Upon initial use of your new GC column, it is recommended to dedicate one specific end of the column for injector installation only. This is particularly important when dealing with active/caustic or contaminating compounds. If these compounds are routinely injected onto the column, degradation of the phase will occur—leading to higher bleed. A typical first step to remedying (removing) this bleed would be to trim 10 cm from the front (injector) end of the column and keep trimming this inlet end of the column as necessary. Trying to remedy any bleed issues by trimming the column may not work if both ends have been interchangeably installed into the inlet.<ol><li>Place a capillary nut and ferrule on the injector end of the GC column, allowing a section of column to protrude. Trim one to two centimeters from the protruding end to remove ferrule contamination that may have entered the column. Inspect the cut with a magnifier to ensure that a smooth, clean, square-cut edge has been made - recut if necessary.</li><li>Carefully hang the column in the GC oven, being cautious not to scratch or damage the polyimide coating on the capillary tubing. Rotate the column to avoid sharp bends of the capillary column and any contact of the column with oven surfaces.</li><li>Insert the column into the injector exactly the correct distance specified in the instrument manual. Tighten the ferrule nut finger-tight then 1/2 turn with a wrench. If the column can still be moved, tighten another 1/4 turn until the column is secure.</li><li>Adjust the carrier gas to obtain the flow rate listed on the test chromatogram.</li></ol>

Gas Chromatography (GC) Column Installation - Injector Installation

When installing your capillary GC column, making accurate connections is essential to ensure trouble free operation. In this technical tip we provide advice on the best way to achieve this.<blockquote>Note: For users with sensitive detectors such as MS and ECD, column conditioning steps should be performed before installing the column to prevent contamination and frequent maintenance of the detector.</blockquote>1) Place the column nut and ferrule past the end of the column and cut a centimeter or two off the end of the column. Be sure that the ferrule is the right size and pointing in the correct direction. Inspect the cut with a magnifier and ensure that the cut is square and smooth. See figure below. Recut if needed.2) Insert the outlet end of the column into the detector exactly the distance prescribed in the instrument manual. Distances will vary between detectors. Tighten the ferrule nut finger-tight then 1/2 turn with a wrench. If the column can still be moved, tighten another 1/4 turn until the column is secure.3) Inspect the column connections for leaks using an electronic leak detector. Leaks at the inlet end may introduce oxygen to the column that will result in increased column bleed and damage to the column phase.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Gas_Chromatography_GC_Column_Installation_Detector_Installation_813b4d81a0.jpg" alt="Phenomenex: Gas Chromatography (GC) Column Installation - Detector Installation: Correctly and Incorrectly Cut GC Capillary." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Gas_Chromatography_GC_Column_Installation_Detector_Installation_813b4d81a0.jpg 245w," sizes="100vw" width="877" height="242">

Gas Chromatography (GC) Column Installation - Detector Installation

In this technical tip we are pleased to bring you some valuable guidelines for Gas Chromatography (GC) related to installation, from column conditioning to installation testing and through leak checks. Ensuring proper column installation and performance is crucial for accurate and reliable analysis. Let's dive into some important good practices:<h4>Column Conditioning</h4><ul><li>Allow sufficient time for the carrier gas to flow through the column to purge any oxygen that may be in the system.</li><li>Raise the temperature of the column to the maximum isothermal operating temperature that is listed on your individual GC Column Test Report. Maintain this temperature until a constant baseline is achieved. Conditioning times will depend on the phase identity and thickness, with thicker films taking longer to stabilize. In order to minimize the downtime of the instrument, columns can be conditioned overnight at the maximum isothermal temperature.</li></ul><h4>Installation Testing</h4><ul><li>Inject a detectable unretained sample, such as methane for an FID, to determine dead volume time and linear gas velocity at the desired column temperature. Adjust gas pressure for optimal flow depending on carrier gas selection.</li><li>The non-retained peak must have ideal peak shape or installation is faulty and needs to be redone.</li></ul><h4>Checking for Leaks</h4><ul><li>Use a thermocouple-thermometer to check for leaks. It is highly sensitive to H2, He, and N2 and will not contaminate the instrument or column. Liquid leak indicators are not recommended for capillary columns. There is the risk of drawing the liquid into the column or fittings and contaminating the system.</li><li>Any carrier gas that is leaking from the column will alter the conductivity across the thermocouple. As such, just watch for fluctuations within the temperature reading, which would indicate a possible leak near the location of the thermocouple. This prevents any contact and possible contamination of the column.</li></ul>Note: If Vespel® ferrules are being used, leakage can occur after the initial heating phase due to ferrule deformation. Be sure that the fitting is re-tightened after this initial heating phase, then carefully check all corrections for leaks.Remember, following these practices will contribute to the optimal performance and longevity of your GC columns, reducing downtime due to system maintenance.

