Analysis of Trace Elements in a Serum Sample

Introduction

To prepare biological samples, acid decomposition and dilution of the organic components are recommended. This procedure can decrease the sample residue on the sample carrier and improve S/N of the TXRF spectra. In the total reflection X-ray florescence (TXRF) method, sample preparation is easy: an aliquot of liquid is pipetted onto a carrier. Multi-element determination is available with the internal standard method without the need to prepare calibration curves. TXRF analysis can reduce time and the cost of consumables compared with atomic absorption spectrometry (AAS) or induced coupled plasma optical emission spectrometry (ICP-OES). In this report, trace elements analysis of a serum sample is described.

Measurement and results

The serum sample was decomposed using an acid solution. The decomposed serum sample was diluted 10 times with distilled water. Ten µL of 10 mg/L of a Ga internal standard solution was added to 990 µL of the diluted sample. Ten µL of the mixture was pipetted onto a quartz glass carrier and was dried under reduced pressure. The TXRF spectrum of the serum sample is shown in Figure 1, and the analytical results compared to those from ICP-MS are shown in Table 1. Major components P, S, K and Ca and minor components Fe, Cu, Zn, Se and Rb were detected by removing the matrix using acid decomposition. The Si fluorescent X-ray peak originates from the quartz glass substrate and the Ga peak is from the internal standard solution. The values show good agreement with those from ICP-MS. Thus, TXRF method is applicable to liquid sample analysis including decomposed solutions of biological samples. 

Table 1.  Analytical values of the serum sample and comparison with analytical results of ICP-MS (Unit: mg/L) 

Figure 1. TXRF spectrum of the serum sample