Accuracy Improvement of In-line Near-Infrared Spectroscopic Moisture Monitoring in a Fluidized Bed Drying Process.

An exploratory analysis of a large representative dataset obtained in a fluidized bed drying process of a pharmaceutical powder has revealed a significant correlation of spectral intensity with granulate humidity in the whole studied range of 1091.8-2106.5 nm. This effect was explained by the dependence of powder refractive properties, and hence light penetration depth, on the water content. The phenomenon exhibited a close spectral similarity to the well-known stochastic variation of spectral intensities caused by the process turbulence (the so-called "scatter effect"). Therefore, any traditional scatter-corrective preprocessing incidentally eliminates moisture-correlated variance from the data. To preserve this additional information for a more precise moisture calibration, a time-domain averaging of spectral variables has been suggested. Its application resulted in a distinct improvement of prediction accuracy, as compared to the scatter-corrected data. Further improvement of the model performance was achieved by the application of a dynamic focusing strategy when adjusting the model to a drying process stage. Probe fouling was shown to have a minor effect on prediction accuracy. The study resulted in a considerable reduction of the root-mean-square error of in-line moisture monitoring to 0.1%, which is close to the reference method's reproducibility and significantly better than previously reported results.

Alignment of laser-induced fluorescence and mass spectrometric detection traces using electrophoretic mobility scaling in CE-LIF-MS of labeled N-glycans.

The combination of optical detection techniques like photometry (UV) or laser-induced fluorescence (LIF) with mass spectrometry for capillary electrophoresis offers advantages, both for later use of stand-alone CE-UV or CE-LIF systems and for combined CE-UV-MS or CE-LIF-MS analysis. Faster method development is enabled, the identification of analytes is facilitated, and it allows christian the optical detection scheme to be used for more precise quantification. However, shortcomings of current methodology and equipment hindered the broader use of such detection combinations mainly due to the long distance between the detection points (at least 20 cm). Large shifts in migration times and changes in resolution are visible between the detection traces hindering their straightforward comparison. We present here novel equipment for a robust coupling of CE-LIF-MS with the shortest possible distance between detection points (12 cm) determined by the length of the electrospray needle. In addition, we encourage the use of a normalization of detection traces using a scale of effective electrophoretic mobility to obtain the same x-scale for both detection traces. As an example, the proposed methodology is applied to a mixture of labeled as well as non-labeled N-glycans.

Calibration-free concentration determination of charged colloidal nanoparticles and determination of effective charges by capillary isotachophoresis.

Although colloidal nanoparticles show an electrophoretic heterogeneity under the conditions of capillary electrophoresis, which can be either due to the particle-size distribution and/or the particle shape distribution and/or the zeta-potential distribution, they can form correct isotachophoretic zones with sharp-moving boundaries. Therefore, the technique of isotachophoresis permits to generate plugs in which the co-ions and counter ions of the original colloidal solution are removed and replaced by the buffering counter ions of the leading electrolyte. It is shown that analytical isotachophoresis can be used to measure directly, without calibration, the molar (particle) concentration of dispersed ionic colloids provided that the transference number and the mean effective charge number of the particles (within the isotachophoretic zone) can be determined with adequate accuracy. The method can also be used to measure directly the effective charge number of biomacromolecules or colloidal particles, if solutions with known molar (particle) concentration can be prepared. The validity of the approach was confirmed for a model solution containing a known molar concentration of bovine serum albumin.

Capillary electrophoresis-laser induced fluorescence-electrospray ionization-mass spectrometry: a case study.

The simultaneous hyphenation of capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection and electrospray ionization-mass spectrometry (ESI-MS) as a novel combined detection system for CE is presented. beta-Carbolines were chosen as model analytes with a forensic background. Nonaqueous CE as well as conventional CE with an aqueous buffer system are compared concerning efficiency and obtainable detection limits. The distance between the optical detection window and the sprayer tip was minimized by placing the optical cell directly in front of the electrospray interface. Similar separation efficiencies for both detection modes could thus be obtained. No significant peak-broadening induced by the MS interface was observed. The high fluorescence quantum yield and the high proton affinity of the model analytes investigated resulted in limits of detection in the fg (nmol/L) range for both detection methods. The analysis of confiscated ayahuasca samples and ethanolic plant extracts revealed complementary selectivities for LIF and MS detection. Thus, it is possible to improve peak identification of the solutes investigated by the use of these two detection principles.