How to Choose the Right LC Guard Column

Guard columns serve as a safeguard to your analysis by preventing unwanted materials from reaching your analytical column, thereby extending column lifetimes and keeping unwanted impurities from showing up in your chromatography. A guard column consists of a holder and cartridge (and sometimes a filter) and installs easily in front of the analytical column to protect it from strongly retained impurities and particulates. Restek offers three guard column configurations—EXP, Roc, and Trident (direct and in-line)—that are each designed to match one of our LC column families for your unique analysis. We also offer a premium inert coating for many of our guards that is especially useful in the analysis of metal-sensitive compounds. Choose the right guard column for your analysis using the steps below.

Step 1: Choose an LC Guard System: EXP, Roc, or Trident (Direct and In-Line)

The first step in finding the right guard column is choosing among our various guard systems: EXP, Roc, or Trident (direct or in-line). Which system to choose depends largely on your technique and analytical column. For example, if you’re performing UHPLC using a smaller particle column that generates high back pressure, you need a holder to accommodate that pressure. If you’re employing traditional HPLC using a legacy column, you will want a holder that houses a legacy cartridge to match. Choose the best option for your analysis among our various guard systems shown in the table below. 

EXP Holders and Cartridges Built to withstand high back pressures of UHPLC instruments (rated to 20,000 psi [1400+ bar]).  Designed for use with Raptor and Force LC columns.   Roc Holders and Cartridges Specifically designed for use with Roc HPLC columns.   Trident Direct Holders and Cartridges Available in three levels of protection. Designed for use with legacy HPLC columns (Ultra, Pinnacle II, Pinnacle DB, Allure, Viva).   Trident In-Line Holders and Cartridges Requires a coupler to attach to the analytical column. Designed for use with legacy HPLC columns (Ultra, Pinnacle II, Pinnacle DB, Allure, Viva). Simple Particulate Protection: While a guard cartridge is the best choice for analytical column protection, it will add some retention delay because it is a packed bed. For protection from particulates with a negligible amount of additional dead volume, choose an UltraLine in-line filter or an UltraShield filter, both of which are suitable for UHPLC pressures and can be used alone or in combination with a phase-matched guard column.

Step 2: Choose an LC Guard Cartridge Packing that Matches the Analytical Column

Once you’ve determined which guard column system is right for you, the next step is choosing an LC guard cartridge with the packing and dimensions that best match your analytical column. To obtain maximum protection without compromising selectivity or efficiency, you should select an LC guard cartridge that contains the same packing material—both stationary phase and silica—as your analytical column. For example, the best LC guard column to use with a Raptor Biphenyl 2.7 μm analytical column is a Raptor Biphenyl 2.7 μm guard cartridge. Use the tables below for Step 2, 3, and 4 in choosing the right guard for your analysis.

Step 3: Select the Correct Inner Diameter Based on Your Column Diameter

In addition to choosing a guard cartridge packing that matches your analytical column, it’s important to select an LC guard cartridge with a proper inner diameter (ID). A good general rule is that the LC guard column cartridge ID should be the same as, or one size smaller than, the ID of the analytical column. For example, a 4.0 mm ID guard cartridge should be used with a 4.6 or 4.0 mm ID analytical column, while a 2.1 mm ID guard cartridge is recommended for 3.2, 3.0, and 2.1 mm ID analytical columns.

Step 4: Consider Inert Coating to Increase Sensitivity

Analyzing metal-sensitive compounds? We offer a premium inert coating on our most popular guard columns to provide additional protection against unwanted interactions between your analytes and the stainless-steel surfaces in your guard column. Pair your inert guard with an inert column for maximum benefits! Learn more about our inert technology here.

