Perfusive particles

Straub et al. (76) reported a method for the identification and quantification of penicillin G, ampicillin, amoxicillin, cephapirin, cloxacillin, and ceftiofur residues in milk using perfusive-particle liquid chromatography combined with ultrasonic nebulization electrospray mass spectrometry. According to this method, a 0.5 ml milk sample is diluted with an equal volume of a solution consisting of acetonitrile/water (1 1), and ultrafiltrated in a microseparation system with a 10000 da molecular mass cut-off filter. An aliquot of the ultrafiltrate is then analyzed on a 15 cm porous II R/H LC (7-8 m) perfusion analytical column using the chromatographic conditions shown in Table 29.3. Concentrations as low as 10 ppb could be readily determined in milk by electrospray mass spectrometric detection. 

R Straub, M Linder, RD Voyksner. Determination of beta-lactam residues in milk using perfusive-particle liquid chromatography combined with ultrasonic nebulization electrospray mass spectrometry. Anal Chem 66 3651-3658, 1994. 

The porosity of particles suitable for packing HPLC columns depends on the size of molecules to be separated. Totally porous particles with a pore size of 7-12 nm and specific surface area of 150-400 m"/g are suitable for the separation of small molecules, but wide-pore particles with a pore size of 15-100 nm and relatively low specific surface area (10-150 nr/g) are required for the separation of macromolecules to allow easy access to the interactive surface within the pores. Packings with perfusion particles contain very broad pores (400-800 nm) throughout the whole particle interconnected by smaller pores. The mobile phase flows through the pores in the particle, which minimises both band broadening and column backpressure (111. Perfusion materials have been designed especially for the separation and isolation of biopolymers. 

Various types of stationary phases are in use Porous particles, nonporous particles of small diameter, porous layer beads, perfusive particles, and monolithic materials. 

Briefly describe the differences between microporous particles, perfusion particles, and nonporous particles. What are their unique features/uses ... 

A very simple way to achieve a reduction in the intraparticular mass transfer is the use of micropellicular, i.e., nonporous particles. However, due to the low capacity of such particles (90% of the adsorptive surface is usually found inside a particle), such nonporous particles are more suitable for analytical than for preparative applications. Another way to increase capacity without relying on the intraparticular surface area, which is more suitable to preparative applications, is represented by the so-called tentacle gels. Gigaporous stationary ( perfusion ) particles and hyperdiffusive ( gel in a shell ) particles can also be envisaged for preparative separations. 

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