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chromatography • spectroscopy 27


circular polarisation (DCPII)4


. Tis


new achievement allows the direct comparison of all four forms of ROA of molecules within or without resonance. Moreover, at present, a theoretical group at Rice University has been calculating DCPI ROA and predicted that DCPI


has


significant advantages over ICP or SCP for measuring much more reliable surface-enhanced Raman optical activities (SEROA) due to its inherent depolarization properties and its removal of large useless parent Raman radiation, which only contributes noise in ROA or SEROA measurements5


. In this case, DCP-


SEROA will improve the detection sensitivity by several thousand orders of magnitude compared to previous spontaneous ROA measurements and significantly decrease the amount of sample needed for down to only several thousands of molecules.


In addition to simultaneous acquisition of all four forms of ROA, all polarisation state (highly polarised, depolarised, unpolarised)


measurements of parent Raman spectra can be obtained at the same time with the current BioTools ChiralRAMAN-2X spectrometer. In addition, the degree of circularity, which can be easily converted to depolarisation ratio, can also be acquired. In Figure 1, eight traces of Raman spectra of neat S-pinene have been shown. All traces were obtained for a single experimental setup. Tey are highly polarised (top spectrum, DCPII


), depolarised (middle spectrum, DCPI DCPII ), and unpolarized


(lower spectrum, SCP or ICP) Raman in the top panel, and SCP, DCPI


, ICP, ROA as labelled in the middle


panel, and the degree of circularity spectrum in the lower panel.


Te most recent development of the ROA spectrometer combines an ROA spectrometer (BioTools ChiralRAMAN-2X) to a multi-port inverted microscope (IX71/81 from Olympus) for Raman microscopy measurements. Te attachment of a Raman microscope allows for micro analysis of trace samples, like particles of micron size, droplets, cells,


spores, bacteria, etc. Te addition of a microscope enables various traditional microscopic observations, like phase contract, relief contrast, differential interference contrast, FRET, TIRFM, to be applied to the same samples undergoing ROA measurement.


Enter 27 or ✔ at www.scientistlive.com/elab


Honggang Li is a Senior Research Scientist, BioTools Inc, Jupiter, Florida, USA. www.btools.com


Laurence A Nafie is a Chief Technology


Officer, BioTools Inc and a Distinguished Professor, Department of Chemistry,


Syracuse University, Syracuse, New York, USA. www.syr.ed


References: 1


Haesler, J; Schindelholz, I; Riguet, E; Bochet, C G; Hug, W Nature


2007, 446 526-529; 2


Barron, L D; Hecht, L; McColl, I H; Blanch, E W. Molecular Phys.


2004, 102, 731-744; 3


5


Hug, W; Hangartner, G J Raman Spectrosc. 1999, 30, 841-852; 4 Li, H; Dukor, R K; Nafie, L A XXII-ICORS 2010, 1267, 159;


Lombardini, R; Acevedo, R; Halas, N J; Johnson, B R J Phys. Chem. C 2010, 114, 7390-7400.


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