Determination of Trace Elements in Cow Placenta by Tungsten Coil Atomic Emission Spectrometry
In this application note, tungsten coil atomic emission spectrometry was used for direct determination of Ca in biodiesel samples. Discrete volumes of biodiesel (10 μL) were directly placed on the tungsten coil with a micropipette and an appropriated heating program was applied to decompose the samples. The first four heating steps (0.32; 0.35; 0.36 and 0.37 V for 20; 50; 50 and 50 s, respectively) were employed to dry the sample and decompose organic matrix. The purge gas flow rate, composed by a mixture of 90 % v/v plus 10 % v/v hydrogen, was stopped during the drying/matrix decomposition steps to minimize temperature gradients in the sample drop in contact with the hot metallic surface. The analytical figures of merit for Ca (emission wavelength = 422.7 nm) were determined with calcium reference solutions. Two different linear ranges were observed, 0.2 – 1.0 and 1.0 – 10.0 mg L -1 . The detection limit (LOD) was estimated as 0.15 mg L -1 , which corresponds to 0.17 mg kg -1 in biodiesel, and the relative standard deviation (n = 10, 2 mg L -1 Ca) was estimated as 2.6 %. Sample throughput was approximately 20 samples h -1 . The accuracy was proved by an addition-recovery experiment.