Confocal Raman Microscopy for in Situ Detection of Solid-Phase Extraction of Pyrene into Single C₁₈–Silica Particles

Journal Article · Tue Jan 07 00:00:00 EST 2014 · Analytical Chemistry

DOI:https://doi.org/10.1021/ac403514r· OSTI ID:2480571

Kitt, Jay P. ^[1]; Harris, Joel M. ^[2]

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1. University of Utah, Salt Lake City, UT (United States); University of Utah
2. University of Utah, Salt Lake City, UT (United States)

Solid-phase extraction (SPE) is a well known method for separating and pre concentrating analytes prior to ex-situ detection and quantification. Despite advances in miniaturization of solid-phase extraction, the technique has not evolved to meet the needs for detection in small scale microfluidic devices. While successful efforts have led to smaller scale extractors that allow preconcentration from small volumes, detection within correspondingly small volumes has remained out of reach because of analyte dilution during a post extraction transfer or “wash off” step prior to detection. In this work, successful extraction into sub-picoliter collection volumes is accomplished by using a single chromatographic particle as an extractor; wash off dilution is totally avoided by using confocal Raman microscopy for in-situ detection within the single-particle collection phase. Specifically, micromolar concentrations of pyrene in methanol water solution were equilibrated with an individual C₁₈-functionalized silica particle, and Raman spectra were acquired from a small confocal sampling volume (~1 fL) within the particle interior. By comparing the Raman scattering intensity of the pyrene with that of the C₁₈-chains in the stationary phase, it was possible to quantify the equilibrium coverage of pyrene relative to the C₁₈ chains. Spectroscopic isotherms were measured to determine the saturation surface coverage of pyrene relative to C₁₈-chains and to study how the preconcentration equilibrium can be controlled by the source-phase solution composition. For extraction from aqueous solutions having the lowest methanol concentration (5% by volume), the preconcentration factor for pyrene into the particle was found to be 4.8 (±0.8) × 10⁴, which allowed detection of pyrene extracted from a 10 nM solution into a 0.52-pL particle volume.

• Research Organization: University of Utah, Salt Lake City, UT (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: FG03-93ER14333
• OSTI ID: 2480571
• Journal Information: Analytical Chemistry, Journal Name: Analytical Chemistry Journal Issue: 3 Vol. 86; ISSN 0003-2700
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Aromatic compounds
Extraction
Hydrocarbons
Preconcentration
Raman scattering