John W. Dolan

This month's column addresses problems submitted by readers, including negative peaks, pressure increases, and peak-width increases.

Dolan examines the causes of LC system leaks and suggests some preventive maintenance to minimize their occurrence.

Flow-rate changes might or might not be acceptable means to adjust retention.

John Dolan provides 10 tips for the proper care and use of LC columns.

Craig Young and John Dolan provide tips and techniques for evaporative light-scattering detection.

Guest authors Lloyd Snyder and John Dolan describe a method for determining reversed-phase column selectivity.

John Dolan examines problems associated with adjusting gradients in reversed-phase LC.

This month's column discusses a performance qualification test designed by PerkinElmer Analytical Instruments (Shelton, Connecticut).

Dolan discusses some of the challenges of separating small peaks from large ones and gives some pointers on how to obtain a separation.

John Dolan focuses on several aspects of column temperature, which can affect retention, selectivity, peak shape, and column pressure.

John Dolan discusses the effects of peak tailing on resolution.

John Dolan focuses on stability-indicating assays for pharmaceutical products.

Dolan reflects on 10 years of change in HPLC and predicts more widespread use of mass spectrometers, faster autosamplers, and better ways of monitoring column health.

John Dolan looks at chemical, physical, and electronic sources of baseline noise and suggests how to reduce or eliminate them.

The authors examine a case in which ion suppression compromised method performance.

Dolan answers readers' questions about a variety of topics, including life-spans of cyano columns, successfully transferring and running a method, why chromatographers water-saturate solvents such as chloroform or methylene chloride, and suggested buffers for high-pH analyses.

Dolan examines some options for increasing the retention of polar compounds, which is a goal when using gradient elution scouting runs to screen the retention characteristics of compounds for separation by reversed-phase liquid chromatography.

This month's installment presents a systematic approach for dealing with a common chromatographic headache -- carryover.

Sometimes you must sacrifice chromatographic performance to obtain analytical results.

This month's "LC Troubleshooting" focuses on the baseline characteristics of several common LC buffers and methods to minimize drift.

The first of a two-part series about LC autosamplers.

This month's column looks at reproducibility and carryover problems associated with the development of a method used to verify analyst proficiency.

This month's column discusses the presence of sample peaks in chromatograms when only blanks are injected.

This month's column discusses the presence of sample peaks in chromatograms when only blanks are injected -- commonly called carryover. Most carryover problems can be eliminated by performing one or more of the approaches discussed in this column.

In this month's installment of "LC Troubleshooting," John Dolan focuses on late-eluted peaks.

Dolan discusses some of the pitfalls that users can encounter when adjusting a gradient-elution LC method.

This month's installment illustrates some potential problems that may arise during method transfer.

The authors focus on problems that may occur when converting conventional methods to LC–MS.

How can you avoid phase collapse when 5% organic solvent is too strong?

A scouting gradient is a separation run under a standardized set of conditions and can be used to determine the complexity of a sample and estimate the difficulty of the separation. John Dolan tells why he believes using a scouting gradient is the best way to begin method development.