Capillary columns particle size

Sample analysis was performed by using an Applied Biosystems (Foster City, CA) API 3000 triple quadrupole mass spectrometer equipped with a TurboIonSpray source and an Agilent 1100 capillary HPLC system (Palo Alto, CA). The capillary HPLC system included a binary capillary pump with an active micro flow rate control system, an online degasser, and a microplate autosampler. The analytical column was a 300 pm I.D.x 150 mm Zorbax C18 Stablebond capillary column (pore size 100 A and particle size 3.5 pm). The injection volume was 5 pL, and a needle ejection rate of 40 pL/min was used. The pLC flow rate was 6 pL/min. In order to minimize dead volume before the column, the autosampler was programmed to bypass the 8 pL sample loop 1.5 min after injection. The mobile phase consisted of (A) 2 mM ammonium acetate (adjusted to pH 3.2 with formic acid) in 10 90 acetonitrile-water, and (B) 2 mM ammonium acetate in 90 10 acetonitrile-water. The percentage of mobile phase B was held at 32 % for the first minute, increased to 80 % over 8 min, and then increased tol00% over the following 1 min. 

A column is essentially a device that holds a stationary phase in place, allowing the mobile phase to carry an injected sample through and allowing analytes to interact with available surface. As we discussed in Section 3.2, the efficiency is mainly dependent on the column type (packed, monolithic, or capillary) and particle size for packed columns, or through-pore diameter for monolithic columns. 

Chromatographic use of monolithic silica columns has been attracting considerable attention because they can potentially provide higher overall performance than particle-packed columns based on the variable external porosity and through-pore size/skeleton size ratios. These subjects have been recently reviewed with particular interests in fundamental properties, applications, or chemical modifications (Tanaka et al., 2001 Siouffi, 2003 Cabrera, 2004 Eeltink et al., 2004 Rieux et al., 2005). Commercially available monolithic silica columns at this time include conventional size columns (4.6 mm i.d., 1-10 cm), capillary columns (50-200 pm i.d., 15-30 cm), and preparative scale columns (25 mm i.d., 10 cm). 

Correlation was found between domain size and attainable column efficiency. Column efficiency increases with the decrease in domain size, just like the efficiency of a particle-packed column is determined by particle size. Chromolith columns having ca. 2 pm through-pores and ca. 1pm skeletons show H= 10 (N= 10,000 for 10 cm column) at around optimum linear velocity of 1 mm/s, whereas a 15-cm column packed with 5 pm particles commonly shows 10,GOO-15,000 theoretical plates (7 = 10—15) (Ikegami et al., 2004). The pressure drop of a Chromolith column is typically half of the column packed with 5 pm particles. The performance of a Chromolith column was described to be similar to 7-15 pm particles in terms of pressure drop and to 3.5 1 pm particles in terms of column efficiency (Leinweber and Tallarek, 2003 Miyabe et al., 2003). Figure 7.4 shows the pressure drop and column efficiency of monolithic silica columns. A short column produces 500 (1cm column) to 2500 plates (5 cm) at high linear velocity of 10 mm/s. Small columns, especially capillary type, are sensitive to extra-column band... 

MIP are often generated as simple bulk polymers to be ground into fine particles, which are subsequently sieved and sedimented - admittedly a time-consuming process, which requires large amounts of solvents. The loss of fine polymer particles in the sedimentation procedure is also not negligible. The result usually is a polymer powder with particle sizes of a relative broad size distribution. After the template has been extracted, this material can be packed into LC-columns [17,29,30], CE-capillaries, or be used directly in the batch mode. 

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