Reagent dispenser

The Chemical Inkjet Printer (ChIP), an inkjet printer-like device which is equipped with a piezoelectric reagent-dispensing system, has been developed by Shimadzu Corporation. The ChIP can dispense picoliter volumes of matrix solution onto a tissue section, which has four printing heads and nozzles that have no contact with the tissue section surface. 

With today s instruments the customer may specify an injector or an automatic reagent dispenser, and a choice of sample formats is available test tube, vial, microplate, Petri dish. The volumes of sample and reagent required to carry out a determination steadily decrease and are typically a few microliters. Sample temperature during the assays is generally controlled. 

The three solid reagent dispensers are particularly interesting and are described below. 

NOTE All pipets and reagent dispensers must be well calibrated for accuracy. 

Liquid dispensers are used in compound screens for dispensing reagents including cell suspensions and other reagent solutions. Due to the different needs of compound handling and cell and reagent dispensing, different instruments are recommended for each step. 

A peptide library can be synthesized using the SPOT synthesis technique to form a low-density peptide spot array (e.g., 25 spots/cm ). In this method, different peptides are synthesized in situ as low-density arrays on cellulose membrane or paper (8). The volume of Fmoc-amino acids and coupling reagents dispensed creates a specific SPOT size that determines both the scale of reaction and the absolute number of peptides that can be arranged on an area of a membrane. Cotton (another form of cellulose) and polystyrene-grafted polyethylene film segments also have been used as solid supports. Recently, polymeric membranes that are chemically, mechanically, and thermally more stable have been developed, which include hydroxy-functionalized PEG acrylate polypropylene membranes and an amino-functionalized ester-free PEG... 

For the actual run, stock solutions of common reagents and building blocks must be prepared, and the solid support or solid-supported reagents dispensed into the appropriate reaction vessels (rvs). The reactions must be set up under the proper conditions, run, and subsequently worked up in an appropriate manner. This is followed by optional purification steps and, finally, isolation of the product For all of these steps, equipment is available that helps to achieve high throughput... 

Multidrop Combi Reagent Dispenser (Thermo Scientific, Waltham, MA, USA). 

Reagent dispenser, e.g.. Multidrop Combi (Thermo Scientiflc), Bravo Automated Liquid Handling Platform (Agilent Technologies). 

How will reagents be added from troughs on the 96-channel dispenser, or from dedicated reagent dispensers ... 

Centrifugal analysers, discussed In Chapter 4, are discrete In nature. Sample collection and reagent dispensation take place In an automated dosing module. However, the transfer disc containing the radially arranged samples and reagents Is transferred manually to the analyser module, where reaction, signal measurement and data acquisition and treatment, all completely automated,... 

Reagent dispensers are chiefly volumetric or coulometric In nature. Formerly, the automation of coulometric titration procedures developed at a higher speed than that of volumetric titration —this was probably a result of the ease with which the current intensity used for reagent generation could be regulated by means of relatively simple electronics. 

A representative example of a flexible, single-parameter analyser with final transfer is the Vitatron Akes, depicted In Fig. 8.5. In the aspiration position, the sample meets the reagent or diluent stream and the reaction mixture is subsequently transferred to the measuring cuvette, from which it is flushed by the aspiration system after detection, the cuvette being suitably washed. The instrument includes a linear sample train, sample turntable, sampling head, dilutor, reagent dispenser, data-input keyboard, photometric detection system, computer, printer, evacuation pump and wash solution doser. It is prepared for kinetic measurements. 

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