Analysis of diluted honey samples from the province of Lower Silesia (Poland) by inductively coupled plasma mass spectrometry

Abstract

The direct determination of 18 elements (B, Ba, Ca, Cd, Cs, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Rb, Sr, Tl, and Zn) in 1% aqueous honey solutions (dilution factor = 100) by ICP MS was presented. The presence of sugar in sample solutions caused a decrease in analytical signals, the appearance of carbon-containing polyatomic ions, and the deposition of carbonaceous products on a sampler cone. On the flip side, these effects did not destabilize the ICP, while the internal standard calibration (⁹Be, ⁸⁹Y, and ¹⁵³Eu as standards) made it possible to correct matrix effects. Additionally, in the case of ¹¹B, ²³Na, ⁴³Ca, and ⁵⁷Fe isotopes, using a collision cell (He, 2 mL min⁻¹) was required. Due to lower sample blanks, the analysis of water-diluted honey samples offered on average 3 times lower detection limits of elements than achieved for microwave-digested samples. The proposed method, characterized by high analytical throughput, was used for the analysis of 120 samples of honey from the apiaries in the Lower Silesia province. The average content of the major elements in the analyzed honey samples was: B 10.4 mg kg⁻¹, Ca 61.0 mg kg⁻¹, Fe 1.0 mg kg⁻¹, K 1049 mg kg⁻¹, Mg 27.8 mg kg⁻¹, Mn 3.4 mg kg⁻¹, Na 9.1 mg kg⁻¹, Rb 1.4 mg kg⁻¹, Zn 2.0 mg kg⁻¹, and the average content of the trace elements: Ba 130 μg kg⁻¹, Cd 3.2 μg kg⁻¹, Cs 4.8 μg kg⁻¹, Cu 315 μg kg⁻¹, Li 3.8 μg kg⁻¹, Ni 90 μg kg⁻¹, Pb 8.0 μg kg⁻¹, Sr 119 μg kg⁻¹, Tl 1.2 μg kg⁻¹. It was found that (1) the concentrations of all tested elements (except B and Tl) were higher in dark honey, (2) the content of Cs and Rb in honey from the mountain areas of the voivodeship was much higher than this in honey from the lowland areas, and (3) the best discriminators in terms of the color and the botanical origin of honey were the concentrations of Cu and Mn, and to a lesser extent also B, Ca, K, Mg, and Na; e.g., honeydew and buckwheat honey contained much higher amounts of Cu and Mn, sunflower honey was characterized by a significantly higher content of Ca, and rape honey showed an increased B content. Given that the proposed sample preparation procedure allows the simultaneous, reliable, and fast determination of major, trace, and ultra-trace elements, it seems to be a convenient method for the profiling of many honey samples in a very short time.