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Displaying 1-5 of 6 results for Tag: Quantitation

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Rapid Analysis of 25-Hydroxyvitamin D3, epi-25-Hydroxyvitamin D3, and 25-Hydroxyvitamin D2 in Plasma for Clinical Research Using High-Resolution Mass Spectrometry

Instrument Type: LCMSMS

Chromatographic separation is required for simultaneous analysis of 25-hydroxyvitamin D3 (25OHD3) and its epimeric form 3-epi-25-hydroxyvitamin D3 (epi-25OHD3) in a liquid chromatography-mass spectrometry (LC-MS) method because both compounds have the same molecular formulas and the same fragmentation spectra. We developed an LC method that provides baseline separation between the two isobaric compounds. We coupled this chromatographic method to an MS method, which collects high-resolution MS/MS spectra for compound identification and quantitation.

Quantitation of Seven Designer Cathinones in Urine Using Q Exactive Mass Spectrometer

Instrument Type: LCMSMS

Substituted cathinones, or “Bath Salts,” have become the latest abused designer drugs. Based on cathinone, a substance found in the African Catha edulis (khat) plant, substituted cathinones are stimulants with amphetamine- and cocaine-like effects. We describe an HPLC-MS method for the forensic toxicological analysis of the three Schedule I cathinones: MDPV, methylone and mephedrone, as well as other substituted cathinones: methedrone, ethylone, butylone and naphyrone in urine with limits of quantitation (LOQs) of 0.5 ng/mL. For forensic use only.

High-Throughput LC-MS/MS Quantification of Pregnenolone in Human Blood Serum for Clinical Research Purposes

Instrument Type: LCMSMS

Pregnenolone is a biosynthetic precursor to other steroids such as corticosteroids, androgens, and estrogens. Researchers investigating conversion to progesterone or to 17-OH-pregnenolone need to quantify pregnenolone within an analytical range of 0.3 to 1.5 nmol/L in blood serum. Since pregnenolone does not ionize well, derivatization with hydroxyl amine was necessary to reliably achieve the desired detection. We pursued this strategy along with liquid-liquid extraction to develop a simple sample preparation that would provide robust and sensitive quantitation of pregnenolone using ESI.

Variable Data-Independent Acquisition (vDIA) Delivers High Selectivity and Sensitivity in Combined Targeted and Untargeted Analyses for Small Molecules

Instrument Type: LCMSMS

Forty-four multi-class veterinary drugs of known concentrations were employed to demonstrate how the use of a generic variable data-independent acquisition (vDIA) method with wide MS/MS precursor isolation windows achieves sensitivity and selectivity comparable to data-dependent MS2 acquisition (using narrow isolation windows) in quantitative and qualitative small molecule applications. In addition, a full record of MS and MS/MS data for the measured sample fit for non-targeted and unknown screening purposes is delivered. vDIA is not available in the United States of America

Zero Cross-talk on the TSQ Quantum

Instrument Type: LCMSMS

We illustrate the absence of cross-talk in a screening assay for 88 different pesticides with closely eluting multi-component compounds belonging to the same chemical classes.