Microbore chromatography columns

Amino acids can also be determined by amperometric detection with a copper electrode under neutral or alkaline conditions. This method is very selective, with the working electrode potential set at only -1-0.10 mV versus Ag/AgCl. In this detection method, amino acids complex with Cu " " ions present on the electrode surface, producing a response that is proportional to the concentration of the amino acid. Detection limits are between 10 and 100 pmol and can be improved if microbore chromatography is employed. The slower flow rates utilized with microbore chromatography columns allow more time for complexation to take place, thus improving the detection limits. 

In order to achieve a major objective of the METSCAN instrument, which is low solvent flow rate over a seven day unattended operating period, it is essential that microbore chromatography columns should be used instead of the more conventional columns. 

T. Cserhati, E. Forgacs, H. Morais and C. Ramos, Use of a microbore ODS column for the separation of paprika (Capsicum annuum) pigments by high performance liquid chromatography. Pol. J. FoodNutr. Sci. 11/52 (2002) 11-13. 

Recent advances in chromatography have made it possible to employ microbore HPLC for the determination of NOC. Its main advantage is that it uses a very low mobile-phase flow (20-100 /rl/min). This might make the TEA compatible with a reversed-phase system. Massey et al. (73), in fact, have successfully used reversed-phase chromatography for the HPLC-TEA determination of V-nitroso-V, 7V -di methylpiperazinium iodide. A 500-mm X 1-mm microbore ODS column and a mobile phase consisting of 0.1 M ammonium heptane-sulfonate in methanol water (70 30) (flow rate 20 /zl/min) was used for the HPLC separation. In another study, Riihl and Reusch (74) used a microbore Spherisorb 3 SW column for HPLC-TEA determination of volatile V-nitrosamines. The mobile phase was a mixture of 2-propanol and n-hexane (2.5 97.5). Further application of such techniques for the determination of various polar NOC, especially A-nitrosamides, in foods is desirable. 

Trojer, L. et al. Comparison between monolithic conventional size, microbore and capillary poly(p-methylstyrene-co-l,2-bis(p-vinylphenyl)ethane) high-performance hqnid chromatography columns synthesis, application, long-term stabihty and reprodncibil-ity. J. Chrvmatogr. A. 2007,1146, 216-224. 

Taylor, R.B. Kendle, K.E. Reid, R.G. Hung, C.T. Chromatography of progesterone and its major metabolites in rat plasma using microbore high-performance liquid chromatography columns with conventional injection and detection systems. J.Chromatogr., 1987, 385, 383—392... 

Liu, Y. Yang, F.Y. Unified high-pressure gas and supercritical fluid chromatography with microbore packed columns. Anal. Chem. 1991,63,926. 

During the initial years of HPLC, the most common internal diameter of conventional analytical columns was 2 mm, except for columns for size exclusion chromatography that often used to be 7-8 mm. Soon, the standard inner diameter changed to 4.6 mm, the standard length was reduced from 60 to 15-25 cm, and the particle size of the column packing materials was reduced from 40-50 to 5-10 pm. The dimensions of the columns were initially related to the commercial availability of stainless steel tubing. Today, the internal diameters of conventional HPLC columns and microbore HPLC columns are in the range of 2-5 and 0.5-1 mm, respectively. Capillary columns typically have 0.1-0.5 mm ID and nanoflow columns have <0.1 mm ID (Table 3.1). 

Figure 5.6 Positive-ion electrospray spectrum obtained from the major component in the LC-MS analysis of a purified recombinant 62 kDa protein using a Cig microbore 50 X 1 mm column and a flow rate of 50 p.lmin . The starting buffer (buffer A ) was 0.1% TEA in water, while the gradient buffer (buffer B ) consisted of 0.1% TEA in acetonitrile-water (9 1 vol/vol). The running conditions consisted of 0% B for 5 min, followed by a linear gradient of 100% B for 55 min. Reprinted from J. Chromatogr., B, 685, McAtee, C. P., Zhang, Y., Yarbough, P. O., Fuerst, T. R., Stone, K. L., Samander, S. and Williams, K. R., Purification and characterization of a recombinant hepatitis E protein vaccine candidate by liquid chromatography-mass spectrometry , 91-104, Copyright (1996), with permission from Elsevier Science.

Capillary column This term refers to a chromatographic column of small diameter and is used in both gas and high performance liquid chromatography. In HPLC, the term is usually apphed to columns with internal diameters of between 0.1 and 2 mm. The term microbore column is often used synonymously to describe these columns but is more correctly applied to columns with internal diameters of 1 or 2 mm. 

Microbore Column Chromatography A Unified Approach to Chromatography, edited by Frank J. Yang... 

F. J. Yang (Ed.), "Microbore Column Chromatography. A Unified Approach to Chromatography", Delcker, New York, NY, 1989. 

Schwartz, H. E., Karger, B. L., and Kucera, F, Gradient elution chromatography with microbore columns, Anal. Chem., 55, 1752, 1983. 

Mei, D.A., Gross, G.J., and Nithipatikom, K., Simultaneous determination of adenosine, inosine, hypoxanthine, xanthine and uric acid in microdialysis samples using microbore column liquid chromatography with diode array detection, Analyt. Biochem., 238,34,1996. 

Kohne, A.P., Welsch, T. (1999). Coupling of a microbore column with a column packed with non-porous particles for fast comprehensive two-dimensional high-performance liquid chromatography. J. Chromatogr. A 845, 463-469. 

M. Verzele and C. Dewale, Microbore Column Chromatography A Unified Approach to Chromatography, J.F. Yang, Ed., Marcel Dekker New York, 1984, p. 37. 

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