Analysis of Trace Elements in Wine

Introduction

Wine contains small or trace amounts of K, Ca, Fe, Mn, and Cu. Component analysis of wine is important from the viewpoints of dietary intake of minerals and identification to prevent improper locality and brand camouflage. One advantage of the total reflection X-ray fluorescence (TXRF) method compared with ICP or AAS is the simple sample preparation. The TXRF method does not require acid decomposition of specimens to remove organic components and alcohol. In this report, trace elements in wine were analyzed by the TXRF method.

Measurement and results

A Chilean red wine was analyzed by TXRF. Analytical errors were decreased by diluting the wine sample with distilled water (sample to distilled water: 1 to 1), thereby reducing matrix effects from light elements such as K and Ca. Ten µL of a Ga internal standard solution of 100 mg/L solution was added to 990 µL of the diluted red wine sample. The mixed sample was pipetted onto a quartz glass carrier (coated with silicone) and dried under reduced pressure. The TXRF spectrum is shown in Figure 1.

Figure 1:  TXRF spectrum of Chilean red wine 

The fluorescent X-ray peak of Si originates from the quartz glass substrate and the Ga peak is from the internal standard solution. X-ray fluorescence peaks for S, K, Ca, Mn, Fe, Cu, Zn, Br, Rb and Sr were detected in the TXRF spectrum. Quantification results using the internal standard method and the reference values of the wine are shown in Table 1. The resultant values are comparable to the reference values of elements in wine. In TXRF spectrometry, liquid samples can be easily  and rapidly analyzed by only pipetting and drying on a sample carrier without extra sample pretreatment. 

Table 1: Analytical results of Chilean red wine (Unit: mg/L) 

References

1) R. Dalip, E. Margui, L. Borgese, F. bilo, L. E. Depero: Spectrochim. Acta B, 120 (2016) 37-43. 
2) S. Kunimura, J. Kawai: Bunseki Kagaku，58 (2009) 1041-1054.