Microbore columns, comparison

Ultra-performance HPLC (UPLC) utilizes sub-2-pm porous particles inside packed microbore columns up to 150 mm long. Significant improvements in terms of resolution, analysis time, and detection sensitivity have been reported. A side-by-side comparison of HPLC and UPLC was made to determine concentrations of alprazolam in rat plasma.10 UPLC provided a four-fold reduction in terms of LC/MS/MS cycle time that translated into higher sample throughput. Another important... 

The most common method is RP-HPLC. Microbore-HPLC [613] and narrow bore columns [614] are applied with good results in increasing sensitivity. A recent comparison between NP and RP microbore columns confirms the better suitability of RP for this purpose [615], The mobile phase is usually composed of acetonitrile or methanol. 

The solvent elimination problem became less of a problem with the commercialization of microbore columns. Hayes et al. (54) studied gradient HPLC-MS using microbore columns and a moving-belt interface. The heart of the system was the spray deposition device designed to be compatible with microbore-column flow rates. Nebulization of the eluent was found to be applicable to a variety of mobile-phase compositions and thus was readily compatible with gradient elution. Figure 13 shows a comparison of UV detection with that obtained with the HPLC-MS system. Applications of this system were demonstrated on water from coal gasification processes. 

The importance of the systematic errors on the isotherm data that can be introduced by the use of an erroneous column diameter in the numerical calculations is illustrated by data from Zhou et al. [178] who compared the isotherm data acquired on three different columns (i.d. 1.07, 4.57, and 10.1 mm) packed with the same stationary phase. The data were eventually shown to be in close agreement, with the band profiles on the large column matching closely the profiles calculated with the isotherm data measured with the microbore column. However, the initial comparison of the isotherm data suggested a marked disagreement. This was explained by a difference of 0.07 mm between the nominal column i.d. of the microbore column supplied by the manufacturer and used in the initial calculations, and the true i.d., measured later with an electronic caliper. A quantitative discussion of the importance of the errors caused by a small error on the column diameter is available [178]. 

J.D. Henion, A comparison of direct liquid introduction LC/MS techniques employing microbore and conventional packed columns, J. Chromatogr. Sci., 18 (1980) 101-115. 

A comparison of monolithic conventional size, microbore, and capillary poly(p-methylstyrene-co-l,2-bis(p-vinylphenyl)ethane) columns confirmed that the efficiency for analysing proteins and oligonucleotides improved with decreasing column internal diameter, even if monolithic capillary columns up to 0.53 mm internal diameter were successfully used for the fractionation of the whole spectrum of biopolymers including proteins, peptides, and oligonucleotides as well as double-stranded DNA fragments under IPC conditions [14,23]. 

W. Wieder and G. K. Bonn, Comparison between monolithic conventional size, microbore and capillary poly (p-methyl-styrenehigh-performance liquid chromatography columns Synthesis, application, long-term stability and reproducibility,... 

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