Quality Evaluation of a Herbal Prescription Through Quantification of 40 Components by HPLC–ESI–MS/MS
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The Kang-nao-shuai (KNS) capsule is a combined herbal prescription used in the treatment of insomnia, amnesia, neurasthenia, age-related dementia and brain injuries. Multiple constituents are considered to be responsible for the therapeutic effects of this herbal prescription. However, the quality control of the multicomponents is limited.To establish a liquid chromatography-electrospray ionisation-mass spectrometry method for the analysis of 40 constituents in KNS capsules.The optimal chromatographic conditions were achieved on an Agilent C₁₈-column with a gradient elution that consisted of methanol and 0.1% formic acid in water. The precursor and product ions of analytes were monitored on a hybrid quadrupole linear ion trap mass spectrometer in positive and negative mode respectively using multiple-reaction monitoring.A total of 40 constituents including organic acid, flavonoid, quinone, terpene, alkaloid and saponin were quantified, most of the 40 components were determined for the first time in the KNS capsule. A quantitative HPLC-ESI-MS/MS method allowing the quantification of 40 marker compounds was optimised and validated for linearity, precision, accuracy, stability, specificity and limits of detection and quantification. The method was successfully applied to analyse 10 batches of KNS capsule.The established method is simple and can be used as a tool for quality evaluation and control of this natural product.Keywords:
Gradient elution
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The water−gas−shift (WGS) reaction (CO + H2O ⇄ CO2 + H2) is investigated in connection to formic acid. Using NMR spectroscopy, the reversible decomposition pathways of formic acid to both sides of the WGS reaction are studied in hot water at 240−260 °C. This reversibility strongly suggests that formic acid exists as an intermediate in the WGS reaction, and it is indeed demonstrated that carbon monoxide is treated in hot water to produce formic acid. The present result enables us to generate and store hydrogen in the liquid form of formic acid and to transform formic acid to hydrogen in water by tuning the thermodynamic conditions.
Water-gas shift reaction
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This study documented the formaldehyde exposures of a group of veterinary medicine students. It also investigated the feasibility of biologically monitoring the exposures. The biological monitoring was based on the fact that the formaldehyde is metabolized in the body to formic acid, and may then be excreted in the urine. Therefore, exposures to formaldehyde could theoretically create a shift in the formic acid levels in the urine. Normal baseline levels of urinary formic acid were first established for each subject. The baselines of most students were quite variable. Very few exhibited a "tight variability" in their baseline. Next, three sets of pre- and post-exposure urine samples were taken. A series of paired t-tests were run on these "pre" and "post" sets. The results indicated that no significant formic acid shift was seen. A subset of the samples was "corrected" for specific gravity. However, this adjustment did not have an effect upon the relative formic acid levels. In addition, no significant formic acid shift was seen in the adjusted group. Exposure levels of the students were less than 0.5 ppm of formaldehyde. Therefore, the main conclusion of the study was that biological monitoring of formaldehyde exposures (via formic acid shifts) at these low levels was not a feasible technique.
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Abstract. Formic acid (HCOOH) is one of the most abundant carboxylic acids in the atmosphere. However, current photochemical models cannot fully explain observed concentrations and in particular secondary formation of formic acid across various environments. In this work, formic acid measurements made at an urban receptor site in June–July of 2010 during CalNex and a site in an oil and gas producing region in January–February of 2013 during UBWOS 2013 will be discussed. Although the VOC compositions differed dramatically at the two sites, measured formic acid concentrations were comparable: 2.3 ± 1.3 ppb in UBWOS 2013 and 2.0 ± 1.0 ppb in CalNex. We determine that concentrations of formic acid at both sites were dominated by secondary formation (> 8%). A constrained box model using the Master Chemical Mechanism (MCM v3.2) underestimates the measured formic acid concentrations drastically at both sites (by a factor of > 10). Inclusion of recent findings on additional precursors and formation pathways of formic acid in the box model increases modeled formic acid concentrations for UBWOS 2013 and CalNex by a factor of 6.4 and 4.5, respectively. A comparison of measured and modeled HCOOH/acetone ratios is used to evaluate the model performance for formic acid. We conclude that the modified chemical mechanism can explain 21 and 47% of secondary formation of formic acid in UBWOS 2013 and CalNex, respectively. The contributions from aqueous reactions in aerosol and heterogeneous reactions on aerosol surface to formic acid are estimated to be −7 and 0–6% in UBWOS 2013 and CalNex, respectively. We observe that air-snow exchange processes and morning fog events may also contribute to ambient formic acid concentrations during UBWOS 2013 (∼20% in total). In total, 50–57% in UBWOS 2013 and 48–53% in CalNex of secondary formation of formic acid remains unexplained. More work on formic acid formation pathways is needed to reduce the uncertainties in the sources and budget of formic acid and to narrow the gaps between measurements and model results.
