The LCGC Blog: Water Immiscible Solvents as Sample Diluents in Reversed-Phase HPLC – You Must be Joking!
This Friday morning session honors the 2021 LCGC award winners: Paul Haddad of the University of Tasmania, and the foundation director of the Australian Centre for Research on Separation Science (ACROSS); and Erik L. Regalado, of the pharmaceutical company Merck & Co.
Liquid chromatography (LC) pumps produce mobile-phase streams with short-term variations in mobile-phase composition. We explain the impact of these waves on retention time in reversed-phase LC and what to do about it.
A new free simulator is available for students, educators, and trainers to teach and perform virtual HPLC experiments that are applicable to real HPLC instrumentation and method development.
Even after 40 years, we have yet to find a perfect solution to the problem of demonstrating and achieving acceptable column precision for high-performance liquid chromatography (HPLC) packing material.
A UHPLC–MS/MS method is described for rapid quantification of five major bioactive alkaloids in rat urine. The results obtained help lay the foundation for the clinical application and safety evaluation of the bioactive ingredients of menispermi rhizoma, used in herbal medicines.
A review of the operating principles of modern liquid chromatography (LC) pumps based on low- and high-pressure mixing designs, and a look at how these pumps produce mobile phase streams with small short-term variations in mobile phase composition, with a focus on the effect of these mobile-phase composition “waves” on detector baselines.
Mixed-mode chromatography columns are on the rise. This article reviews recent fundamental research, stationary phase development and design, and areas of application.
Ron Majors was the 2020 recipient of the Chromatography Forum of the Delaware Valley (CFDV) Award, which is given to those who have provided exceptional service for the Forum in addition to outstanding contributions within the field of chromatography. Readers of LCGC are well aware of his nearly 60 years of research and leadership in this area (1), but few outside the Delaware Valley region know of his decades of membership on the CFDV Executive Committee, including two terms as president. As part of this well-deserved honor, Ron gave a (remote) address to the organization in October 2020, detailing his many accomplishments in the field and summarizing the current state-of-the-art in high performance liquid chromatography (HPLC) column technology (2). However, it was his introduction describing the early days of HPLC that stood out to me, specifically a name I had not heard before: Elmar Piel. For this month’s blog post, I invited Ron to join me in writing a bit more about this scientist who may be unfamiliar to many chromatographers.
Mixed-mode chromatography columns are on the rise. We review recent fundamental research, stationary phase development and design, and areas of application.
Liquid chromatography (LC) pumps produce mobile-phase streams with small short-term variations in mobile phase composition. We explain the origin of these variations and their effects on chromatographic performance.
Paul Haddad and Erik L. Regalado are the winners of the 14th annual LCGC Lifetime Achievement and Emerging Leader in Chromatography Awards, respectively. We review their achievements.
A method is described using a triple quadrupole LC–MS instrument with isotopic dilution to obtain the highest accuracy and confidence for analysis of per- and polyfluoroalkyl substances (PFAS) in water. Excellent method spike recoveries and robustness were found in wastewater.
Sometimes our approach to troubleshooting specific problems has to change in response to changes in high performance liquid chromatography (HPLC) technology over time. In this installment, we discuss changes in technologies for mobile-phase degassing, silica-based stationary phases, and models for reversed-phase selectivity.
Sometimes our approach to troubleshooting specific problems has to change in response to changes in high performance liquid chromatography (HPLC) technology over time. In this installment, we discuss changes in technologies for mobile-phase degassing, silica-based stationary phases, and models for reversed-phase selectivity.
We investigate a phenomenon observed by many practitioners of reversed- phase LC: a dramatic loss in retention volume or time after the column flow is stopped and resumed when using highly aqueous mobile phases with certain columns.
Recombinant adeno-associated viral therapy (rAAV) products are particularly complex. Are liquid chromatography and LC–MS the right tools for their characterization?
Charged aerosol detection is a powerful complement to UV and MS, but successful implementation requires understanding a few key factors, including response dependencies on temperature, nebulization process, analyte volatility, and mobile-phase composition.
As we approach the holiday season, in what has a been the most challenging of years both inside and outside of the laboratory, I wanted to produce a more light-hearted yet inspiring review of 2020 within the Arch Sciences Group laboratories.
Reversed-phase LC–MS has limitations in numerous analytical applications. Alternative MS-compatible chromatographic techniques separate analytes in the liquid phase based on different retention mechanisms compared with reversed-phase LC. This article describes these alternative chromatographic approaches, relevant applications, and the future of these techniques.
A common problem encountered in the development of 2D-LC methods is that the first dimension mobile phase properties can negatively affect the quality of subsequent second dimension separations. This installment reviews the origin of this problem and discusses potential solutions.
In 2D-LC, properties of the mobile phase used in first step can negatively affect the second step. We explain why this problem happens and how to avoid it.
How good are your calibration procedures for environmental analysis methods using GC or LC? We demonstrate the overall value of a calibration measured by RSD. We also demonstrate the use of relative standard error (RSE) as a way of evaluating the quality or goodness of calibration methods.
In the pharmaceutical industry, method validation is essential. But what are the best practices? We review regulatory requirements, validation parameters, methodologies, acceptance criteria, trends, and software tools.
Column hardware in liquid chromatography—that is, the tubing, the frits, and fitting—has a strong influence on separation performance or the reproducibility of chromatographic data. Flow distributors and frits can introduce serious band broadening when separation is performed in short, narrow-bore columns. The kinetic performances of packed and monolithic columns are usually similar for well-retained analytes. However, monolithic columns may show significantly better performance for early-eluting compounds, which can be attributed to the moderate mobile phase dispersion caused by the simpler column hardware because no frits are required.
