Seeking help with the color change issue in EDTA-4Na solution
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Hello everyone, I urgently need help. Our company received a batch of EDTA-4Na material; after dissolving it in water, we noticed that it turned yellow after being left for some time. However, previous batches didn’t have this issue. Currently, this batch of material has been put on hold at the factory. We conducted ICP and TOC analyses, and found that, in comparison, this batch had a yellowish color. The differences in ion levels were as follows: for Al, the level was below 5 mg/l in the non-yellowish batch and 8 mg/l in the yellowish batch; for Ca, it was below 10 mg/l in the non-yellowish batch and 61 mg/l in the yellowish batch; for SiO2, it was below 20 mg/l in the non-yellowish batch and 630 mg/l in the yellowish batch. I would like to ask everyone what causes the aqueous solution of this material to turn yellow – could there be other impurities contributing to this effect?
This post was last edited by qugd on 2020-6-5 at 10:23. It seems that the impurity content is high; conduct a full analysis of the sample. But I believe the main reason for the yellowing is not the high levels of calcium and silicon; there are other factors at play, and it’s even possible that during the EDTA purification process, certain organic substances and transition metal ions exceed the allowed limits.