Gas Chromatography (GC) Column Conditioning, Testing and Checks

<h4>1) Polarity&nbsp;</h4>Some indication of polarity will usually be provided by the GC column manufacturer, the value provided is normally determined using Kovats retention time indices together with McReynold’s numbers. The general advice is that stationary phase polarity should closely mirror the polarity of the analytes of interest, so a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products?category=355&amp;manufacturerItems=50">non-polar phase</a> such as a ZB-1 (rated as 5 on the polarity scale) would be a good choice for hydrocarbon analysis whilst a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products?category=7&amp;manufacturerItems=50&amp;search=WAX">ZB-Wax</a> (57 on the polarity scale) is often chosen for alcohols.<h4>2) Selectivity&nbsp;</h4>This is controlled by the different functional groups present within the polymeric stationary phase, the base of which is either polysiloxane or polyethylene glycol. Polysiloxane phases will typically have methyl groups, phenyl groups or cyanopropyl groups attached to the polysiloxane chains which allow for a variety of different interactions to occur:<ul><li>Methyl groups: van der waals or London forces,</li><li>Phenyl groups: π-π interactions,</li><li>Cyano groups: π-π and dipole-dipole interactions.</li></ul>Increasing the percentage of phenyl or cyanopropyl substituents in the stationary phase increases polarity. Polyethylene glycol (PEG)phases offer sites for dipole-dipole and hydrogen bonding interactions to take place, PEG phases are typically some of the most polar phases available.<h4>3) Length</h4>Increasing the length of the column increases the number of theoretical plates, which aids resolution, however increasing column length also increases the run time of any analysis conducted. A 30 m column is generally a good starting point for general method development whereas 60 m columns are typically used for the fingerprint analysis of complex mixtures. 15 m columns are generally utilised when the rapid separation of less complex mixtures is required.<h4>4) ID</h4>The choice of column ID impacts both column capacity (how much analyte you can inject) and efficiency. The narrower the column ID the higher the efficiency, but the lower it’s capacity. A good place to start with method development is a 0.25 mm ID column, which show a good compromise between efficiency and capacity. If you are converting a method from an old-style packed GC column to capillary GC columns then 0.53 mm ID columns are often chosen due to their higher analyte capacity.<h4>5) Film thickness</h4>Thin films provide the highest efficiency but have lower analyte retention. Thicker films have a higher capacity but lead to more bleed at high temperatures. If choosing to use a thin film (0.1 - 0.25 µm) with active analytes it is preferential to select a column which is highly deactivated to prevent peak tailing. Such columns generally provide lower bleed too.

What parameters should I consider when selecting a GC column for my application?

