Determination of zinc in fingernails by non-flame atomic absorption spectroscopy.

The determination of Zn in fingernails directly using the graphite furnace presented certain difficulties due to the anomalous behavior of the analyte in the furnace. The appearance of two peaks which were due to Zn and not to any background interference was noted. The Zn value obtained by adding the area of these two peaks compared fairly well with Zn levels determined by wet ashing and subsequent determination either in the furnace or flame. Wet ashed samples gave only a single peak. It was possible to produce a model of the phenomenon with various Zn salts in a non aqueous matrix. Under these conditions ZnSO4 and ZnO gave a discretely different peak from ZnC12 or metallic Zn. Several tissues such as serum, whole blood, cuticle, and hair were examined for multiple peak formation. Direct determination of Zn in fingernails with the graphite furnace is possible for certain applications such as the determination of Zn levels of white spots in fingernails. For this purpose it is possible to use a sample size as small as 20 mug using the 2138 Zn line. This allows one to run several determinations on a single white spot. However, where sample size is not a limitation, wet ash digestion prior to determination in the furnace is probably the preferred procedure.