Clinical, Forensic & Toxicology Solutions
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.
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.
A Rapid and Sensitive LC-MS/MS Method for the Analysis of Three Forms of Thyroid Hormones Using Raptor™ Biphenyl LC Columns
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.
4.5 Minute Analysis of Benzodiazepines in Urine and Whole Blood Using LC/MS/MS and an Ultra Biphenyl Column
Sample throughput for benzodiazepines in urine and whole blood can be increased by adopting this dilute-and-shoot LC/MS/MS method which uses an Ultra Biphenyl HPLC column. Partial validation data are presented in this application note.
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. (PDF - 1751kB)
New Rtx®-BAC Plus 1 and Rtx®-BAC Plus 2 columns provide definitive results quickly, so you can maximize sample throughput. These columns baseline separate all critical blood alcohol compounds, including ethanol, methanol, acetone, tert-butanol, acetaldehyde, isopropanol, and n-propanol, in less than 2 minutes. (PDF - 882kB)
New Rtx-BAC Plus 1 and Rtx-BAC Plus 2 Columns: Advanced Technology for Fast, Reliable Measurement of Alcohol in Blood
New Rtx-BAC Plus columns outperform other blood alcohol column pairs and ensure baseline separation of all critical compounds. These columns provide definitive data in a fast, 2-minute analysis, so you can be certain of your results and maximize sample throughput. (PDF - 940kB)
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. (PDF - 487kB)
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 - 5848kB)
Separating fat‐soluble vitamins and their metabolites by LC can be quite time consuming, taking up to 20 minutes or longer by some methods. However, the new Raptor™ ARC‐18 LC column can analyze these difficult compounds using reversed phase chromatography (RPC) in much less time, which helps increase sample throughput and overall lab productivity. This technical poster presents methodology that provides excellent quantitative results for metabolites 25‐hydroxyvitamin D2 and 25‐hydroxyvitamin D3 in analysis times of less than 2 minutes. Parent compounds vitamin D2 and vitamin D3 eluted in less than 4 minutes. (PDF - 337kB)