vitamin c determination in various fruit juices over time andrew mullenax sam yatzkan
TRANSCRIPT
Procedure
• Samples diluted– 1:10 (v/v)
• Room Temperature
• Half Opened, Half Closed
• Vacuum Filtered-Samples with visible solids
Ascorbic Acid Standards
• 5, 10, 20, 30ppm
• Spiked Samples
• Characterized Wavelength: 262nm
• HPLC: Retention Time of ~1.6 minutes– Solvent Mixture of .50mL/min degassed H2O and Methanol
• LC/MS: Retention Time of ~1.6 minutes– Solvent Mixture of .75mL/min degassed Methanol and .25mL/min
degassed H2O
Data – UV-VisSamples Day 1 Characterized
WavelengthDay 2 Characterized
Wavelength (nm)Day 3 Characterized
Wavelength (nm)Day 4 Characterized
Wavelength (nm)
Cran-Apple Juice Closed 255 257 251
Pineapple Juice Closed 276 278 274
White Grapefruit Closed 301 316 298
Lemonade Closed 227 228 226
Cran-Apple Juice Opened 252 253 250
Pineapple Juice Opened 280 284 307
White Grapefruit Opened 200 331
Lemonade Opened 232 281
HPLC Calibration Curve
0 5 10 15 20 25 30 350
200000
400000
600000
800000
1000000
1200000
1400000
1600000
f(x) = 40878.8813559322 x + 78171.6779661018R² = 0.986656891788446
Concentration v. Area
Concentration (ppm)
Area
Data - HPLCSamples Day 1 Concentration (ppm) Day 2 Concentration (ppm) Day 3 Concentration (ppm) Day 4 Concentration (ppm)
Cran-Apple Juice Closed 423.0 1094.0 1117.0 1249.0
Pineapple Juice Closed 1101.0 940.0 1171.0 1073.0
White Grapefruit Closed 353.0 354.0 67.0 99.0
Lemonade Closed 69.0 183.0 163.0 262.0
Cran-Apple Juice Opened 1160.0 873.0 781.0 1231.0
Pineapple Juice Opened 1296.0 922.0 563.0 460.0
White Grapefruit Opened 534.0 178.4 64.0
Lemonade Opened 35.0 230.0 36.0
LC/MS Calibration Curve
0 5 10 15 20 25 30 350
5
10
15
20
25
f(x) = 0.713694915254237 x − 0.872542372881354R² = 0.958536471126957
Concentration v. % Area
Concentration (ppm)
Area
(%)
Data – LC/MSSamples Day 1 Concentration
(ppm)Day 2 Concentration
(ppm)Day 3 Concentration
(ppm)Day 4 Concentration
(ppm)
Pineapple Juice Closed 264.0 220.2 30.7
Lemonade Closed 266.5 291.1 1080.2
Cran-Apple Closed 733.3 126.3 291.9
White Grapefruit Closed 699.5 640.3 246.0
Pineapple Juice Opened 542.2 30.7 299.5
Lemonade Opened 300.9 161.1 535.2
Cran-Apple Juice Opened 348.7 203.8 73.5 446.4
White Grapefruit Opened 924.4 1268.3 307.2
Conclusion
• Results not very reliable since we had varying retention times
• Did not get very good separation in chromatographs of the samples
• Too difficult to tell whether or not vitamin c concentration actually decreased over time
Improvements To Be Made
• Better solvent system
• Better/Different Instrument Settings
• Dilute more
• Vacuum Filter All Samples Regardless
References• Lee, H. S. HPLC Method for Separation and Determination of
Nonvolatile Organic Acids in Orange Juice. JAFC, 1993, 41(11), pp. 1991-1993.
• Nisperos-Carriedo, M. O.; Buslig, B. S.; Shaw, P. E. Simultaneous Detection of Dehydroascorbic, Ascorbic, and Some Organic Acids in Fruits and Vegetables by HPLC. Chem. Anal. 1992, 40(7), pp 1127-1130.
• Silva, F. O.; Total ascorbic acid determination in fresh squeezed orange juice by gas chromatography. Food Control, 2005, 16(1), pp 55-58.
• V., K.; D., S.; E., M. Ascorbic acid content of commercial fruit juices and its rate of loss upon storage. Food Chemistry, 2000, 70(3), pp 325-328.