Quick and simultaneous determination of caffeine and taurine in beverages using UPLC-ESI-MS

A rapid UPLC-ESI-MS method was developed for simultaneous determination of caffeine and taurine in beverages (energy drinks and soft drinks). The molecular ions of caffeine and taurine were identified in single ion recording mode at m/z 194.98 and 125.86, respectively. The mass spectrometer parameters were optimized as: capillary voltage 3.0 kV, cone voltage 35 V, extractor 3 V, RF Lens 0.1 V, source temperature 150 °C, desolvation temperature 350 °C, nitrogen 600 L/h, LMR1 7.9, HMR1 15.2, IE1 0.30. The mobile phase comprising methanol (0.1% formic acid) (A) and water (5 mM ammonium acetate) (B) was used in gradient mode. The mobile phase components A and B were pumped in 80:20 (v:v) ratio from 0-0.44 min, and then 100% of component A was pumped between 0.45-0.68 min, and at 0.69 min the composition was returned to 80:20 (v:v) ratio of A and B till 2.0 min. Caffeine and taurine were eluted at 0.46 and 0.43 min, respectively. The samples of energy drinks and soft drinks were diluted in a solvent system comprising methanol and water in 80:20 (v:v) ratio. Our investigations showed that soft drinks SD1 and SD2 have 88.8±4.2% and 110.7±3.6% (w:w) caffeine of their labeled claim. The caffeine content in energy drink brands ED1, ED2, ED3, and ED4 was 76.9±2.5, 65.6±3.4, 88.1±12.6, and 89.1±2.8% (w:w) of labeled claims, respectively. While taurine content in ED1, ED2, ED3, and ED4 was 86.5±8.4, 81.3±27.5, 101.9±4.8, and 97.1±0.3% (w:w) of labeled claim, respectively.

AQbD-Oriented UHPLC/MS/MS Method Development for Glycopeptides Assessment in Pharmaceutical Forms

Vancomycin and teicoplanin are glycopeptide antibacterials that inhibit the bacteria cell wall synthesis showing activity against gram-positive bacteria. Development of the sensitive method is of great importance for quality control of these drugs that are fermentation products. Modification of the fermentation conditions could cause the differences in the relative amount of the total substance or component, as it is the case with teicoplanin. The main objective of this study was development of the sensitive and effective ultra high performance liquid chromatography - tandem mass sprectrometry (UHPLC-MS/MS) method for simultaneous quantification of vancomycin, all six subcomponents of teicoplanin, and its pharmacopoeial impurity A in pharmaceutical forms. The scientific-based Quality by Design approach was implemented in the MS and UHPLC method development. Detection and quantification of analytes were carried out in positive electrospray ion mode by multiple reaction monitoring. Capillary voltage, cone voltage and collision energy were optimized by implementing experimental design methodology and optimal values for each fragment ion were obtained by performing experiments according to ‘Rechtschaffen’ design matrix. An ACQUITY CSH Phenyl-hexyl (2.1 × 50 mm, particle size 1.7 μm) column was chosen for the separation under the gradient elution mode with the mobile phase consisted of 0.1% formic acid in water (mobile phase A) and acetonitrile (mobile phase B). Optimal gradient elution parameters were achieved by applying ‘Rechtschaffen’ design too. Method operable design regions were constructed for investigated MS and chromatographic parameters. The method was fully validated, and its applicability was confirmed throughout the ability to follow the behavior of vancomycin and teicoplanin under stress conditions.

A Validated Chiral-RP-UPLC-MS/MS Method for the Enantiomeric Detection of Rivaroxaban In vitro

Background: Rivaroxaban is the first oral, selective direct FXa inhibitor with rapid onset of action and its biological toxicity may be related to the enantiomer. </P><P> Objective: The aim of the current study was to develop and validate a precise, accurate, and specific direct Chiral-RP-UPLC-MS/MS method for the enantiomeric separation and detection of rivaroxaban and its enantiomer. Methods: The present study screened various conditions of chromatographic and mass spectra, including chromatographic column model, flow velocity, phase ratio, column temperature, and collision energy, parent/daughter ion pairs, etc. Try to match the chromatographic and mass spectrometric conditions. Results: Good Rs (Rs>2.5) was achieved on a Chiralpak IC column (4.6 × 250 mm, 5µm) using H2O:acetonitrile (10:90) as mobile phase at 25 oC column temperature. The rate of flow was set at 0.4 ml/min and enantiomers were detected by triple-quadruple tandem mass spectrometry using positive electrospray ionization (ESI) with MRM transitions of m/z 436.07>144.95. The cone voltage and collision energy were kept at 48 V and 28 eV, respectively. The limit of detection and quantification of (S)- rivaroxaban were 0.39 and 1.30 ng/ml, respectively. This method was validated and found to be selective, precise, accurate, linear and robust for the quantitative determination of chiral impurities. It is also a good application for the blood samples analysis in vitro. Conclusion: Chiral-RP-UPLC-MS/MS method has entirely detected (S)-rivaroxaban and its (R)- enantiomer in very low concentration and complex matrix directly, especially for blood samples.

