The solubility of L-tryptophan is 11.4g/l in water. I tried dissolving 1.14 g in 100 ml PBS but still, it's not fully dissolved. Should I add NaOH or HCl? Also, can we stir the solution, or should put it on a shaker to dissolve fully?
Dear Meenakshi Pundir ,
L-Tryptophan has a water solubility of 0.23 g/L at 0 °C, 11.4 g/L at 25 °C, 17.1 g/L at 50 °C, 27.95 g/L at 75 °C, 49.9 g/L at 100 °C, at pHs in the range of 5.5 - 7.0 check O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 1682
The PBS (Phosphate-Buffered-Saline) may be purchased in two pH ranges, 7.2 and 7.4, slightly higher than the solubility reference for L-Tryptophan.
Nevertheless, it is soluble in hot alcohol and solutions of dilute acids and alkali hydroxides. Reynolds, J.E.F., Prasad, A.B. (eds.) Martindale-The Extra Pharmacopoeia. 28th ed. London: The Pharmaceutical Press,1982., p. 61.
Higher solubility may be achieved by gentle heating the sample without the need for any additional chemical compound. For the PBS at 7.4, some dilute acid solution will favor the solubility.
Gentle stirring would be enough.
Best regards,
WNM
PBS is a buffer and HCl or NaOH will be buffered at low concentrations. pKa of tryptophan is 2.8; therefore, you need to go at lower pH to solubilize but PBS (pH=7.4)is no use at this pH. Trp is soluble in ethyl acetate or ethylene glycol. Check if you can use aqueous solutions of these solvents for your purpose.
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