Microwave-digest the saliva sample with concentrated nitric acid - in a proper microwave digestion oven!
What type of techinques you plan to use for trace elements? is it ICP- OES, AAE or XRF.
you can follow the following procedure:
Microwave–assisted acid digestion
Triplicate of 0.5 ml of HB samples, of each DM, HTN patients and normal subjects, were directly placed into porcelain crucible. Three milliliters of concentrated HNO3–H2O2 (2:1, v/v) was added to each crucible. The crucibles were covered and kept at room temperature (~35 oC) for about 5 min as a pre-digestion time, then placed in a microwave oven. Then, crucibles were heated following a one-stage digestion program at 30 % of total power (900 W). Complete digestions of all samples required 2-3 min. After the digestion was completed, the crucibles were left to cool at room temperature and the resulting solution (about 0.5 ml of semi-dried mass) was dissolved by 5 ml of 0.1 mol l-1 HNO3. Then, transferred quantitatively to 10 ml volumetric flasks, diluted with DDDW up to mark and transferred to a polyethylene storage bottle for further analysis. Blank and spike sample solutions were carried out simultaneously through the complete digestion procedures and similar acid matrices. The presence of ca. 0.1 mol l-1 HNO3 in the final solution was necessary to maintain acidic environment and avoid formation of insoluble hydroxides before measurement steps. This procedure is similar to that stated by Kazi et al. [2], Afridi et al. [10] and Memon et al. [29], with some modifications in digestion time and microwave oven program. The validity of the digestion procedure was checked by spiking of different HB samples of normal subjects with a known amounts of multi-element standard solution before (pre) and after (post) digestion procedures. All target elements were determined in the prepared solutions by ICP-OES.
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