Apparatus sample valves

The solvent consumption appears to be in conflict with the corresponding optimum flow rates. Substances with high (a) values have a very high optimum flow rate (over 11 per min. for (a=1.2) and the column diameter is over 6 mm which would indicate a very large solvent consumption. However, because the separation is simple, a very rapid separation is achieved with analysis times of less than a second. As a consequence, only a few ml of solvent is necessary to complete the analysis. The apparatus, however, must be designed with an exceedingly fast response and very special sample valves would be necessary. In contrast, a very... 

In the bypass position, the carrier solution flows through the bypass loop and across the ISFET. The sample is injected into the sampling valve and is introduced into the carrier solution. The bypass loop has a high hydrodynamic resistance and thus the solution proceeds to the detector. The reference electrode is always immersed only in the carrier solution and is electrically connected with the ISFET through the solutioa The apparatus is regularly calibrated by K, Ca and pH standard solutions. 

Fig. 2. Schematic illustration of a newly designed friction apparatus. The valve A is opened immediately after the valve B is closed when the measurement begins. The velocity of water flow in the micropipette is measured by a microscope which is set on a mechanical taranslational stage with micrometers with an accuracy of 0.001 mm. After the measurement, the value A is dosed and the valve B is opened to equalize the pressures of the either sides of the sample gel. The valve C is used to change the hydrostatic pressure...

Temperature programmed desorption (TPD) of C02 (5 °/min, flow of He, 15 ml/min) was carried out on a conventional flow apparatus. In a typical experiment, 0.29 g of the catalyst were activated as above reported, then the system was cooled to 25°C and approximately 2 10 5 mol of Co2 were injected by means of a gas sampling valve. After degassing in flow of helium for 60 min the amount of the irreversibly adsorbed C02 was determined with an on-line g.l.c. equipped with a thermal conductivity detector,... 

Conditions. Table II provides temperature, pressure, and other conditions for the experiments. The surface area/volume ratio for all experiments was 2.7 x 103 cm 1. The hydrothermal apparatus was a Dickson-type sampling autoclave with a gold-titanium reaction cell, a gold-lined sampling tube, and a titanium sampling valve block (11). Samples of the reacting fluid could be taken over time without disturbing the pressure-temperature conditions of a run. The autoclaves were rocked 180 at about 4 cycles/min. 

Phase equilibria and pressure-temperature coordinates of critical points in ternary systems were taken with a high-pressure apparatus based on a thermostated view cell equipped with two liquid flow loops which has been described in detail elsewhere [3]. The loops feed a sample valve which takes small amounts of probes for gas-chromatographic analysis. In addition to temperature, pressure and composition data, the densities of the coexisting liquid phases are measured with a vibrating tube densimeter. Critical points were determined by visual oberservation of the critical opalescence. 

The apparatus necessary is the detector itself with its associated electronics and recorder or computer system, a mobile phase supply, pump, sample valve and virtually any kind of column. In practice the chromatograph itself which will be used for the subsequent analyses is normally employed. The solute is chosen as typical of the type of substances that will be analyzed and a mobile phase is chosen that will elute the solute from the column in a reasonable time. Initial sample concentrations are chosen to be appropriate for the detector under examination. 

We wish to emphasize that the design of experimental apparatus for pVTxy measurements of supercritical fluid-liquid equilibrium in fatty ester systems has to be undertaken with special care to avoid adsorption of the fatty acid on the sampling apparatus. Since the equilibrium fluid mixture passes through the sampling valve in our design, it is neither necessary nor advisable to use very small diameter lines. 

A diagram of the experimental apparatus is provided in Figure 1. The Perkin-Elmer GC was equipped with a single flame ionization detector and was capable of operating at temperatures below 450°C. The injector was a computer controlled Carle gas sampling valve in a thermostated box. Flow control was provided by two flow controllers the first with a 0 to 5 mL/min element and the second with a 0 to 60 mL/min element. The second controller was connected to the injector through a computer-controlled solenoid. All facets of the experiment were controlled and the data analyzed, using an IBM PC computer. 

