1064 nm Dispersive Raman Microspectroscopy and Optical Trapping of Pharmaceutical Aerosols
JournalArticle (Originalarbeit in einer wissenschaftlichen Zeitschrift)
ID 4525665
Author(s) Gallimore, Peter J.; Davidson, Nick M.; Kalberer, Markus; Pope, Francis D.; Ward, Andrew D.
Author(s) at UniBasel Kalberer, Markus
Year 2018
Title 1064 nm Dispersive Raman Microspectroscopy and Optical Trapping of Pharmaceutical Aerosols
Volume 90
Number 15
Pages / Article-Number 8838-8844
Mesh terms Science & TechnologyPhysical SciencesChemistry, AnalyticalChemistry
Abstract Raman spectroscopy is a powerful tool for investigating chemical composition. Coupling Raman spectroscopy with optical microscopy (Raman microspectroscopy) and optical trapping (Raman tweezers) allows microscopic length scales and, hence, femtolitre volumes to be probed. Raman microspectroscopy typically uses UV/visible excitation lasers, but many samples, including organic molecules and complex tissue samples, fluoresce strongly at these wavelengths. Here we report the development and application of dispersive Raman microspectroscopy designed around a near-infrared continuous wave 1064 nm excitation light source. We analyze microparticles (1-5 pm diameter) composed of polystyrene latex and from three real-world pressurized metered dose inhalers (pMDIs) used in the treatment of asthma: salmeterol xinafoate (Serevent), salbutamol sulfate (Salamol), and ciclesonide (Alvesco). For the first time, single particles are captured, optically levitated, and analyzed using the same 1064 nm laser, which permits a convenient nondestructive chemical analysis of the true aerosol phase. We show that particles exhibiting overwhelming fluorescence using a visible laser (514.5 nm) can be successfully analyzed with 1064 nm excitation, irrespective of sample composition and irradiation time. Spectra are acquired rapidly (1-5 min) with a wavelength resolution of 2 nm over a wide wavenumber range (500-3100 cm(-1)). This is despite the microscopic sample size and low Raman scattering efficiency at 1064 nm. Spectra of individual pMDI particles compare well to bulk samples, and the Serevent pMDI delivers the thermodynamically preferred crystal form of salmeterol xinafoate. 1064 nm dispersive Raman microspectroscopy is a promising technique that could see diverse applications for samples where fluorescence-free characterization is required with high spatial resolution.
ISSN/ISBN 0003-2700
edoc-URL https://edoc.unibas.ch/74521/
Full Text on edoc No
Digital Object Identifier DOI 10.1021/acs.analchem.8b00817
PubMed ID http://www.ncbi.nlm.nih.gov/pubmed/29956916
ISI-Number 000441476600019
Document type (ISI) Journal Article

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