AND WU METHOD OF BLOOD GLUCOSE ESTIMATION BY

The methods most commonly employed for the estimation of blood glucose are dependent upon the ability of glucose to reduce alkaline copper solutions. Reagents containing phosphomolybdic acid are then frequently used to form a blue com-plex by combination with the reduced copper. All these methods suffer the disadvantage that the final colour fades at such a rate as to imperil its accu-rate comparison with a standard glucose solution similarly treated. Fading was neither very apparent nor of much importance when visual colorimeters were em-ployed with direct comparison of standard and unknown colours. Folin (1929) first recorded the existence of fading and described a method to combat it. Interest was aroused by the general adoption of the photoelectric colorimeter, and many technical modifications were introduced to circumvent fading. These were remarkable for their variety rather than for their success in routine use. In the present investigation the factors influenc-ing fading have been determined and a new modifi-cation of the Folin and Wu technique has been evolved which simplifies the standard technique at the same time as it eliminates fading. Although the Folin and Wu (1920) method was chosen for this investigation the principles involved are applicable to other methods of blood glucose esti-mation in which similar reagents are used. Reagents and Apparatus Analar grade materials were used in the prepara-tion of all reagents. Copper Reagent.-This was made up as described by Folin and Wu (1920) but stored as two solutions as recommended by Folin (1929). Copper reagent was freshly prepared from the two constituent solu-tions each day