ISI 41-1e Determination of COD


1. Scope The method is applicable to starch milk and hydrolysates

 

 LT 12. Dec. 1966
Rev. LT 16. Dec. 1997
2. Principle Titration with NaOH to pH 8.3.

 
3. Apparatus 3.1 Burette
3.2 pH meter
3.3 Volumetric flask 50 ml

 
4. Reagents 4.1 Sodium hydroxide 0.1 N
4.2 Phenolphtalein: 1 g in 1 l ethanol 90%

 
5. Procedure Fill volumetric flask (3.3) with liquid sample. Transfer to 300 ml conical flask.

Titration 

 Add 1 ml (4.2) and titrate with (4.1) to faint persistent pink  or use pH meter to 8.3
V = ml (4.2). N = normality of (4.2)

 
6. Calculation Calculate acidity as normality N of sample by averaging results of two samples with one decimal.

N = N V / 50

 
7. Notes J. Assoc. Off. Anal. Chem. 66 (1983) no. 6, 1395-1399 recommend pH 6.0 as end point, but AOAC limits this method to HFCS

 
8. Reference AOAC Official Methods of Analysis (15th edition)

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