a chromatographic technique in which an unknown substance is applied to a chromatographic support together with one or more known compounds, in the expectation that the relative behaviour of the unknown and known substances will assist in the identification of the unknown one., a procedure in which the extract prior to the chromatographic step(s) is divided into two parts. Part one is chromatographed as such. Part two is mixed with the standard analyte that is to be measured. Then this mixture is also chromatographed. The amount of added standard analyte has to be similar to the estimated amount of the analyte in the extract., meetod, mille puhul uuritav ekstrakt jagatakse kaheks, üks osa ekstraktist kromatografeeritakse kohe, teisele osale lisatakse enne kromatografeerimist mõõdetava analüüdi standardit, mille hulk on lähedane eeldatavale analüüdi sisaldusele ekstraktis.