Browsing by Author "Pavon-Perez, Jessy"

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    Chemometric optimization of trypsin digestion method applying infrared, microwave and ultrasound energies for determination of caseins and ovalbumin in wines
    (2021) Pavon-Perez, Jessy; Henriquez-Aedo, Karem; Salazar, Ricardo; Herrero, Miguel; Aranda, Mario
    Caseins and ovalbumin are frequently used as wine fining agents to remove undesirable compounds like polymeric phenols. Their presence in wines is a subject of concern because may cause adverse effects on susceptible consumers, especially when their presence is not labeled. A key step for its determination is trypsin digestion, which is considered the bottleneck ofbottom-upapproach workflow because usually requires several hours. To reduce this time, the objective of this work was to carry out a chemometric optimization of trypsin digestion method applying infrared, microwave and ultrasound energies to determine caseins and ovalbumin in wines. The conditions of each accelerated digestion method were optimized using a Response Surface Methodology based on central composite design. The parameters optimized were digestion time and trypsin: protein ratio. The response variable evaluated was digestion yield, which was determined through the peak area of each protein transition determined by liquid chromatography-mass spectrometry. The most effective technique was microwave followed by ultrasound and infrared. Since optimal values of microwave and ultrasound-assisted digestion were the same, the later was chosen considering sample preparation and cost. Applying the proposed approach, a reduction ofca.140 and 240-fold on digestion time was achieved compared with optimized and non-optimized conventional methods, respectively. With this workflow, both proteins were digested in a single 3 min process allowing its detection by liquid chromatography-mass spectrometry at mu g L(-1)level, which isca.60 times lower than the current limit of 0.25 mg L-1.
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    LC-MS/MS METHOD FOR L-DOPA QUANTIFICATION IN DIFFERENT TISSUES OF VICIA FABA
    (2019) Pavon-Perez, Jessy; Oviedo, Claudia A.; Elso-Freudenberg, Mhartyn; Henriquez-Aedo, Karem; Aranda, Mario
    A rapid, sensitive, precise and accurate liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for levo 3,4-dihydroxyphenylalanine (L-DOPA) determination in Vicia faba during different growth stages. The method applied a simple sample preparation step followed by a chromatographic separation on a Kinetex XB Core-Shell C-18 (100 mm x 4.6 mm, 2.6 mu m) column, using a mixture of ultrapure pure water (A) with 0.5 % (v/v) formic acid and methanol (B) as mobile phase. Analysis of L-DOPA was carried out by MS/MS applying a Multiple Reaction Monitoring (MRM) method using the transition m/z 198 -> m/z 152. This LC-MS/MS method allowed a well-resolved detection of L-DOPA in ca. 2 min within 6 min run. Method was validated showing a linear range from 0.05 to 10 mg L-1 (R-2 = 0.99); repeatability showed RSD value of 1.40%. Recoveries ranged from 94.14 to 116.62% with RSD values <= 5.66% and detection and quantification limits were 0.01 and 0.05 mg L-1, respectively. Applying this validated method, L-DOPA was determined in Vicia faba samples to determined its tissue distribution. As expected, a broad range of L-DOPA content finding the lowest content in seeds (4.72 +/- 2.12 mg g(-1)) and the highest in sprouts (133.60 +/- 5.65 mg g(-1)).