Overcoming the Effects of Highly Organic Protein Precipitation Extracts on LC Peak Shape Using Direct Injection

ByAudrey Crater

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

ByAudrey Crater

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

ByAudrey Crater

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.

Sulfinert-Treated Sample Cylinders

ByAudrey Crater

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

ByAudrey Crater

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

Successful Strategies for the Analysis of EtG and EtS in Urine

ByAudrey Crater

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.

“The Big Pain“: Development of Pain-Free Methods for Analyzing 231 Multiclass Drugs and Metabolites by LC-MS/MS

ByAudrey Crater

As the demand for testing of pain management drugs increases, many laboratories are turning to LC-MS/MS for its increased speed, sensitivity, and specificity. The methods shown here use a Raptor Biphenyl column because it provides fast, accurate analysis of 231 drugs and drug metabolites.

Evaluation of a Simple Method for Methylmalonic Acid Analysis in Human Plasma by LC-MS/MS

Evaluation of a Simple Method for Methylmalonic Acid Analysis in Human Plasma by LC-MS/MS

ByAudrey Crater

A new LC-MS/MS method for methylmalonic acid (MMA) analysis was developed that provides complete chromatographic resolution from isobaric succinic acid in plasma samples. Excellent chromatographic results were obtained from the direct injection of a protein crash sample supernatant onto a Force C18 column, providing a much simpler sample preparation compared to typical methods.