![\"\"](\"https:\/\/discover.restek.com\/wp-content\/uploads\/blog-cannabis-potency-testing-calibration-curves-01.jpg\" "\\"-\\"")
<\/figure>\n\n\n\nFigure 1. Upper and lower confidence intervals calculated for calibration curves containing 3, 5, and 7 points.<\/p>\n\n\n\n
The confidence limits were calculated using the same data, just using either 3, 5, or 7 points. If we zoom in on the calibration curve we can start to see the significance the number of calibration points has on the upper and lower confidence intervals.<\/p>\n\n\n\n Figure 2. Zoomed in portion of Figure 1.<\/p>\n\n\n\n When we look at Figure 2 we can see that for more points on a calibration curve the narrower the band is for upper and lower confidence intervals. We can say with 95% confidence that the true value lies within this region. The more points that you have in a calibration curve, the narrower the range that your \u201ctrue value\u201d will likely occur, so you\u2019re getting a more accurate quantitation for your unknown. As less points are used in the calibration curve the larger the range in which the \u201ctrue value\u201d could lie and the greater error you can expect when calculating concentration of an unknown.<\/p>\n\n\n\n Now that we understand the effect the number of points has on quantitation, the question next comes up, \u201chow often do I need to run a calibration curve?\u201d The best place to look to answer this question is to your laboratory\u2019s guidelines or SOPs. If your guidelines do not require daily runs of calibrations you can ensure that the instrument is working properly by running daily quality control (QC) points to verify that calibration is still valid. When performing this test, the QC accuracy values should fall between 95-105% to be considered acceptable.<\/p>\n\n\n\n Plotting the points on a calibration curve should result in a linear response. A trend line can be fit to the data to give an equation of the line and R2<\/sup> value. R2 <\/sup>shows the proportionality of instrument response to quantity being analyzed. In most cases the closer to 1 the R2 <\/sup>value the more linear the line is. There can be instances where you have a value of 0.99 and not have a linear relationship. In these cases lack-of-fit can be more reliable to confirm linear relationship between concentration and instrument response.<\/p>\n\n\n\n The way calibration standards are made can affect linearity. Each standard should be made individually from a concentrated stock solution and not by serial dilution. Serial dilution is when the most concentrated standard is made, and then used to make the next concentration of standard and so on. Serial dilution of standards introduces propagation of error and can adversely affect the linearity of the calibration curve. The concentration of standards should ideally range over 3 orders of magnitude, be within the concentration range of the samples being quantitated, and should fall within the linear dynamic range of the instrument. For instance, if your calibration curve is \u201cflattening out\u201d near the high concentration points then you are reaching the upper limit of your detector and are no longer in the ideal linear range.<\/p>\n\n\n\n Interested in a certain topic and want it covered in the next blog? Send us an email with your cannabis laboratory\/workflow questions and topics and it could be our next blog post!<\/p>\n\n\n\n Cannabis Potency Testing & Calibration Curves<\/p>\n","protected":false},"author":47,"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":[790],"tags":[],"industries-application":[2173,2175],"post-badge":[],"resource-type":[],"product-library":[],"resource-technique":[],"hf_cat_post":[623],"ppma_author":[579],"class_list":["post-51626","post","type-post","status-publish","format-standard","hentry","category-blogs-zh","industries-application-cannabis-zh","industries-application-medical-recreational-cannabis-zh"],"acf":[],"taxonomy_info":{"category":[{"value":790,"label":"\u535a\u5ba2"}],"industries-application":[{"value":2173,"label":"\u5927\u9ebb"},{"value":2175,"label":"\u533b\u7597\u6216\u5a31\u4e50\u7528\u5927\u9ebb"}]},"featured_image_src_large":false,"author_info":{"display_name":"Jamie L. 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<\/figure>\n\n\n\n