Separation simultaneous

Finally, ion chromatography can be used to determine the a-sulfo fatty acid esters. The chromatographic column is a nonpolar poly sty rene/divinylbenzene column and the ion pair reagent is 0.005 M ammonia. In order to reduce the elution time, acetonitrile is added as a modifier with increasing concentration. This gradient technique makes it possible to separate simultaneously ester sulfonates and disalts by chain length. Determination is achieved by standards with defined chain length [107]. 

The two examples of sample preparation for the analysis of trace material in liquid matrixes are typical of those met in the analytical laboratory. They are dealt with in two quite different ways one uses the now well established cartridge extraction technique which is the most common the other uses a unique type of stationary phase which separates simultaneously on two different principles. Firstly, due to its design it can exclude large molecules from the interacting surface secondly, small molecules that can penetrate to the retentive surface can be separated by dispersive interactions. The two examples given will be the determination of trimethoprim in blood serum and the determination of herbicides in pond water. 

The popularity of reversed-phase liquid chromatography (RPC) is easily explained by its unmatched simplicity, versatility and scope [15,22,50,52,71,149,288-290]. Neutral and ionic solutes can be separated simultaneously and the rapid equilibration of the stationary phase with changes in mobile phase composition allows gradient elution techniques to be used routinely. Secondary chemical equilibria, such as ion suppression, ion-pair formation, metal complexatlon, and micelle formation are easily exploited in RPC to optimize separation selectivity and to augment changes availaple from varying the mobile phase solvent composition. Retention in RPC, at least in the accepted ideal sense, occurs by non-specific hydrophobic interactions of the solute with the... 

Separations Simultaneous (including standards, calibration) Sequential... 

The truly parallel approach of this technology permits many different samples to be separated simultaneously using a minimum number of common system components such as pumps and pulse dampers. To increase the automation of the system, a plate loader and exchanger that accommodate... 

Isotachophoresis. In isotachophoresis (ITP), or displacement electrophoresis or multizonal electrophoresis, the sample is inserted between two different buffers (electrolytes) without electroosmotic flow. The electrolytes are chosen so that one (the leading electrolyte) has a higher mobility and the other (the trailing electrolyte) has a lower mobility than the sample ions. An electric field is applied and the ions start to migrate towards the anode (anions) or cathode (cations). The ions separate into zones (bands) determined by their mobilities, after which each band migrates at a steady-state velocity and steady-state stacking of bands is achieved. Note that in ITP, unlike ZE, there is no electroosmotic flow and cations and anions cannot be separated simultaneously. Reference 26 provides a recent example of capillary isotachophoresis/zone electrophoresis coupled with nanoflow ESI-MS. 

This not only shows how the extent of extraction varies with phase ratio at a constant distribution ratio, but also how varying the phase ratio affects the relative purity of the product. Increasing the phase ratio by a factor of 100 nearly doubles the recovery, but drops the relative purity by a factor of over 25. Note that, in a single stage, it is not possible to achieve both high recovery and a high degree of separation simultaneously. Also,... 

Sensors based on integrated dialysis, reaction and detection differ from those described in Section 4.3.1 in the fact that a (bio)chemical reaction takes place after separation (simultaneously with detection). They thus fit the generic configuration depicted in Fig. 5.1. A. Some of the ingredients of such a reaction may be immobilized at the sensing microzone, even though the reaction may also take place in the solution passed through it. 

As the gradient time and other parameters (temperature, pH, or initial concentration of solvent B) often show synergistic effects on separation, simultaneous optimization of two or more parameters... 

Ion chromatographic methods have been described for the co-determination of anions and cations in rainwater. Thus Jones and Tarter [138], using the conditions given in Table 2.19 reported determinations down to lmg L 1 of anions (chloride, bromide and sulphate) and cations (sodium, potassium, magnesium and calcium) in rainwater without converting the cations to anion complexes prior to detection [139], The technique uses a cation separator column, a conductivity detector, an anion suppressor column, and either a second conductivity detector or an electrochemical detector in sequence. The use of different eluants provides a means for the detection of monovalent cations and anions and divalent cations and anions in each of the samples. Using an eluant with a basic pH, it is possible to separate simultaneously and detect the monovalent cations (with the exception of the ammonium ion) and anions, while an eluant with an acidic pH allows for the separation and detection of divalent cations and anions. 

Continuous chromatography in the packed annular space between the walls of two concentric cylinders can be done by rotating the assembly about its longitudinal axis (1, 2, 3). Rotation transforms the temporal separation that would be obtained under fixed, pulsed operation into a spatial separation that permits continuous operation. It has recently been shown that continuous reaction chromatography can be done in similar apparatus (4, Jj). This not only provides a means of carrying out chemical reaction and separation simultaneously in one unit, but for A B + C the product separation suppresses the rate of the back reaction and provides a means of enhancing the reaction yield. Yield enhancement in pulsed column chromatography has been demonstrated (6, 8). Yields of... 

