Experimental and theoretical mass spectrometric quantification of diffusion parameters and 3D structural determination of ions of L-tryptophyl-l-tryptophan in electrospray ionization conditions in positive operation mode

Determination of oroxin A, oroxin B, oroxylin A, oroxyloside, chrysin, chrysin 7-O-beta-gentiobioside, and guaijaverin in mouse blood by UPLC-MS/MS and its application to pharmacokinetics

In this study, a UPLC-MS/MS method was developed to measure the concentrations of the flavonoids oroxin A, oroxin B, oroxylin A, oroxyloside, chrysin, chrysin 7-O-beta-gentiobioside, and guaijaverin in the blank mouse blood, and the method was then used in the measurement of the pharmacokinetics of the compounds in mice. Oroxin A, oroxin B, oroxylin A, oroxyloside, chrysin, chrysin 7-O-beta-gentiobioside, and guaijaverin were administered intravenously at a dose of 5 mg kg−1, and the mouse blood (20 μL) was withdrawn from the caudal vein 0.08333, 0.25, 0.5, 1, 2, 4, 6, 8, and 10 h after administration. The mobile phase used for chromatographic separation by gradient elution was composed of acetonitrile and water (0.1% formic acid). The analytes were detected by operating in electrospray ionization (ESI) positive-ion mode using multiple reactions monitoring (MRM). The intra-day and inter-day accuracy ranged from 86.2 to 109.3%, the intra-day precision was less than 14%, and the inter-day precision was less than 15%. The matrix effect ranged from 85.3 to 111.3%, and the recovery of the analytes after protein precipitation were all above 78.2%. This method had the advantages of high sensitivity, accuracy, and recovery, and it had excellent selectivity, which enabled it to be applied to measuring the pharmacokinetics of the analytes in mice.

A mass spectrometric stochastic dynamic diffusion approach to selective quantitative and 3D structural analyses of native cyclodextrins by electrospray ionization and atmospheric pressure chemical ionization methods

The paper addressed shortcoming with highly precise and selective 3D structural analysis of native cyclodextrins in mixture using ions observable at low m/z-region by ESI- and APCI-mass spectrometry. Because of, the quantitative and structural analyses of CDs, in general, are vexed by a set of complications. The study outlines our own stochastic dynamic approaches to the latter issues based on new model relations, quantifing the measurable MS outcome intensity. They introduce the so-called stochastic dynamic mass spectrometric diffusion "D_SD" parameter, exhibiting high accuracy, precision, sensitivity and selectivity, respectively. It is linearly connected with the so-called quantum chemical diffusion parameter "D_QC" according to Arrhenius's theory. The most important upshot is that statistical parameters r = 0.99₆₃₉-0.99₉₈₁ has been obtained correlating between D_SD and D_QC parameters. Therefore, we determine high accurately 3D molecular and electronic structures of analytes by mass spectrometry. Fragment peaks at m/z 313, 279, 272, 252, 231, 214, 198, 171, 158 and 141 are examined. Mixtures of CDs and monomeric and acyclic oligomer carbohydrates glucose (1), sucrose (2), raffinose (3), melezitose (4) and cellotriose (5) are also studied. Our method is able to account precisely for the effect of the temperature under ESI- and APCI-MS conditions, as well. Correlative analysess between D_SD parameters of ESI- and APCI-MS measurements under different temperatures is also shown. Chemometric tests are used. Another important results and conclusions, among others, to draw from this research are: (i) excellent linear correlation between D_SD and D_QC parameters of r = 0.99₆₃₆ is found looking at common ions at m/z 141, 158 and 171, belonging to 2-formyl-3,4-dihydroxy-pyranylium, 4,5,6-trihydroxy-6H-pyran-2-carbaldehyde and 3,4,5-trihydroxy-6-oxo-6H-pyran-2-ylmethylidyne-oxonium ions. Thus, we distinguish precisely between the last structure and 3-formyl-4,5-dihydroxy-2,7-dioxa-8-oxonia-bicyclo[4.2.0]octa-1(8),3,5-triene cation. In the case of ion at m/z 141 subtle electronic effects are distinguished between the mentioned structure and the charged 3,4-dihydroxy-6H-pyran-2-carbaldehyde one. The method determines precisely very similar structurally poly-OH-substituted derivatives. Because of, (ii) absolute reproducibility (r = 1) of D_SD parameters of ESI-MS spectra is obtained studying the shown in point (i) MS peaks of β-CD between j^th and j^th numbers of experiments. The statistical equation is Dⁱ_SD = (0.51 ± 3.1.10^-5) × D^j_SD; (iii) the APCI- and ESI-MS provide identical results studying common MS ions of CDs and the correlation between D^APCI_SD and D^ESI_SD parameters excludes from error, due to, experiment; and (iv) The correlation between theory and experiment accounting for the factor temperature within our model equations shows r = 0.98₂₈ looking at the MS peaks at m/z 313 280, 279, 274 and 252, respectively. The effect of the temperature under both ESI- and APCI-MS conditions on the 3D molecular and electronic structures of CDs is precisely studied, respectively.