You can use ammonium hydroxide. Try different ratios.

You can also try using 5 mmol/L phosphate buffer (pH 3.3) containing 5 mmol/L I-heptanesulphonic acid.

There are a few other solvents and a combination of solvents that may be used.

Ammonium hydroxide for dissolving Uric acid?

I don't want to use buffer.....so is there any other solvent system.....than please suggest.

Thanks

ANUJA

For measurement of uric acid in serum, calibrators of known concentration must be prepared in a suitable solvent. Uric acid is virtually insoluble in water or common organic solvents, but it can be dissolved in basic solution such as aqueous solutions of Li2CO3, KOH, NaOH, and ammonium hydroxide

https://academic.oup.com/clinchem/article/52/11/2117/5626754

Prepare a stock uric acid solution of 100 mg/L. Dilute it to give working concentrations of 5, 10, 20, 30, 40, and 50 mg/L. Weigh 100 mg uric acid, transfer to a 1 L volumetric flash, add about 900 ml distilled water, and then add about 100 µl of 0.6 N NaOH to help dissolve the uric acid.

http://www-naweb.iaea.org/nafa/aph/purine-cd/html/uricacid/html/06_3.htm