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Assay for Glutaraldehyde and Formaldehyde

The method involves a titration against a blank followed by the titration against the unknown sample. The method is based formation of an aldehyde-bisulphite complex followed by iodometric titration of the unreacted bisulphite. Accuracy is about 0.2% (FRIGERIO and SHAW, 1969).

Solutions required:

0.125 M Na₂S₂O₅
2.37 g Na₂S₂O₅ to 100ml with distilled water
0.1 M potassium tri-iodide
11.00 g KI + 6.44 g resublimed I₂ to 250ml with distilled water

Perform two titrations with 0.1 M I₃^- judging the end point as follows:

The solution turns yellow at first but within 0.2 ml of the endpoint becomes colourless - continue titrating until the solution again turns yellow and remains yellow for three minutes.

Titration 1 to give V1

1 ml aldehyde solution (0.6% to 6%) 20 ml 0.125M Na₂S₂O₅

Titration 2 to give V2

1 ml water 20 ml 0.125M Na₂S₂O₅

Aldehyde concentration

$\small \% \left (w/v \right ) = 100 \times \left [ {I_{3}}^{-} \right ] \left ( V2-V1 \right ) \left (molecular\; wt\; of\; aldehyde \right ) / \left (no\; of\; aldehyde\; groups \right) / \left (sample\; volume \right)$

For example - for formaldehyde

V1 = 44.6ml

V2 = 47.3ml

$\small \%formaldehyde = 100 \times 0.1 \times \left ( 47.3 - 44.6 \right ) \times 0.001 \times 30 / 1 = 0.81\%$

Molecular weight of formaldehyde = 30

Molecular wt of glutaraldehyde = 100.12

number of aldehydes = 2

References

FRIGERIO, N. A., and M. J. SHAW. 1969. A SIMPLE METHOD FOR DETERMINATION OF GLUTARALDEHYDE. Journal of Histochemistry & Cytochemistry. SAGE Publications, March 1. http://dx.doi.org/10.1177/17.3.176.

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