1. Requirements for pre-treated solution samples:
   a. The solution must be transparent and clear (the solution must be stable with no precipitation). For colored solutions, please confirm whether they are ionic solutions. If unsure, perform acid dissolution before using the instrument to avoid damaging it. Provide 5-10ml of solution, which should be neutral to slightly acidic, with acid concentration controlled below 5% (solutions dissolved with HF acid cannot be tested directly; fluoride ions must be volatilized completely, and even if already digested, they need to be diluted).
   b. Organic solutions, including those containing carbon, cannot be measured directly and must be digested with nitric acid until carbon is no longer present in the solution.
   c. The solution must not contain any insoluble impurities or organic matter! It is recommended to filter solution samples through a 0.45 µm membrane. After capping liquid samples, be sure to seal them with sealing film to prevent leakage.

2. Requirements for unprocessed liquid samples:
   a. For routine water quality samples (those requiring reference to national standards for testing), at least 50 milliliters of the sample is needed. For homemade or other liquid samples, generally, 10ml should be provided, and the sample composition should be indicated to facilitate the selection of digestion methods.
   b. After capping liquid samples, be sure to seal them with sealing film to prevent leakage.

3. Requirements for unprocessed solid samples:
   a. Powder samples should be more than 100mg. Please grind them finely in advance, and if possible, sieve through a 200 mesh. If microwave digestion is required, please provide at least 200mg.
   b. If there is a small quantity of solid sample, wrap it in weighing paper and place it in a tube.

4. Recovery reminder: This test is destructive, and the sample submitted for testing cannot be recovered; only the remaining sample (if any) can be recovered.