MICROSCOPY & IMAGING
FIG. 2. Correlative Raman-SEM (RISE) analysis of particles from an anti-asthma inhaler.
A: Raman image of a particle, color-coded according to the spectra
B: Raman spectra. API (red), lactose (blue, green), milk constituents (pink)
API was the glucocorticoid fluticasone propionate (red). A fourth component represented milk constituents (pink). Te SEM image revealed the particle’s porous surface structures at high resolution (Fig. 2C). It was recorded under low vauum conditions (30Pa) using 15kV accelerating voltage and a BSE detector. Te resulting correlative RISE image is shown in Fig. 2D.
C: SEM image of the same particle
SYNOPSIS Raman microscopy combined with complementary techniques can analyse pharmaceutical particle samples with greater speed and detail than conventional techniques in isolation. Raman together with confocal white light microscopy and an advanced particle analysis software enables thousands of particles to be located, categorised and chemically identified
D: RISE image: overlay of Raman and SEM images
through rapid, automated routines. Raman integrated with SEM can provide a more comprehensive view of a particle by overlaying chemical and structural properties in a composite image.
Damon Strom is with WITec.
www.witec.de
NEW VERTICAL POSITIONING SYSTEM INTRODUCED
rom genome sequencing through to multiphoton fluorescence microscopy, deep tissue inspection, laser materials processing, and wafer inspection to magnetic tweezers in research, vertical positioning systems with large travel range, high dynamics and precision are required in numerous applications in microscopy and industry. With the new V-308 voice coil PIFOC, PI now offers a magnetic direct drive-based solution that unites all these requirements.
F
The core element of the V-308 PIFOC is a single axis slider with high-precision lateral crossed roller guides placed on the base body. The slider is driven by a centred PIMag voice coil motor, which was specifically developed for high dynamics. The 7mm large travel range can be limited upwards and downwards with adjustable hard stops by the user. Acceleration is up to 8m/s², the maximum velocity 200mm/s. This results in step-and-settle times of below 15 msec for 100nm and 250nm step sizes at ±15nm error band. Therefore, a very fast positioning of the focusing unit, rapid data acquisition and high productivity can be achieved. The high-resolution optical PIOne linear encoder is used to achieve the high precision requested. A minimum incremental motion of 10nm and a bidirectional repeatability of 25nm (at 100nm travel) can be realised. A special feature of the new V-308 PIFOC is the magnetic weight force
compensation. This ensures a levitation of the slider and mounted load without power supply and therefore prevents an uncontrolled crash in case of a power failure or when switching off the controller. For a flexible use of the axis – when switching the objective, for example – the user can adjust the counteracting force and compensate an overall load (objective and holder) of up to 1kg. Because of this, the axis acts as a horizontal axis even when being used vertically. With dimensions of 87 x 77 x 30mm (H/W/D), the drive is very compact. An adapter plate ensures mounting on an optical bench or plate, with a metric or imperial hole pattern. Two different objective holders (for vertical or horizontal mounting) as well as a set of adapter rings for different diameter objectives, up to size M32 x 0.75, are available.
For more information visit
www.pi.ws
www.scientistlive.com 55
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