X-Ray Spectroscopy in the Clinical Laboratory

Abstract

Abstract Chlorine and sulfur are assayed in serum with the X-ray spectrometer. The serum samples are dried in confined spots on a long strip of filter paper. The strip is passed continuously through the X-ray field and the element assayed by the peak of the curve drawn on the recorder. An attachment for the spectrometer is described for this purpose, as well as an instrument for making the confined spots. Results for chlorine in serum are compared with those obtained by mercurimetric titration. The results are comparable as regards accuracy and reproducibility. Using 20 µ1. of serum and the automatic feed, the results for chlorine indicate a reproducibility, by X-ray, of ± 3.4 per cent (2σ). No significant difference was observed in comparing the values for sulfur obtained by X-ray with those obtained by ashing and treatment with barium chloranilate. The X-ray technic with 25 µ1. of serum is reproducible to ± 2.2 per cent (2σ). Serum was dialyzed against saline and assayed for sulfur content before and after dialysis. The dialyzable sulfur is small in comparison with the total protein sulfur. In comparing normal and pathologic sera with respect to their sulfur-to-protein content ratio it is observed that this varies apparently because the serum globulins contain amounts of sulfur different from serum albumin. The abnormal protein observed in multiple myeloma contains less than half the sulfur of the albumin from the same patient. This was determined by scanning the electrophoretic pattern of the serum for sulfur and protein. It is pointed out that the X-ray technic is practical for routine analysis in the clinical laboratory in that no reagents are required for total sulfur, chlorine, calcium and potassium; furthermore, only an ultramicrosample is needed and the instrument is easily adapted to automatic operation. Results are comparable with those obtained by conventional methods with regards to accuracy and precision.