Lab on valve system

C.-H. Wu, L. Scampavia, J. Ruzicka, B. Zamost, Micro sequential injection fermentation monitoring of ammonia, glycerol, glucose, and free iron using the novel lab-on-valve system, Analyst 126 (2001) 291. 

In flow-based analytical procedures where the chemical reactions involved and/or the steps of analyte separation/concentration are relatively slow, the analytical signal can be attenuated by reducing the mean available time for the development of these physico-chemical processes. From a practical point of view, the result is equivalent to in-line analyte dilution. This possibility has been exploited in the spectrophotometric determination of hydrogen peroxide in contact lens care solutions using a sequential injection lab-on-valve system [60]. In view of the high sensitivity of the reaction between the analyte and 2,2,-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) in the presence of the enzyme... 

Hydrogen peroxide Lens care solutions Dialysis UV-Vis Up to 342 mg L 1 Sequential injection lab-on-valve system low dialysis efficiency (1.25 %) to promote in-line dilution, thus sensitivity reduction enzymatic assay [60]... 

Pyrolysis can also be used in flow-based determinations with electrothermal atomic absorption spectrometry, as demonstrated in the determination of nickel in environmental and biological reference materials using a sequential injection system with renewable beads [313]. After analyte sorption, the beads were directed towards the furnace of the spectrometer and stopped there pyrolysis was accomplished as usual in order to release the analyte and destroy the beads. This innovation has often been exploited in the lab-on-valve system, but spectrophotometric applications have not been proposed to date. 

Mono-segmented flow system. The sample mono-segment behaves as a titration vessel to which exact titrant amounts are added [328,329]. This innovation has also been implemented in the lab-on-valve system [330]. 

S.S.M.P. Vidigal, I.V. Toth, A.O.S.S. Rangel, Sequential injection lab-on-valve system for the on-line monitoring of hydrogen peroxide in lens care solutions, Microchem. J. 91 (2009) 197. 

J. Jakmunee, L. Pathimapomlert, S.K. Hartwell, K. Grudpan, Novel approach for mono-segmented flow micro-titration with sequential injection using a lab-on-valve system a model study for the assay of acidity in fruit juices, Analyst 130 (2005) 299. 

In addition to compactness, other advantages of these lab-on-valve systems is the permanent rigid position of the sample processing channels that ensures repeatability of microfluidic manipulations and a large volume to surface ratio, which minimizes the unwanted adsorption on channels walls that may result in carryover. This provides proven robusmess and reliability of operation, and makes the microfluidic system compatible with real-life samples and peripheral instruments. 

Micro-sequential injection environmental monitoring of nitrogen and phosphate in water using lab-on-valve system furnished with a microcolumn. HC holding coil LOV lab-on-valve RC reaction coil. 

R. Rodriguez, J. Avivar, L. Ferrer, L.O. Leal, V. Cerda, Automated total and radioactive strontium separation and pre-concentration in samples of environmental interest exploiting a lab-on-valve system, Talanta 96 (2012) 96-101. 

Wang, J.-FI. and E.H. Hansen. 2001. Interfacing sequential injection on-line preconcentration using a renewable micro-column incorporated in a lab-on-valve system with direct injection nebulization inductively coupled plasma mass spectrometry. /. Anal. At. Spectrom. 16 1349-1355. 

Note FIA, flow injection analysis Vis, visible SIA, sequential injection analysis MSFIA, multisyringe flow injection analysis LOV, mesofluidic lab-on-valve system CUPRAC, cupric reducing antioxidant capacity FRAP, ferric reducing antioxidant power ESR, electron spin resonance n.g., not given. 

Sequential injection analysis with lab-on-valve was conceived by Ruzicka in 2000 [84] as a progression of the sequential injection system towards downscaling. All components are integrated in a single unit mounted on a multi-position valve. The detector compartment is reduced and placed very close to the sample inlet, thus minimising the required volumes of sample, reagent and wash solution. 

