Extraction devices

D. Eigeys, A. Dua et and R. Aebersold, Identification of proteins by capillary electrophoresis-tandem mass specti ometiy . Evaluation of an on-line solid-phase extraction device , J. Chromatogr. A 763 295-306 (1997). 

These instruments, sometimes referred to also as sediment accumulation devices, weight the sediment as it accumulates on a weigh-pan at the base of the sedimentation column. The methods are cumulative ones. With the development of sensitive electro balances, the cumulative sedimentation technique is generally easier to perform and more accurate than is the incremental technique. The powder may be dispersed initially in the bulk of the fluid or added instantaneously at the top. An advantage of this type of equipment is the absence of the conical base, needed in sediment extraction devices, upon the walls of which some sediment may adhere. The danger of particles sticking to the vertical walls is however still present... 

The archetypal, stagewise extraction device is the mixer-settler. This consists essentially of a well-mixed agitated vessel, in which the two liquid phases are mixed and brought into intimate contact to form a two phase dispersion, which then flows into the settler for the mechanical separation of the two liquid phases by continuous decantation. The settler, in its most basic form, consists of a large empty tank, provided with weirs to allow the separated phases to discharge. The dispersion entering the settler from the mixer forms an emulsion band, from which the dispersed phase droplets coalesce into the two separate liquid phases. The mixer must adequately disperse the two phases, and the hydrodynamic conditions within the mixer are usually such that a close approach to equilibrium is obtained within the mixer. The settler therefore contributes little mass transfer function to the overall extraction device. 

Principles and Characteristics Although early published methods using SPE for sample preparation avoided use of GC because of the reported lack of cleanliness of the extraction device, SPE-GC is now a mature technique. Off-line SPE-GC is well documented [62,63] but less attractive, mainly in terms of analyte detectability (only an aliquot of the extract is injected into the chromatograph), precision, miniaturisation and automation, and solvent consumption. The interface of SPE with GC consists of a transfer capillary introduced into a retention gap via an on-column injector. Automated SPE may be interfaced to GC-MS using a PTV injector for large-volume injection [64]. LVI actually is the basic and critical step in any SPE-to-GC transfer of analytes. Suitable solvents for LVI-GC include pentane, hexane, methyl- and ethylacetate, and diethyl or methyl-f-butyl ether. Large-volume PTV permits injection of some 100 iL of sample extract, a 100-fold increase compared to conventional GC injection. Consequently, detection limits can be improved by a factor of 100, without... 

Fig. 4. a Schematic of porous membrane-based separation of immiscible liquids with different wetting characteristics, b Liquid-liquid extraction device (Kralj et al. 2007)... 

A variety of online solid extraction devices and applications have been developed for bioanalysis. Many are easy to build in laboratories or commercially available. Unlike offline methods, minimal operator intervention is needed for daily sample analysis after online applications are set up, so the approach is both labor- and cost-effective. The technique can also minimize errors arising from manual operations, eliminate potential inconsistencies caused by different operators, and provide accessibility of LC/MS/MS applications to laboratories that have minimal analytical expertise. 

AFID = alkali flame ionization detector ECD = Electron capture detection EPA = Environmental Protection Agency FPD = flame photometric detection GC = gas chromatography GPC = gel permeation chromatography HRGC = high resolution gas chromatography NPD = nitrogen- phosphorus detection SPE = solid phase extraction device... 

Fig. 11 Extraction device consisting of A CO2 cylinder, B syringe pump, C oven, D extraction cell, E particle filter, F back-pressure regulator, G sampling tube...

Oliver BG, Nicol KD. 1985. Field testing of a large volume liquid-liquid extraction device for halogenated organics in natural waters. Intern J Environ Anal Chem 25 275-285. 

Atomic A pressurised liquid extraction device and hydride gen-... 

By analogy to solvent extraction, the column containing the solid adsorbent corresponds to the separatory funnel containing the immiscible organic solvent. The transfer of the solute to the solid adsorbent occurs in an unattended operation requiring no manual effort or additional equipment such as the shakers used in solvent extraction or the distillation apparatus used in some of the automatic extraction devices. This simplicity allows for facile automation either off-line or on-line with the separation and detection procedure (495, 512, 536). 

The designer of a plant needs information about the availability of devices and unit operations. A market study executed by the Institut fur Mikrotechnik Mainz and YOLE Developpment [51] helps to make a first survey of commercially available devices. It also estimates future needs and objectives of the chemical industry and delivers a comparison between offered and required components (Figure 4.6). The providers of micro structured devices can deliver most of the components required by the chemical industry. On the other hand, there is a lack of separation devices but this is not fully transparent in Figure 4.6. Extraction devices are under represented and the important rectification units were not asked for by the interviewers, possibly because they hardly exist. 

R 18] A modular set of devices was developed within the pChemTec project introduced above. It consists of a base plate which is identical for all four devices. This base plate acts as the fluidic interface to the piping and is equipped with a micro structured mixer. The base plate can be combined with a heated tube to deliver a mixer-tube reactor. A combination with a porous tube delivers a degasser unit. A combination with a membrane unit (not shown) or a settler results in an extraction device (Figure 4.58). 

Another format of the HF-SLM procedure was to employ a 15-20 cm long piece of HF as the extraction device. The HF lumen was then filled with acceptor solution using a microsyringe, and a loop made out of the HF. This loop was then soaked in an organic liquid before being added to the sample agitated on a shaker.71... 

To simplify the above-mentioned MMLLE systems and, unlike the automated flowing MMLLE, the nonautomated, nonflowing design of MMLLE is simple to prepare manually and is an easy-to-use extraction procedure that is always done off-line prior to GC analysis. In this context, only a short piece of HF membrane is employed as an extraction device after the HF lumen and pores96 or only the pores97 have been filled with an appropriate organic solvent, the membrane is immediately immersed in the aqueous sample. The principle of this two-phase HF-MMLLE system is also called HF liquid-phase microextraction (HF-LPME) and will be briefly commented on in the next section. 

A hot water dynamic extraction device was constructed using the solubilization apparatus of Miller and Hawthorne (10) as a model and was used for pressurized extraction of milk thistle seed meal. Figure 2 shows a schematic diagram of the apparatus. Water, the extraction solvent, was pressurized and pumped using a Bio-Rad 2800 HPLC solvent delivery system (Hercules, C A) to an extraction cell housed in the oven of a Hewlett-Packard 5890 gas chromatography (GC) oven (Wilmington, DE). Before... 

Figure 3.2. Schematic diagram of an automatic Soxhlet extraction device (Soxtec).

Figure 5.7. Solid-phase extraction devices come in a variety of forms, with different sorbents for different applications. Shown are packed bed with a built-in reservoir to hold the sample solution, a syringe tip packed cartridge, and a filter disk in a holder for rapid extraction from large volumes.

After the sample is passed through the solid-phase extraction device, the analytes are removed with a small amount of acid and collected for analysis. The advantage of these systems is that the analyte is both separated from a large volume of matrix and concentrated into a small volume of acid, ready for analysis. 

B. A. Bildenmeyer, Guidelines for proper usage of solid-phase extraction devices, LC, 2 578 (1984). 

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