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JEOL
235 Birchwood Ave., Cranford, NJ 07016 201-272-8820
CIRCLE 111 ON READER SERVICE CARD
Villi Your N e x t FT NMR
be
S u p e r Con? Consider the FX200 or FX270:
• Proven Reliability of the FX Series Console • OXFORD Magnet/ Dewar System
Solids Samplers. This discussion has been limited to fluids sampling. However, solids occasionally require sampling. There is a "mechanical hand" available for this purpose. It is useful when it is impossible or inconvenient to place a process analyzer in a solids stream. This situation can be illustrated in the case of a process infrared moisture analyzer. This is a reflectance-type analyzer that can be placed above a conveyer belt, say, downstream from a forced-air or convection dryer. However, the analyzer would not be appropriate for a forcedair conveyance system such as in a grain elevator or similar plant; the analyzer would not respond well to a dry sample dispersed in a gas and would likely suffer maintenance problems from the continuous abrasive action of the particles. But a "mechanical hand," fabricated from rugged parts, can periodically "grab" a sample from the process stream, transport it a few inches to the analyzer and return it to the stream when the analysis is complete. This solids sampler eliminates both the abrasive effect of the flying solid particles and the spectral noise due to the inhomogeneous, dustlike process stream. Sample System Design Considerations
• Probe Configurations engineered by the development team that produced the first dual probe, the versatile O M N I " Probe, and now the first MICRO-TILT Probe for super-conducting NMR Spectrometers. Impressed? Contact..
essential for viscous samples or thick slurries. Centrifugal pumps do not have the possibly undesirable pulsing action. Centrifugal pumps are available in corrosion-resistant exotic metals as well as in a variety of hard synthetic materials. Peristaltic and diaphragm pumps are available with oiland solvent-resistant wetted parts. Integration of a pump into a sampling system should not be approached casually. While there are many extremely reliable pumps for sale commercially, a good general philosophy in designing a sampling system is to minimize maintenance by minimizing moving parts. Most pumps are electrically operated and therefore must not be used where an explosion hazard is likely. Pneumatic and fluid-operated pumps are available for limited applications, as are explosion-proof electric pumps.
JEOL
235 Birchwood Ave.. Cranford. NJ 07016 201-272-8820
See us at the Pittsburgh Conference, Booths 559-565 CIRCLE 112 ON READER SERVICE CARD
496 A · ANALYTICAL CHEMISTRY, VOL. 53, NO. 3, MARCH 1981
In the foregoing discussion, some aspects of overall sample system design considerations were touched upon. Particularly, it was mentioned that the lag or delay time between sampling and analysis should be kept as low as possible. For tubing and pipe, it is possible to use the flow rate, internal cross section of the tubing and the length of the sample line to calculate the approximate lag time. If filters, regulators, or strippers are part of the sampling system, this calcula-
