2 ,4-Dinitrophenylhydrazine reagent—Prepare as directed in the Identificationtest under Glutaral Concentrate.

Procedure— Add 5mLof Disinfectant Solution to 20mLof 2,4-Dinitrophenylhydrazine reagent,mix by swirling,allow to stand for 5minutes,and proceed as directed for Procedurein the Identificationtest under Glutaral Concentrate,beginning with “Collect the precipitate on a filter.”

Buffer— Dissolve 2.59g of monobasic potassium phosphate and 6.77g of anhydrous dibasic sodium phosphate in 500mLof water in a 1000-mLvolumetric flask,dilute with water to volume,and mix.

Hydroxylamine hydrochloride solution— Prepare a solution of hydroxylamine hydrochloride in Buffercontaining 70µg per mL.

Standard preparation— Transfer an accurately weighed quantity of Glutaral Concentrate,previously assayed as directed in the Assayunder Glutaral Concentrate,equivalent to about 2.5g of glutaraldehyde,to a 100-mLvolumetric flask,dilute with water to volume,and mix.Dilute an accurately measured volume of this solution quantitatively and stepwise with water to obtain a solution having a known concentration of about 50µg per mL.

Standard preparation blank solution— Transfer 10.0mLof Standard preparationand 10.0mLof Bufferto a 50-mLvolumetric flask,dilute with water to volume,and mix.

Assay preparation— Transfer an accurately weighed portion of Disinfectant Solution,equivalent to about 100mg of glutaraldehyde,to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 5.0mLof this solution to a second 100-mLvolumetric flask,dilute with water to volume,and mix.

Assay preparation blank solution— Transfer 10.0mLof Assay preparationand 10.0mLof Bufferto a 50-mLvolumetric flask,dilute with water to volume,and mix.

Reagent blank solution— Transfer 10.0mLof Bufferand 10.0mLof Hydroxylamine hydrochloride solutionto a 50-mLvolumetric flask,dilute with water to volume,and mix.

Procedure— Transfer 10.0mLeach of the Standard preparationand the Assay preparationto separate 50-mLvolumetric flasks,to each add 10.0mLof Hydroxylamine hydrochloride solution,dilute with water to volume,mix,and allow each to stand for 25minutes.Concomitantly determine the absorbances of both solutions and of the respective blank solutions at the wavelength of maximum absorption at about 238nm,with a suitable spectrophotometer,using the Reagent blank solutionto set the instrument to zero.Calculate the percentage,by weight,of C5H8O2in the Disinfectant Solution taken by the formula: in which Cis the concentration,in µg per mL,of C5H8O2in the Standard preparation;Wis the weight,in g,of Disinfectant Solution taken;AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively;and AUband ASbare the absorbances of the Assay preparation blank solutionand the Standard preparation blank solution,respectively.