Binuclear copper complexes with non-steroidal anti-inflammatory drugs as studied by electrospray ionization mass spectrometry

The solutions containing one of the copper salts (CuCl2, Cu(ClO4)2, Cu(NO3)2, and CuSO4) and one of the non-steroidal anti-inflammatory drugs (NSAIDs, ibuprofen, ketoprofen or naproxen) were analyzed by electrospray ionization mass spectrometry. Three of the salts, namely CuCl2, Cu(ClO4)2 and Cu(NO3)2, yielded binuclear complexes of drug:metal stoichiometry 1:2. Existence of the complexes of such stoichiometry has not been earlier observed. For copper(II) chloride the complexes (ions of the type [M-HCOOH+Cu2Cl]+ and [M+Cu2Cl]+, M stands for the drug molecule) were formed in the gas phase. When copper(II) perchlorate or copper(II) nitrate was used, the observed binuclear copper complexes (ions of the type [M-H+Cu2(ClO4)2+CH3OH]+, [M-H+Cu2(ClO4)2]+ and [M-H+Cu2(NO3)2+CH3OH]+, [M-H+Cu2(NO3)2]+) were observed at low cone voltage, thus these complexes must have already existed in the solution analysed. Therefore, such complexes may also exist under physiological conditions.

Collision-Induced Dissociation of Imidazolium-Based Zwitterionic Liquids

Fragmentation pathways of some imidazolium based zwitterionic liquids—3-(3-alkyl-1-imidazolio)-propane sulfonates and 3-(2-methyl-3-alkyl-1-imidazolio)-propane sulfonates—have been studied by tandem electrospray mass spectrometry and collision-induced dissociation. The relative abundances of the lowest energy fragment ions depend on the length of the alkyl chain at the IIN of the imidazolium ring and the cone voltage. The first fragment ions originate from the scission of Cnon aromatic–N bond of compounds investigated, but with increasing collision energy, scission of C–C bonds occurs. Aggregates of the general formula [(M + H) x + (M) y]+ ( x;y = 1–2) formed. Methyl substituted zwitterionic liquids show higher molecular stability than 3-(3-alkyl-1-imidazolio)-propane sulfonates.

Collision Energy and Cone Voltage Optimisation for Glycopeptide Analysis

Instrument tuning commonly used for peptide analysis and for proteomics causes a high degree of fragmentation for glycopeptides. This results in a strongly biased glycosylation pattern. To obtain correct results for glycopeptides, both the cone voltage and the collision energy has to be reduced significantly. A suitable standard for tuning the instrument for glycopeptide analysis is aspartic acid (which fragments under similar conditions as glycopeptides); while low mass sugar fragments (for example, at 657.3 Da) are good indicators for the presence/absence of glycopeptide fragmentation.

Structural Characterization and Differentiation of Isomeric ω-Bromoalkoxy Derivatives of (E)-Chalcone by Means of Mass Spectrometry

Mass spectrometry with electron ionization and electrospray ionization have been applied to characterize and differentiate the isomeric ortho-, meta- or para-( E)-bromoalkyloxychalcones 1–15. The difference in the values of μ1–μ5 (i.e. the ratio of abundances of the selected fragment ions to those of the molecular ions) in the series of isomeric chalcones studied and the so-called “in-source” fragmentation induced by increasing cone voltage have been found to be important and reliable indicators differentiating the isomers studied.

Retinal bipolar cells: Temporal filtering of signals from cone photoreceptors

The temporal dynamics of the response of neurons in the outer retina were investigated by intracellular recording from cones, bipolar, and horizontal cells in the intact, light-adapted retina of the tiger salamander (Ambystoma tigrinum), with special emphasis on comparing the two major classes of bipolars cells, the ON depolarizing bipolars (Bd) and the OFF hyperpolarizing bipolars (Bh). Transfer functions were computed from impulse responses evoked by a brief light flash on a steady background of 20 cd/m2. Phase delays ranged from about 89 ms for cones to 170 ms for Bd cells, yielding delays relative to that of cones of about 49 ms for Bh cells and 81 ms for Bd cells. The difference between Bd and Bh cells, which may be due to a delay introduced by the second messenger G-protein pathway unique to Bd cells, was further quantified by latency measurements and responses to white noise. The amplitude transfer functions of the outer retinal neurons varied with light adaptation in qualitative agreement with results for other vertebrates and human vision. The transfer functions at 20 cd/m2 were predominantly low pass with 10-fold attenuation at about 13, 14, 9.1, and 7.7 Hz for cones, horizontal, Bh, and Bd cells, respectively. The transfer function from the cone voltage to the bipolar voltage response, as computed from the above measurements, was low pass and approximated by a cascade of three low pass RC filters (“leaky integrators”). These results for cone→bipolar transmission are surprisingly similar to recent results for rod→bipolar transmission in salamander slice preparations. These and other findings suggest that the rate of vesicle replenishment rather than the rate of release may be a common factor shaping synaptic signal transmission from rods and cones to bipolar cells.

Interactions of Nucleobases with Alkali Earth Metal Cations—Electrospray Ionization Mass Spectrometric Study

Interactions of nucleobases with alkali earth metal cations have been studied by electrospray ionization mass spectrometry (ESI-MS). Nucleobases containing at least one oxygen atom form stable complexes with alkali earth metal cations. This phenomenon can be explained on the grounds of the well known theory of hard and soft acids and bases. Uracil and thymine make complexes only when in their deprotonoted forms. The cations of great radii (Sr2+, Ba2+) are more prone to form complexes of stoichiometry 1:1 with uracil and thymine than the cations of small radii (Mg2+, Ca2+). On the other hand, Mg2+ forms complexes of stoichiometry 2:1 and 3:2 with uracil and thymine. Gas-phase stabilities of the 1:1 complexes are higher for the cations of small radii, in contrast to the solution stabilities. For cytosine and 9-methylhypoxantine the 1:1 complexes of their deprotonated forms are observed at higher cone voltage as a result of HCl molecule loss from the complexes containing the counter ion (Cl−). In solution, more stable complexes are formed with metal cations of low radii. Gas-phase stability of the complexes formed by deprotonated 9-methylhypoxantine increases with increasing metal cation radius.