Development of a Method for the Determination of Total Selenium in Soil, Maize Plants, and Maize Flour by Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS)

Abstract

Selenium (Se) is a micronutrient that has multiple biochemical effects ranging from a nutritional deficiency at low levels to toxicity at high levels. Its quantification in environmental systems is vital to protect the health of people and animals. This study developed and validated methods to determine the total selenium (Se) concentration in soil, maize plants, and maize flour. The performance of the methods was ascertained using matrix certified reference materials (CRMs), namely NMIJ CRM 7303-a (trace elements in lake sediments), NIST SRM 1646-a (estuarine sediments), NIST SRM 1570-a (spinach leaves), NIST SRM 1571 (orchard leaves), NCS ZC 73010 (maize flour) and NIST RM 8437 (hard red spring wheat flour). All methods fulfilled the performance requirements of the AOAC International. An acceptable accuracy was achieved with percentage recoveries between 57 and 102% and $E_n‐\mathrm{\text{scores}}$ within ±1 limits. Repeatability $({\mathit{\text{RSD}}}_r,\%$) and intermediate precision ${ (\mathit{\text{RSD}}}_R,\%)$ ranged from 4 to 12%, and 9 to 15%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for soil were 0.024 ng. g⁻¹ and 0.082 ng. g⁻¹, respectively. The LODs and LOQs for maize plants and flour were 0.0036 and 0.0179 ng. g⁻¹, respectively. The performance characteristics of the methods were comparable with previously reported methods, confirming reliability. The measurement uncertainty was evaluated following the guide to the expression of uncertainty in measurement (GUM). Relative expanded uncertainty at a 95% level of confidence $(k=2$) was less than 24% for the final measurement results for all the different matrices.

Keywords:

• Inductively coupled plasma tandem mass spectrometry (ICP-MS/MS)
• maize
• method validation
• selenium
• soil

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Metrology Institute of South Africa (NMISA), University of Johannesburg (UJ.), National Research Foundation (NRF) grant number 108508, a University of Pretoria Paraclinical Science department, Department Agriculture & Rural Development (Tugela Ferry) and Villa Crop.