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ANALYTICAL CURRENTS SERRS remote detection to dye for W. Ewen Smith and colleagues at the University of Strathclyde, the University of Leeds, MOD, CBD Environmental Services, and the Police Scientific Development Branch (all in the United Kingdom) have designed a remote surfaceImage not available for use on the Web. enhanced resonance Raman scattering (SERRS) detection system. Using the system, the researchers successfully analyzed a dye sample as far as 10 m away from the spectrometer in 20 s using only 3.6 mW of laser power. They say the design of the system’s collection optics makes it possible to create a small, portable instrument. SERRS spectrum at a distance of 10 m. Excitation of 3.6 mW at 532 nm; 1-s collection Smith’s group used a probe developed time. (a) 600-mm, ƒ/4.5 Canon telephoto lens; (b) 75-mm, ƒ/1.5 closed-circuit television from a telephoto or closed-circuit television lens lens; and (c) 300 mm, ƒ/5.6 Mamiya telephoto lens. (Adapted with permission. Copyright and fiber-optically coupled it to a Raman spec2002 Society for Applied Spectroscopy.) trometer. They focused on the sample target microscope slide. The researchers report that the rhodamine by passing a HeNe 632.8-nm wavelength laser through the optical fiber. The researchers then positioned two frequency-dou- 6G did not adhere well, but the ABT DMOPA dye strongly adsorbed onto the silver particles. bled Nd:YAG laser pointers with a 532-nm wavelength to illuThey found that the SERRS intensity distribution across minate the substrate within the focused HeNe spot. the surface was more homogeneous when an ultrasonic bath Two dyes were tested as targets: rhodamine 6G and 4(5´treatment was used in sample preparation. Scattering intensity azobenzotriazyl)-3,5-dimethozyphenylamine (ABT DMOPA), from samples kept in the dark up to one year showed little a dye specifically designed to give good surface adhesion. The change, but when left in direct sunlight, intensity dropped dyes were adsorbed onto an aggregated silver colloid consignificantly, although they could still determine the samples sisting of silver particles dispersed in poly(vinyl acetate) and after eight months. (Appl. Spectrosc. 2002, 56, 820–826) pure-color nail varnish and sprayed or painted onto the glass
Microchips get their own PAD Charles Henry and Joseph Fanguy of Mississippi State University report the first microchip with pulsed amperometric detection (PAD). The electrochemical detector is shown to determine the simple sugars glucose, maltose, and xylose. PAD uses a three-pulse sequence to detect, clean, and reactivate the electrode. This approach avoids the problem of electrode fouling with carbohydrates that plagues some other methods, such as direct amperometric detection. The researchers used a platinum working electrode to detect 500-µM solutions of glucose, maltose, and xylose. More detailed work with glucose found reproducible peaks with repeated detection and a linear response from 20 to 500 µM. Next up, say the researchers, is combining PAD with CE. (Analyst 2002, 127, 1021–1023)
Image not availble for use on the Web.
Overlay of PAD of glucose, xylose, and maltose at the optimized potential of +0.4 V vs. Ag/AgCl reference electrode. (Adapted with permission. Copyright 2002 Royal Society of Chemistry.)
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