Determination of carbon in natural freshwater biofilms with total reflection X-ray fluorescence spectrometry

There is a growing interest in determination of low Z elements, i.e., carbon to phosphorus, in biological samples. Total reflection X-ray fluorescence spectrometry (TXRF) has been already established as suitable trace element analytical method with low sample demand and quite good quantification limits. Recently, the determinable element range was extended towards Z=6 (carbon). Biofilms can be used for biomonioring purposes in the aquatic environment. Besides the trace metals, especially the determination of the carbon content is important for the better understanding of the early stage of biofilm formation. For this, an ATI low Z spectrometer equipped with Cr-anode X-ray tube, multilayer monochromator, vacuum chamber, and a Si(Li) detector with ultra thin window was used. Biofilms were grown on two different artificial supports (granite and plexiglass), freeze dried, suspended in high purity water and analyzed. As an internal standard the natural titanium content of the biofilms was used. The accuracy of the method was checked by total carbon measurement using a combusting carbon analyzer. (C) 2009 Elsevier B.V. All rights reserved.