High precision spectrophotometry. Part I. Assessment of the performance of the Unicam SP3000 spectrophotometer and its application to the determination of phosphate in fertilisers and related materials

Abstract

By using conventional, single-beam spectrophotometers the ultimate precision that can be achieved by direct absorbance measurements is about 0·5 per cent. relative. Greater precision can be obtained if measurements are made differentially. Recently, more advanced spectrophotometers have become available that enable measurements to be carried out directly with a precision comparable with that obtained by use of differential techniques. In this paper the performance of such an instrument, the Unicam SP3000, is discussed and its application to the precise determination of phosphate in fertilisers and intermediates is described.