Reducing Column Internal Diameter
Scaling down column size is simple to do and can help reduce solvent use. Here is an easy-to-follow example that teaches you how to reduce column internal diameter.
Tech Tip: Why do I Lose Retention on my C18 in Highly Aqueous Mobile Phases?
Learn what de-wetting is, and how to avoid it, by using an Aqueous C18 column, instead of a conventional C18, when analyzing polar compounds by HPLC.
Overcoming the Effects of Highly Organic Protein Precipitation Extracts on LC Peak Shape Using Direct Injection
Protein precipitation is frequently used to minimize matrix impact when analyzing biological samples. However, the effects of highly organic protein precipitation sample extracts on LC peak shape can negatively impact accurate quantification. Dilution or further sample preparation steps are often used to minimize these effects; however, here we show that direct injection of sample extracts is a viable option that can be used to prevent peak distortion, while avoiding the time and variability associated with additional sample preparation.
Using Micropacked Columns
Micropacked columns are 1-2 meter, 0.75-1.0mm ID packed stainless steel columns with performance characteristics intermediate between conventional packed columns and capillary columns. They are inexpensive, very durable, and easy to install and operate. They have a wide range of applications, but are especially useful for analyses of gas mixes, including sulfur compounds or light hydrocarbons, for which a packed column is needed to obtain baseline separations of sample components.
Influencing Selectivity in LC-MS Peptides Analysis on the Raptor ARC-18 Column
Methods for LC-MS peptide analysis often use acidified mobile phases, which can alter retention and selectivity. Here, we demonstrate the effects of modifying acid type, acid concentration, temperature, and gradient slope using several test probes. A Raptor ARC-18 column was employed for this work because it is sterically protected making it extremely stable and resistant to acid damage at low pHs, which is an important characteristic when developing LC-MS methods for peptide analysis.
How to Condition a New Capillary GC Column
Proper conditioning is essential for optimal performance from a capillary GC column, but inexperienced chromatographers might not know the proper procedures for installing and conditioning a new column. Here, we summarize our recommendations for installation and conditioning procedures.
A Primer on Gas Flow
A basic understanding of gas flow principles is fundamental to obtaining accurate flow measurements. This primer contrasts mass flow and volumetric flow regimes, and illustrates the effect of flow impedance and loading on the flow source in gas chromatography.
Sulfinert-Treated Sample Cylinders
Recovery of a 17 ppbv test standard of hydrogen sulfide exceeded 85% after 54 hours in a Sulfinert-treated cylinder; recoveries of methyl mercaptan, ethyl mercaptan, carbonyl sulfide, and dimethyl disulfide exceeded 90%. A Sulfinert-treated sampling/transfer system can assure accurate sulfur content data for natural gas, beverage-grade carbon dioxide, or other samples.
Analysis of Synthetic Cannabinoids and Metabolites: Adding New Compounds to an Existing LC-MS/MS Method
The analysis of synthetic cannabinoids and their metabolites can be a difficult and challenging task. Keeping up with the ever-growing list of synthetic cannabinoids that illicit drugmakers produce further complicates the analysis. As shown here, the retention and selectivity of the Raptor Biphenyl column allows new drugs to be added to an existing method, providing labs with an important vehicle for improving efficiency and productivity.
Successful Strategies for the Analysis of EtG and EtS in Urine
LC-MS/MS analysis of EtG and EtS is challenging due primarily to poor retention and resolution of EtG and EtS from matrix components. This article presents a foundation method that is useful for many samples and also demonstrates effective strategies for improving sensitivity and mitigating matrix effects.
