Greening microwave-assisted acid digestion of animal feed samples

SAVIO, MARIANELA; FIALHO, LUCIMAR L.; NÓBREGA, JOAQUIM A.

Analytical Methods

RSC

Año: 2019 vol. 11 p. 5857 - 5863

1759-9660

Nowadays it is well-established that microwave-assisted digestion of organic matrices can be efficientlyperformed in closed vessels using dilute nitric acid solutions. In this work microwave-assisted samplepreparation procedures compatible with green chemistry recommendations were developed for grains andcereals used to raise swine. Digestion efficiency was evaluated by determining the residual carbon content,which was lower than 3.5%. Residual acidity was also evaluated and was lower than 0.65 mol L1. Calcium,Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, Sr, and Zn were determined using either ICP OES or ICP MS depending onrespective concentrations. Certified reference materials were evaluated and most determined concentrationswere between 80 and 120% compared to certified values. Finally, after analytical measurements an apparatusfor recovering nitric acid by sub-boiling distillation was used. To the best of our knowledge, this is the firstapplication of sub-boiling distillation for recovering nitric acid of digests. Then, the purified acid could bereused in further digestions. This is a promising alternative for increasing the green chemistry attributes oftrace inorganic analysis. The combination of these strategies, i.e. dilute nitric acid digestion followed byrecovery of the acid digests, represents steps towards green chemistry approaches: ?reduce the use, recycleand reuse?, strictly following the major green chemistry recommendations.