{"id":48511,"date":"2012-08-13T14:30:00","date_gmt":"2012-08-13T14:30:00","guid":{"rendered":"https:\/\/discover.restek.com\/uncategorized\/how-to-choose-the-correct-gc-column-part-4\/"},"modified":"2026-01-28T15:54:23","modified_gmt":"2026-01-28T15:54:23","slug":"how-to-choose-the-correct-gc-column-part-4","status":"publish","type":"post","link":"https:\/\/discover.restek.com\/de\/blog-it\/gnbl4706\/how-to-choose-the-correct-gc-column-part-4","title":{"rendered":"How to choose the correct GC column \u2013 Part 4"},"content":{"rendered":"\n<p>In Parts 1-3, I explained the process I use to help select the correct GC column. Hopefully it has provided a foundation of how someone may go about choosing an appropriate column for a particular compound, or group of compounds. For the fourth and final post in my series, I would like to present a few situations which, while not unique, don\u2019t really fit into the normal selection process.<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-wp-embed is-provider-wordpress-embed wp-block-embed-wordpress-embed\"><div class=\"wp-block-embed__wrapper\">\n<blockquote class=\"wp-embedded-content\" data-secret=\"2OBh1ReZqi\"><a href=\"https:\/\/discover.restek.com\/gnbl4703\/how-to-choose-the-correct-gc-column-part-1\/\">How to choose the correct GC column &ndash; Part 1<\/a><\/blockquote><iframe loading=\"lazy\" class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; visibility: hidden;\" title=\"&#8220;How to choose the correct GC column &ndash; Part 1&#8221; &#8212; \" src=\"https:\/\/discover.restek.com\/gnbl4703\/how-to-choose-the-correct-gc-column-part-1\/embed\/#?secret=IFzrFd7Sl9#?secret=2OBh1ReZqi\" data-secret=\"2OBh1ReZqi\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\n<\/div><\/figure>\n\n\n\n<figure class=\"wp-block-embed is-type-wp-embed is-provider-wordpress-embed wp-block-embed-wordpress-embed\"><div class=\"wp-block-embed__wrapper\">\n<blockquote class=\"wp-embedded-content\" data-secret=\"Zfo023yJG1\"><a href=\"https:\/\/discover.restek.com\/gnbl4704\/how-to-choose-the-correct-gc-column-part-2\/\">How to choose the correct GC column &ndash; Part 2<\/a><\/blockquote><iframe loading=\"lazy\" class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; visibility: hidden;\" title=\"&#8220;How to choose the correct GC column &ndash; Part 2&#8221; &#8212; \" src=\"https:\/\/discover.restek.com\/gnbl4704\/how-to-choose-the-correct-gc-column-part-2\/embed\/#?secret=x8WA874MZc#?secret=Zfo023yJG1\" data-secret=\"Zfo023yJG1\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\n<\/div><\/figure>\n\n\n\n<figure class=\"wp-block-embed is-type-wp-embed is-provider-wordpress-embed wp-block-embed-wordpress-embed\"><div class=\"wp-block-embed__wrapper\">\n<blockquote class=\"wp-embedded-content\" data-secret=\"jONjUDiTBP\"><a href=\"https:\/\/discover.restek.com\/gnbl4705\/how-to-choose-the-correct-gc-column-part-3\/\">How to choose the correct GC column &ndash; Part 3<\/a><\/blockquote><iframe loading=\"lazy\" class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; visibility: hidden;\" title=\"&#8220;How to choose the correct GC column &ndash; Part 3&#8221; &#8212; \" src=\"https:\/\/discover.restek.com\/gnbl4705\/how-to-choose-the-correct-gc-column-part-3\/embed\/#?secret=b0U2ens5aq#?secret=jONjUDiTBP\" data-secret=\"jONjUDiTBP\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\n<\/div><\/figure>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"200\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-01.jpg\" alt=\"\" class=\"wp-image-15172\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-01.jpg 200w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-01-150x150.jpg 150w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/figure>\n\n\n\n<p>Gas sample loops pictured above.<\/p>\n\n\n\n<p>The first situation I would like to discuss is how to select the proper column&nbsp;<em><strong>internal diameter (ID)<\/strong><\/em> when the sample introduction involves a gas sample loop. Please note that I will only be discussing pressure-loop systems which use multi-port gas sampling valves, like the one shown below. These systems are very common for natural gas analysis and greenhouse gas analysis.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"200\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-02.jpg\" alt=\"\" class=\"wp-image-15178\" title=\"-\" srcset=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-02.jpg 200w, https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-02-150x150.jpg 150w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/figure>\n<\/div>\n\n\n<p>6-Port gas sampling valve pictured above.<\/p>\n\n\n\n<p>The rule-of-thumb I use goes something like this (and yes, I know units are mismatched, but please hear me out);&nbsp;<strong>the volume of a sample loop (in mL) should not exceed 1\/10th of the carrier gas flow rate (in mL\/min)<\/strong>&nbsp;to keep the compound peaks reasonably sharp. For example, if using a 1mL sample loop, in order to keep the compound peaks from becoming excessively broad, the carrier gas flow rate should be at least 10mL\/min. Since this is a common flow rate for a 1\/16\u201d OD (1mm ID) micropacked column, this is the minimum ID column which should be used.<\/p>\n\n\n\n<p>Let\u2019s look at one more example. Let\u2019s say you are using a 0.25mm ID column with a carrier gas flow rate of 1mL\/min; then the size of the sample loop should not exceed 0.1mL (or 100\u00b5L).<\/p>\n\n\n\n<p>Please keep in mind a few things concerning this rule-of-thumb:<\/p>\n\n\n\n<p>1.&nbsp; This is only for gas sample loops, not gas-tight syringes (which can inject a sample much quicker than a sample loop).<\/p>\n\n\n\n<p>2.&nbsp; This only applies when the compounds are not able to condense within the column or instrument (and become refocused into a narrow band). If the compounds are able to condense at the head of the column, larger gas volumes can be injected without getting broader peaks.