ABSTRACT
The knowledge of product particle size distribution (PSD) in crystallization processes is of high interest for the pharmaceutical and fine chemical industries, as well as in research and development. Not only can the efficiency of crystallization/production processes and product quality be increased but also new equipment can be qualitatively characterized. A large variety of analytical methods for PSDs is available, most of which have underlying assumptions and corresponding errors affecting the measurement of the volume of individual particles. In this work we present a method for the determination of particle volumes in a bulk sample via micro-computed tomography and the application of artificial intelligence. The particle size of bulk samples of sucrose were measured with this method and compared to classical indirect measurement methods. Advantages of the workflow are presented.
ABSTRACT
We present a novel multi-emitter electrospray ionization (ESI) interface for the coupling of microfluidic free-flow electrophoresis (µFFE) with mass spectrometry (MS). The effluents of the µFFE outlets are analyzed in near real-time, allowing a direct optimization of the electrophoretic separation and an online monitoring of qualitative sample compositions. The short measurement time of just a few seconds for all outlets even enables a reasonable time-dependent monitoring. As a proof of concept, we employ the multi-emitter ESI interface for the continuous identification of analytes at 15 µFFE outlets via MS to optimize the µFFE separation of important players of cellular respiration in operando. The results indicate great potential of the presented system in downstream processing control, for example, for the monitoring and purification of products in continuous-flow microreactors.
Subject(s)
Spectrometry, Mass, Electrospray Ionization , ElectrophoresisABSTRACT
Microfluidic gradient generators have been employed in several works in the literature. However, these are typically application specific and especially limited in the range of flow rates that result in the required concentration gradient outputs. Here, a flow rate independent gradient generator designed as a modified Christmas tree-like microfluidic channel network including micromixers at each channel branch is demonstrated. The device was characterized theoretically, modeled using finite element analysis and tested experimentally. Input flow rates up to 200⯵l/min, resulting in a maximum speed of about 333â¯mm/s, for the generation of linear and mirrored linear gradients were demonstrated. As an application example, the gradient generator was monolithically integrated with microfluidic free-flow electrophoresis for the separation/concentration of fluorophores using a novel E-field gradient free-flow electrophoresis mode. The separation of fluorophores, having different charge stages, showed concentration factors of up to 10 fold. In addition, an extended theoretical description of the realizable concentration gradients and the electric field gradient is presented as supplementary information.
ABSTRACT
A general difficulty in the miniaturization of free-flow electrophoresis relates to the need to separate electrodes and separation bed compartments. This is usually performed by using membranes, which are either difficult to fabricate and integrate into microfluidic channels, or not stable over time. Here, we propose the use of track-etched polycarbonate membranes. Fabrication of the miniaturized device and integration of the membrane was simple, reproducible and allows for long shelf times. Furthermore, the membranes were resistant to high pressure values (up to 105 Pa), and contributed negligible electrical resistance, allowing setting of electric fields at the separation bed with high efficiency. A second microfluidic device was connected to the microfluidic free-flow electrophoresis chip via tubing, ensured flow stability over time and was used as a chip-to-world interface to a 96 well plate. We demonstrated microfluidic free-flow zone- and field-stacking electrophoresis, and isoelectric focusing proof-of-principle experiments, using fluorescent analytes and monitoring via fluorescence microscopy. Furthermore, the separation of a mixture of 7 proteins was performed in microfluidic free-flow zone electrophoresis mode. Subsequent analysis via protein mass spectrometry of the collected fractions revealed separation of the protein mixture, indicating a wide range of applications in the characterization of proteins and biosimilars.
