Éva Ács

Chlorophyll-a determination with ethanol - A critical test

Chlorophyll-a content is widely used as an indicator of the quality of freshwater bodies. Quantification of chlorophyll-a is a routine procedure in the test laboratories of water works, and in research laboratories. Although attempts have been made to standardise the measurement procedure, there are nonetheless many procedures currently in use. This work is focused on a careful re-examination of the ISO: 10260, 1992 standard, which prescribes 90% (v/v) ethanol for chlorophyll extraction and measurement. Chlorophyll contents of cultures of the cyanobacterium Synechococcus elongatus Nägeli and the chlorophyte Scenedesmus acutus Meyen were determined by means of a series of concentrations of ethanol/water mixtures which were employed as extracting agents – the water content was gradually decreased from 20 to 0%. The extraction procedure was verified by measuring the amount of retained water after using both water and oil pumps for filtering the samples. The spectroscopic effects of the presence of water were studied and the molecular background of these spectral phenomena is discussed. The extraction yields obtained with 90% ethanol were compared to those obtained with methanol and acetone. On the basis of the calculated error level, improvements to the ISO: 10260, 1992 standard method have been suggested.

Investigation of lead and nickel contaminated natural biofilms

Total reflection X-ray fluorescence spectrometric method was developed for elemental analysis of lead and nickel contaminated natural biofilms grown on polycarbonate substrates. The biofilms were grown in the Lake of Velence for 4 weeks and then in the laboratory in contaminated lake water for other 2 weeks. It was established that the accumulation of these bivalent cations were practically the same and in their presence the accumulation of zinc decreased by approximately 20% while the other elements (Ca, K, Fe, Mn, Sr, Ti, Rb) showed smaller changes within the statistical interval. From biological point of view, these two bivalent cations reduced the abundance of the algae, to a similar extent; however, the total biomass production was significantly hampered only by nickel (14%).