Polyetheretherketone column

Digestion is usually performed in a solution at specified conditions of pH, temperature, and buffer (see T able 1) and in a denaturing environment to ensure complete endpoint digestion. Volatile buffers such as ammonium carbonate and ammonium bicarbonate are preferred because they can be easily removed by lyophilization. A practical method for the removal of a nonvolatile buffer and salts is to use solid-phase extraction (SPE) cartridges prior to mass spectrometry analysis. One can also use immobilized trypsin packed into a small-diameter PEEK (polyetheretherketone) column or covalently attached to an activated MALDI probe for on-probe digestion.15... 

The head is made of polypropylene and polyetheretherketone-based materials and is designed to run at an operating pressure of maximal 10 bar. All feed and eluent solutions are pumped directly into the column through tubes, to minimize dead zones and prevent fouling. 

Five monolithic columns (100 x 4.6 mm) with a graded macropore diameter between 1.9 and 6.0 pm at constant mesopore diameter of 12 nm were obtained as research samples by Merck KGaA, Darmstadt They were synthesised according to a procedure published elsewhere [1,2]. The silica monoliths are cladded with polyetheretherketone (PEEK). 

Monolithic columns are another approach to provide lower pressure drops and higher rates of mass transfer. These are continuous solid columns of porous silica stationary phase instead of packed particles. Like perfusion packings, they have a bimodal pore structure (Figure 21.7). Macropores, which act as flowthrough pores, are about 2 fim in diameter. The silica skeleton contains mesopores with diameters of about 13 nm (130 A). It can be surface modified with stationary phases like Cig. The rod is shrink-wrapped in a polyetheretherketone (PEEK) plastic holder to prevent waU effects of solution flowing along the walls. The surface area of the mesopores is about 300 mVg, and the total porosity is 80%, compared with 65% for packed particles. The colunm exhibits a van Deemter curve approximating... 

In some cases, steel filters are undesirable. An analyte may adsorb to the steel or may decompose in the presence of steel. In these cases, plastic frits made from PEEK (polyetheretherketone) or polyethylene can be substituted for the stMl filters. They are not as strong as steel frits and are not completely compatible with all mobile phases. Polyethylene swells in solvents such as hexane, methylene chloride, or tetrahydrofuran (THE). PEEK also is incompatible with methylene chloride and THF. In combination with PEEK or glass tubing, these frits can be used for the construction of columns with a metal-free flow path. 

PEEK Polyetheretherketone. PEEK is a polymer that has become frequently used in systems where stainless steel causes problems (e.g., metal ion analysis and some protein/peptide analyses). Connecting tubing, iiyector loops, and even column tubing are now fabricated from PEEK. 

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