Quantative analysis of caffeine content

Quantative depth psychology of caffein contentCaffeine was extracted from decaffeinated burnt umber and normal afternoon afternoon teatimetime leaf leaf using DCM as the solvent and comp bed with prepared solutions of caffeine using reverse arrange HPLC. The tasteally determined result was a caffeine concent proportionalityn of 7.598?g/ml for decaffeinated coffee compared with 5.9?g/ml quotation and 0.4049mg/ml for tea against 0.26mg/ml1*.IntroductionCaffeine (1) is the close to commonly consumed non-prescription stimulant. It is a member of the xanthine (2) family1 and is structurally related to other plant alkaloids such as theobromine (3), commonly open in cocoa beans and chocolate.The average person in the UK drinks over thee cups of tea a day,2 and so quantatively knowing the amount of caffeine that is contained in a cup of tea is particularly important. Caffeine acts on certain adenosine receptors in the brain3, although there is evidence that action on these speci fic receptors may earn others such as dopamine receptors, commonly associated with reward4. More chronic effects of caffeine consumption include irritability, impaired parsimony, muscle-aches, nausea, vomiting and blurred vision5.HPLC denotes naughty pressure liquid chromato representy. In this investigate, reverse stagecoach HPLC was used, meaning that part polar organic solvents were used as a mobile phase against a non-polar stationary phase, in this case, octadecyl silane chains6. HPLC is a useful tool in analysing quickly and accu sum uply relative abundances of various chemicals contained within a sample.The experiment was undertaken to evaluate the caffeine content in an average cup of tea and an average cup of decaffeinated coffee.ExperimentalThe experiment was carried out according to the University of Bristol endorsement Year science laboratory Manual. Results were analysed by reverse HPLC using an isocratic solvent trunk consisting of 10 mM ammonium acetate, meth anol and tetrahydrofuran at a ratio of 908.51.5. The non-polar phase featured octadecyl silane chains at a fraction size of 5 ?m. The injection volume was 10 ?l, flow rate was 1.5ml min-1 with UV monitoring at 273nm.Preparation of afternoon teaOne tea bag was added to 200ml of boiling deionised water and boiled (ca. 10 minutes) with occasional agitation. Tea bag was choosed and solution allowed to cool to room temperature. Sodium chloride (5g, 0.856moles) added with atomic number 20 hydroxide (1g, 0.0135moles) twice filtered by Bchner filtration. 20ml transferred to extraction displace, extracted with DCM (20ml) three times. magnesium sulphate added to dry DCM thoroughly of all water. Evaporated to dryness via rope evaporation. stay solid dissolved in DCM and made up to 20ml.Preparation of Decaffeinated coffee berry1.50g of Decaffeinated Coffee granules was added to 200ml of boiling water and allowed to cool to room temperature. Calcium hydroxide added (1g, 0.0135moles) to d ecaffeinated coffee solution. Solution twice filtered via Bchner filtration. 20ml of solution transferred to extraction funnel and extracted with three equivalents of DCM (20ml). Magnesium sulphate added to dry the DCM, Bchner filtered and evaporated to dryness via rotary evaporation. Remaining solid dissolved in DCM and made up to 20ml.Results and word of honorThe tea solution was originally brown and transparent, and the coffee was black. Addition of calcium hydroxide changed the colour of both solutions to an opaque dark brown. Tannins are precipitated by lime water, and so this is likely to be what precipitated out in the tea and coffee solution.7 This precipitate was then removed by Buchner filtration. It was also launch that both solutions, coffee especially, readily formed emulsions and bubbles in the extraction funnel, and so a large quantity of magnesium sulphate was needed to remove all water from the extractions. This may have interfered with the full extraction of the caffeine.The acculturation warmth for Tea was 7108493 units. Substituting this into equation 1 allows us to elaborate the caffeine concentration in Tea. The solved concentration is 0.4049mg/ml.The absorption intensity for Decaffeinated Coffee was 79233 units. Substituting into equation 1 allows us to calculate the caffeine concentration in decaffeinated coffee. The solved concentration is 0.007598mg/ml.Errors in solution concentrationThe fallacy for the balance used to measure out the caffeine pulverization for the standard solutions was 0.00005g. The error for the 20ml volumetric flasks used was 0.1ml. Substituting these to find utmost and minimum determine into the moles equation allows for finished error analysis.Substituting these value into the data and plotting onto a graph grants the ability to draw the same graph above with error boxes. It also allows for maximum and minimum gradients to be raddled with the maximum and minimum values. From this information precise e rrors in the concentration of tea and decaffeinated coffee abide be calculated.Substituting maximum values into a graph enables the gradient and intercept to be calculated, and hence the positive error in caffeine concentration of the tea and decaffeinated coffee solutions. The same can be done with minimum values.Substituting in values of absorbance for tea gives a maximum value of 0.4069mg/ml and minimum value of 0.4029mg/ml. For decaffeinated coffee the maximum value of 7.639?g/ml and minimum value of 7.558?g/ml.Literature values for the caffeine content of decaffeinated coffee are in the region of 0.5-1.5mg per 177.44ml1, which is between 0.0003-0.009mg/ml. This is close to the recorded value of 7.598?g/ml . The literature values for the caffeine content in tea are 15-75mg/ml per 177.44ml, which is between 0.088-0.440mg/ml. This is close to the recorded value of 0.4049mg/ml . some(prenominal) of the obtained values are within the range given in extension phone however both results are in the upper end of values that should be obtained. This could be due to poor measurement of either the reference caffeine peaks or clamant coffee measurement.ConclusionThe isolation of caffeine from tea and instant coffee was successful and the values obtained from the quantative analysis of a sample by reverse HPLC compared favourably to reference values. More accurate values for caffeine content could be obtained by larger quantities of instant coffee samples and by repetition of assays involving caffeine extraction from tea. The importance of formation the quantity of caffeine in decaffeinated coffee is important since the concentration must(prenominal) remain low.AcknowledgementsI would like to thank my demonstrators Jack Davidson and Chun Zhu for helping me with the experiment and my lab partner Ben Gough.ReferencesB. A. Weinberg,B. K. Bealer, The world of caffeine the science and refining of the worlds most popular drug, Routledge (2001) pp. 216.G. A. Spiller, Caffeine, CRC Press, (1998) pp. 38.U. Gupta, Caffeine and behavior current views and research trends, CRC Press (1999) pp. 1.R. S. J. Frackowiak, merciful brain function, Academic Press (2004) pp. 446.B. A. Weinberg, B. K. Bealer, The world of caffeine the science and culture of the worlds most popular drug, Routledge (2001) pp. 304.University of Bristol, School of Chemistry, Level 2 Teaching Laboratory Manual 2009/2010.P. J. Van Soest, Nutritional ecology of the ruminant, Cornell University Press (1994) pp. 204-205.