These are probes made for absorption or transmission measurements. Typically, these probes are used to take measurements in liquids, hence the term “dip probe”, which came from how they are used–often being dipped into a fluid. The material being measured enters the aperture or gap in the probe tip which is set for a given pathlength. Interchangeable tips allow various fixed pathlengths to be used, or on a Variable Pathlength Probe the gap or pathlength can be adjusted over some range.
We have developed many different probes including Micro design with probe tip ends only 1.6mm in diameter. Our probes can be made to operate at high temperatures, in acids, bases and solvents, or in pressure vessels or vacuum chambers. Our design capabilities are almost unlimited, with a variety of fiber types, probe materials and end fittings, including custom fitting to interface to proprietary instruments or processes.
These are Dip Probes tailored to dissolution measurements common in the pharmaceutical industry, though they are just a type of Dip Probe made to operate at body temperature and a pH of 2 to simulate the gastric environment. In a dissolution measurement, a simulated gastric environment is established, and a pharmaceutical is introduced. The probe in conjunction with a suitable light source and detection system, often a spectrometer, then monitors the simulated gastric fluid to determine the rate at which the pharmaceutical dissolves and appears in the fluid. This is a measure of its bioavailability and is an important characteristic of any medicine taken by the mouth.
All XSOF™ dip probes and dissolution probes are used to make absorption or transmission measurements and are of the transflectance type.
Transflectance probes are two-sided. One side is connected to a light source and that leg brings light energy to the probe tip, where it passes through the gap, reflects off a mirror (hence the term transflectance), travels back across the gap, and is refocused into the other side of the probe that is ultimately connected to an analyzer, typically a spectrometer.
At XSOF™, our probes are designed with materials compatible with the environment in which they are expected to be used. Therefore, careful understanding of our customer’s application is critical.
Interchangeable tips with fixed pathlengths, and variable path length probes are available.
Fluorescence and Reflectance Probes
Fluorescence and Reflectance are important techniques in spectroscopy. They are both one-sided techniques useful with solids and powders. These techniques require illuminating the sample with a known wavelength or spectrum and then comparing that to the emitted or reflected (scattered) wavelength or spectrum. These techniques are ideally suited to fiber optic probes.
Fluorescence probes deliver suitable excitation energy to cause a fluorescence (absorption of light at the excitation wavelength and conversion of that light to a longer wavelength which is the emitted light). This conversion is a characteristic of the material or surface under study. Fluorescence is an absorption/emission phenomena and is one-sided (not a transflectance). The same probe end has fibers available to collect some of the emitted fluorescence and route it to an analyzing instrument, often a spectrometer.
Reflectance is an absorption/scattering phenomenon. Again, the spectrum illuminating the sample is compared to the spectrum reflected from the sample.
Reflectance and Fluorescence probes often are identical, in that you can use the same probe to make both types of measurements.
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XSOF™ is a manufacturer of standard and custom fiber optic probes for a variety of specialty applications. For more information about our products, or to request a quote, please feel free to contact us today.