# Microwave-Assisted Digestion Method and Dispersive Magnetic Solid-Phase Microextraction for the Determination of Major and Trace Elements in Lignocellulosic Biomass by ICP-OES

## TL;DR

This paper introduces a new method to analyze elements in plant biomass using microwave digestion and magnetic extraction techniques.

## Contribution

The study introduces a novel combination of microwave-assisted digestion and dispersive magnetic solid-phase microextraction for element analysis in lignocellulosic biomass.

## Key findings

- The method achieved optimal recovery of major and trace elements in lignocellulosic biomass.
- Limits of detection for elements like As, Pb, and Se were as low as 0.01–0.03 μg g–1.
- The proposed method was successfully applied to five different types of lignocellulosic biomass.

## Abstract

This paper proposes a sample preparation method for the
determination
of major (Ca, Cu, Fe, Mn, Mg, Na, and Zn) and trace elements (As,
Pb, and Se) in lignocellulosic biomass by inductively coupled plasma
optical emission spectrometry (ICP-OES). Major composition was determined
directly after microwave-assisted digestion with dilute nitric acid,
while trace elements were determined using dispersive magnetic solid-phase
microextraction (DMSPE). For DMSPE, maghemite nanoparticles were synthesized
using the alkaline hydrolysis coprecipitation method and characterized
by high-performance scanning microscopy, X-ray diffraction, Fourier
transform infrared spectroscopy, and thermogravimetric analysis. Optimization
of the microwave-assisted digestion and DMSPE procedures was performed
using a central composite design, with optimal conditions achieved
at a sample mass of 280 mg, 2.5 mL of HNO3, and 2.0 mL
of H2O2 for MAD and a sorbent mass of 10 mg,
a stirring time of 100 min, and a pH of 9.5 for DMSPE. The analytes
were recovered with a HCl solution of 5% (w v–1).
The accuracy of the method was assessed by recovery tests and certified
reference material analysis. The limits of detection of the method
were, in μg g–1, As (0.01), Pb (0.03), Se
(0.01). Ca (2), Cu (1), Fe (0.8), Mg (0.2), Mn (0.2), Na (5), and
Zn (0.8). The enrichment factors determined were 21, 31, and 42 for
As, Pb, and Se, respectively. Five different lignocellulosic biomasses
were analyzed using the proposed method, which yielded concentrations,
in μg g–1, for Ca (367–834), Cu (2–33),
Fe (39–3,339), Mg (170–822), Mn (11–58), Na (21–3,967),
and Zn (8–27), while As, Se, and Pb were lower than the LOQs.