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.
High-Quality Analysis of Pesticides in Cannabis Using QuEChERS, Cartridge SPE Cleanup, and GCxGC-TOFMS
As medical marijuana is more frequently prescribed, patient safety must be ensured. Pesticide residue testing is an important part of assuring safe product is dispensed, but analysis can be extremely challenging due to matrix complexity. The use of QuEChERS, cartridge SPE cleanup, and GCxGC-TOFMS as presented here produces high-quality quantitative data for this difficult analysis.
Raptor LC columns combine the speed of superficially porous particles (i.e., SPP or “core-shell”) with the resolution of highly selective USLC technology. Featuring Restek's most popular LC stationary phase, the rugged Raptor Biphenyl is extremely useful for fast separations in bioanalytical testing applications like drug and metabolite analyses, especially those that require a mass spectrometer (MS). (PDF - 6071kB)
When we engineered our superficially porous particle (SPP or "core-shell") Raptor LC columns, we developed the bonding chemistries that are best suited to both the SPP construction and our highly selective USLC phases. But we didn't stop here. Take a closer look at a new species as we dissect the upgraded hardware and new, proprietary packing techniques behind Raptor LC columns and Raptor EXP guard columns. (PDF - 1725kB)
Characterizing Cellular Fatty Acid Methyl Ester (FAME) Profiles to Identify Bacteria Using Gas Chromatography
Dr. Radomír Čabala, Head of the Toxicology Department at the General University Hospital in Prague, presents work on the potential utility of GC-TOFMS analysis of cellular fatty acid methyl esters (FAMEs) in identifying clinically relevant bacteria.
Unlike C18 columns, Ultra IBD (intrinsically base deactivated) columns can interact in normal phase mode with analytes that possess charged functional groups, providing greater versatility for LC-MS analyses. Excellent peak shape in either normal phase mode or reversed phase mode increases sensitivity and improves quantification. The 4-page note shows example analyses of penicillins and cephalosporins. (PDF - 0kB)
Analyze volatile compounds and polar analytes with greater confidence using Rxi-624Sil MS columns. Optimized selectivity, higher inertness, and lower bleed result in reliable separations and accurate, trace-level determinations. Includes environmental and pharmaceutical applications. (PDF - 0kB)
Not all column deactivations are appropriate for analyzing basic compounds. Here, we demonstrate the effect of column inertness on peak shape and discuss its role in improving method accuracy, sensitivity, and development time. (PDF - 0kB)
Two options for the analysis of PGIs in API have been developed by Merck and Restek to meet different laboratory needs. The first option is a fast method for the analysis of sulfonate esters on the Rxi-5Sil MS column. The second option is a comprehensive method for the analysis of both sulfonate esters and alkyl halides on the Rtx-200 column. Both methods require very little sample preparation, which helps increase laboratory productivity.
Analyzing basic compounds can be somewhat troublesome on traditional alkyl stationary phases, namely conventional C18 columns. This is largely due to the interaction of analyte molecules with silanol groups present on the silica surface. To better understand the workings of silanol interactions, it is important to consider the composition of the support material. Silica is the most commonly used support in the production of HPLC columns, mainly because it is well-suited to high-pressure chromatographic separations, giving high efficiencies and good reproducibility. Silica offers bed and pressure stability and is highly porous, which ultimately gives rise to its large surface area, increased bonding capacity and high peak efficiencies. Silica also possesses widely-studied and effective bonding chemistries, making possible diverse analyte selectivities through a wide variety of bonded stationary phases.
To make column selection for residual solvents easy, Restek has benchmarked the ICH Class 1, 2 and 3 residual solvents on our most popular OVI columns.
Non-steroidal anti-inflammatory drugs (NSAIDs) are typically separated on C18 phases. Separations on our Allure Biphenyl HPLC column are based on pi-pi interactions, resulting in optimized retention and selectivity. Increased retention requires higher organic content in the mobile phase, increasing desolvation efficiency in LC/MS. Simple mobile phase changes enhance selectivity, making this column a great alternative to conventional phenyl phase columns, especially in method development.
Among hydroxybenzoic acids, hydroxyl groups on the benzene ring vary by position and number, creating differences in overall polarity and solubility. The unique bonding chemistry of the Ultra Aqueous C18 phase assures high resolving power, the best separations across a broad range of analyte polarity, and compatibility with 100% aqueous mobile phases.
An Rxi-5ms column and a wool-packed inlet liner provide the stability and inertness needed for these basic, active analytes. Chromatography from a six-replicate system suitability analysis was well within normal acceptance criteria. USP tailing factors were approximately 1.00 for all analytes; retention times and area responses were very stable.
Single-injection, dual-column detection/confirmation assay is feasible for regulated solvents in pharmaceutical products, but no temperature program provides sufficient resolution on both columns. Using a Restek G43/G16 column pair and independent temperature programs in a Gerstel MACH column heating system, we analyzed and confirmed 23 Class 2 solvents in 8 minutes.