{"id":27,"date":"2024-04-03T23:09:23","date_gmt":"2024-04-03T20:09:23","guid":{"rendered":"https:\/\/sisu.ut.ee\/measurement\/105-practical-example-uncertainty-estimation-using-nordtest-approach\/"},"modified":"2024-08-30T09:01:46","modified_gmt":"2024-08-30T06:01:46","slug":"105-practical-example-uncertainty-estimation-using-nordtest-approach","status":"publish","type":"page","link":"https:\/\/sisu.ut.ee\/measurement\/105-practical-example-uncertainty-estimation-using-nordtest-approach\/","title":{"rendered":"10.5.\tNordtest approach in practice: Determination of acrylamide in snacks by LC-MS"},"content":{"rendered":"<p style=\"text-align: center;\"><\/p><div class=\"ratio ratio-16x9 mb-3\"><div class=\"video-placeholder-wrapper video-placeholder-wrapper--16x9\">\n\t\t\t    <div class=\"video-placeholder d-flex justify-content-center align-items-center\">\n\t\t\t        <div class=\"overlay text-white p-2 w-100 text-center d-block justify-content-center align-items-center\">\n\t\t\t            <div>To view third-party content, please accept cookies.<\/div>\n\t\t\t            <button class=\"btn btn-secondary btn-sm mt-1 consent-change\">Change consent<\/button>\n\t\t\t        <\/div>\n\t\t\t    <\/div>\n\t\t\t<\/div>\n<\/div>\n<h4 style=\"text-align: center;\"><strong>Nordtest approach in practice: Determination of acrylamide in snacks by LC-MS<\/strong>\u00a0<a href=\"#\" data-bs-toggle=\"modal\" data-bs-target=\"#popup-modal\" data-title=\"[1]\" data-content=\"Please note that in the tables of the slide &amp;#8220;Measurements with the CRMs&amp;#8221; the measurement units must be \u00b5g\/kg, not mg\/l.\">[1]<\/a>\u00a0<br><a href=\"http:\/\/www.uttv.ee\/naita?id=18163\" target=\"_blank\" rel=\"noopener\">http:\/\/www.uttv.ee\/naita?id=18163<\/a><\/h4>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.youtube.com\/watch?v=P94xWjC6Og0\" target=\"_blank\" rel=\"noopener\">https:\/\/www.youtube.com\/watch?v=P94xWjC6Og0<\/a><\/p>\n<p>Some comments on this example:<\/p>\n<p><span style=\"line-height: 1.6em;\">1. We use relative uncertainties in this example. The reason is that the concentration in these samples is quite high and in LC-MS analysis variability of the results is often roughly proportional to the values of the results.<\/span><\/p>\n<p><span style=\"line-height: 1.6em;\">2. In this example we assume that the matrixes of the used CRMs \u2013 potato chips and crisp bread \u2013 are sufficiently similar. This means that both reproducibility and bias obtained with these matrixes are similar. In such case the calculated uncertainty is applicable to both of these matrixes. If afterwards we will analyse some matrix that is different from potato chips and crisp bread then we cannot apply to that result the uncertainty estimate that we obtained here. Assessing whether a new matrix is sufficiently similar to the one used for bias evaluation is usually based on experience.<\/span><\/p>\n<p><span style=\"line-height: 1.6em;\">3. The uncertainty estimate <\/span><em style=\"line-height: 1.6em;\">u<\/em><sub>c<\/sub><span style=\"line-height: 1.6em;\">rel that we have obtained is a relative uncertainty, so it is assigned to a result <\/span><em style=\"line-height: 1.6em;\">C<\/em><sub>A<\/sub><span style=\"line-height: 1.6em;\"> by the following formula:<\/span><\/p>\n<table class=\"table table-hover\" border=\"0\" align=\"center\">\n<tbody>\n<tr valign=\"middle\">\n<td><img loading=\"lazy\" decoding=\"async\" width=\"156\" height=\"47\" class=\"alignnone wp-image-71\" style=\"vertical-align: middle;\" title=\"valem10-1.png\" src=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/18\/valem10-1.png\" alt=\"valem10-1.png\"><\/td>\n<td>\u00a0(10.8)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><br style=\"line-height: 1.6em;\"><span style=\"line-height: 1.6em;\">In principle it can be assigned to a result of any magnitude, however, it would not be correct to apply this uncertainty to analysis results that are very different from the one presented here. The difference should not be higher than 3-4 times.