Magnesium nitrate as a chemical modifier to improve sensitivity in manganese determination in plant materials by tungsten coil atomic emission spectrometry

Abstract

In this work, magnesium nitrate is used for the first time as a chemical modifier in atomic emission spectrometry to improve sensitivity and minimize matrix effects in Mn determination. Magnesium–Mn interactions in the condensed and gas phases contribute to increasing the population of excited-state Mn atoms, which result in improved sensitivity, precision and accuracy in plant analysis by tungsten coil atomic emission spectrometry (WCAES). The limit of detection calculated for Mn determination in the presence of 750 mg L⁻¹ Mg was 0.05 mg L⁻¹, which is a 17-fold improvement when compared to determination without using the chemical modifier. Repeatabilities also improved from 6.4 to 3.6% (RSD, n = 10, Mn 2.5 mg L⁻¹) when Mg was used, and linear responses were observed in the 0.1–7.5 mg L⁻¹ Mn range. Manganese concentrations in standard reference materials of plants were 2-fold higher than the certified values for determinations without the modifier. For determinations using Mg(NO₃)₂, no statistically significant difference was observed between determined and certified Mn values at the 95% confidence level.