A slurry sampling high resolution continuum source graphite furnace atomic absorption spectrometry approach to determine metals in biomass bottom ash

Abstract

Industrial by-products such as biomass bottom ash (BBA) should be reused in the context of the Circular Economy, but their use depends on the content of major, minor, and toxic elements. In this work, a slurry sampling method based on High Resolution Continuum Source Graphite Furnace Atomic Absorption Spectroscopy (HR-CS GFAAS) was developed for the determination of Pb, Cu, and Fe in these by-products. Using a two-step multivariate experimental design, the optimal conditions for the preparation of the sample suspensions (dispersion of 10.0 mg of 32 µm sieved BBA sample in 10.0 mL of 1.4% (v/v) HNO3 and 0.7% (v/v) Triton X-100 solution using an ultrasonic bath for 1.0 min (50% power; 80 kHz)) were established. The GFAAS temperature program was optimized using both aqueous standards and BBA slurries, allowing the determination of the three metals in a single analytical run and with the same sample aliquot. Under the optimal conditions the limits of detection (LODs) were 0.55 µg g−1, 0.21 µg g−1, and 0.72 mg g −1 for Pb, Cu, and Fe, respectively. Different BBA samples were analyzed using the proposed method. The suitability of the method was probed by determining the concentrations of the metals in the solutions obtained after microwave acid digestion of the BBA samples, obtaining statistically comparable results (Student-t test for two independent samples at a 95% confidence level).

Keywords

• Biomass bottom ash
• Multivariate optimization
• Slurry sampling
• HR-CS GFAAS
• Multielement determination