<\/span><\/p>\n<p style=\"text-align: left;\">When we use the Nordtest approach for uncertainty estimation then in general we can assume that the number of degrees of freedom is sufficiently large so that the <em>k<\/em> = 2 uncertainty can be assumed to have roughly 95% coverage probability.<\/p>\n<p style=\"text-align: left;\">***<\/p>\n<p style=\"text-align: left;\">[1]\u00a0Please note that in the tables of the slide \u201cMeasurements with the CRMs\u201d\u00a0the measurement units must be \u00b5g\/kg, not mg\/l.<\/p>\n<p><a title=\"\" href=\"https:\/\/sisu.ut.ee\/measurement\/self-test-10-5-a\/\" data-url=\"https:\/\/sisu.ut.ee\/measurement\/measurement-1-10\" data-wplink-edit=\"true\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-60\" style=\"margin-left: auto; margin-right: auto;\" title=\"selftest.png\" src=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/18\/selftest.png\" alt=\"selftest.png\" width=\"104\" height=\"41\"><\/a><\/p>\n<p><span style=\"line-height: 1.6em;\">The slides of this example and the calculation files \u2013 both the initial and the solved file \u2013 are available from here:<\/span><\/p>\n\n\n<div class=\"wp-block-group attached-files-group is-layout-constrained wp-block-group-is-layout-constrained\">\n<div class=\"wp-block-file\"><a id=\"wp-block-file--media-8ab95398-e0f7-466e-adee-bbe711dff7a7\" href=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/18\/nordtest_uncertainty_example_acrylamide_lc-ms.pdf\" target=\"_blank\" rel=\"noreferrer noopener\">nordtest_uncertainty_example_acrylamide_lc-ms.pdf<\/a><\/div>\n\n\n\n<div class=\"wp-block-file\"><a id=\"wp-block-file--media-ae0160d8-f785-4c74-8021-c22fc50b52f4\" href=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/18\/nordtest_uncertainty_example_acrylamide_lc-ms_initial.xls\" target=\"_blank\" rel=\"noreferrer noopener\">nordtest_uncertainty_example_acrylamide_lc-ms_initial.xls<\/a><\/div>\n\n\n\n<div class=\"wp-block-file\"><a id=\"wp-block-file--media-3856d3ba-8ea4-4e36-b700-834a9c914527\" href=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/18\/nordtest_uncertainty_example_acrylamide_lc-ms_solved.xls\" target=\"_blank\" rel=\"noreferrer noopener\">nordtest_uncertainty_example_acrylamide_lc-ms_solved.xls<\/a><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>To view third-party content, please accept cookies. Change consent Nordtest approach in practice: Determination of acrylamide in snacks by LC-MS\u00a0\u00a0http:\/\/www.uttv.ee\/naita?id=18163 https:\/\/www.youtube.com\/watch?v=P94xWjC6Og0 Some comments on this example: 1. We use relative uncertainties in this example. The reason is that the concentration &#8230;<\/p>\n","protected":false},"author":14,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"class_list":["post-27","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/pages\/27","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/users\/14"}],"replies":[{"embeddable":true,"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/comments?post=27"}],"version-history":[{"count":4,"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/pages\/27\/revisions"}],"predecessor-version":[{"id":825,"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/pages\/27\/revisions\/825"}],"wp:attachment":[{"href":"https:\/\/sisu.ut.ee\/measurement\/wp-json\/wp\/v2\/media?parent=27"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}