Dip probe

In this section we will review calcium tolerance studies by Borchardt [40] at 75°C using a dipping probe colorimeter. The transmittance value of the... 

Turbidity measurements were determined using the dipping probe colorimeter. The light frequency was 650 nm. Deionized water transmittance was set at 90. The surfactant test solutions were stirred ( — 3500 rpm) and maintained at 75°C. Active surfactant concentration was 0.1% wt. Solution volume was 100 cm1. A 26.5% CaCU (95,699 ppm CaJ+) solution was added via syringe in 0,10 ml increments to the lower portion of the surfactant solution. 

The homogeneous catalysis method is suitable to measure rate constants over a very wide range, up to the diffusion limit. The lower limit is determined by interferences, such as convection, which occur at very slow scan rates. It is our experience that, unless special precautions are taken, scan rates below lOOmV/s result in significant deviations from a purely diffusion-controlled voltammetric wave. For small values of rate constants (down to 10 s ), other potentiostatic techniques are best suited, such as chronoamperometry at a rotating disk electrode UV dip probe and stopped-flow UV-vis techniques. ... 

Chemical reaction monitoring Polymerizations, esterifications and other condensation reactions, diazo reactions, oxidation, and reduction On-line and dip-probe applications... 

Table 4. Standard potentials of some aromatic and heteroaromatic compounds, E°, the wavelength corresponding to maximum absorption, -imax, the extinction coefficients measured by means of the dip probe are given by fiprobe (see Section 2.6.3 and Ref [65] for details), and those by the flow technique are given by enow...

Figure 32. UV dip probe based on light guides, from Ocean Optics.

Fig. 19 Schematic of the CWBP. WF - waste port for the fluid, DF - fluid port for denature solution, S/B - port for sample and buffer, can be connected to a carousel dip probe, PV - 3-way pinch valve, V - isolation valves,...

Fig. 20 Schematic of the electronics module controlling the CWBP. DA -darlington amplifiers, DAC -digital to analog converter, ADC - analog to digital converter, Amp-disc -amplifier discriminator for the photomultiplier (PMT), PS -pulse stretcher, OSC -oscillator, Zero pos - zero position sensor, Top pos -dip probe position sensor, RM - carousel rotary stepper motor, UPM - linear actuator for the dip probe of the carousel, RT - resistance thermistor, TEC -thermoelectric heat exchanger, Tset - set temperature. (Reprinted from Dhadwal et al. [2], with permission of Elsevier)...

Probes have been designed that can overcome most of such risks and therefore can be regarded as closed-transfer systems, but these are relatively costly, complex and slower in operation than a simple dip probe. 

Figure 25-1 shows the calculated results, giving the range in which the steel industry uses dipping probes extensively. 

With a fiber optic dip probe, many liquids and solutions can be analyzed with no sample preparation. The use of a dip probe for transmission measurements requires that the liquid or solution be free from small particles or turbidity. Suspended particles scatter light and reduce the sensitivity of the measurement. The already low absorptivity of NIR bands makes transmission measurements of limited use for liquid samples that are not clear. 

As an alternative to the use of a thin layer electrolysis method, systems based on the use of fiber optic cable for transmission of infrared radiation may be used in an in situ dip probe made for monitoring the course of conventional bulk electrolysis experiments. Unlike thin layer cell methods, this spectroelectrochemical technique requires no cell design compromises which diminish the accuracy of the voltammetric data that also may be obtained during the course of the electrolysis. 

As previously discussed, liquids ATR cells may be used and, in general, the horizontal ATR format is the most appropriate and convenient—in use and for cleaning. Alternatively, either a boat cell cylindrical ATR accessory or a ATR dipping probe may be used. In all cases, pay careful attention to cleaning. Trace contamination of the surface of the ATR element will result in a major interference to the sample spectrum. 

The most common UV-vis spectrometers are designed to accept samples in glass or quartz cuvettes, 1 cm on a side. Fiber optics now allow remarkable versatility in how the radiation is transmitted to the sample and returned to the spectrometer. Dip probes combine two optical fibers for the delivery and return of the radiation, with a tiny sample compartment and mirror arrangement at the probe tip, allowing the probe to sample analytes in a wide range of environments. 

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