Liquid continuous sampling

Fig. 4. 33 The AKUFVE solvent extraction apparatus Efficient mixing is achieved in the separate mixing vessel, from which the mixture flows down into the continuous liquid flow centrifugal separator (the H-centrifuge, hold-up time <1 s). (From Refs. 83a,b.) The outflow from the centrifuge consists of two pure phases, which pass on-line detectors, AMXs, for on-line detectors or continuous sampling. (From Refs. 80a-80d, 81.)...

The experimental results obtained with these reactors are summarized in Table I. Both reaction temperature and the molar ratio of propane to oxygen in the feed were kept constant at 430°C. and 3, respectively, while residence time was varied from 5 to 15 sec. Each experimental run was continued for about 4 hours. The hydrogen peroxide concentration in the liquid product sample was frequently checked by titration during the run. After the constant analytical value was attained, the products were subjected to the analytical procedure described before for obtaining the data given in the table. 

Liquid Chromatography of Nonvolatile Acids For liquid food samples la. Place a few drops of a sample on the lower prism of a refractometer and measure and record °Brix. If the sample is in the range of 11 to 12.5 °Brix, continue with step 5a. If the sample is >12.5 °Brix (i.e., it is too concentrated), continue with step 2a. If the sample is < 11 °Brix, concentrate the sample using a rotary evaporator and remeasure °Brix. If the sample is a carbonated beverage it must first be degassed for 5 min in an ultrasonic bath prior to step la. 

We define an experimental quantity, which we call the quadrupole splitting (13), as the distance (in Hz) between two adjacent peaks obtained in the CW (continuous wave) NMR spectrum, corresponding to the distance A-B or B-C in Figure 2. For an oriented liquid crystalline sample one obtains from Equation 6 ... 

Figure 3. Continuous wave 2H NMR spectrum of a lamellar liquid crystalline sample containing dimyristoyllecithin with a choline-N-C2H3 group. The water content of the sample was 25% (w/w), and the temperature was 25° C.

This chapter demonstrated that microchip electrophoresis reached maturity and is appropriate for analysis of nitrated explosives. However, to create easy-to-operate field portable instruments for pre-blast explosive analysis would require incorporation of world-to-chip interface, which would be able to continuously sample from the environment. Significant progress towards this goal was made and integrated on-chip devices which allow microfluidic chips to sample from virtually any liquid reservoir were demonstrated [25,31]. 

D. B. Wall, S. J. Berger, J. W. Finch, S. A. Cohen, K. Richardson, R. Chapman, D. Drabble, J. Brown, and D. Gostick, Continuous sample deposition from reversed-phase liquid chromatography to tracks on a matrix-assisted laser desorption/ionization precoated target for the analysis of protein digests, Electrophoresis, 23 (2002) 3193-3204. 

Separations Apparatus. Separations were performed using water-jacketed liquid-chromatographic columns allowing continuous sample elution via solvent recycling (25). The solvent was removed from each fraction using a roto-evaporator and a room-temperature water bath (oa. 25 C) until a constant sample weight (+0.02g) was obtained. 

These were attached to a fraction collector, whose timing mechanism was altered to allow continuous sampling of 28 separate diffusion cells with increased sample and timing capacity. Radiolabeled drugs were used and were measured in a liquid scintillation counter directly interfaced to a computer network. We describe the details of this system which enable us to conduct reproducible flow-through diffusion experiments, assay the samples, and analyze the data quickly and efficiently. 

The analytical precision and accuracy are controlled by a peristaltic pump that meters out exact amounts of the various reagent solutions. The flow rates for the absorbent liquid, probe sample, enzyme, acid, ATCI, and DTNB, as well as the waste products, are all precisely controlled so the analytical process can be continually repeated. The color thus formed in the absence of inhibitor and the color loss when inhibitor is present are always predictable ( 1%). 

The earliest work reported in this field was by Burguera et al. [103], who applied a flow injection system for on-line decomposition of samples and determined metals (Cu, Fe, Zn) by flame atomic absorption spectroscopy (F-AAS). The methodology involved the synchronous merging of reagent and sample, followed by decomposition of serum, blood, or plasma in a Pyrex coil located inside the microwave oven. This approach permits essentially continuous sample decomposition, drastically reduces sample processing time, and is suitable for those samples that require mild decomposition conditions (especially liquids). 