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The electrospray ionisation (ESI) of selected coumarin derivatives and their subsequent fragmentation using an ion trap mass spectrometer have been investigated. Sequential product ion fragmentation experiments (MS(n)) were performed in order to elucidate the degradation pathways for these compounds. A comparison was also made between these ESI spectra and those obtained under electron impact (EI) conditions. The data presented in this paper provides useful information on the effect of different substituents on the ionisation/fragmentation processes and can be used in the characterisation of these compounds.
Fragmentation
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Abstract This Communication describes the use of a bench‐top ion trap mass spectrometer for the study of structurally diagnostic ion/molecule reactions. The power of the experiment is increased by the broad‐band ion‐isolation and tandem mass spectrometry capabilities of the ion trap which are used to isolate the reactant ion and study its reactions under controlled conditions. The availability of multiple‐stage mass spectrometry (MS n where n = number of stages) provides additional information on the nature of the productions. The compound to be ionized is conveniently introduced into the ion trap from aqueous solution using membrane introduction techniques while the neutral reagent is leaked into the trap through the calibration gas inlet. Polar Diels–Alder reactions of the [4 + 2 + ] type are investigated and comparisons are made between the reactions occurring in the ion trap and those in a pentaquadrupole mass spectrometer. Three‐stage tandem mass spectra (MS 3 ) are used to characterize the ion/molecule reaction products in the quadrupole ion trap.
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Top-down proteomics
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Direct hydrogenation of CO2 into formic acid is an atom-economic reaction, but it is thermodynamically limited, and the production of free formic acid is challenging. Herein, we report a protocol of CO2 hydrogenation to free formic acid over Pd/C in ionic liquid (e.g., 1-butyl-3-methylimidazolium acetate, [Bmim][OAc]) without base under mild conditions. Detailed study indicates that [Bmim][OAc] plays multiple roles in the reaction process with activating CO2, modifying the Pd nanoparticles to improve their activities, and stabilizing generated formic acid. This Pd/C-[Bmim][OAc] catalytic system is very effective for the production of free formic acid at 40 °C, affording a production rate of 233.5 mmol·g–1.h–1 and turnover number (TON) of 594, and the concentration of free formic acid in the reaction solution could reach up to 5.20 mmol/L.
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Abstract Following measurements in the winter of 2012, formic acid (HCOOH) and nitric acid (HNO 3 ) were measured using a chemical ionization mass spectrometer (CIMS) during the Summer Clean Air for London (ClearfLo) campaign in London, 2012. Consequently, the seasonal dependence of formic acid sources could be better understood. A mean formic acid concentration of 1.3 ppb and a maximum of 12.7 ppb was measured which is significantly greater than that measured during the winter campaign (0.63 ppb and 6.7 ppb, respectively). Daily calibrations of formic acid during the summer campaign gave sensitivities of 1.2 ion counts s −1 parts per trillion (ppt) by volume −1 and a limit of detection of 34 ppt. During the summer campaign, there was no correlation between formic acid and anthropogenic emissions such as NO x and CO or peaks associated with the rush hour as was identified in the winter. Rather, peaks in formic acid were observed that correlated with solar irradiance. Analysis using a photochemical trajectory model has been conducted to determine the source of this formic acid. The contribution of formic acid formation through ozonolysis of alkenes is important but the secondary production from biogenic VOCs could be the most dominant source of formic acid at this measurement site during the summer.
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