EXP Holders Raptor Guard Cartridges Force Guard Cartridges UltraShield Filters LC Column Family Column Particle Size Guard Cartridge Phases Available Inert Phases 1.8 (UHPLC) Raptor UHPLC guards: C18, ARC-18, Biphenyl, FluoroPhenyl   2.7 Raptor 2.7 µm guards: C18, C8, ARC-18, Biphenyl, FluoroPhenyl, HILIC-Si, Polar X Raptor Inert 2.7 µm guards: C18, ARC-18, Biphenyl, HILIC-Si 5 Raptor 5 µm guards: C18, ARC-18, Biphenyl, FluoroPhenyl   1.8 (UHPLC) Raptor UHPLC guard cartridge in matching phase for maximum protection, or 0.2 µm UltraShield filter for clean samples when minimal dead volume is desired†   3 Force 5 µm guards: C18, Biphenyl, FluoroPhenyl Force Inert 5 µm guards: C18, Biphenyl 5 Force 5 µm guards: C18, Biphenyl, FluoroPhenyl Force Inert 5 µm guards: C18, Biphenyl †Raptor UHPLC cartridges are packed with Raptor particles, but they are compatible with any UHPLC column so they can be used with matching phases of 1.8 µm Force and 1.9 µm Pinnacle DB UHPLC columns.

ROC Holders Roc Guard Cartridges Column Family Column Particle Size Column Phases Guard Cartridge Phases 3 C18, C8, Phenyl-Hexyl, Cyano, Silica Roc 5 µm guards: C18, C8, Phenyl-Hexyl, Cyano, Silica 5 C18, C8, Phenyl-Hexyl, Cyano, Silica Roc 5 µm guards: C18, C8, Phenyl-Hexyl, Cyano, Silica

Trident Holders Ultra Guard Cartridges Pinnacle DB Guard Cartridges Pinnacle II Guard Cartridges Viva Guard Cartridges Allure Guard Cartridges Column Family Column Particle Size Column Phases Guard Cartridge Phases Ultra 3 C18, C8, C4, C1, Biphenyl, Aromax, Aqueous C18, PFP Propyl, Cyano, IBD, Amino, Silica, Quat, Carbamate Ultra 5 µm guards: C18, C8, C4, C1, Biphenyl, Aromax, Aqueous C18, PFP Propyl, Cyano, IBD, Amino, Silica, Quat, Carbamate 5 C18, C8, C4, C1, Biphenyl, Aromax, Aqueous C18, PFP Propyl, Cyano, IBD, Amino, Silica, Quat, Carbamate Ultra 5 µm guards: C18, C8, C4, C1, Biphenyl, Aromax, Aqueous C18, PFP Propyl, Cyano, IBD, Amino, Silica, Quat, Carbamate Pinnacle DB 1.9 C18, C8, Biphenyl, Aqueous C18, PFP Propyl, Cyano, IBD, Silica, PAH Raptor UHPLC guard cartridge in matching phase for maximum protection, or 0.2 µm UltraShield filter for clean samples when minimal dead volume is desired* 3 C18, C8, Biphenyl, Aqueous C18, PFP Propyl, Silica Pinnacle DB 5 µm guards: C18, C8, Biphenyl, Aqueous C18, PFP Propyl, Silica 5 C18, C8, Biphenyl, Aqueous C18, PFP Propyl, Cyano, Silica Pinnacle DB 5 µm guards: C18, C8, Biphenyl, Aqueous C18, PFP Propyl, Cyano, Silica Pinnacle II 4 PAH Pinnacle II 4 µm guards: PAH Viva 3 C18 Viva 5 µm guards: C18 5 C18, C8, C4, Biphenyl, PFP Propyl, Silica Viva 5 µm guards: C18, C8, C4, Biphenyl, PFP Propyl, Silica Allure 5 Organic Acids, AK, Silica Allure 5 µm guards: Organic Acids, AK, Silica   *Raptor UHPLC cartridges are packed with Raptor particles, but they are compatible with any UHPLC column so they can be used with matching phases of 1.8 µm Force and 1.9 µm Pinnacle DB UHPLC columns.   Note: Trident direct holders are available in three configurations, so you can select the level of protection that is best for your application. For more details, review our Trident brochure. Trident in-line filters are also available.