Multiple Reaction Monitoring Scan Mode Research Articles

LIQUID CHROMATOGRAPHY/POSITIVE-ION ELECTROSPRAY TANDEM MASS SPECTROMETRY ASSAY FOR NISOLDIPINE IN HUMAN PLASMA AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

A rapid, sensitive, and specific method was developed for the identification and quantitation of the calcium antagonist nisoldipine in human plasma by liquid chromatography coupled with tandem mass spectrometry using nimodipine as an internal standard. Nisoldipine was extracted from human plasma (0.2 mL) by a liquid/liquid procedure using diethyl ether as the eluent. The mass spectrometer was operated in the multiple reaction-monitoring scan mode using an electrospray ionization source. The analyte and internal standard could be separated in 2 min on a C18 analytical column with a mobile phase of acetonitrile:water (66:34, v/v) at a flow rate of 0.4 mL · min−1. The calibration curve of nisoldipine in human plasma was linear over the range from 0.1 to 30 ng · mL−1 (r2 ≥ 0.9994). The precision, determined as the relative standard deviation of replicate quality controls, was 9.35% (0.2 ng · mL−1), 11.61% (2.0 ng · mL−1), and 4.68% (20 ng · mL−1). This method was successfully applied to pharmacokinetic studies and determination of nisoldipine concentration in vivo.

Methyldibenzothiophene isomer ratio in crude oils: Gas chromatography tandem mass spectrometry analysis

The quantification of Methyldibenzothiophene isomers (MDBTs) is used in the geochemical characterization of crude oils. The relative ratio of these isomers can give useful information about the nature and the maturity of the source rock. This paper describes a novel analytical technique for the quantitative determination of MDBTs through triple quadrupole tandem mass spectrometry (GC–MS/MS). Through the multiple reaction monitoring (MRM) scan mode, it was possible to reach high selectivity for the MDBTs and their quantification was obtained without preliminary fractionation of the crude oil. In order to reduce the carryover of high boiling components, a recently developed backflush system in the GC program was applied. This novel protocol has been tested on sixteen samples of crude oil from different oil fields around the world. It was concluded to be more reliable than previously reported analytical methods based on selected ion monitoring (SIM) scan mode.

Screen and confirmation of PEG‐epoetin β in equine plasma

Methods have been developed to screen for and confirm darbepoetin alfa, recombinant human EPO, and methoxy polyethylene glycol-epoetin β (PEG-epoetin β) in horse plasma. All three methods screen samples with an enzyme-linked immunosorbent assay (ELISA) and confirm by liquid chromatography-tandem mass spectrometry (LC-MS/MS). This report focuses on PEG-epoetin β. The ELISA assay was able to detect PEG-epoetin β at 0.02 ng/mL in 50 µL of horse plasma. Many samples had high background levels of immunoreactivity; however, introducing polyethylene glycol 6000 (PEG 6000) into the samples before the ELISA assay removed the high background and increased the apparent concentrations of PEG-epoetin β. In samples collected following the administration of 100 µg of PEG-epoetin β by the intravenous (IV), intramuscular (IM) and subcutaneous (SC) routes, PEG-epoetin β was detectable up to 72, 144, and 120 h, respectively. The samples were prepared for LC-MS/MS analysis by extraction with anti-rHuEPO-antibodies-coated Dynabeads followed by digestion with trypsin. The LC-MS/MS confirmation method used the multiple reaction monitoring (MRM) scan mode to monitor four precursor-product ion transitions of the EPO-derived peptide T₆. All four transitions of T₆ were detectable with S/N > 3. The limit of confirmation for PEG-epoetin β was 1.0 ng/mL in 2 mL of horse plasma. The method successfully confirmed the presence of PEG-epoetin β in a sample collected from a Mircera®-treated horse. Compared to PEG-epoetin β, better sensitivity was achieved for darbepoetin alfa and recombinant human EPO. Darbepoetin alfa was detected in horse plasma four days after IM administration of 100 µg.

Determination of imidacloprid in paddy water and soil by liquid chromatography electrospray ionization-tandem mass spectrometry

A method for the determination of imidacloprid in paddy water and soil was developed using liquid chromatography electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). Separation of imidacloprid was carried out on a Shimadzu C18 column (150 mm × 4.6 mm, 4.6 μm) with an acetonitrile-water (50: 50, v/v) mobile phase containing 0.1% of acetic acid. The flow rate was 0.3 mL/min in isocratic mode. The product ion at 209 m/z was selected for quantification in multiple-reaction monitoring scan mode. Imidacloprid residues in soil were extracted by a solid-liquid extraction method with acetonitrile. Water samples were filtered and directly injected for analysis without extraction. Detection limits of 0.5 μg/kg and 0.3 μg/L were achieved for soil and water samples, respectively. The method had recoveries of 90 ± 2% (n = 4) for soil samples and 100 ± 2% (n = 4) for water samples. A linear relationship was observed throughout the investigated range of concentrations (1–200 μg/L), with the correlation coefficients ranging from 0.999 to 1.000.

