IMPORTANT NOTICE: As of December 21, 2025, we will no longer provide the old free Moodle hosting plan with pre-installed plugins that your site currently uses.
After that date, all sites that use it and have not switched to a paid hosting plan will be migrated to the current free hosting plan (wihout plugins and with only 2 GB of disk space).
You can switch to a payment plan for only
$19.95 USD per month or $219.95 USD per year (plus local taxes).
In analytical chemistry , a calibration curve is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration .