Thin-film solid-state proton NMR measurements using a synthetic mica substrate: polymer blends.

Solid-state proton nuclear magnetic resonance (NMR) measurements are performed successfully on polymer blend thin films through the use of synthetic mica as a substrate. When used as a substrate, synthetic fluorophlogopite mica with its proton-free, diamagnetic character, allows for adequate measurement sensitivity while minimally perturbing the proton thin-film spectra, especially relative to more commonly available natural micas. Specifically, we use multiple-pulse techniques in the presence of magic-angle spinning to measure the degree of mixing in two different polymer blend thin films, polystyrene/poly(xylylene ether) and poly(1-methyladamantyl methacrylate) (PMAdMA)/triphenylsulfonium perfluorobutanesulfonate (TPS-PFBS), spin-coated onto mica substrates. Our earlier studies had focused on bulk systems where NMR signals are stronger, but may not be representative of thin films of the same systems that are relevant to many applications such as photoresist formulations in the electronics industry. The superiority of synthetic over natural paramagnetic mica is demonstrated by the maintenance of resolution and spinning sideband intensities (relative to bulk samples) for the synthetic mica samples. In contrast, degraded resolution and large spinning sidebands are shown to typify spectra of the natural mica samples. This approach can be applied to many other proton measurements of solid thin films, thereby greatly extending the types of systems to be investigated. Magnetic susceptibility measurements are also reported for all micas used.

A rapid spectrophotometric method for the determination of mefloquine hydrochloride.

A simple ultraviolet spectrophotometric method for the estimation of mefloquine hydrochloride in methanol (ME(2)) has been developed and has been compared with the reported ultraviolet spectrophotometric method in 0.1 N hydrochloric acid (ME(1)). Analytical parameters such as stability, selectivity, accuracy and precision have been established for both the methods and evaluated statistically to assess the application of the individual methods. Both the methods were compared with the existing pharmacopoeial method for estimation of the drug. Both the methods were found to have the advantages for simplicity, stability, sensitivity, reproducibility and accuracy for using as an alternate to the existing non-spectrophotometric methods for the routine analysis of the drug in pharmaceutical formulations and also in pharmaceutical investigations involving mefloquine hydrochloride.