{"id":51863,"date":"2013-03-04T13:30:00","date_gmt":"2013-03-04T13:30:00","guid":{"rendered":"https:\/\/discover.restek.com\/uncategorized\/why-are-there-different-resolution-equations-in-chromatography\/"},"modified":"2025-10-28T13:34:42","modified_gmt":"2025-10-28T13:34:42","slug":"why-are-there-different-resolution-equations-in-chromatography","status":"publish","type":"post","link":"https:\/\/discover.restek.com\/es\/blogs\/gnbl4872\/why-are-there-different-resolution-equations-in-chromatography","title":{"rendered":"Why are there different resolution equations in chromatography?"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n
<\/div>\n\n\n\n

It must be confusing for people that see the resolution equations that are used to \u201cexplain\u201d chromatography in GC or LC.<\/p>\n\n\n\n

The challenge is that for different equations, assumptions are made, which are not listed with each equation.<\/p>\n\n\n\n

Resolution, R, is dependent on 3 main parameters: The capacity factor, \u201ck\u201d, the theoretical plate number , \u201cNth\u201d, and the selectivity factor, \u201calpha\u201d.<\/p>\n\n\n\n

<\/div>\n\n\n\n

\"Alpha-fig1\"
Equation 1<\/p>\n\n\n\n

<\/div>\n\n\n\n

As R is a measure how well 2 peaks are separated, this value depends on the k and Nth for BOTH components. This makes the resolution equation very complex (equation 1). When the k of both compounds is almost the same, one can use just the \u201ck\u201d value. The same is possible for Nth. As the difference in k is very small, also the alpha will be small and the resolution equation can be simplified to equation 2.<\/p>\n\n\n\n

<\/div>\n\n\n\n

\"Alpha-fig2\"
Equation 2<\/p>\n\n\n\n

<\/div>\n\n\n\n

Equation 2 should not be used as generic anymore as its ONLY applicable for small values of alpha. If the difference in k between the 2 compounds increases the alpha also increases rapidly and according to equation 2, the \u201calpha-term\u201d approaches \u201c1\u201d, meaning R value will not increase at higher alpha\u2019s, which is not correct.<\/p>\n\n\n\n

<\/div>\n\n\n\n

\"Alpha-fig3\"
Equation 3<\/p>\n\n\n\n

<\/div>\n\n\n\n

That\u2019s why equation 3 is the most straightforward equation to explain the impact of all contributing parameters.<\/p>\n\n\n\n

R  increase always with increasing \u201calpha\u201d values, independent of magnitude;<\/p>\n\n\n\n

R  increase also linear when small k-values are increased and fade off at higher k\u2019s (this term becomes  \u201c1\u201d);<\/p>\n\n\n\n

R increase linear with the square root of the plate number.<\/p>\n\n\n\n

For details about all equations, you can read J.P Foley, Analyst, December 1991, Vol. 116, p.1275.<\/p>\n\n\n\n

<\/div>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

It must be confusing for people that see the resolution equations that are used to \u201cexplain\u201d chromatography in GC or LC. The challenge is that for different equations, assumptions are made, which are not listed with each equation. Resolution,…<\/p>\n","protected":false},"author":19,"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":[9],"tags":[],"industries-application":[],"post-badge":[],"resource-type":[],"product-library":[],"resource-technique":[],"ppma_author":[439],"class_list":["post-51863","post","type-post","status-publish","format-standard","hentry","category-blogs"],"acf":[],"taxonomy_info":{"category":[{"value":9,"label":"Blogs"}]},"featured_image_src_large":false,"author_info":{"display_name":"Jaap de Zeeuw","author_link":"https:\/\/discover.restek.com\/es\/author\/jaap-de-zeeuw\/"},"comment_info":0,"category_info":[{"term_id":9,"name":"Blogs","slug":"blogs","term_group":0,"term_taxonomy_id":9,"taxonomy":"category","description":"","parent":0,"count":436,"filter":"raw","cat_ID":9,"category_count":436,"category_description":"","cat_name":"Blogs","category_nicename":"blogs","category_parent":0}],"tag_info":false,"authors":[{"term_id":439,"user_id":19,"is_guest":0,"slug":"jaap-de-zeeuw","display_name":"Jaap de Zeeuw","avatar_url":{"url":"https:\/\/discover.restek.com\/wp-content\/uploads\/people-de-zeeuw-jaap.jpg","url2x":"https:\/\/discover.restek.com\/wp-content\/uploads\/people-de-zeeuw-jaap.jpg"},"author_category":"1","first_name":"Jaap","last_name":"de Zeeuw","user_url":"","job_title":"","description":"Jaap is a world-renowned chromatographer with over 40 years of experience, including 15 years with Restek and 27 years with Varian\/Chrompack prior to joining Restek. Throughout his career, Jaap has focused the chromatographic challenges of industrial analysis. For his 1979 graduation from The Institute for Higher Education, where he specialized in chemistry, Jaap authored a paper titled \"The Challenge of Coating Flexible Fused Silica Capillary Columns\" and has since distinguished himself as an authority on the subject. Jaap has been directly involved with the creation of numerous chemically bonded columns, including the first bonded PEG column and the stabilized PLOT columns widely used in the petrochemical arena. He has also helped develop new techniques, such as fast GC-MS using vacuum GC technology (low-pressure GC or LPGC). Over his innovative career, he has filed several patents for his work. Based out of the Netherlands, Jaap is extensively published and regularly travels internationally to share his knowledge. After retiring from Restek, Jaap founded CreaVisions, where he works as a GC Consultant and teaches master classes on key GC topics as well as on creativity in science."}],"_links":{"self":[{"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/posts\/51863","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/users\/19"}],"replies":[{"embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/comments?post=51863"}],"version-history":[{"count":3,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/posts\/51863\/revisions"}],"predecessor-version":[{"id":58574,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/posts\/51863\/revisions\/58574"}],"wp:attachment":[{"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/media?parent=51863"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/categories?post=51863"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/tags?post=51863"},{"taxonomy":"industries-application","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/industries-application?post=51863"},{"taxonomy":"post-badge","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/post-badge?post=51863"},{"taxonomy":"resource-type","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/resource-type?post=51863"},{"taxonomy":"product-library","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/product-library?post=51863"},{"taxonomy":"resource-technique","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/resource-technique?post=51863"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/discover.restek.com\/es\/wp-json\/wp\/v2\/ppma_author?post=51863"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}