October 29th 2024
Manitoba Centre for Proteomics and Systems Biology scientists produced a new means of predicting peptide retention times for hydrophilic interaction liquid chromatography (HILIC) at acidic pH in formic-acid based eluents.
The Perfect Method, IV: Controlling Peak Spacing
September 1st 2007In the fourth installment in a series on method development for liquid chromatography (LC), with an emphasis on devloping trouble-free methods quickly. John Dolan started out by considering some of the goals we might have and some method development strategies.
Technology Forum: HPLC/Ion Chromatography
September 1st 2007This month's Technology Forum looks at the topic of HPLC/Ion Chromatography Focus and the trends and issues surrounding it. Joining us for this discussion is Chris Pohl, VP and Chief Science Officer at Dionex Corporation, Larry Tucker from Metrohm-Peak, and Yuichi Fusho of Shodex.
HPLC Column Expert Predictions - Revisited
August 1st 2007In this installment of "Column Watch" columnist Ron Majors revisits expert predictions from a survey conducted in 1987. A cross section of column experts of the time were asked a series of questions on the future directions in high performance liquid chromatography (HPLC) column technology. Now, 20 years later, these predictions are contrasted against current column technology. In many cases, the experts were entirely correct, while in other cases, they were dead wrong. Some current trends were not even considered 20 years ago. The author backs up his analysis with current survey information.
Practical Guidelines in the Care and Maintenance of Capillary GC Columns
July 1st 2007Modern gas chromatography (GC) capillary columns are rugged and forgiving but some care should be taken when handling and using these high-efficiency columns. In this instalment of "Column Watch", the authors discuss the issues surrounding avoiding column breakage, stationary phase damage and column contamination. Prolonging the life of a column by keeping an oxygen-free system, providing a cleaner sample and not exceeding the upper temperature limit of the stationary phase are highlighted in this practical discussion.
Factors Affecting Sensitivity of Evaporative Light Scattering Detection
July 1st 2007An evaporative light scattering (ELS) detector is a powerful detection tool if the solutes are less volatile than the eluent. Three main processes occur successively: nebulization, evaporation of the liquid chromatographic (LC) effluent and measurement of the light scattering by the residual particles. This leads to a non-linear calibration curve such as, A= a.m b where A is the peak area,m the sample mass and b the response coefficient measured as the slope of Log A = b>Log m + Log a.
How Does Temperature Affect Selectivity?
July 1st 2007Column temperature plays an important role in controlling peak spacing (selectivity) in reversed-phase liquid chromatography (LC) separations. Temperature has long been known to affect retention time, and more recently, its use in adjusting selectivity has gained popularity (see reference 1 for a review of temperature selectivity). In preparation of a paper for the most recent Pittsburgh Conference, I had an opportunity to reexamine some data that compare temperature selectivity with other variables used to control selectivity in LC separation. This month's instalment of "LC Troubleshooting" examines temperature selectivity and its relationship to pH selectivity.
Multimodal HPLC Screening of Polysaccharide-based Chiral Stationary Phases
June 1st 2007High-performance liquid chromatography (HPLC) is a powerful tool for the enantioselective separation of chiral drugs. However, the selection of an appropriate chiral stationary phase (CSP) and suitable operating conditions is a bottleneck in method development and a time- and resource-consuming task. Multimodal screening of a small number of CSPs with broad enantiorecognition abilities has been recognized as the best strategy to achieve rapid and reliable separations of chiral compounds. This paper describes the generic screening strategy developed at Johnson & Johnson Pharmaceutical Research and Development (J&J PRD) to successfully develop enantioselective HPLC methods for chiral molecules of pharmaceutical interest.
Preparative and Process Chromatography
June 1st 2007lthough liquid chromatography (LC) is most commonly associated with analytical techniques that are found inside the laboratory, LC also has been used in industrial applications for separation of a wide range of products for decades. The technique recently has been applied to requirements in the pharmaceutical and biotechnology industries, both inside the laboratory and in industrial settings. With global sales of over $1.7 billion, the market for preparative LC has encountered a stellar growth over the past few years.
Variability — How to Control It
June 1st 2007The topic of this month's instalment of "LC Troubleshooting" was prompted by a manuscript I recently reviewed and a question I received from a reader of this column. Both inputs related to the variability of retention times observed in liquid chromatography (LC) methods. Variable retention is a topic that has been touched on many times over the history of this column, sometimes just in passing and other times in depth. Yet, it seems to be a problem that keeps recurring, so I think it is worth considering again.
Ultrafast HPLC: Different Approaches to Increased Throughput
May 1st 2007Over the years, LC instrumentation has undergone continuous development in pursuit of greater performance. More recently, the focus of progress has been on shorter run times, as a direct response to greater user demand to perform faster chromatographic analyses, particularly for their LC–MS applications. This has led to separations on short (30–50 mm) columns with a small internal diameter (i.d. ~2.0 mm), packed with small particle size phases (1.5–3.0 μm). The trend for smaller column particle size has now reached a practical limit on current hardware and innovative technological solutions for further gains in performance are required. Several manufacturers offer fast LC instruments designed for greater productivity, while maintaining low carryover, high sample capacity, resolution and reliability. With ultra-fast run times of under 1 minute, these companies have achieved increased throughput using contrasting technological approaches. Here we examine the background to this current trend,..
Pressure-driven Chromatography in Perfectly Ordered Pillar Array Columns
April 1st 2007his article reveals the first liquid chromatography (LC) separations performed on a microfabricated pillar array column under pressure-driven conditions. The pillars were non-porous and produced using a Bosch-type deep reactive ion etch (DRIE) to pattern the surface of a silicon wafer and had a diameter of approximately 5 μm. Two different packing densities were compared: one similar to the packing density of a packed bed (external porosity of approximately 49%) and one similar to the packing density of monolithic columns (external porosity of approximately 70%).