How to Avoid Common Problems with HILIC Methods

Author: Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: www.restek.com/Technical-Resources/Technical-Library/General-Interest/general_GNAR2716-UNV

Abstract:

Whether you’ve run HILIC methods before or are attempting to for the first time, there are significant differences between reversed-phase and HILIC methods that must be considered. This article addresses common problems that analysts encounter when running HILIC methods and details how to avoid them and successfully use the technique.

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

Author: Sharon Lupo and Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: www.restek.com/Technical-Resources/Technical-Library/Clinical-Forensic-Toxicology/cft_CFAN2667-UNV

Abstract:

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.

High-Throughput Analysis of Immunosuppressive Drugs from Whole Blood by LC-MS/MS

Author: Shun-Hsin Liang and Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: www.restek.com/Technical-Resources/Technical-Library/Clinical-Forensic-Toxicology/cft_CFAN2666-UNV

Abstract:

The success of organ transplant therapy depends in large part on the accurate and timely analysis of immunosuppressive drugs. In this study, we developed a fast, accurate method for the analysis of cyclosporin A, tacrolimus, sirolimus, and everolimus in whole blood. The method pairs a single precipitation step with LC-MS/MS analysis using a Raptor Biphenyl column. A fast, 3-minute analysis time was obtained with no interference from matrix components. Excellent results were obtained for linearity, robustness, accuracy, and precision, demonstrating that the method is suitable for high-throughput therapeutic drug monitoring.

Direct Analysis of Morphine, M3G and M6G Metabolites, and Related Compounds in Urine by LC-MS/MS

Author: Justin Steimling and Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: www.restek.com/Technical-Resources/Technical-Library/Clinical-Forensic-Toxicology/cft_CFAN2665-UNV

Abstract:

The analysis of total morphine is typically conducted by first subjecting urine samples to acid or enzymatic hydrolysis in order to cleave the glucuronide conjugates from morphine’s primary metabolites [morphine-3β-D-glucuronide (M3G) and morphine-6β-D-glucuronide (M6G)] prior to analysis. With the glucuronide moiety removed, the resulting morphine molecule is much less polar and, therefore, more amenable to traditional reversed-phase chromatography. However, both hydrolysis procedures cost an analyst time and result in sample variability due to incomplete hydrolysis or analyte conversion. By utilizing the retention characteristics of the Restek Force Biphenyl column, hydrolysis was not required and direct analysis of morphine, its M3G and M6G metabolites, and several related compounds using a simple “dilute-and-shoot” sample preparation was performed.

Accurate Detection of Residual Solvents in Cannabis Concentrates

Author: Chris English

Restek Corporation

Published By: Cannabis Industry Journal

Year of Publication: 2017

Link: https://www.cannabisindustryjournal.com/category/the-practical-chemist/

Abstract:

Edibles and vape pens are rapidly becoming a sizable portion of the cannabis industry as various methods of consumption popularize beyond just smoking dried flower. These products are produced using cannabis concentrates, which come in the form of oils, waxes, or shatter. Once the cannabinoids and terpenes are removed from the plant material using solvents, the solvent is evaporated leaving behind the product. Extraction solvents are difficult to remove in the low percent range, so the final product is tested to ensure leftover solvents are at safe levels. While carbon dioxide and butane are most commonly used, consumer concern over other more toxic residual solvents has led to regulation of acceptable limits.

Preventing GC Septum Problems

Author: Mark Badger, Scott Grossman

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: http://www.restek.com/Technical-Resources/Technical-Library/General-Interest/general_GNAR2671-UNV

Abstract:

Handy tips for choosing the right septum for your application and instrument. Includes an overview of common GC septum problems, such as coring and bleed. Guidelines help you avoid extraneous peaks and optimize your system’s performance.

Influencing Selectivity in LC-MS Peptides Analysis on the Raptor ARC-18 Column

Author: Sharon Lupo, Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: http://www.restek.com/Technical-Resources/Technical-Library/Pharmaceutical/pharma_PHAN2615-UNV

Abstract:

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 the stationary phase ligand 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.

Method Development and Column Selection: How the FluoroPhenyl Phase Provides the Power of HILIC and Reversed-Phase Modes in One Column

Author: Sharon Lupo, Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: http://www.restek.com/Technical-Resources/Technical-Library/General-Interest/gen_GNAR2613

Abstract:

Column selection is an important part of method development, as the quality of critical separations is determined in large part by the retention and selectivity of the analytical column. Although C18 columns are commonly employed, FluoroPhenyl columns provide an orthogonal alternative for method development because they incorporate multiple retention mechanisms and can be used in both reversed-phase (RP) and hydrophilic interaction liquid chromatography (HILIC) modes. This paper explores how FluoroPhenyl columns can be used to improve separations, especially for compounds that are difficult to analyze on a C18, such as basic analytes or small polar compounds.

Analysis of Synthetic Cannabinoids and Metabolites: Adding New Compounds to an Existing LC-MS/MS Method

Author: Sharon Lupo, Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: http://www.restek.com/Technical-Resources/Technical-Library/Foods-Flavors-Fragrances/fff_FFAN2614-UNV

Abstract:

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 allow new drugs to be added to an existing method, providing labs with an important vehicle for improving efficiency and productivity.

Rapid Analysis of C3 Epimers of 25-Hydroxyvitamin D in Serum by LC-MS/MS

Author: Shun-Hsin Liang, Frances Carroll

Restek Corporation

Published By: Restek Corporation

Year of Publication: 2017

Link: http://www.restek.com/Technical-Resources/Technical-Library/Clinical-Forensic-Toxicology/cft_CFAN2612-UNV

Abstract:

The C3 epimers of 25-hydroxyvitamin D have lower bioactivity than the primary metabolites and, unless they are chromatographically separated, can cause clinical vitamin D levels to be overestimated. Raptor FluoroPhenyl columns provide baseline resolution of all key compounds, and the method established here allows accurate quantification in a fast, 5-minute analysis time (7-minute total cycle time). This method is recommended for labs interested in reporting C3 epimer concentrations separately in order to obtain more accurate results for the clinical diagnosis of vitamin D status.