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Interferometric Rl detector The Optilab DSP is an interferometerbased differential RI detector designed for static RI measurements, on-line use with HPLC or GPC to determine analyte concentration, or use with a light-scattering instrument for absolute MW determination. The use of an interferometer to measure RI changes in a liquid simplifies detector calibration and eliminates problems with temperature variation encountered in standard RI detection. In the interferometer, plane-polarized light is split by a prism; a vertically polarized beam passes through the sample while a horizontally polarized beam passes through the reference cell. The two beams are then recombined, and the rotation of the plane of polarization is measured to calculate the RI increment. Unlike detectors that measure the sample RI directly and must be recalibrated for each different solvent used, the Optilab detector needs only a single calibration. The Optilab's response in its linear region is directly proportional to the difference in RI between the sample and a reference cell. An arc cosine correction extends the useful range of the detector be-
Dissolution analysis A tablet dissolution analysis system automatically collects and filters dissolution samples, transfers them to an autosampler, performs HPLC, and prepares reports. The TS1000 Sampling Station, which is part of the system, collects samples from up to 8 vessels per bath using a proprietary pumping system and low deadvolume switching valves. Thermo Separation Products • 404 yond the linear region. Temperature regulation is also important because solvent RI changes with fluctuations in temperature. The detector electronics compensate for temperature and pressure fluctuations and permit the use of a simple external water bath for temperature control. The detector, rated to 175 psi, has a referenceflushvalve and a safety loop to equilibrate pressure between the reference and sample cells and to prevent backpressure damage in on-line HPLC. Three sample flow cells with different pathlengths are available for preparative, standard on-line HPLC, or high-sensitivity applications; cell volumes range from 1.4 to 12 pLThe standard detector can be ordered for operation at 690, 633, 514, or 488 nm or at customer-specified wavelengths. Wyatt Technology • 402
Mercury m o n i t o r i n g Model 2537A mercury vapor analyzer conICP-AES tinuously monitors total gaseous merModule EOP, an ICP-AES spectrometer cury with a detection limit of 25 parts per with a horizontal plasma configuration, is quadrillion and an update rate of 5 min. available as a sequential, simultaneous The mercury is preconcentrated onto a multielement, or combination system. To pure gold adsorbent for thermal desorpavoid matrix effects, it uses a water-cooled tion and cold vapor atomic fluorescence interface in which a high-pressure Ar spectroscopy. The vapor analyzer perstream causes the plasma to "blossom" forms recalibration on demand or at specand thereby removes the upper part of the ified intervals and contains dual cartridges plasma, where matrix effects often occur, for continuous operation. The instrument from the spectrometer window. The wave- can be configured for laboratory use with a length range extends down to 120 nm for high-sensitivity UV detector and a permehalogen detection at part-per-billion levels. ation injection source for calibration. Spectro Analytical • 401 Tekran • 403 INSTRUMENTATION
140 A
Analytical Chemistry, Vol. 67, No. 3, February 1, 1995
ECD Model DP90 electrochemical detector is designed for voltammetric detection in HPLC, FIA, and in-stream process control applications. Data can be observed in real time, and parameters can be changed during a run. Data can also be viewed postrun as contour plots, ID voltammograms, and chromatograms. Other data analysis features include graphic overlays, integration of single or overlapped chromatographic peaks, and statistical analysis. Groton Technology • 405 Benchtop ICP-AES The Horizon is an automated benchtop sequential ICP-AES system designed for routine analyses in small laboratories. It features 1.0-m optics, a plasma torch with reduced Ar consumption, and a solid-state rf generator. Fisons • 406 AFM NanoScope Dimension 3000 atomic force microscope accommodates samples up to 8 in. in diameter for imaging in air or liquid and provides manual or automated stepping. Multiple areas of a sample can be scanned automatically. Areas of interest can be localized using top-view video optics with a motorized zoom function, and a laser tracking system monitors the scanning probe tip to reduce image artifacts. Digital Instruments • 407
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