Identifying an environment that avoids induction of undesired enzymes and repression of desired ones and implementing bioreactor control systems that maintain these desired conditions in a bioprocess are subjects of future importance. For example, accumulation of a product in the cell environment can often repress synthesis of some of the enzymes required for production of that compound. Product repression and inhibition phenomena have motivated special interest recently in combined bioprocessing operations which accomplish separation simultaneously with bioreaction. By continuously removing a product that inhibits its own synthesis, production of that material is improved. Development of new selective membranes and other process strategies for accomplishing these separations is an important area for future research. 

To investigate the pharmacokinetics of insulin glulisine following subcutaneous (s.c.) administration of insulin glulisine immediately premixed in a syringe with NPH insulin versus separate simultaneous injections of insulin glulisine and NPH insulin. 

Table 15 Pharmacokinetic parameters of HMR1964 (insulin glulisine). Separate simultaneous (Treatment A) versus immediately premixed (Treatment B).

The total systemic insulin glulisine availability as presented by [AUC(o-ciamp end)] was similar for the two modes of administration of insulin glulisine and NPH insulin, mixed in a syringe immediately before injection (treatment B), and the separate simultaneously injections (treatment A). 

The maximum insulin glulisine concentration Cmax was somewhat attenuated, being 27% less, when insulin glulisine was premixed with NPH insulin as compared to the separate simultaneous administration. Nevertheless, the time to Cmax did not differ between the two treatments with Tmax values of 47 and 50 minutes (min). 

This brings me back to methods development. Running a 96-capillary instrument with a poorly constructed method presents the opportunity to perform 96 horrible separations simultaneously. 

A decision must be made whether the two recycle loops, units 10 and 11, are to be converged simultaneously or separately. Simultaneous convergence, as illustrated by Fig. 4-8o, is approached by checking and reestimating both tear streams once in each iteration. Separate convergence proceeds by converging the... 

Depolarization of metal deposition sometimes occurs when two metals which separate simultaneously form compounds or solid solutions. The reversible potential of a solid solution generally lies in between those of the pure constituents hence an alloy containing both metals may be deposited at a potential that is less cathodic than that necessary for the less noble constituent in the pure state. This probably accounts for the fact that zinc and nickel are deposited simultaneously at a potential of about — 0.6 volt, whereas that required for pure zinc is nearly 0.2 volt more cathodic. The simultaneous deposition of the iron-group metals is partly due to the similarity of the discharge potentials, but the formation of solid solutions also plays an important part. Although the deposition potentials of cobalt and nickel are lower than that of iron, the cathodic deposit almost invariably contains relatively more of the latter metal. ... 

Polarization can be transferred simultaneously within several spin pairs without cross-talk if different rf amplitudes are used for each pair of spins in the multiply selective irradiation scheme. This principle has been used in Hartmann-Hahn Hadamard spectroscopy (HAHAHA), where a phaseencoding scheme is used to separate simultaneously acquired spectra that represent individual doubly selective Hartmann-Hahn transfer experiments (Kupce and Freeman, 1993e). 

Although the enhanced speed of reaction in the highly polar, aprotic solvent makes it possible to effect the reaction in the minimum time, if the optimum yield of product is also desired it is preferable for the concentration of ions in the solvent not to exceed 1 molar. Preferably the concentration of these ions is maintained as low as possible by slowly adding the catechol... to the reaction mixture. During the course of this slow addition the ions react as they are formed, and are therefore always present in a very high dilution. When the alkaline conditions needed for the reaction are provided by the addition of an alkali metal hydroxide to the reaction mixture, it is usually most convenient and satisfactory to add the catechol... and the alkali metal hydroxide separately, simultaneously and slowly to a solution of methylene chloride in the highly polar, aprotic solvent. 

Reactive separation processes are of significant industrial importance owing to the potential opportunities in generating novel products and their substantial technical and commercial advantages. Some of the advantages of conducting reaction and separation simultaneously include ... 

Sensitivity of the Techniques with Respect to Phase Separation. Simultaneous cloud-point and viscoelastic measurements were made at 130 °C. Figure 3 shows that phase separation is not detected at the same time by these two techniques. Complex viscosity is more sensitive to the beginning of phase separation. Cloud-point sensitivity is a function of the wavelength of the light. For our experiment, the use of white light determines the sensitivity at approximately 0.1 xm. However, in the last step of phase separation (when the transmitted light intensity still varies), the increase of viscosity due to gelation of the resin hides the end of the phenomenon. 

J.F. van Staden, S.I. Tlowana, On-line separation, simultaneous dilution and spectrophotometric determination of zinc in fertilizers with a sequential injection system and xylenol orange as complexing agent, Talanta 58 (2002) 1115. 

In Section 4.2.2.2 some processes are described in which the organic products are separated - simultaneously or successively - by extraction with a nonpolar extractant. In the cases presented in this section, not the product but the catalyst will be extracted and recycled to the reactor. Theoretically, this can be done simultaneously in the reactor, as shown in Figure 12. However, this arrangement is highly unfavorable, because it means that the catalyst is taken away from the reaction medium during the catalytic conversion. The successive variant, shown in Figure 13, makes much more sense the reaction is first carried out in the reaction unit, then the catalyst is extracted by an extractant which does not dissolve the products C... 

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