Well, I'd rather leave the spectro work to the professionals, given that I only have cursory knowledge of analysis, doing anything on my own will be little more than a waste of time.
Another remark not directly related to glycin synthesis, but generally useful(I think) : It may be possible to regenerate old brown glycin if you dissolve it in an alkaline solution and add ascorbic acid at 1/10 of the weight of the glycin. Boil until solution clears up and its color lightens. Note that this works for me, but your results may vary, so try it on a small (1/8g) amount and see if it works before going for a large batch.