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LC-DAD separation of Kahweol and cafestol oleate and palmitate from coffee

<p>Analysis of diterpene esters (kahweol oleate -KO; cafestol oleate -CO; kahweol palmitate -KP; cafestol palmitate -CP) by LC DAD in standards and coffees.</p> <p><strong>Separation conditions:&nbsp;</strong></p> <p>Coffee brews were extracted using 5 mL of diethyl ether. The mixture was vortexed for 2 min, and after centrifugation, the upper phase was transferred to a clean test tube. Next, the aqueous solution was re-extracted using diethyl ether, and the combined ether phase was washed with 5mL of 2 M NaCl solution followed by centrifugation (4000 rpm, 10 min. Finally, the clean ether phase was dried under an azote stream. Samples were kept at &ndash;22&ordm;C until analysis using LC&ndash;DAD. Separation was achieved using a Purospher STAR LichroCART RP 18 end-capped (250 &times; 4 mm, 5 &micro;m) column attached. Before injection, the dried extract was dissolved in 2.5 mL of acetonitrile and filtered through 0.45 &micro;m filter membrane (PTFE, VWR, USA). Twenty microliters of sample were injected, and the separation was achieved using isocratic conditions for 35 min with the mobile phase made of acetonitrile/isopropanol (70:30, v/v) and pumped at 0.4 mL/min. A diode array detector, in the range of 200&ndash;400 nm, was used. After each run, the acquisition software exported data as a comma-separated-values format (EZChrom Elite 3.1.6).</p> <p>For the calibration curves, mixtures of the four diterpenes esters at similar concentrations were used in the range of 2 to 200 mg/L. Eight samples were prepared and run in duplicates</p> <p>&nbsp;</p> <p><strong>Files:&nbsp;</strong></p> <p><a href="https://zenodo.org/api/files/9c2c7a63-966d-4b4b-a1bf-5b8d8228ac48/FTIRATR_Pulse.mat">Data.mat</a>: Matlab structure with, as fields:<br> &nbsp; &nbsp; &nbsp;&lt;Time&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;: a 3751 length vector. Time axis in min<br> &nbsp; &nbsp; &nbsp;&lt;Wavelength&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;: a 201 length vector, Wavelength of detection<br> &nbsp; &nbsp; &nbsp;&lt;Names_calibration&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;: Name of the samples for calibrations<br> &nbsp; &nbsp; &nbsp;&lt;Data_calibration&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;: a 3751x201x16 matrix with in first dimension the retention time, in second dimension the wavelength for detection and third dimension the calibration samples.<br> &nbsp; &nbsp; &nbsp;&lt;Data_samples&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; : a 3751x201x4 matrix with in first dimension the retention time, in second dimension the wavelength for detection and third dimension the coffee samples.<br> &nbsp; &nbsp; &nbsp;&lt;Names_Samples&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;: Name of the samples<br> &nbsp; &nbsp; &nbsp;&lt;Concentrations_calibration&gt;: Table with the real concentration (mg/L) used in the standard&nbsp;samples.</p>