The apparatus used by Wiedemann (37) is shown in Figure 8.11. In order to keep the time delay in gas transfer to a minimum, he reduced the furnace volume to about 35 cm3. Gases were introduced into the gas chromatograph by means of a gas sampling valve that could be opened at specific intervals. Wiedemann commented tha compared to a mass spectrometer the gas chromatograph is slower, but as far as the quality of results is concerned the methods are about equal. 

The plate colunm (with diameters up to 90 mm) in the author s Destinorm apparatus (Fig. 139), on the other hand, has internal reflux like industrial columns, so that distillations with this form of apparatus are comparable in this respect. The various trays may be provided as required with sampling valves and thermometers, in order that concentration and temperature gradients may be followed during the... 

Helium (99.99% pure) obtained from Matheson was employed as the sweep gas in the gas permeability apparatus. Helltm (99.99% pure) was the carrier gas In the Varlan 1420 Gas Chromatograph (GC) having a thermal conductivity detector (TCD) and a gas sampling valve (GSV). 

The solutes chosen were (S) and (R) 4-benzyl-2-oxazolidinone. The apparatus consisted of an LC pump, a 1 pi internal loop sample valve and the column was situated in a thermostatically controlled oven. The oven could be operated at temperatures between 5°C and 85°C with a precision of 0.2°C. The mobile phase was passed through a preheater, consisting of 1 m length of coiled stainless steel tube, 0.010 in. ID., situated in the thermostat, between the sample valve and the column. The column outlet was connected directly to a UV detector operating at 220 nm. The eluent from the detector was passed to a 50 ml Grade A burette and the retention volumes were measured directly in ml of mobile phase. The burette was read with an accuracy of 0.02 ml. The output of the detector was displayed on a digital meter and an electronic recorder/integrator. 

Hydroformylation reactions were performed in a 90-mL Fischer-Porter bottle equipped with a gas inlet valve, liquid sampling valve, and star-head magnetic stir bar. The pressure apparatus was immersed in a constant-temperature bath maintained at 33.6 0.5 °C in a well-ventilated fume hood. A magnetic stirrer placed below the bath provided efficient stirring. 

Since PGCs are required to operate automatically and unattended for extended periods, the sample injection valve in these systems is of critical importance. A PGC sample valve must be more robust than the injection apparatus for a LGC. 

Figure 2.37 Schematic diagram of the DTA-EGD-GC online coupled simultaneous apparatus (reproduced by permission of Tian Ping Instrumental Factory, China). 1, Gas cylinder for DTA system 2, carrier gas (or GC system 3, reducer valve 4, gas drying 5, governor valve 6, float meter 7, six-way valve 8, gasifier, 9, 5A molecular sieve 10, 401 organic support 11, soap film flow meter 12, sampling valve 13, infrared lamp 14, recorder for DTA/T 15, recorder for EGD-GC 16, tail gas...

It was found during studies of ammonia synthesis on iron that the incorporation of a condenser downstream of the sample valve in the external circulation loop of the HPLP apparatus (Fig. 7), enabled the system to be run as a flow rather than a batch reactor. This is true for any reaction system where the reactants are more volatile than the products, since the condenser temperature can be adjusted to trap the products almost exclusively, allowing a nearly pure stream of reactants to impinge on the catalyst. In the case of ammonia synthesis, (where, next to the product, nitrogen at a partial pressure of 5 atm was the most condensable species) a slurry of isopentane (— 159.9 °C) was found to be the ideal condenser medium. During a study of rhenium-catalyzed ammonia synthesis the isopentane condenser was switched in periodically to reduce the ammonia partial pressure to below that at which it appeared to poison the catalyst. In this way, the rhenium was able to produce ammonia in excess of the amount usually leading to poisoning. 

Modern high-speed GC systems are able to separate some light hydrocarbons within a second [117, 118]. This approach requires special sampling valves, narrow-bore columns (diameter = 0.005 cm), and detectors with a fast response. However, in EGA these fast separations are not necessary. Taking samples on-line from the reactor and separating them within 1 minute is frequently satisfactory in order to better understand degradation kinetics. The apparatus for this approach can be constructed of commercially available parts. 

Apparatus Preparation—With the proper column(s) and liquid sample valve in place, adjust operating conditions to optimize the resultant chromatogram. Using the reference standard, introduce the sample in the following manner. 

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