The rheological properties of the complex network structure of tomato pastes may be assumed to be made up of two contributions (1) one network structure contributed by the solids phase, in proportion to 0s, and (2) another network structure contributed by the liquid (continuous phase), in proportion to 0i = 1 - 0s- However, the effective continuous phase is not the low-viscosity serum itself, but a highly viscous liquid that is an integral part of the tomato paste. Also implicit is that the solids fraction plays a major role in the structure of the TP samples, that is, it can be considered to be the structuring component. These assumptions are also in line with the weak gel behavior indicated by the dynamic shear data. 

The qualifiers continuous and discrete as applied to pervaporation refer to different aspects of the process. In fact, analytical pervaporation is a continuous technique because, while the sample is in the separation module, mass transfer between the phases is continuous until equilibrium is reached. Continuous also refers to the way the sample is inserted into the dynamic manifold for transfer to the pervaporator. When the samples to be treated are liquids or slurries, the overall manifold to be used is one such as that of Fig. 4.18 (dashed lines included). The sample can be continuously aspirated and mixed with the reagent(s) if required (continuous sample insertion). Discrete sample insertion is done by injecting a liquid sample, either via an injection valve in the manifold (and followed by transfer to the pervaporator) or by using a syringe furnished with a hypodermic needle [directly into the lower (donor) chamber of the separation module when no dynamic manifold is connected to the lower chamber]. In any case, the sample reaches the lower chamber and the volatile analyte (or its reaction product) evaporates, diffuses across the membrane and is accepted in the upper chamber by a dynamic or static fluid that drives it continuously or intermittently, respectively, to the detector — except when separation and detection are integrated. 

The opportunity to measure the dilute polymer solution viscosity in GPC came with the continuous capillary-type viscometers (single capillary or differential multicapillary detectors) coupled to the traditional chromatographic system before or after a concentration detector in series (see the entry Viscometric Detection in GPC-SEC). Because liquid continuously flows through the capillary tube, the detected pressure drop across the capillary provides the measure for the fluid viscosity according to the Poiseuille s equation for laminar flow of incompressible liquids [1], Most commercial on-line viscometers provide either relative or specific viscosities measured continuously across the entire polymer peak. These measurements produce a viscometry elution profile (chromatogram). Combined with a concentration-detector chromatogram (the concentration versus retention volume elution curve), this profile allows one to calculate the instantaneous intrinsic viscosity [17] of a polymer solution at each data point i (time slice) of a polymer distribution. Thus, if the differential refractometer is used as a concentration detector, then for each sample slice i. 

Figure 28-5 Continuous sample introduction methods. Samples are frequently introduced into plasmas or flames by means of a nebulizer, which produces a mist or spray. Samples can be introduced directly to the nebulizer or by means of flow injection (FIA) or high-performance liquid chromatography (HPLC). In some cases, samples are separately converted to a vapor by a vapor generator, such as a hydride generator or an electrothermal vaporizer.

Schnydrig, S., Renaud, P., Continuous sampling and analysis by on-chip liquid/ solid chromatography. Sens. Actuators A 2006, in press. 

Procedure. Methods for collecting and analyzing the gas and liquid samples taken with the probes allow continuous samples to be withdrawn simultaneously at all four points within the catalyst bed. The bed ranged from 25 to 200 cc. in volume. Since the total flow rate of the probe samples is only a few percent of the total exit stream flow rate, the stability of reactor operation is not impaired, and the flow rate in the bed does not vary appreciably. A Chronofrac gas chromatograph (Precision Scientific Co.) was installed for analyzing probe and product gas samples. 

Thermospray was in several ways the forerunner of electrospray and atmospheric pressure chemical ionization sources, and in current practice has largely been superseded by them. Thermospray (TSP) is a combination of interface and ion source for LC-MS and other liquid-phase sample introduction systems [7,31-33]. A continuous flow of liquid is rapidly vaporized in a resistively heated metal capillary tube forming a supersonic... 

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