Author/Editor		Lušin, Maja; Krbavčič, Aleš
Title		Tehnika nadprostora, plinska kromatografija
Translated title		Headspace gas chromatography
Type		članek
Source		Farm Vestn
Vol. and No.		Letnik 49, št. 3
Publication year		1998
Volume		str. 259-71
Language		slo
Abstract		Headspace method is a gas chromatographic methodsthat is used to analyse the volaite compounds in samples when it is difficult or impossible to inject the actual sample into a gas chromatograph. The volatile compounds are extracted from sample by gas. The technique works by incrasing temperature. There are two means of extracting -single or multiple headspace extraction (MHSE). Single headspace extraction is used for samples for which there are no matrix effects. Quantitative analysis can be performed by using either suitable internal, external standards or standard addition method. Multiple headspace extraction is used for samples for which no calibration standards can be pepared easily, e.g. solid samples. The total amount of volatiles inthe sample is determinated. With each ectraction the concentration of the volatile compound in both the gas phase and the sample becomes smaller, although the ration remains constant. For the change in concentration per time the first order reaction can be applied.
Summary		Metoda nadprostora (headspace tehnika) je analizna metoda v plinski kromatografiji, namenjena za analizo lahkohlapnih sestavin vzorcev. Uporablja se takrat, kadar je vzored težko ali nemogoče direktno injicirati na kolono. Lahkohlapne sestavine vzorca ekstrahiramo s plinom, ekstrakcija navadno poteka pri povišani temperaturi. Učinkovine iz vzorca ekstrahiramo z enkratno ali večstopenjsko ekstrakcijo (MHSE). Enkratna ekstrakcija je primerna za analizo učinkovin v vzorcih, kjer matriks na ekstrakcijo ne vpliva. Za kvantitativno analizo uporabljamo interno oz. eksterno standardizacijo ali metodo standardnega dodatka. Večstopenjsko ekstrakcijo uporabljamo, kadar za kvantitativno analizo ne moremo pripraviti ustreznega standarda (npr. trdni vzorci). Določimo celotno količino analizirane učinkovine v vzorcu. Z vsako ekstrakcijo s ekoncentracija analizirane učinkovine v nadprostoru in v vzorcu zmanjšuje, porazdelitveni koeficient pa ostaja nespremenjen. Koncentracija učinkovine se s časom spreminja po kinetiki prvega reda.
Descriptors		CHROMATOGRAPHY, GAS CHEMISTRY, PHARMACEUTICAL