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.
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 cyclosporin A, tacrolimus, sirolimus, and everolimus in whole blood. The method pairs a single protein 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.
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 off of 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 than the metabolites are. 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.
The Raptor Biphenyl column is excellent for rapid and sensitive analysis of thyroid hormones. With the method described here, concentrations of thyroid hormones as low as 2 pg/mL (T3) or 5 pg/mL (T4 and rT3) can be determined with less than 3.5 minutes of total analysis time. The analytical method is thus applicable to the clinical analysis of free thyroid hormone at low pg/mL levels.
New Rxi-5Sil MS columns produce consistent results for amphetamine—even after 400 injections of derivatizing reagent—resulting in less time and money spent on column maintenance and replacement.
Rxi-5Sil MS columns produce excellent results for a number of forensic applications. The versatile selectivity separates a wide variety of compounds, which lets you keep analyzing samples instead of changing columns between methods.
Rtx-BAC Plus 1 and Rtx-BAC Plus 2 columns provide definitive data in a fast, 2-minute analysis, so you can be certain of your results, maximize sample throughput, and get accurate, reliable results quickly, which is is critical for analyzing blood alcohol concentration (BAC). (PDF - 963kB)
Rtx-BAC Plus 1 and Rtx-BAC Plus 2 columns provide definitive data in a fast, 2-minute analysis, so you can be certain of your results, maximize sample throughput, and get accurate, reliable results quickly, which is is critical for labs analyzing blood alcohol concentration (BAC). (PDF - 5471kB)
Filtering sample extracts with syringe filters will greatly extend the life of costly chromatographic columns and replacement parts, particularly for HPLC systems. This 2-page fact sheet includes helpful membrane, porosity, and size selection guides.
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)