<\/p>\n\n\n\n<p>3.&nbsp; Do not confuse sample loop volume with sample concentration. The rule above only references sample loop volume, not the compound concentrations in the sample.<\/p>\n\n\n\n<p>4.&nbsp; Generally speaking, the smaller the sample loop volume, the sharper the peaks.<\/p>\n\n\n\n<p>The next situation involves samples which <strong><em>only<\/em><\/strong> contain either acidic (&amp; neutral) or basic (&amp; neutral) compounds. Fortunately, there are columns which have either an acidified or basic liquid phase or packing which produces better peak shapes (less tailing) which may result in more compound sensitivity. &nbsp;<strong>To minimize column damage, please remember to keep the pH of what you are injecting between 5 and 9 for most columns, between 5 and 7 for acidified columns and between 7 and 9 for basic columns.&nbsp;&nbsp;<\/strong><\/p>\n\n\n\n<p>Common&nbsp;<strong>acidified<\/strong>&nbsp;capillary columns include the Stabilwax-DA (similar to the liquid phase FFAP for packed columns).<\/p>\n\n\n\n<p>Other acidified packings include any solid support listed with a small % of H3PO4 and\/or CarboBlack B-DA.<\/p>\n\n\n\n<p>Common <strong>basic<\/strong>&nbsp;capillary columns include the Stabilwax-DB, Rtx-5 Amine, Rtx-35 Amine, and Rtx-Volatile Amine.<\/p>\n\n\n\n<p>Basic packings include any support listed with a small % of KOH or HayeSep B.<\/p>\n\n\n\n<p>The last situation I will discuss involves very reactive samples (including highly acidic or basic samples); those that are so reactive that they will damage the phase of capillary and packed columns.&nbsp; For situations when this happens, there are two columns which are more robust than virtually all other columns produced.&nbsp; They are both packed columns:<\/p>\n\n\n\n<p>5% Krytox on CarboBlack B in Nickel or Hastelloy tubing.&nbsp;&nbsp;<\/p>\n\n\n\n<p>Chromosorb T in PTFE or Nickel or Hastelloy tubing.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"174\" height=\"100\" src=\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-how-to-choose-the-correct-gc-column-part-4-03.jpg\" alt=\"\" class=\"wp-image-15184\" title=\"-\"><\/figure>\n<\/div>\n\n\n<p>If you simply cannot use one of these packed columns and need to use a&nbsp;<em><strong>capillary<\/strong><\/em> column, then try a thick film Rtx-1, as it is the most robust of WCOT (wall-coated open tubular) columns.<\/p>\n\n\n\n<p>I hope you have all enjoyed reading my posts on how to select the correct GC column. While I couldn\u2019t cover every conceivable situation that each of you will encounter, I am hoping that I provided you the tools necessary to help you develop your own selection process.&nbsp;<\/p>\n\n\n\n<div style=\"height:100px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n","protected":false},"excerpt":{"rendered":"<p>In Parts 1-3, I explained the process I use to help select the correct GC column. Hopefully it has provided a foundation of how someone may go about choosing an appropriate column for a particular compound, or group of compounds&#8230;.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[793],"tags":[],"industries-application":[],"post-badge":[],"resource-type":[567],"product-library":[],"resource-technique":[2316],"hf_cat_post":[623],"ppma_author":[582],"class_list":["post-48511","post","type-post","status-publish","format-standard","hentry","category-blog-it","resource-type-selection-guides","resource-technique-chromatographie-en-phase-gazeuse-gc"],"acf":[],"taxonomy_info":{"category":[{"value":793,"label":"Blog"}],"resource-type":[{"value":567,"label":"Selection Guides"}],"resource-technique":[{"value":2316,"label":"Chromatographie en phase gazeuse (GC)"}]},"featured_image_src_large":false,"author_info":{"display_name":"Patrick Gallagher","author_link":"https:\/\/discover.restek.com\/de\/author\/patrick-gallagherrestek-com\/"},"comment_info":0,"category_info":[{"term_id":793,"name":"Blog","slug":"blog-it","term_group":0,"term_taxonomy_id":793,"taxonomy":"category","description":"","parent":0,"count":442,"filter":"raw","cat_ID":793,"category_count":442,"category_description":"","cat_name":"Blog","category_nicename":"blog-it","category_parent":0}],"tag_info":false,"authors":[{"term_id":582,"user_id":0,"is_guest":1,"slug":"alan-sensue","display_name":"Alan Sensue","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts\/48511","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/comments?post=48511"}],"version-history":[{"count":4,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts\/48511\/revisions"}],"predecessor-version":[{"id":85343,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/posts\/48511\/revisions\/85343"}],"wp:attachment":[{"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/media?parent=48511"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/categories?post=48511"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/tags?post=48511"},{"taxonomy":"industries-application","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/industries-application?post=48511"},{"taxonomy":"post-badge","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/post-badge?post=48511"},{"taxonomy":"resource-type","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/resource-type?post=48511"},{"taxonomy":"product-library","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/product-library?post=48511"},{"taxonomy":"resource-technique","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/resource-technique?post=48511"},{"taxonomy":"hf_cat_post","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/hf_cat_post?post=48511"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/discover.restek.com\/de\/wp-json\/wp\/v2\/ppma_author?post=48511"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}