ENHANCEMENT OF PRECISION AND ACCURACY IN DERIVATIVE SPECTROPHOTOMETRY OF HIGHLY ABSORBING SAMPLES

The extension of relative absorptiometric methods to derivative spectrophotometry is proposed as a way of improving precision and accuracy for extremely high absorbance values. The concept was developed by applying the transmittance-ratio method to second-derivative measurements of two model systems where the total absorbance is kept very high, leading to a significant enhancement of precision and accuracy. The variation of the signal to noise ratio and of the total error as a function of absolute and relative absorbance was studied. Some of the factors affecting the analytical behavior of this method are discussed.