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Extraction of conifer waxes as the basic principle of Härtel's turbidity test
Author(s) -
PFEIFHOFER HARTWIG W.
Publication year - 1995
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1995.tb04321.x
Subject(s) - epicuticular wax , chemistry , chromatography , wax , turbidity , extraction (chemistry) , gas chromatography , composition (language) , biochemistry , oceanography , linguistics , philosophy , geology
SUMMARY Hartel's turbidity test (‘Trübungstest’) has been one of the most widely used diagnostic tests for air pollution injury. It relies on the extraction of lipophilic substances into an aqueous suspension, whose light absorption is used as an indication of exposure to pollution. As a first step towards a better understanding of the test's reaction mechanism, the identity of the turbidifying compounds was analyzed. For that purpose, needles of Norway spruce [ Picea abies (L.) Karst.] were extracted with boiling water following the standardized procedures of the turbidity test. The lipids were recovered by centrifugation and fractionated by preparative chromatography. The isolated compounds were identified by gas chromatography (GC), GC‐mass spectrometry and comparison with authentic samples. The samples were hydrolyzed with methanolic HCl. Quantitative analysis of the lipid composition was completed by GC without prior class separation. The composition of the turbidifying substances was equal to control samples of epicuticular waxes of Norway spruce needles, with w‐hydroxy‐n‐alkanoic acids, n ‐alkanoic acids, α,ω‐alkanediols, and the secondary alcohol 10‐nonacosanol as the predominant compound classes. The content of unsaturated fatty acids (C 18:1 , C 18:2 , C 18:3 ), which are characteristic constituents of membrane lipids, was negligible. Extraction of needles with sodium oxalate, which resulted in enhanced turbidity, was connected only with an enhanced recovery of extracted epicuticular lipids, whereas the lipid composition showed only minimal variation. Therefore, the reaction mechanism of Härtel's turbidity test seems to be solely controlled by factors that influence the interaction of epicuticular wax compounds with water. The previously published supposition, that filtration of compounds through the epidermal cell wall should be the main principle of the test's reaction mechanism, could not be confirmed.