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Noninvasive testing for counterfeit drugs
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SORS spectrum to reduce or The global drug market has be400,000 eliminate the impact of surface come inundated with generic Ref 300,000 Raman signals. The effort reand counterfeit drugs that may 200,000 sulted in a SORS spectrum carry inappropriate active phar100,000 that almost perfectly matched maceutical ingredients (APIs) or the reference spectrum. are ineffective. Unfortunately, 700,000 600,000 “The scaled subtraction pharmaceutical products come in 500,000 makes the most of the SORS various forms and are packaged SORS 400,000 concept,” Eliasson explains. in materials that complicate at“This makes it a more objective tempts to verify their authenticimethod [than the point-toty. Opening packages to conduct 200,000 point subtraction]. The only analyses wastes perfectly good CR 100,000 thing you have to agree upon products. is the scaling factor, but here it In the February 15 issue of 400 600 800 1000 1200 1400 1600 1800 was quite obvious which [one] Analytical Chemistry (pp 1696– –1 Wavenumbers / cm gave the best result. Ideally, 1701), Charlotte Eliasson and you want this to be automated, Pavel Matousek of the RutherThe SORS spectrum looks more like the original formulation and we are in fact currently ford Appleton Laboratory (U.K.) (Ref) and has fewer contaminating peaks from the packaging working on software to do describe their application of spamaterial (asterisks). this.” tially offset Raman spectroscopy To expand the utility of SORS, the (SORS) to the noninvasive identification the spectra obtained through the packresearchers would like to modify the inaging materials were weaker than the of APIs in various blister-packed and strument so that it could be taken out bottled pills. As the name implies, SORS reference spectra. The spectra also were into the field or used in more locations. contaminated with Raman signals from starts with conventional Raman (CR) “Our instrument is an open bench the packaging materials, which often spectroscopy, but rather than detect the device occupying about one square Raman signal directly at the point of laser overlapped with and/or buried API sigillumination, SORS detects the signal at a nals. However, the researchers found the meter,” Matousek says. But he adds that “there is no reason why the ultimate decontaminating spectra to be less prodistance from the incident position. vice could not be of similar dimensions nounced with SORS analysis. As Matousek explains, CR spectrosto the existing conventional handheld, “The biggest challenge lies in analyzcopy has limited utility in samples that battery-operated Raman instruments.” ing and interpreting the spectra, to asdiffusely scatter the laser light (e.g., Matousek and Eliasson are also plansign the Raman bands to APIs, packagopaque samples) because the signal dening to expand the range of applications ing, excipients, or to an analyte of tected becomes heavily dominated by for SORS. “The SORS technique deficounterfeit origin,” Eliasson says. “But the surface components, which mask nitely has the potential to be used inthat is obviously not an exclusive probany weaker contributions from subsurlem for the SORS technique, as it is true line or at-line during pharmaceutical face constituents. production and quality control,” Eliasfor all data analysis.” “The SORS concept overcomes this To facilitate API signal identification, son says. “We are currently working on problem by reducing the ‘blinding’ efthese matters in collaboration with the the researchers performed point-tofect of the surface layers and permitting pharmaceutical industry.” much clearer observations of sublayers,” point background subtraction of inherAccording to Matousek, SORS could ent fluorescent signals. For the CR he says. “In essence, it is like trying to also be applied to the security screening spectra, they found that not only did see a candle at a distance against the of envelopes for powders or containers the subtraction step improve the API sun. If you move it away against a darkfor the presence of liquid explosives, as er background, you would stand a much signal but it also highlighted the packwell as the authentication of beverages. aging signal, complicating the peak better chance of seeing it.” At present, the researchers are collaboEliasson and Matousek compared CR overlap problem. With SORS detection, rating with external partners to examine however, the subtraction predominantly and SORS spectra of commercial, packthe use of SORS in disease diagnosis, aged formulations that included the pain improved the API signal identification. including bone disease and breast In another experiment, the rerelievers ibuprofen or paracetamol with cancer. a searchers subtracted a zero-offset specreference Raman spectra of the interior —Randall C Willis trum, scaled down to 10.3%, from a surfaces of broken tablets. As expected, M A R C H 1 , 2 0 0 7 / A N A LY T I C A L C H E M I S T R Y
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