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Poster Contributed Presentation

ATOM

Thursday Poster Sessions

Th1 - A single standard calibration approach for Al, Fe, Mg, K, Cu, Si, Cr, Mn, and Ti quantitative measurements in sewage sludge by Laser Ablation Inductively Coupled Plasma Optical Emission Spectroscopy

Thursday, October 9, 2025
9:45 AM - 4:00 PM EDT
Location: Riverview Lobby
In fifteen words or less, explain the significance of this contribution (Novel Aspect).: LA-ICP OES combined with SRC addresses matrix effects in SS analysis using a single standard.

Abstract Text:

Sewage sludge (SS), a by-product of wastewater treatment, rich in organic matter and essential nutrients such as K, Mg, and Fe, is an interesting alternative for agriculture. An accurate chemical analysis is essential to ensure safe application and/or appropriate disposal strategies. In this study, a direct solid analysis method using Laser Ablation Inductively Coupled Plasma Optical Emission Spectroscopy (LA-ICP OES) is proposed for the quantification of Al, Cr, Cu, Fe, K, Mg, Mn, Si, and Ti in SS. Direct analysis by LA-ICP OES eliminates the need for laborious sample digestion but faces inherent challenges such as matrix effects and elemental fractionation. To address these challenges, two calibration strategies were evaluated: external calibration (EC) using certified reference materials (CRMs) and slope ratio calibration (SRC). Samples and CRMs were pelletized using 10% w w-1 of cellulose as a binder to enhance laser-sample interaction and surface homogeneity. For more reliable results, all laser and transport parameters were optimized. Although EC was hindered by the mismatch between CRMs and the SS matrix, resulting in less accurate values, SRC proved to be a more effective approach. The main advantage of SRC is the need of only one standard to carry out the calibration curve. This approach involves obtaining analytical signals by accumulating successive laser pulses for both the sample and the standard and then comparing their slopes. When a matrix-matched standard is used, SRC compensates for matrix effects ensuring more reliable quantification. Given the limited availability of matrix-matched CRMs for SS, SRC represents a practical alternative, simplifying the analytical procedure while maintaining accuracy. The results indicated that the values obtained were in close agreement with reference values, showing a relative error ranging from 5 to 18% with matrix-matched standard and about 40% with non-matched standards, confirming the method's reliability for SS characterization. Additionally, SRC was applied to a cement CRM to assess its versatility across different solid matrices.