DuPont flow controller

Figure 5.21 High purity flow controller and buret. (Courtesy Mace Products and DuPont Companies.)...

The DuPont 833 Precision Flow Controller is used in connection with a pneumatic... 

DuPont system when the Model 833 precision flow controller is coupled with the gradient elution accessory immediately after the pneumatic pump on solvent A line (Fig. 7). The air pressure is adjusted so that the flow-rate is kept constant. Also in the DuPont device, solvents that differ widely in viscosity can be difficult to mix and the shape of the gradient can be altered. 

A stainless steel column (4.6 mm internal diameter by 250 mm length) packed with 7 micron Zorbax ODS (Dupont) was equilibrated with 82 % Acetonitrile in water at a flow rate of 2.0 ml/min. provided by a Spectra Physics Model 87(X) pump and controller. The effluent was monitored at 230 nm using either a Tracor UV-Visible detector Model 970A or a Jasco Uvidec UV detector Model 1(X)-V. Peaks were recorded and calculated on a SpectraPhysics recording integrator. Model 4200 or Model 4270. Samples of 0.5 mg/ml in toluene were applied to the column automatically with a Micromeritics Autosampler Model 725 equipped with a 10 pi loop. 

Thermal Analysis. The DuPont Instruments Model 9900, computer controlled thermal analyzer and Model 951 TGA module were used in the experiments, using a gas flow rate of 100 cc/min. Experiments were performed in dynamic and isothermal mode using air and argon. 

Boersma5) showed that quantitative calorimetric data could be obtained from a modified DTA instrument in which the sample and reference are in separate containers connected by a controlled thermal resistance, and with external thermocouples. In such an instrument the sample-reference temperature difference can be related to the heat flow, and this is the basis of heat flux DSC. The DuPont 910 DSC is based on a further development of this principle, and it is illustrated by Fig. 2. 

Due to high dust concentrations inside the elevators, samples were collected with Dupont low flow sampling pumps (model P125) operated at a flow rate of approximately 120 cc/min. The outside control samples were collected using a Bendix Sequential Air Sampler modified for membrane filtration and operated at a flow rate of approximately 6 1pm due to low particulate concentrations of the ambient atmosphere. All of the samples were collected on Millipore Type HA filters which have a pore size of 0.45 pm. 

Thermogravimetry (TG) data were obtained on the NH4+- and H30+-exchanged ZSM-5 samples, as well as on a separately prepared NH -exchanged sample of similar composition, for confirmation purposes. A duPont Model 951 thermogravimetric analyzer was used in conjunction with a Model 990 Recorder-Controller. The TG curves were obtained on approximately 25 mg samples, at a heating rate of 10°C per minute, and under flowing air at a rate of 38 cnP per minute. 

Many systems that have been used consist of a commercial fluorimeter fitted with a micro flow-through cell. Descriptions of such systems can be found in the papers by Katz and Pitt , Cassidy and Frei and Roth and Hampai , while the manufacturers of the fluorimeters used also market flow cells (Aminco and Turner Assoc.). Conmercial equipment especially designed for use in HPLC has also been available for several years, with emission lines and filters (Siemens, Dr. Ing. Herbert Knauer, Laboratory Data Control, DuPont, Varian), as well as with monochromators (Winopal Forschung, Perkin-Elmer, Schoeffel, Aminco, Turner Assoc., Jasco). Cells of these designs are small enough (ca. 20 gl) to be able to give a small contribution to the peak width with suitable connection lines and electronics. However, adequate information on this point is not generally available, in some instances perhaps because the reaction systems frequently used with these instruments contribute much more to the peak width. 

Analysis of particle size is important in a wide range of industries. When the particles are powders, the information is required for research and development as well as for process quality control. Allen states that two thirds of the 3000 products of Dupont s products were sold as powders and that another fifteen percent contained powders. Whilst figures for other companies may be lower, this illustrates the importance of powders for the chemical process industry. If drops are being considered, the interest usually arises from research and development into sprays from nozzles or from confined two-phase flows. The former can have applications from combustion to crop protection. In two-phase flows, the size of drops can affect momentum, heat and mass transfer. In addition, drop sizes are essential for the design of compact gas/liquid separators. 

---