1 / 19

Analysis of Vitamin C in Fruit Juices

Analysis of Vitamin C in Fruit Juices. Instrument Metrohm Polarograph. formula weight 176.13g Water Soluble melting point 190-192° C, unstable in solutions containing oxygen as it is readily oxidized. Vitamin C (Ascorbic Acid). Why is Vitamin C important?.

winchell
Télécharger la présentation

Analysis of Vitamin C in Fruit Juices

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Analysis of Vitamin C in Fruit Juices Instrument Metrohm Polarograph Rebekah Livesley, 2008

  2. formula weight 176.13g Water Soluble melting point 190-192° C, unstable in solutions containing oxygen as it is readily oxidized Vitamin C (Ascorbic Acid)

  3. Why is Vitamin C important? • It is involved in over 300 biological processes in the body for example • Antioxidant • Collagen manufacture & neurotransmitters • Immune function • It is a Nutrient not synthesized by the body • Complete deficiency results in scurvy • Deficiency symptoms • Bleeding gums • Joint pain • Bruising & wounds that don’t heal • Fatigue & muscular weaknesses

  4. Recommended Daily intake is 30-60mg • The RDI is what you need to consume to prevent a deficiency • 100ml (which is less than ½ a cup) of the Popper Juice orange Juice is all you would need to consume • excess vitamin C is usually eliminated through the urine • An excess of Vitamin C can cause diarrheaas water is pulled into the colon from the circulatory system

  5. Fruit Juices Expected concentrations of Vitamin C in Fruit Juices

  6. Samples Popper Juice Apple and Blackcurrant Popper Juice Orange Juice Popper Juice Apple And Mango Juice WESTCLIFF Apple Juice Popper Juice Apple Juice And V8 Vegetable Juice

  7. Metrohm Polarograph Photographed by Shay

  8. ProceduresDifferential Pulse Polarography Standard Addition Method • Dilute sample accurately to approximate concentration of 40mg/L • Place in sample cell with water and buffer solution • Run scan -0.4 to +0.1 V • 3 standard additions Normal Calibration Method • Prepare 0, 5, 10, 25mg/L standard solutions in buffer solution • Dilute sample accurately to an approximate concentration of 10mg/L in buffer • Runs scans as above

  9. Differential Pulse Polarography Standard Addition Results

  10. Differential Pulse Polarography Normal Calibration Results

  11. Concentration Range of Vitamin C

  12. Choice of method • normal calibration • simpler for sample delivery (no pipetting required) • more consistent results • better RC values

  13. What went wrong Standard Addition Method • Lack of precision in the results obtained • Caused by • Micropipettes • Human error • 3 aliquots to be transferred to sample cell per run

  14. What went wrong Normal Calibration Method • An aliquot of the V8 vegetable juice could not be taken by pipette as the juice was so viscous • Had to weigh a mass and do a density calculation before diluting the juice • JUST JUICE – Apple Juice concentration was outside the concentration range of the standards used in the calibration graph • Easily fixed – just recalibrate

  15. Polarography Disadvantages • Not time efficient • Must use a buffer solution

  16. Conclusion • The normal Calibration polarographic method for the analysis of vitamin C is better than the standard addition method • All sample analyzed had considerably more vitamin C than specified on the packet except Just Juice apple juice which had about a 1/5

More Related