Cleaning fritted filters

Column—A metal tube in which the HPLC separation occurs, packed with porous packing held in place at each end by a fritted filter in an end-cap. End-caps are secured to the column with ferrules and can be opened for frit cleaning. 

Because different materials get onto and in a frit, different cleaning processes are required to clean a frit. For this reason, storage is an important aspect of frit cleaning. If you know what got on a frit, you know how to clean it. Keeping a frit in a clean, dry, and dust-free area will simplify your cleaning needs. Before a fritted filter is first used, it should be rinsed with hot sulfuric acid and then with distilled water until the filtrate is neutral in pH. This procedure will remove any glass particles and dust that may be on the new frit. 

Blocked frit. —> Replace or clean frit, install 0.5-um porosity in-line filter between pump and injector to eliminate mobile-phase contaminants or between injector and column to eliminate sample contaminants. 

FIGURE 3.9 Circulating water photoreactor system for determination of photomicro-biocidal activity under water flow conditions, a, reinforced membrane used in the study b, water jacket, continuous flow, infrared filter c, light source d, air pump e, bacterial air filter f, 3-way tap/pressure release g, 2-way taps h, frit for aeration J, peristaltic pump k, reservoir 1, ground glass Joints for ease of cleaning and sterilization (Bonnett et ai, 2006). 

If you reconnect the column and start the pump and the pressure persists, then you need to remove the outlet end frit in the same way. (Remember the white packing on the shoes ) Outlet pressure is due to fines in the column collecting in this filter usually only a problem if you are using the original irregular-shaped microporous columns. Sonicating with 10% sodium hydroxide can clean them since they are silica. Wash the base out repeatedly with water, replace the frit, and run the column. 

Clamp the clean, dry 25-mL filter flask in an ice bath to prevent it from falling over and place the Hirsch funnel with filter paper in the flask. Wet the filter paper with the solvent used in the crystallization, turn on the water aspirator (see below), and ascertain that the filter paper is pulled down onto the frit. Pour and scrape the crystals and mother liquor onto the Hirsch funnel, and as soon as the liquid is gone from the crystals, break the vacuum at the filter flask by removing the rubber hose. Cool the filter flask in ice. The filtrate can be used to rinse out the container that contained the crystals. Again break the vacuum as soon as all of the liquid has disappeared from the crystals this prevents impurities from drying on the crystals. The reason for cooling the filter flask is to keep the mother liquor cold so that it will not dissolve the crystals on the Hirsch funnel. With a very few drops of ice-cold solvent, rinse the crystallization flask. That container should still be ice cold. Place the ice-cold solvent on the crystals and then reapply the vacuum. As soon as the liquid is pulled from the crystals break the vacuum. Repeat this washing process as many times as necessary to remove colored material or other impurities from the crystals. In some cases only one very small wash will be needed. After the crystals have been washed with ice-cold solvent, the vacuum can be left on to dry the crystals. 

Robot-compatible syringes, standard syringe, maxi-clean cartridge, Novo-Clean membranes (ion exchange and reversed phase), many types of syringe filters, reservoirs, inlet and outlet caps, adapters, frits, and filter columns, vacuum manifolds, reversed-phase, normal-phase, and ion-exchange sorbents. 

Elimination of the need to clean filter frits can save a great deal of experimental time. 

In the spray calciner, liquid waste is pumped to a nozzle at the top of the calciner where it is atomized by pressurized air, producing droplets with diameters less than 70 irni that are dried and calcined in-fli t in the 700 C-wall-temperature spray chamber. Sintered stainless steel dust filters collect a portion of the powder with a mean diameter of 10 fjm. They are periodically cleaned by a reverse pulse of air. Calcine from the spray chambers and filters drops directly into the melting canister. Frit is fed to the cone of the calciner. 

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