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BRIEF NOTES

845

Improvement of a new SGOT and SGPT ultramicro method Calibration

procedure

In a previous paper we described a new ultramicro procedure for serum trans-

aminase SGOT and SGPT) determinationl.

In this note we report an improvement of the calibration curve which consists

in using solutions of chemically reduced tetrazolium salt INT) which are most suit-

able to serve as standard solutions because of their stability.

Ca~~~~at~o~w ve of chern~ca~~yeduced I NT

The INT formazan is prepared in a separatory funnel by mixing IOOml of

6 M INT [z- ~-iodophenyl)-3- p-nitrophenyl)-5-phenyl-tetrazolium chloride] BDH

Reagent) with IO mg of ascorbic acid and IO ml of 0.4 N NaOH.

After shaking for a few minutes, the INT is extracted from its solution by treat-

ment with ethyl ether until the aqueous layer is completely colourless we used

200

ml of ether). The INT is obtained by drying the solution. The whole preparation

procedure has to be accomplished in the dark and the product is stable when kept

in the dark and dry.

The calibration curve is made by using 32.58, 24.44, 16.23 and 8.15 PM solu-

tions of INT formazan mol. wt. 471.25) which had been first dissolved in I ml of

dimethyl formamide and then diluted with water.

The absorbance of the coloured solutions is measured at 520 nm against water.

Fig. I Absorbance of the solutions of INT formazan.

The absorbance values of the solutions correspond to 200, 150, IOO, 50 I.U. of trans-

aminase activity respectively. The points perfectly fit a straight line passing through

the origin Fig. I). The calibration curve of the chemically reduced INT is the same

as that obtained with the enzymatically reduced INT.

Department of Pat hology,

“P. Cosma” Hospit al

35012, ~ rn~os rn~~~ro I ta iy )

I U

LIPPI AND G. GUIDI, C a. CAim.

Acta 28 1970) pg.

Received July 30, 1970

u.

LIPPI

G. GUIDI

R.

PAVAN

Clin. Chim. Acta, 30 1970) 845