New Column Technologies

This chapter is intended to serve as a general overview of new and emerging HPLC technologies and is divided into four sections simplifying sample preparation, new column technologies, improvements in detectors, and improvements in HPLC throughput. 

Simplifying Sample Preparation New Column Technologies Improvements in Detectors Improvements in HPLC Throughput... 

To achieve increased resolution of closely related compounds, new column technologies have een introduced for the separation of nucleosides and their bases (AS, Sll). The use of microbore columns will play an increasingly important role for achieving difficult separations or where sample size is limited (K34, R2, S12, S13, SIS). 

The quest for improved efficiency provides the continuing impetus to the study of reduced diameter columns, and though still in their early stage of development, these new column technologies are having considerable influence on the practice of HPLC [104,105]. The incentive for the development of microcolumns for HPLC lies in the various practical advantages they have over standard analytical columns [106] ... 

NPLC stationary phases include metal oxides and moderately or strongly polar chemically bonded phases. Unmodified silica gel and silica-based bonded phases are most frequently used nowadays. Considerable effort in the development of new HPLC column packing materials in the past years has resulted in significant improvement of the column efficiency, reproducibility, and increased stability at elevated temperatures and at higher pH, enabling better compatibility with HPLC/mass spectrometry techniques and rapid analyses. Even though the new column technologies were primarily focused on RPLC separations, normal-phase HPLC also benefits from the improved properties of the support materials with uniform small particles and well-defined pore size. 

The analysis of proteins falls under the umbrella of proteomics. For years, the field of proteomics rehed on two-dimensional polyacrylamide gel electrophoresis for the separation of complex protein mixtures. With the drive to produce methods with more selective and structural methods, HPLC with new column technology combined with the mass spectrometer has revolutionized the analysis of proteins. The quality and quantity of information generated by this approach has given rise to a... 

Microbore and packed capillary HPLC column technology has not yet met the requirements for breakthrough of new technologies [554]. On commercial instruments in general efficiency and detectability with microbore columns are lower than with normal-bore columns. Microbore and capillary HPLC suffer from... 

This overview concerns the new chromatographic method - capillary electrochromatography (CEC) - that is recently receiving remarkable attention. The principles of this method based on a combination of electroosmotic flow and analyte-stationary phase interactions, CEC instrumentation, capillary column technology, separation conditions, and examples of a variety of applications are discussed in detail. 

Thermodynamic behaviors and retention mechanisms for SFC are unique. Low temperatures and high pressures or high densities usually favor fast separation of enantiomers in SFC. In the case that the isoelution temperature is below the working temperature, the selectivity increases as temperature increases and higher temperatures are favorable for chiral separation. Future development in SFC will likely include new chiral column technologies and instrumentation refinement. A greater variety of chiral columns packed with smaller particles will open up more areas of application for fast chiral separations. In addition, improvement in signal-to-noise ratio of... 

Although HPLC column technology is considered to be a mature field now, improvements and new developments are being made continuously in the stationary phases. One of the improvements has been the reduction in particle sizes. Smaller particles help to improve mass transfer and provide better efficiency. Manufacturers are producing particles down to 1.5 J,m in diameter, although 3- and 5- J,m particles are still the most popular. Because of the smaller particle sizes, the backpressure increases proportionally to the inverse of the square of the particle size. Most commercially available HPLC systems cannot accommodate the pressures required to operate these columns at optimum flow rates. This has led to the introduction of systems that run at high pressures. 

Recent advances in circuit miniaturization and column technology, the development of microprocessors and new concepts in instrument design have allowed sensitive measurement at the parts per billion and parts per trillion levels for many toxicants. This increased sensitivity has focused public attention on the extent of environmental pollution, because many toxic materials present in minute quantities could not be detected until technological advances reached the present state of the art. At present, most pollutants are identified and quantified by chromatography, spectroscopy, and bioassays. 

Part II shows you how to make the best use of the common columns and how to keep them up and running. (Chapter 6 on column healing should pay for the book in itself) It discusses the various pieces of HPLC equipment, how they go together to form systems, and how to systematically troubleshoot system problems. We will take a look at the newest innovations and improvements in column technology and how to put these to work in your research. New detectors are emerging to make possible analysis of compounds and quantities that previously were not detectable. 

Pescar, R. E. (1971) Preparative Column Technology, in A. Zlatkis and V. Pretorius (eds) Preparative Gas Chromatography, Wiley-Interscience, New York. pp. 73-141. 

In practice, however, due mainly to a number of technical difficulties, most of which are attributable to lack of column ruggedness, it has yet to be shown that the theoretically predicted potential of CEC will fulfill its promise and result in a widespread routine technique. In the past 5-8 years, there has been a sustained effort in the separations community to understand theoretical aspects, based on which new developments arose in the field of column technology [9,13,14], application [4,5], and detection [7]. A number of these observations are summarized here, with an emphasis on their bearing on extending the application range of CEC. 

There have been many advances in the field of gas chromatography, and the rate at which new developments occur has been increasing in a manner that is almost exponential. Among those developments are some that hold special significance for the flavor chemist these include advances in 1) sample preparation, 2) injection hardware and methodology, and 3) column technology. 

Improvements in column technology, detector sensitivity and the development of new detection systems, have made possible the routine separation of picomole quantities of nucleic acid components in complex physiological matrices. The very sensitivity of most LC systems, however, which is invaluable in the analysis of biological samples, is often the limiting factor because of inadequate or ambiguous identification methods. Although tremendous advances have been made in the on-line combination of HPLC with spectroscopic techniques [e.g., mass spectrometry, Fourier transform infrared (FT/IR), nuclear magnetic resonance], their application has not become routine in most biochemical and biomedical laboratories. 

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