Abstract :
H?rtelʹs turbidity test (Trübungstest) has been one widely used diagnostic test for air pollution injury for decades. This test is based on the extraction of lipophilic substances into an aqueous suspension, whose light absorption is used as an indication of exposure to pollution. Little is known about the underlying principles controlling the response of the test. In this study, the influence of the cations Li+, Na+, K+, and Ca2+ and that of the anions Cl-, Br-, I-, and SO42- on the response of H?rtelʹs test was reinvestigated. In contrast to an earlier study, both the extractsʹ absorbance and acidity were monitored. Additionally, the effects of the Ca-chelating agents ethylenediaminetetraacetate (EDTA) and oxalic acid were compared with that of deionized water and different buffers. All effects of ions including that of Ca2+ on the response of the test were accompanied by shifts of the extractsʹ acidity. Even small changes in the pH caused significant variations in the testʹs response. On the other hand, addition of the Ca chelating agents EDTA and oxalic acid to the solvent did not affect the response of the test when the pH was equal to solvents without Ca chelating compounds. Therefore, the previously published assumption that the availability of Ca2+ could be the main principle of the testʹs reaction mechanism was not confirmed.