Lack of specificity for the analysis of raltegravir using online sample clean-up liquid chromatography–electrospray tandem mass spectrometry

Background Raltegravir is the first antiretroviral agent to target the human immunodeficiency virus-1 (HIV-1) integrase. It is indicated, in association with other antiretrovirals, in the treatment of acquired immunodeficiency syndrome (AIDS) in antiretroviral treatment-experienced adult patients with viral resistance. To evaluate the feasibility of raltegravir therapeutic drug monitoring, we developed a rapid and specific analytical method for the quantification of raltegravir in human plasma by online sample clean-up liquid chromatography–tandem mass spectrometry (LC–MS/MS). Methods After protein precipitation (with 100 μL of acetonitrile/methanol (50/50)) of 25 μL of plasma, fast online matrix-clean-up was performed using a column switching program. The chromatographic step was optimized to separate raltegravir and its glucuronide metabolite (G-raltegravir). Multiple reaction monitoring (MRM) was used for detection of raltegravir and G-raltegravir. In the absence of G-raltegravir standard, G-raltegravir identification was confirmed by β-glucuronidase pre-treatment. Results A total analysis of 3.8 min was needed to separate raltegravir to G-raltegravir. The method was linear between 10 and 3000 ng/mL for raltegravir. Analytical recovery was 94 ± 1%. Variation coefficients ranged between 5% and 8.4%. Pre-treatment of plasma from a patient under raltegravir treatment with β-glucuronidase suppressed G-raltegravir peak. Conclusion We describe a fast online LC–MS/MS assay that is valid and reliable for the quantification of raltegravir, despite the lack of specificity that could occur in MRM scanning mode experiments.

Systematic screening and characterization of flavonoid glycosides in Carthamus tinctorius L. by liquid chromatography/UV diode-array detection/electrospray ionization tandem mass spectrometry

The traditional Chinese medicine (TCM) is a complex system, which always consists of numerous compounds with significant difference in the content and physical and chemical properties. In this paper, a screening method based on target molecular weights was developed to characterize the flavonoid glycosides in the flower of Carthamus tinctorius L. The screening tables of aglycone and glycan were designed, respectively, in order to select and combine freely. The multiple reaction monitoring (MRM) scan mode with higher sensitivity and selectivity was adopted in the screening, which benefit the characterization for the minor components. Seventy-seven flavonoid glycosides were screened out finally, and their structures were characterized by tandem mass spectrometric method in both positive and negative ion modes. The glycosylation mode, aglycone, sequence and/or the interglycosidic linkages of the glycan portion and glycosylation position were elucidated by the fragmentation rule in the MS. Numerous compounds screened out with this method showed the structure variety in secondary plant metabolites, and the purposeful screening systemically and subsequent structure characterization offered more information about the chemical constitutions of TCM.

Validated LC–MS–MS method for determination of m-nisoldipine polymorphs in rat plasma and its application to pharmacokinetic studies

A sensitive and specific liquid chromatography-tandem mass spectrometric (LC-MS-MS) method has been developed to determine m-nisoldipine in rat plasma. Sample was pretreated by a single-step protein precipitation with acetonitrile, in contrast to the liquid-liquid procedure frequently used for the extraction of 1,4-dihydropyridines from biologic samples. Separation of analyte and internal standard (I.S.) was performed on a Symmetry RP-C(18) analytic column (50 mm x 4.6 mm, 3.5 microm) with a mobile phase consisting of acetonitrile-water (80:20, v/v) at a flow rate of 0.5 ml/min. The API 4000 triple quadrupole mass spectrometer was operated in multiple reaction monitoring (MRM) scan mode using TurboIonSpray ionization (ESI) source. The method was sensitive with a lower limit of quantification (LLOQ) of 0.2 ng/mL, with good linearity (r>or=0.9982) over the linear range of 0.2-20 ng/mL. All the validation data, such as accuracy, precision, and inter-day repeatability, were within the required limits. The method was successfully applied to pharmacokinetic and relative bioavailability studies of m-nisoldipine polymorphs in rats.

Determination of glucosinolate profiles in Chinese vegetables by precursor ion scan and multiple reaction monitoring scan mode (LC-MS/MS)

Liquid chromatography-electrospray ionization (ESI) mass spectrometry was used to describe the glucosinolate (GSL) profiles in three Chinese vegetables. The strategy was based on first screening for possible glucosinolates via precursor ion scan mode (PreIS). Further validating was done using the multiple reaction monitoring scan mode (MRM). The obtained fragment ions [S=C=NOH]− for m/z 75 and [SO4H]− for m/z 97 were used in both scan modes to reveal the masses of the GSL precursor ions [M-H]− which were further validated by the mostly known chromatographic behavior of the resulting intact GSL. The feasibility of the strategy was first demonstrated using crude extracts of broccoli. The tandem mass spectrometric experiments in negative ion ESI proved to be sensitive and selective enough to rapidly examine the GSL profiles even of crude plant extracts. The results adequately characterize the target differences between various GSL distributions in vegetables induced by treatment of methyl jasmonate.

Determination of in vitro formed DNA adducts of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine using capillary liquid chromatography/electrospray ionization/tandem mass spectrometry.

On-line reversed-phase capillary liquid chromatography/tandem mass spectrometry with electrospray ionization was used for the detection of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) adducts of DNA and compared to analysis by 32P-postlabeling. Structural information was obtained on low nanogram levels of a synthetic N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP) standard using collision-induced dissociation, and low picogram level detection was achieved for the targeted dG-C8-PhIP adduct using the selective multiple reaction monitoring scanning mode. The method was applied to the analysis of an in vitro reaction mixture identifying the dG-C8-PhIP adduct and providing evidence for the presence of two additional PhIP-modified deoxyguanosine adducts. The results were in qualitative agreement with those obtained by the 32P-postlabeling method. In addition, the mass spectrometric results revealed the occurrence of an unexpected product in the in vitro reaction mixture presumably resulting from cleavage through the guanine base.