Marta Pastor-Belda1, Natalia Arroyo-Manzanares1, Kateryna Yavir2, Paloma Abad3, Manuel Hernández-Córdoba1 and Pilar Viñas1
Onion organosulfur compounds (OSC) are well known for their health-related properties, which mainly related to the presence of thiosulfinates, volatile sulfur compounds. PDS is the sulfide found mostly in onions and PTSO is the most studied onion thiosulfonate, and it is the responsible for the smell of freshly cut onion. In recent years, the use of PTSO as a feed additive has increased due to improves the digestibility of nutrients, and reduces methane inhibition in ruminants. Besides, PTSO presents antimicrobial activity against Enterobacteriaceae, Escherichia Coli, Salmonella spp., Campylobacter jejuni and Eimeria acervulina. The determination of PDS and PTSO in animal feed was proposed using two analytical methodologies using gas chromatography coupled to mass spectrometry (GC-MS). After extraction of the compounds from animal feed with acetonitrile, a cleaning stage with C18, or dispersive liquid-liquid microextraction (DLLME), using 100 µL of CHCl3, were tried. Pig feed sample were used to validate both methodologies. After the comparison of both validation parameters, DLLME was selected due to this technique provided cleaner extracts, five-times greater linear ranges and lower detection limits than the simple cleaning due to the enrichment factor achieved. The relative standard deviation decreased from 22 % with the solid-based cleaning stage to 13% with DLLME. The usefulness of DLLME-GC-MS methodology was tested by analysing 10 different samples of chicken, hen, cow and fish feed. The concentrations of PDS were in the range 0.1-1.7 µg g-1 and those of PTSO were between 0.09-2.1 µg g-1.
The authors acknowledge the financial support of the Comunidad Autónoma de la Región de Murcia (CARM, Fundación Séneca, Project 19888/GERM/15), the Spanish MICINN (PGC2018-098363-B-I00), the European Commission (FEDER/ERDF) and DMC Research Center S.L.U. Kateryna Yavir also acknowledges the financial support of the Erasmus + Program.
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