J.-H. Wang, Lab-on-valve mesofluidic analytical system and its perspectives as a world-to-chip front end, Anal. Bioanal. Chem. 381 (2005) 809. 

In summary, the versatility of a mixing chamber, the multiple tasks it can be used for and the distinct role it can have in the flow manifold are the driving forces for more advanced methodologies using mixing chambers, not only as a component of a flow system but also as a complete small-scale laboratory. Based on an active chamber module, flow batch [107] and lab-on-valve [108] systems can be included in this category, as they can perform diverse and relatively complex functions, as discussed in 2.6 and 5.3.3. 

The Lab-on-Valve flow system resembles the sequential injection analyser but the main components are assembled on a multi-position valve. Exploitation of optical fibres permits spectrophotometric measurements to be performed very close to the main reaction coil. The compact geometry of the system makes it attractive for, e.g., in situ assays. For more details of this system, see 2.4.2. 

Currently, pTAS [112] and sequential injection systems using the lab-on-valve approach [22] are more popular. The former exploits hydrodynamic injection and is now known as Lab-on-Chip due to the extreme reduction in dimensions. Reproducible analytical channels are made by micro-drilling, etching, photolithography or laser erasing, and different channel profiles can be obtained at a reasonable cost. 

On the other hand, sequential injection with the lab-on-valve approach (5.5.3) does not exploit the strategy of downscaling the channel diameter but decreases the channel length and maintains the same approach as used in conventional sequential injection systems. 

Lab-on-valve (LOV) is a development of FI A whereby a microchannel chip (microconduit) is combined with a switching valve. It is a type of pTAS system. The function of the... 

Some of the interesting applications of LOV inclnde the manipnlation of beads and microcolnmns for sample clean-up or separation. In particnlar, one version of the system has received considerable attention and is called microseqnential injection-lab-on-valve (pSl-LOV). The J,SI-LOV device can be used for sample pretreatment alone or in seqnence with analysis and detection (usually absorbance or flnorescence). It has also been employed as the front end of a miniaturised CE system. An interesting nse of J,SI-LOV has been in conjunction with suspensions of specially coated beads. These beads can be manipulated by the multiport valve to flow into the holding coil and from there into the detector flow cell to form a temporary microcolnmn. The sample is then mixed with the bead column and any reactions are detected, e.g. adsorption over time. After measurements have been made, the beads are sent to waste. The formation and removal of these temporary microcolumns has advantages over the nse of fixed colnmns snch as ... 

J. Avivar, L. Ferrer, M. Casas, V. Cerda, Lab on valve-multisyringe flow injection system for fully automated uranium determination in environmental samples, Talanta 84 (2011) 1221—1227. 

Lab-on-valve , Lab-on-chips , Micro Total Analytical Systems (p-TAS) or Micro Electro Mechanical Systems (MEMS) that operate on micro- and nanometer scales are good examples of new trends and achievements in the area of instrumentation. These enable complex processes such as sampling, reagent addition, calibration, temperature control, and analysis, to be incorporated into... 

Beads packed in microcolumns is the most reported in literature, since users can customize the quantity of resin according to the capacity of it, to the volume of sample to be loaded, and to the minimum detectable activity (MDA) of the detector used. In general, packing is manually replaced in flow systems based on flow injection analysis G A), sequential injection analysis (SIA), multisyringe flow injection analysis (MSFIA) and multipumping flow systems (MPFS). By the contrary, lab on valve (LOV) allows the manipulation of heterogeneous solutions, i.e. bead injection, achieving the automated replacement of the resin. In Chapter 3 are described in detail the parts of the microcolumns and the way to fill them. Table 8.1 summarizes the variety of available resins from TrisKem International [4]. 

Miro, M., H. M. Oliveira, and M. A. Segundo. 2011. Analytical potential of mesoflu-idic lab-on-valve as a front end to column-separation systems. Trends Anal. Ghem. 30 153-161. 

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