This month’s technical tip focuses on a basic and crucial topic: How to choose the correct GC column dimensions? When starting a new project or when improving an existing method, it’s important to evaluate the contribution that each column dimension (Length, Internal Diameter (ID) and film thickness) brings to the method resolution, sensitivity, and robustness.Another factor to keep in mind, when investing in GC columns, is to choose a reliable source. Manufacturers perform multiple tests on their columns before they find their way to customers. These tests include resolution of critical pairs, column bleed test, retention factor of probe analytes, efficiency of the column and so on. Make sure to select a manufacturer that provides columns that are individually QC tested.To maximize efficiency in GC, column length, internal diameter (ID) and film thickness, each has a significant effect. Knowing the effect of column dimensions on a GC separation will help not only to select the right column dimension, but also to pick an alternate dimension to achieve efficient chromatographic separation, as well as possibly reducing the analysis time.Let’s see how these parameters influence separation in detail.<h4>Column Length</h4>The length of your column affects the rate of resolution improvement. As the length of the column increases, so does the resolution improvement. However, it will also increase run times. Under isothermal conditions, doubling column length only increases resolution by 41 %, but it doubles the run time! Choose a column length that balances efficiency with acceptable run times.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_GC_Column_Selection_by_Column_Dimension_1_8c584730ec.jpg" alt="Phenomenex: GC Column Selection by Column Dimension: Column Lenght." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_GC_Column_Selection_by_Column_Dimension_1_8c584730ec.jpg 245w," sizes="100vw" width="1702" height="598"><h4>Internal Diameter</h4>Column internal diameter (ID) has a major impact on both resolution and sample capacity. Unlike column length, using smaller ID columns can lead to faster run times, because the column length required with a small ID is often shorter due to increased efficiency.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_GC_Column_Selection_by_Column_Dimension_2_c95f77d2fa.jpg" alt="Phenomenex: GC Column Selection by Column Dimension: Internal Diameter." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_GC_Column_Selection_by_Column_Dimension_2_c95f77d2fa.jpg 245w," sizes="100vw" width="1740" height="583"><h4>Film Thickness</h4>Film thickness determines solute retention and plays an important role in column sample capacity. Thin film columns are faster and provide higher resolution, but lower sample capacity. In most instances, choose the thinnest film possible that still provides adequate retention. When working with active samples, using a slightly thicker film can significantly improve peak shape.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_GC_Column_Selection_by_Column_Dimension_3_8fb68c44cb.jpg" alt="Phenomenex: GC Column Selection by Column Dimension: Film Thickness." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_GC_Column_Selection_by_Column_Dimension_3_8fb68c44cb.jpg 245w," sizes="100vw" width="1740" height="583">

GC Column Selection by Column Dimension

More often than not, GC column problems are traceable to something improperly done during installation. The table below may assist you in identifying and correcting common installation problems highlighted by your Column Performance Test Mixture.&nbsp;<h3>Symptom: Tailing Peaks</h3><h4>Possible Cause &nbsp;&nbsp;/ &nbsp;&nbsp;Suggested Remedy</h4><ul><li>Contaminated or active injector liner or column:&nbsp;<ul><li>Clean or replace injector liner.</li><li>Solvent rinse or replace the column.</li></ul></li><li>Dead volume due to poorly installed liner or column: Reinstall liner and column as necessary.</li><li>Ragged column end: Score the tubing lightly with a sapphire scribe or a ceramic scorer wafer before breaking it. Examine the end (a 20-power magnifier glass is recommended). If the break is not clean and the end square, cut the column again. Point the end down while breaking it, and while installing a nut and ferrule, to prevent fragments from entering the column. Reinstall the column.</li><li>A bad match between the polarities of the stationary phase and the solvent: Change the solvent.</li><li>A cold region in the sample flow path: Remove any cold zones in the flow path. Debris in the liner or column:&nbsp;<ul><li>Clean or replace the liner.</li><li>Cut a centimeter or two off the ends of the column and reinstall.</li></ul></li><li>Injection takes too long: Improve injection technique.</li><li>Split ratio is too low: Increase split ratio.</li><li>Overloading the inlet: Decrease the sample volume.</li><li>Some types of compounds such as alcoholic amines, primary and secondary amines, and carboxylic acids tend to tail:&nbsp;<ul><li>Try a different column.</li><li>Make a derivative of the sample.</li></ul></li></ul>

