Capillary mixer

Many process mixtures, notably fermentations, require sample preconcentration, microdialysis, microfiltration, or ultrafiltration prior to analysis. A capillary mixer has been used as a sample preparation and enrichment technique in microchromatography of polycyclic aromatic hydrocarbons in water.8 Microdialysis to remove protein has been coupled to reversed phase chromatography to follow the pharmacokinetics of the metabolism of acetaminophen into acetaminophen-4-O-sulfate and acetaminophen-4-O-glucu-ronide.9 On-line ultrafiltration was used in a process monitor for Aspergillus niger fermentation.10... 

Dolozel, P., Krejci, M., and Kahle, V., Enrichment technique in an automated liquid microchromatograph with a capillary mixer, ]. Chromatogr. A, 675, 47,... 

Capillary-in-capillary mixers were used for electrospray ionization mass spectrometry (ESI-MS), which allows one to perform on-line kinetic studies for a wide range of applications in chemistry, bioorganic chemistry, isotope exchange experiments and enzymology, just to name a few [133], ESI-MS is a method alternative to the traditionally employed quench-flow techniques with off-line analysis. 

The mixing volume of the capillary-in-capillary mixer is adjustable and can be controlled automatically, i.e. it is not necessary to have a set of various capillaries and to exchange them to match the single conditions of each new experiment [133],... 

P 47] The capillary-in-capillary mixer was especially developed for millisecond time-resolved studies by ESI-MS. Since this ranges involves an application and characterization of the mixer itself was not performed, for further information on the... 

M 52] [P 47] The capillary-in-capillary mixer proved functionality for millisecond time-resolved studies by ESI-MS [133]. The experiments were performed in two modes of operation in a spectral mode with recording of entire mass spectra and in a kinetic mode where the intensity of selected ion signals can be monitored as a function of the average reaction time. This enabled new means of resolving kinetic data, i.e. to measure reliably first-order rate constants up to at least 100 s 1. This performance is four times better than for reported ESI-MS experiments. 

Wilson, D. J., Konermann, L, A capillary mixer with adjustable reaction chamber volume for millisecond time-resolved studies by electrospray mass spectrometry, Anal. Chem. 2003, 75, 6408-6414. 

Figure 4.3 Schematic cross-sectional diagram of the experimental apparatus used for time-re-solved ESI-MS experiments. Syringes I and 2 deliver a continuous flow of reactants mixing of the two solutions initiates the reaction of interest. The inner capillary can be automatically pulled back together with syringe I (as indicated by the dashed arrow), thus providing a means to control the average reaction time. Solid arrows indicate the directions of liquid flow. Small arrows in the ESI source region represent the directions of air flow [95]. Reprinted with permission from Wilson, D.J., Konermann, L. (2003) A Capillary Mixer with Adjustable Reaction Chamber Volume for Millisecond Time-Resolved Studies by Electrospray Mass Spectrometry. Anal. Chem. 75 6408-6414. Copyright (2003) American Chemical Society...

Wilson, D.J., Konermann, L. (2003) A Capillary Mixer with Adjustable Reaction Chamber Volume for Millisecond Time-resolved Studies by Electrospray Mass Spectrometry. Anal. Chem. 75 6408-6414. 

Serizawa et al. (2002) studied experimentally, through visualization, the two-phase flow patterns in air-water two-phase flows in round tubes. The test section for air-water experiments consisted of a transparent silica or quartz capillary tube with circular cross-section positioned horizontally. The two-phase flow was realized through a mixer with different designs, as shown in Figs. 5.4 and 5.5. The air was injected into the mixer co-axially while water was introduced peripherally. 

Molar ratios of bromine to m-nitrotoluene ranging from 0.25 to 1.00 were applied. The reactants were contacted in an interdigital micro mixer followed by a capillary reactor. At temperatures of about 200°C nearly complete conversion is achieved (see Fig. 6). The selectivity to the target product benzyl bromide is reasonably high (at best being 85% at 200°C and higher being 80%). The main sideproduct formed is the nitro-substituted benzal bromide, i.e. the two-fold brominated side-chain product. 

OS 79] ]R 17] ]no protocol] 4-Methoxybenzaldehyde and methyl diethoxyphos-phonoacetate were reacted by means of the Wittig-Horner-Emmons reaction [85] (see a more detailed description in [42]). A modified micro reaction system consisting of two mixers, for deprotonation of the phosphonates and introduction of the aldehyde, connected to an HPLC capillary of 0.8 m length and 0.25 mm diameter was employed. The micro reactor showed higher yields than laboratory batch synthesis. 

Fig. 2.5.6 Schematic of the experimental setup used to monitor reaction kinetics with a multiple microcoil system. Two syringes on the pump inject the reactants into two capillaries. The reactants are mixed rapidly with a Y-mixer. After mixin g, the solution flows through the...

FIGURE 14.18 Flow diagram of split flow capillary LC system. 1. Solvent reservoirs. 2. Model 5000 syringe pump (Varian, Walnut Creek, California). 3. Static mixer. 4. Injection port. 5. Column. 6. Detector. 7. Pressure transducer. 8. Pulse dampener. 9. Purge valve. 10. U-flow controlling device. 11. Waste. 

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