Estimation of Titrable Acidity and Ammonia in Urine Sample

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BACKGROUND

Titrable acidity is the amount of M/10 NaOH needed to make urine 7.4 alkaline. In a urine sample the titrable acidity is determined by titrating urine with a standard solution and the end point of this titration the ammonium salt that is present in urine is decomposed by adding neutral formalin solution that gives our equal amount of acid. Then this acid is titrated with an alkaline solution for determining ammonia in urine. So, the basic objective of this experiment is to estimate the titrable acidity and ammonia in urine sample.

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REQUIREMENTS

Reagents:       Neutral formaline solution: 10 ml formalin+2 drops of phenolpthaline+0.1 M NaOH (drop wise) till pink colour                           is achieved.

0.1 M NaOH Solution

Phenolphthalein Indicator

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PROCEDURE

Titrable acidity estimation

In a 250 ml conical flask take 25 ml urine sample. To it add 4 gm of potassium oxalate so that calcium is precipitated and then mix the content. To this add about 2-3 drops of phenolphthalein indicator and then perform titration with 0.1 M NaOH solution and shake till pink colour appears.¹

Standard value of acidity per 24 hours urine is 200-500 ml of 0.1N HCL

Titrable acidity = (number of ml of NaOH/urine in ml)×0.75

Ammonia estimation

Add 10 ml of neutral formalin solution to the above titrated solution and mix it properly. As acid is liberated pink colour goes away.² Then again titrate this content with 0.1M NaOH until pink colour appears. Note the burette reading.

Ammonia excretion in adult is 0.6-0.9 g.

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CONCLUSION

Titrable acid or base is one of the important parameter for biological fluid description.

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REFERENCES

1. Boulton, R. (1980c): The Relationship Between Total Acidity, Titratable Acidity and pH in Grape Tissue. Vitis, Vol. 19, pp. 113-120.
   
2. Boulton, R.B., Singleton, V.L., Bisson, L.F. and Kunkee, R.E (1996): Principles and Practices of Winemaking. Chapman&Hall, New York, NY 10003.