we still got very high Detection limit of 0.6 ppb for Zinc after we rinsed the Digi Tube with 2% HNO3. Does anybody know how to reduce the detection limit?
we use 2% HNO3 to rinse the Digi Tube, then fill the tube with 2% HNO3, and let them stand overnight with a lid covering. next day , we created the following calibration curve, but still have high background which lead to 0.6ppb.
we assume there are possibly two reasons to introduce this high background:
1. water quality. we use water for injection from Baxter. please see the below picture. we want to know what the background reading if milli Q water is used.
2. another is the instrument setting. we set the instrument setting: