Analysis of complex mixtures with benchtop nuclear magnetic resonance: Solvent suppression with T₂ and diffusion filters

Abstract

Benchtop nuclear magnetic resonance (NMR) spectrometers are being employed in a wide variety of applications from undergraduate teaching and research in academia to quality control and process monitoring in industrial settings. Incorporating benchtop NMR in some of these applications presents opportunities for new practical uses of the technology and challenges that truly test the capabilities of compact NMR spectrometers. For instance, the use of protonated solvents in manufacturing or process monitoring requires separating and quantitating the analyte signals of interest from the strong (overwhelming) response from the solvents. Furthermore, due to the lower field strength available with permanent magnet spectrometers, the NMR spectra of complex mixtures can be more difficult to analyze due to partial or complete signal overlap. To address some of these challenges and to extend the range of applications of benchtop NMR, we investigate NMR techniques that enable quantitative analysis of different components in mixtures. These pulse sequences can be used to suppress one or multiple solvent peaks, to filter out signals by spin–spin relaxation time (T2), or to separate signal components by a molecule's diffusion coefficient (NMR diffusometry). In this paper, we discuss quantitative analysis of excipients in buffers for therapeutic proteins to highlight the usefulness of these NMR pulse sequences in the analysis of complex samples with benchtop NMR spectrometers.

Quantification of Biopharmaceutically Relevant Nonionic Surfactant Excipients Using Benchtop qNMR

“…Extension of PS80 quantification in HPV VLP vaccine to low-field has recently been suggested by Rustandi . Additionally, while this manuscript was undergoing peer review, a study by Le-McClain et al (independent of the work reported here) demonstrated the application of T 2 and diffusion filters with WET water suppression for the quantification of P188 in formulated bovine serum albumin (BSA) solutions …”

“…18 Additionally, while this manuscript was undergoing peer review, a study by Le-McClain et al (independent of the work reported here) demonstrated the application of T 2 and diffusion filters with WET water suppression for the quantification of P188 in formulated bovine serum albumin (BSA) solutions. 31 In this study, we demonstrate that benchtop NMR spectroscopy is a greener alternative to common LC-based methods suitable for the routine quantification of NISE under conditions relevant to the biopharmaceutical industry. We first consider the need for a rapid method to verify quantitatively that surfactant stock solutions used in biopharmaceutical manufacturing are accurately prepared.…”