Effect of operating parameters on a centrifugal partition chromatography separation

International audienceCentrifugal partition chromatography (CPC) is the branch of countercurrent chromatography (CCC) that works with single axis hydrostatic columns with rotary seals. The hydrodynamic of the liquid stationary phase-liquid mobile phase equilibrium in the CPC chambers has been studied theoretically and with specially designed CPC columns. In this work, we selected a simple analytical separation (no loading study) of three test solutes, coccine red, coumarin and carvone, with a commonly used heptane/ethyl acetate/methanol/water 1:1:1:1 v/v biphasic liquid system and two different rotors: a commercially available 30-mL CPC instrument and a 80-mL prototype rotor designed for productivity. We fully studied this separation in many possible practical operating conditions of the two rotors, aiming at a generic column characterization. The rotor rotation was varied between 1000 and 2800 rpm, the aqueous mobile phase flow rate was varied between 1 and 22 mL/min with the 30-mL rotor and 10 and 55 mL/min with the 80-mL rotor, the upper limits being mechanical constraints and some liquid stationary phase remaining in the rotor. The variations of Sf, the volume ratio of stationary phase in the rotor, were studied versus mobile phase flow rate and rotor rotation speed. A maximum mobile phase linear velocity was found to depend on the centrifugal field for the 30-mL rotor. This maximum velocity was not observed with the 80-mL rotor. Studying the changes in coumarin and carvone peak efficiencies, it is established that the number of cells required to make one theoretical plate, i.e. one chromatographic exchange, is minimized at maximal rotation speed and, to a lesser extent, at high mobile phase flow rate (or linear velocity). Considering the throughput, there is evidence of an optimal flow rate depending on the rotor rotation that is not necessarily the highest possible

Near infrared spectrometry to evaluate the feed value of forages

International audienceNear Infrared Spectrometry (NIRS) is used to evaluate the nutritional value of forages and even their feed value if applied to fresh material. Indeed, it allows to estimate the contents of nitrogenous matter, crude cellulose (or walls or ligno-cellulose), organic matter and dry matter as well as the cellulase digestibility. These data are used to predict the feed value of forages (Forage Units: FU, Digestible Protein in the Intestine: DPI, and Bulking Units: BU) using different regression models. The NIRS estimates are based on the establishment of a relationship between the values obtained by a reference method and the spectral absorbance data. A calibration base is thus built and must correspond to the diversity of the analyzed samples. For this, it is regularly completed by adding "atypical" points. An increasing diversity of forages is used in agriculture to cope with climatic hazards and the desire to reduce inputs. In particular, more and more species mixtures are used in different forms: green, hay or silage. This diversity requires the collection of absorption spectra and the chemical analysis of several hundred or even several thousand samples. Faced with these constraints, CIRAD and INRAE have chosen to pool their respective forage databases and thus benefit collectively from the diversity of each. This was possible thanks to a standardization of chemical reference analyses and absorbance spectra between laboratories. This method, non-destructive and inexpensive, tends towards an evolution of the devices which become miniaturized and allows an analysis in the farms. The advances in this field are discussed in this article