Sealing filter plates

FIG. 18-114 Section detail of a caiilked-gasketed-recessed filter plate a) cake recess (h) filter cloth (c) drainage surface of plate (d) caulking strip (e) plate joint (f ) sealing gasket. (ElMCO Process Equipment Co.)... 

The immobilized carbamates (40 pmol) were transferred to a sealable 96-well Weflon plate, and admixed with 10 pmol each of various primary or secondary amines dissolved in 400 iL of anhydrous toluene. After sealing, the plate was irradiated in a multimode microwave instrument, first generating a ramp to reach 130 °C within 45 min and then holding this temperature for an additional 15 min. After cooling, the resins were filtered with the aid of a liquid handler and the filtrates were concentrated to obtain the desired substituted ureas in good purity and reasonable yields. Anilines reacted rather sluggishly and 2-substituted benzyl carbamates afforded somewhat inferior results. 

FIGURE 1.41 Captiva 20-j.lm polypropylene 96-well filter plate with top and bottom duo-seals.160 (Repro duced with permission from the American Chemical Society.)... 

Carefully transfer the cleared bacterial lysate supernatants from each of the 24 wells into the wells of a 96-well filter plate. Cover the filter-plate top with clear plate-seal tape, to prevent cross-contamination. 

The reactions are carried out in a 1-1. round-bottomed flask (Fig. 18) sealed to a dropping funnel and a gas inlet tube A.% The neck of the flask is closed with a rubber stopper bearing a gas inlet C and an outlet tube B (i.d. at least 5 mm.). The latter is connected to a filter assembly which consists of a 25-mm.-i.d. filter tube with a fritted-glass filter plate D (porosity B). The distance from the filter plate to the top of the tube should be at least 35 cm. As shown in Fig. 18, tubes B and C extend into the flask through glass sleeves and are attached to these sleeves by means of rubber tubing so that B and C may be raised or lowered. 

The extraction cells used in DPHSE include those typically employed in SFE [109,151], empty HPLC columns [149] and specially designed stainless steel chambers [57,75,148]. The use of an SFE chamber as extraction cell is not recommended because the polyimide seals in it can fail at high temperatures [6]. On the other hand, the problem with empty HPLC columns is that they usually have small diameters and hence low volumes — this can result in excessive pressure build-up and bursting of the column. As a rule, DPHSE extraction cells consist of a stainless steel cylinder closed with screws at either end that permit the circulation of the leaching solvent through them. The screw caps also contain stainless steel filter plates to ensure that the sample remains in the extraction chamber. 

A potential problem with the analysis of biological fluids, especially plasma samples from in vivo studies, is the risk of clogging of SPE cartridges and/or analytical columns. Therefore, filtration of such samples prior to LC or SPE is recommended. Combined filtering and protein precipitation in 96-well plate format was described [97-98]. The samples are collected and stored frozen in sealed 96-well polypropylene filter plates. Prior to SPE and LC-MS analysis, the seals are removed and the plate is placed on top of a 96-well SPE manifold As the plasma thaws, it passes through the filter and into the SPE device. 

In each filter plate, the filter medium is attached to a moving belt (Fig. 18-190). An elastomer seal is used at the edge of the filter chamber. The slurry is fed into the filter chamber, and the operation starts as a pressure filtration. After filtration, the diaphragm is inflated to squeeze on the... 

In order to blow out CIO2 with nitrogen, the extractor is then sealed with the sintered plate insert, and the column sleeve with filter plate and screw cock, filled with 10 ml of freshly prepared KI solution of pH 2.5, is mounted. 

The chief disadvantages of a Buchner funnel for filtration are (i) it is impossible to see whether the underside of the perforated plate is perfectly clean, and (ii) the larger sizes are top heavy. The first drawback is absent in the Jena slit-sieve funnel (Fig. 11,1, 7,/) this is an all-glass funnel provided with a sealed-in transparent plate, perforated by a series of angular slots, upon which the filter paper rests. The sintered glass... 

Plate-and-Frame Filter Presses. In the conventional plate-and-frame press (Fig. 14), a sequence of perforated square, or rectangular, plates alternating with hoUow frames is mounted on suitable supports and pressed together with hydrauHc or screw-driven rams. The plates are covered with a filter cloth which also forms the sealing gasket. The slurry is pumped iato the frames and the filtrate is drained from the plates. 

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