COMPARISON OF TWO WET DIGESTION PROCEDURES FOR MULTI-ELEMENT ANALYSIS OF MILL BYPRODUCTS

CONCERNS EXIST OVER the long-term application of mill mud and ash without appropriate product monitoring, but these can be at least partially addressed by developing simple, rapid measurement techniques. Well established wet chemistry preparation and analysis methods for measurement of nutrient elements in mill byproducts are accurate and reproducible; however, they are time consuming and are subject to the limitations of representative sampling procedures. Thus the measurement of the nutrient content in mill by-products employing traditional chemical methods is difficult to conduct on a regular basis. This paper presents the development of novel wet chemistry analytical methods, utilising a microwave assisted digestion procedure, leading to the development of NIR methods for the prediction of phosphorus, potassium, sulfur, calcium and magnesium levels in mill byproducts. Mill mud and mud/ash samples were obtained from sugar mills in the Mackay, Broadwater, Bundaberg and Burdekin regions. Each sample was sub-sampled and analysed using standard chemical methods utilising a hotplate acid digestion procedure. The same samples were prepared by microwave-assisted digestion procedures and all digests were analysed by ICP-OES for P, K, S, Ca and Mg. The results obtained by ICP-OES for samples prepared using traditional techniques correlated well with those acquired by microwave-assisted digestion, providing high r2 values (0.94–0.99). This work has shown that modern digestion procedures can improve laboratory throughput without compromising output data quality, affording fast development of NIR calibrations for nutrient elements in mill byproducts and therefore providing economic benefits for both millers and growers.