Flow-through column measurement procedure

Differential procedures are of interest when looking for the very small differences in the polymer molar mass distributions. The differentiation can be made so that (<) The samples are simultaneously applied into two identical columns and the effluent flows through adjacent measuring cells of a differential detector ... 

The schematic diagram of the experimental setup is shown in Fig. 2 and the experimental conditions are shown in Table 2. Each gas was controlled its flow rate by a mass flow controller and supplied to the module at a pressure sli tly higher than the atmospheric pressure. Absorbent solution was suppUed to the module by a circulation pump. A small amount of absorbent solution, which did not permeate the membrane, overflowed and then it was introduced to the upper part of the permeate side. Permeation and returning liquid fell down to the reservoir and it was recycled to the feed side. The dry gas through condenser was discharged from the vacuum pump, and its flow rate was measured by a digital soap-film flow meter. The gas composition was determined by a gas chromatograph (Yanaco, GC-2800, column Porapak Q for CO2 and (N2+O2) analysis, and molecular sieve 5A for N2 and O2 analysis). The performance of the module was calculated by the same procedure reported in our previous paper [1]. 

Since each calibration point is performed in a newly packed column, there is important data dispersion around the calibration line. In addition, the entire calibration procedure is rather time consuming. Therefore, another approach was developed, that provides more accurate results in a considerably shorter time. This recently published approach [32] employs a slightly modified version of the same FMC equipment. Instead of a flow-through arrangement enabling the measurement in steady state, the measurement is performed in a system with continuous circulation, as shown in Fig. 1. 

Procedures. Procedures were developed for measuring plutonium distribution coefficients for batch equilibrium adsorption measurements and for measuring plutonium breakthrough concentrations for column flow-through adsorption experiments. 

Demeny and Haszpra have demonstrated a procedure to elfectively measure CO2 concentration plus its stable isotope compositions. Air samples are pumped through silica gel and Mg(C104)2 traps and 3 1 glass bottles equipped with two Teflon stopcocks. Moisture can thus be removed from the collected air. In spite of its small amounts in the air samples, N2O must be separated from CO2 because they have very similar nth values. This effect is important especially when an IRMS is employed as the detector. A Chromosorb 101 column is used and shows acceptable separation characteristics. Another alternative to separate CO2 from N2O is to pump the sample by helium flow through a liquid nitrogen trap. Under the experimental conditions, CO2 can be detected at about 4.5 min and N2O at 6 min. The acmal volume of CO2 in the 3 1 air sample at 1 atmospheric pressure is around 2 to 3 ml. 

Leaching onto Ion-Exchange Resins. A more sophisticated procedure for determining leachabilities of radioactive waste forms has been developed(7). Flowing deionized water is continuously circulated across the sample surface and then through ion-exchange resins where the leached ions are adsorbed. The adsorbed ions are subsequently eluted from the resin columns for atomic absorption analyses. Leachabilities measured by this procedure are claimed to be lower and more consistent than those made in stagnant water in the absence of continuous ionic control (7 ). 

The details of the microcalorimeter (C-80, Setaram, France) and the procedure followed in this study are given in our earlier publications (1,2). The effluent from the sample cell was analysed with an assembly of Porapak-P and molecular sieves-5A columns, both connected in tandem and each followed by a thermal conductivity detector. Prior to calorimetric measurements, a sample was treated in situ at 475 K for 2h in H2 flow (20 ml min l), followed by evacuation (475 K, 1 h) and heating of the sanq>le for Ih under helium flow at 475 K. While maintaining a sanq)le under helium flow (20 ml min l), several successive 100 pi (4.1 pmol) pulses of CO or H2 were dosed over catalyst sanq)le through an injection port. The amount of a gas adsorbed and that of the corresponding heat evolved were recorded simultaneously. 

Moore and Arnold (1996) married the delayed coincidence system of Giffin et at. (1963) with a gas flow system described by Rama et al. (1987) for the measurement of Ra and Ra in seawater. In this procedure Ra is quantitatively extracted from a known volume of seawater onto a column of Mn-fibre. The meeisurement is based on the observation that Rn produced by Ra decay is quantitatively ejected from the Mn-fibre (Butts et al., 1988 Rama et al., 1987). The partially dried Mn-fibre is placed in an air circulation system and helium is circulated over the Mn-fibre and through a scintillation cell where alpha particles from the decay of Rn and daughters are recorded. Fig. 13-6 is a schematic diagramme of the gas flow system. 

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