Distributional homogeneity and penetration depth assessment of antibiotic added by surface coating to pellets with mid Infrared imaging and multivariate curve resolution.

Fourier Transform Mid Infrared with Attenuated Total Reflection Imaging (FTIR-ATR imaging) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) were used in a multiblock fashion to study the presence, distribution and penetration depth of very low concentrations of florfenicol (FF) in a complex matrix like feed pellets for salmonids. Images from the surface, at 150 µm deep and 200 µm deep from the surface were analyzed to certify the penetration power of FF added by surface coating methodology. Besides, the unique homogeneity index was calculated in order to evaluate the distributional homogeneity of each component. The results demonstrated the reliability of MCR-ALS in studying the distributional homogeneity of FF. It was demonstrated that FF remains mostly on the surface of the pellets with almost no penetration. The rest of the components of the pellets (oil, protein and carbohydrates) were also analyzed. These three nutrients are distributed on the three layers analyzed with a relatively homogeneous location, being carbohydrates (%H = 51 ± 3) the component with the best homogeneous distribution, unlike protein (%H = 45 ± 5), and oil (%H = 40 ± 7). This is the first publication where the penetration of an antibiotic, added with surface-coating to feed pellets, was analyzed with FTIR-ATR imaging and multivariate analysis, showing the contribution these analytical tools can make to the medicated feed industry.