8 research outputs found
A quartz crystal microbalance-assisted method for the assessment of iodine content in organoiodines
Introduction: A new experimental quantitative approach for evaluating iodine content in organoiodine compounds has been proposed, based on the quartz crystal microbalance (QCM) method. This approach relies on following the time behavior of the resonance frequency of the quartz plate under temperature activation of iodine-containing analyte deposited on its surface.Materials and Methods: We have applied the QCM method and the pharmacopoeial titrimetric method.Results and Conclusion: From the mass variations observed, the quantity of emitted iodine is precisely obtained, which readily delivers its initial content in the studied sample. The obtained value corresponds exactly to the theoretical prediction, in contrast to the value obtained by applying the conventional pharmacopoeial metrics
Diltiazem-loaded Eudragit RS 100 microparticles for drug delivery: the challenge of viscosity
Strongly shape-dependent viscosity has been found in drug loaded and `empty` polymeric microspheres (drug delivery systems) made of pharmacopoeial Eudragit RS 100 representative. The dramatically increased viscosity of a layer of spherical particles deposited on the gold electrode surface of quartz resonators from water suspension leads to a large dynamic resistance and inability to sustain stable oscillations in a frequency measuring circuit. The viscosity is also affected by loading the polymer matrix with Diltiazem. Its adverse impact is removed by exposing the deposed layer to acetone vapor leading to `dissolving` the investigated spheres and changing their shape to a thin layered one
Influence of Al Doping on the Morphological, Structural and Gas Sensing Properties of Electrochemically Deposited ZnO Films on Quartz Resonators
The detection of hazardous gases at different concentration levels at low and room temperature is still an actual and challenging task. In this paper, Al-doped ZnO thin films are synthesized by the electrochemical deposition method on the gold electrodes of AT-cut quartz resonators, vibrating at 10 MHz. The average roughness, surface morphology and gas sensing properties are investigated. The average roughness of Al-doped ZnO layers strongly depends on the amount of the doping agent Al2(SO4)3 added to the solution. The structural dependence of these films with varying Al concentrations is evident from the scanning electron microscopy images. The sensing properties to ethanol and ammonia analytes were tested in the range of 0–12,800 ppm. In the analysis of the sensitivity to ammonia, a dependence on the concentration of the added Al2(SO4)3 in the electrochemically deposited layers is also observed, as the most sensitive layer is at 3 × 10−5 M. The sensitivity and the detection limit in case of ammonia are, respectively, 0.03 Hz/ppm and 100 ppm for the optimal doping concentration. The sensitivity depends on the active surface area of the layers, with those with a more developed surface being more sensitive. Al-doped ZnO layers showed a good long-term stability and reproducibility towards ammonia and ethanol gases. In the case of ethanol, the sensitivity is an order lower than that for ammonia, as those deposited with Al2(SO4)3 do not practically react to ethanol
Growth and toxic gas sensing properties of poly(urethaneimide) thin films
In this work we present a study on the growth and the gas sensing properties of poly(urethane imide) thin films. We first deeply characterized by atomic force microscopy (AFM) the nanostructuration of the poly(urethane imide) holding different amine groups. We further studied the interaction between highly toxic gases such as hexamethyleneimine (HMI) and pyridine and the polymer by using an unconventional method based on Quartz Crystal Microbalance (QCM) measurement. We showed for the first time that weak interactions, i.e. hydrogen bonding between the gas molecules and the polymer film allow the diffusion of the gas molecule deep in the polymeric film and the recovery of the film once the gas molecules leave the sensor. This first work paves a new way for the design of a completely recoverable sensor able to detect highly toxic gases for environmental concern
Highly Mass-Sensitive Thin Film Plate Acoustic Resonators (FPAR)
The mass sensitivity of thin aluminum nitride (AlN) film S0 Lamb wave resonators is theoretically and experimentally studied. Theoretical predictions based on modal and finite elements method analysis are experimentally verified. Here, two-port 888 MHz synchronous FPARs are micromachined and subsequently coated with hexamethyl-disiloxane(HMDSO)-plasma-polymerized thin films of various thicknesses. Systematic data on frequency shift and insertion loss versus film thickness are presented. FPARs demonstrate high mass-loading sensitivity as well as good tolerance towards the HMDSO viscous losses. Initial measurements in gas phase environment are further presented.VR "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications
Ammonio Methacrylate Copolymer (Type B)-Diltiazem Interactions in Solid Dispersions and <i>Microsponge</i> Drug-Delivery Systems
This paper presents a complex analytical study on the distribution, solubility, amorphization, and compatibility of diltiazem within the composition of Eudragit RS 100-based particles of microspongeous type. For this purpose, a methodology combining attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX), and in vitro dissolution study is proposed. The correct interpretation of the FTIR and drug-dissolution results was guaranteed by the implementation of two contrasting reference models: physical drugâpolymer mixtures and casting-obtained, molecularly dispersed drugâpolymer composites (solid dispersions). The spectral behavior of the drugâpolymer composites in the carbonyl frequency (ÎœCO) region was used as a quality marker for the degree of their interaction/mutual solubility. A spectral-pattern similarity between the microsponge particles and the solid dispersions indicated the molecular-type dispersion of the former. The comparative drug-desorption study and the qualitative observations over the DSC and SEM-EDX results confirmed the successful synthesis of a homogeneous coamorphous microsponge-type formulation with excellent drug-loading capacity and âcontrolledâ dissolution profile. Among them, the drug-delivery particles with 25% diltiazem content (M-25) were recognized as the most promising, with the highest population of drug molecules in the polymer bulk and the most suitable desorption profile. Furthermore, an economical and effective analytical algorithm was developed for the comprehensive physicochemical characterization of complex delivery systems of this kind