Problems in determining melamine content using the picric acid method

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Determination of melamine content in waste residues by picric acid method: The sample is weighed and heated to dissolve it; after cooling, phenolphthalein is added. If a color appears, dilute sulfuric acid is used to make the solution colorless. The insoluble substances are then filtered out, and the content is determined using the filtrate. Due to the varying solubility of melamine in water at different temperatures, cooling may cause some of the melamine to precipitate, thereby affecting the results. We compared the test results by not cooling before filtration, and the levels obtained without cooling were significantly higher than those measured after cooling. I would like to ask everyone: why is the cooling step necessary in the current process? (Since there must be a reason for cooling,) which method is actually the most accurate, and what impact does skipping this cooling step have on the results?