Peak Shape Problems: Tailing Peaks

<h4>No Peaks - Some or all peaks are missing from the run</h4>How many times have you found that some or all peaks are suddenly missing from the run?In this month’s GC technical tip, we explore some of the possible causes and solutions to overcome peak disappearance, by evaluating three possible scenarios that should cover all possible real cases.<h3>Symptom: All Peaks Missing</h3><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Peak_Shape_Problems_No_Peaks_b0d5e8c344.jpg" alt="Phenomenex: Peak Shape Problems: No Peaks" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Peak_Shape_Problems_No_Peaks_b0d5e8c344.jpg 245w," sizes="100vw" width="1516" height="943"><h4>Possible Cause &nbsp;/ &nbsp;Suggested Remedy</h4><ul><li>Defective or clogged syringe.: Try a new or proven syringe.</li><li>“Blown” septum or massive leaks at the inlet.: Find and fix leaks.</li><li>Problems with carrier gas flow.: Adjust gas flow.</li><li>Column may be broken or installed in the wrong detector or inlet.: If breakage is close to the beginning or end, cut off the short piece. Breakage in the middle can be repaired with a press-fit connector. For multiple breakages, replace or reinstall the column.<ul><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/labrulez-bucket-strapi-h3hsga3/GC_Column_Instalation_Guide_73f12586a8.pdf">See column installation</a>.</li></ul></li><li>The detector is not functioning or is not connected to the recorder or integrator.: Ensure detector is working properly. (e.g. is the flame in a FID lit?) Check connection to the output device.</li><li>Incorrect injector temperature:<ul><li>Injector too cold: sample is not vaporized.: Cold injector: check injector and oven temperature with an accurate thermometer. If accurate, increase temperature as necessary, but do not exceed the maximum temperature limit of the column. Inject the sample directly onto the column.</li><li>Injector too hot: thermally labile sample is decomposing.: Hot injector: check injector and oven temperature with an accurate thermometer. If accurate, reduce temperature as necessary, ensuring compatibility with sample and column minimum limit.</li></ul></li></ul><h3>Symptom: No Peaks After Solvent Peak</h3><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Peak_Shape_Problems_No_Peaks_2_5f1459f9d3.jpg" alt="Phenomenex: Peak Shape Problems: No Peaks" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Peak_Shape_Problems_No_Peaks_2_5f1459f9d3.jpg 245w," sizes="100vw" width="1481" height="943"><h4>Possible Cause &nbsp;/ &nbsp;Suggested Remedy</h4><ul><li>Sample volume is too high.: Inject less sample or use a higher split ratio.</li><li>For FID detectors, the flame is blown out by the solvent peak.: Check the detector temperature.</li><li>Carrier gas flow is too high.: Reduce the flow rate.</li><li>Incorrect column temperature; column is too hot and sample is eluting in solvent peak.: Check oven temperature with an accurate thermometer. If accurate, reduce temperature as necessary, ensuring compatibility with sample and column minimum limit.</li><li>Column cannot separate components from solvent.: Change solvent or column.</li></ul><h3>Symptom: Some Peaks Missing</h3><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Peak_Shape_Problems_No_Peaks_3_be7fd462a8.jpg" alt="Phenomenex: Peak Shape Problems: No Peaks" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Peak_Shape_Problems_No_Peaks_3_be7fd462a8.jpg 245w," sizes="100vw" width="1453" height="886"><h4>Possible Cause &nbsp;/ &nbsp;Suggested Remedy</h4><ul><li>Activity in the inlet liner or column if the missing peak is an active compound.: Clean or replace the inlet liner. Ensure an inert column is used. If necessary, replace the column. See column installation.</li></ul>When some or all peaks are missing in a GC analysis most causes are related to the detector, which plays a crucial role, but do not dismiss other possible causes, such as a defective syringe, an improper injection or an activated column or liner.See you on the next technical tip, feel free to contact us if you need support in troubleshooting or for your method development.

Peak Shape Problems: No Peaks

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