Validation of methods for determination of urinary estriol during pregnancy using mass fragmentography

A specific and accurate method for determination of urinary estriol during pregnancy is described. After acid hydrolysis of 1 ml urine, a fixed amount of [2,4-2H2] estriol (usually 15 mug) is added and the mixture is extracted with diethyl ether. The extracted estriol is converted into the tri-trimethylsily derivative and the amount of unlabeled estriol is determined from the ratio between the recordings at m/e 504 and m/e 506 obtained after analysis with a gas chromatograph-mass spectrometer equipped with an MID (multiple ion detector). The two ions used correspond to the molecular peak in the mass spectrum of unlabeled and (2,4-2H2)-labeled tri-trimethylsilyl derivative, respectively. The relative standard deviation of the method was about 6%. The method was compared with a photometric method using the Kober reaction and the gas liquid chromatographic method used in routine analysis. There was a good correlation in both cases and the regression coefficient was 1.5 and 1.3, respectively.