X-ray spectroscopy in the clinical laboratory. II. Chlorine and sulfur; automatic analysis of ultramicro samples.

N A PREVIOUS PAPER a method for the estimation of potassium and calcium by X-ray spectroscopy (fluorescence) was described for amounts of serum of the order of 5-25 (1). This paper is a report of a continuation of studies on those elements that permit direct estimation without processing of the serum. Specifically, this reporl concerns chlorine and sulfur. As was shown in an earlier report (2, 3), sulfur and chlorine are readily detected by X-ray spectrometry by applying a serum sample to a confined spot on a piece of filter paper, allowing the specimen to dry, and then counting the response at the peak for the Ke lines of these elements. In this technic an ethylene diamine ditartrate (EDDT) crystal was used. As has been pointed out (1), inserting the sample into the counting chamber, counting, and then replacing the sample constitute a relatively slow and tedious process in view of the large numbers of determinations performed in the clinical laboratory. For this reason it was suggested the process needed to be automated. This was accomplished, as shown in Fig. 1, by passing the serum, dried on paper in confined spots, through the X-ray field. The goniometer is set at the angle for the required element, and the results continuously recorded. The instrument for preparing the paper with the confined spots also is shown in Fig. 1. Figure 2 illustrates a typical tracing obtained with the recorder,