Hypodermic probe

It should be noted when carrying out reactions using cooling baths, that the reaction itself may not be at the same temperature as the bath due to exothermic processes taking place, so where possible the internal reaction temperature should also be monitored. A particularly convenient way of doing this is to use a digital low-temperature thermometer. These are commercially available, and most come with a hypodermic probe which can be inserted into the reaction flask through a sepmm (Fig. 9.21). 

Fig. 3.6. A low temperature reaction assembly using a digital-low temperature thermometer and a hypodermic probe .

Dialysis is the process in which small molecules diffuse across a semipermeable membrane that has pore sizes large enough to pass small molecules but not large ones. A microdialysis probe has a semipermeable membrane attached to the shaft of a hypodermic needle, which can be inserted into an animal. Fluid is pumped through the probe from the inlet to the outlet. Small molecules from the animal diffuse into the probe and are rapidly transported to the outlet. Fluid exiting the probe (dialysate) can be analyzed by liquid chromatography. 

By inserting the Raman probe into the channel of various endoscopes, we can access the inside of the stomach, the large and small intestines, the bronchus, and portions of the pancreatic and bile ducts. If it is used with a laparoscope, the accessible areas expand to the liver and the outer walls of the digestive organs. If the probe is narrow enough to insert in hypodermic... 

Fig. 8.3.1. Simplified representation of the Knauer Model 11.00 Vapor pressure osmometer / Thermostat 2 measurement cell 3 lid 4 porous wicks 5 thermostated heating block 6 hypodermic syringes 7 bead thermistors 8 thermistor probe...

To study enzymic reactions, cell extracts were prepared by Hughes press or sonic probe (7), and activity was assayed in a Warburg flask which was closed with a rubber serum stopper. A hydrogen atmosphere was added to the flask, and after isolation of the flask, the substrate was tipped into the main compartment of the flask. Samples of the gas atmosphere were removed with a hypodermic syringe and were injected into a gas chromatograph which contained a silica gel column (7). 

Figure 1 Equipment used for measuring dissolved oxygen and pH profiles from the soil surface. On the left is shown, the specially-designed steel probe (with white markings for each 5 cm), with the inner rod which has the measuring sensor attached. The middle image shows the dissolved oxygen micro-sensor with protective hypodermic needle. The image to the right shows the pH electrode...

For micro-pyrolysis-td-GC-MS, the sorbent tube is modified to end in a short section of stainless steel hypodermic tubing the open end of which can be placed immediately adjacent to the heated thermal probe using a micro-manipulator. As the tip is heated, a pump is used to draw gas through the tube. After sampling, the tube is placed in a suitable carrier that fits into a standard thermal desorption unit interfaced to a GC-MS system. Blank desorption runs of the... 

Further development of the pH probe for practical use was continued by Markle and colleagues [21]. They designed the fiber optic probe in the form of a 25-gauge (0.5 mm OD) hypodermic needle, with an ion-permeable side window, using 75-p.m-diameter plastic optical fibers. The sensor had a 90% response time of 30 s. With improved instrumentation and computerized signal processing and with a three-point calibration, the range was extended to 3 pH units, and a precision of 0.001 pH units was achieved. 

This technique employs a single thermistor serving as both a temperature sensor and a heater. Typically in this technique, either a thermistor is inserted through the lumen of a hypodermic needle, which is in turn inserted into the tissue, or the thermistor is embedded in a glass-fiber-reinforced epoxy shaft. Figure 2.4 shows the structure of a thermistor bead probe embedded in an epoxy shaft. Each probe can consist of one or two small thermistor beads situated at the end or near the middle of the epoxy shaft. The diameter of the finished probe is typically 0.3 mm, and the length can vary as desired. Because the end can be sharpened to a point, it is capable of piercing most tissues with very minimal trauma. 

Yang el al. developed Pitot-static tube probes to measure radial gas velocity profiles at different heights in their riser [68]. They encased 0.5 mm ID hypodermic needles in a 5 mm OD tube. The static tube was sealed at the tip, and two 0.5 mm holes were drilled perpendicular to the planes of the tube 10 mm from the tip. The tip of the impact tube was flush with the surface. Using a standard equation for Pitot static tubes gives the local velocity. 

In FIA, chemical-sensing field-effect transistors (Chem. FETs) and ion-selective field-effect transistors (ISFETs) (see sections 2.1.3 and 2.1.4) can be used with notable advantages over the more familiar membrane electrodes - namely miniaturization capability, high signal-to-noise ratio, faster response, decreased contribution of the detector to the creation of sample dispersion, etc. [346]. These types of potentiometric detectors can be reduced in size, enabling their incorporation into a hypodermic needle or other suitable probe, for making in vivo measurements [347]. 

The present state of fibre-optic technology has provided miniaturized spectrometers, multiple sensing possibilities, remote measurement capabilities and even miniaturization of optical probes for incorporation into hypodermic needles for clinical and other biomedical measurements. This fast-moving technology offers many exciting possibilities for the future in the area of chemical sensing. 

In real life, the line source takes the form of a hypodermic sensor probe of finite length and diameter [2]. Typical probes are 50 mm (2 in.) long and about 1.5 mm (1/16 in.) in diameter. They contain a heater element that runs the whole length of the hypodermic. A thermocouple sensor is also located halfway down the length of the probe, to measure the temperature rise associated with the transient. These and other nonlinearities require that the probes be calibrated against a reference material. The resultant probe constant is the ratio of the actual thermal conductivity of the reference material to that measured by the instrument. Silicone fluids have been used for the purpose. 

MARI J, BONAMi J R and LiGHTNER D (1993), Partial cloning of the genome of infectious hypodermal and hematopoietic necrosis virus, an unusual parvovirus pathogenic for penaeid shrimps diagnosis of the disease using a specific probe, J Gen Virol, 14, 2637-2643. 

The use of an infections hypodermal and hematopoietic necrosis vims gene probe serodiagnostic field kit for the screening of candidate specific pathogen-free Penaeus vannamei broodstock. Aquaculture 147 1-8. 

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