Preparation of deionized glyoxal
Mix 25 ml of 40 % glyoxal to be deionized with 2.5 g of mixed bed resin .
Mix the solution by magnetic stirrer for 30 minutes at room temperature .
The resin color will change from blue to amber , when its capacity is reached .
Separate the deionized material from the resin by decanting or ( sterile ) filtration .
Repeat the deionization process ( steps 2 . and 4 . )
until the color of the resin does not change anymore .
Approximately half of the resin particles remain blue and half become amber after a 30 - minute incubation .
Check the pH of the glyoxal solution by mixing 200 μl of glyoxal with 2 μl of a 10 mg / ml aqueous solution of bromocresol green and observing the color change .
Bromocresol green is yellow at pH < 4.8 and blue - green at pH > 5.2 .
Alternatively , use pH indicator strips instead of a bromocresol green solution .
Repeat the deionization process ( steps 2 . and 4 . )
until the pH of the glyoxal is > 5.5 .
Final resin removal should be done through a small pore - size filter ( e . g . 0.22 - 0.45 µm , gamma sterilized ) to avoid carry - over of the resin .
Deionized glyoxal can be stored indefinitely at - 20 °C ( or - 80 °C ) under nitrogen in tightly sealed small aliquots ( e . g . microcentrifuge tubes ) . Use each aliquot only once , then discard .
