CHROMATOGRAPHY/SPECTROSCOPY 35


Non-linear optical materials hold promise for better imaging


hen photographers zoom in on an object to see it better, they lose the wide-angle perspective – they are forced to trade off 'big picture' context for detail. But now an imaging method developed by Princeton researchers could lead to lenses that show all parts of the scene at once in the same high detail. The method could help build more powerful microscopes and other optical devices. Cameras and other optical devices – including the human eye – are limited by the amount of light that they can collect through their lens openings, or apertures. In order for a light ray to be recorded, it has to pass through the lens and reach the device's 'detector' – such as the eye's retina or a digital camera's detector. But many light rays never make it to the detector, either because they are too weak, or because they are deflected. This problem is particularly acute with details that are smaller than the wavelength of light. (Each colour of light has a distinct wavelength – green, for instance, has a wavelength of 530 nanometres, roughly the size of a typical bacterium's internal structure.) Light rays from such tiny features fade before they reach the lens. To capture these rays, devices have to probe very near the surface of the object, and scan it point- by-point, stitching together a full image. The new method addresses the shortcomings of small apertures by taking advantage of the properties of substances called non-linear optical materials. The core component, a non-linear


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wave mixer, is a rectangular pill-sized crystal of a material called strontium barium niobate. The researchers placed the object to be imaged on one side of the crystal and image-capturing equipment on the other. They tested the system by obtaining images of various objects, including a chart developed by the Air Force that is widely used to calibrate optical devices. u


For more information, visit www.princeton.edu


New chromatography column chemistries P


all Life Sciences has launched a full palette of scaleable AcroSep 1ml columns with ion exchange, affinity, and mixed-mode chromatography chemistries. Pall AcroSep pre-packed chromatography columns are ideal for preparatory protein purification research. These columns can also be utilised as an efficient screening tool for best chromatography conditions prior to process development. Pall AcroSep


chromatography columns offer: u True scaleability. Pall offers the same resin chemistry for small-scale discovery through to biopharmaceutical manufacturing. u Versatility. Pall AcroSep columns


feature luer inlet and outlet for convenient use with syringe, pump or automated chromatography system. u High binding capacities, fast flow rates. By tailoring attributes such as chemistry, pore size, and sorbent diameter to applications, Pall resins and columns exhibit the highest performance characteristics. u User-friendly column design. Colour coded and labelled by chemistry type. The AcroSep columns


feature a hexagonal collar so columns will not unexpectedly roll off lab surface. u


Enter 35 or ✔ at www.scientistlive.com/elab


Pall Life Sciences is based in East Hills, NY, USA. www.pall.com/acrosep


Mass spectrometric comparison and evaulation of GC-MS and LC-MS analyses


samples. Real life samples with complex matrices have complex chromatograms that make the evaluation for presence of contamination or residual components a difficult and time consuming task. The Compare tool recently developed for the mass spectra evaluation software package MassLib finds both qualitative and quantitative differences between two GC-MS or LC-MS analyses and presents the results graphically and in tabular form. The only prerequisite is that the


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two analyses have been acquired under chromatographically comparable conditions.


For an efficient and successful analyses compare tool several features are required which all are provided in the MassLib software. A peak finder algorithm must


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frequent task in an analytical laboratory is the comparison of two


be capable of finding component spectra even if coelutions and variable background is present. It must be possible to compare the two analyses based on retention index scaling and on absolute intensities. The spectral comparison must reliably


recognize that a spectrum is contained in the comparison spectrum even if not readily visible. MassLib’s SISCOM algorithm (Search for Identical or Similar COMpounds) is better suited for this task than algorithms that are optimised for determination of spectral identity. In addition, library searching must


be available to identify the components where differences are found. And finally, the comparison must run autonomously and document its results. u


Enter 35A or ✔ at www.scientistlive.com/elab


MSP KOFEL is based in Zollikofen, Switzerland. www.msp.ch


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