Determination of Vitamin C Content in Foods

Determination of Vitamin C Content in Foods Zheng Xiao Introduction Vitamin C, also known as L-ascorbic acid, is an essential component of our diets. It is a good antioxidant, a key component that helps to prevent damage to proteins and deoxyribonucleic acids. In the food industry, vitamin C is added to increase the nutritional content of food products and also for preservative purposes. As the human body is unable to synthesise vitamin C, it would have to be consumed as part of our diet. Fresh fruits and vegetables for instance are common sources of vitamin C. Vitamin C is a labile compound and is easily degraded by enzymes and atmospheric oxygen. Its oxidation can be accelerated by excessive heat, light, and heavy metal cations (Pisoschi, Danet, Kalinowski, 2008). During the manufacturing process, some vitamin C would be lost. Thus, in fruit juice products, vitamin C level is commonly used as a gauge for quality. This prompts manufacturers to fortify their products with high levels of vitamin C to ensure that sufficient vitamin C is present in the product throughout the storage process. Due to the wide use of ascorbic acid in both food products and in the pharmaceutical industry, many analytical methods exist for the determination of ascorbic acid, including titrimetric, spectrophotometric and chromatographic methods, each with their advantages and disadvantages. An example of a titrant used is 2,6-dichlorophenolindophenol (DCIP), which will oxidise the ascorbic acid that is present in the sample. While titrimetric methods are simple to use, they are also known to overestimate the amount of ascorbic acid present due to the presence of oxidisable species other than ascorbic acid (Hernà ¡ndez, Lobo, Gonzà ¡lez, 2006). In addition, many interferences often occur with coloured samples (Arya, Mahajan, Jain, 2000). An example would be the masking of colour change at the end point of titration by highly coloured extracts from fruits and vegetables (Eitenmiller, Landen, Ye, 2007). Spectrophotometric methods work by determining the absorbance of vitamin C which is compared against standard concentrations. However, such methods are susceptible to possible interference due to absorbance exhibited by other components that is present in the sample matrix. Lastly, chromatographic methods are commonly used because of their simplicity, short analysis time and sensitivity (de Quirà ³s, Fernà ¡ndez-Arias, Là ³pez-Hernà ¡ndez, 2009). The sample is separated into its components based on their relative affinity with the mobile and stationary phase. Reversed-phase high performance liquid chromatography (RP-HPLC) for instance is a very efficient method that is used in ascorbic acid analysis of fruits, vegetables and beverages. Ascorbic acid is relatively hydrophilic due to the presence of several hydroxyl groups. Thus, it has a higher affinity to the polar mobile phase than the non-polar stationary phase, allowing it to be separated from the other components in a sample. The retention time gives a qualitative analysis of the sample while the area under the peak allows for the quantitative determination of ascorbic acid content present. However, a major disadvantage of this method is its high cost compared to other conventional methods. The objective of this experiment is to determine the ascorbic acid content in commercial guava juice by RP-HPLC. Materials and Methods The product analysed was commercial guava juice. The experimental procedure was as stated in the laboratory manual, with the slight amendments as follows. The filtrate (2mL) from the centrifuged sample was diluted (1 part sample: 4 part acetic acid) with 2% acetic acid. Five sets of standard ascorbic acid solutions were prepared (40ppm, 80ppm, 120ppm, 160ppm and 200ppm for each set) using a stock solution (1000ppm ascorbic acid) and 2% acetic acid for dilution. The standard solutions were filtered using the 0.45 micron cellulose acetate syringe filter, beginning with the lowest concentration. The column used was a Phenomenex Ultrasphere 5u C18 column (1504.6mm) and the wavelength used was 254nm. Results and Discussion A calibration graph was plotted (Figure 1) using average peak area (Table A1 in appendix) for standard solutions versus their respective concentrations. For each standard solution, four duplicates were prepared. This was done to increase the accuracy of the calibration curve. The r2 value obtained (0.9984) was close to the ideal value 1, indicating a good linear correlation between the area under peak of interest and ascorbic acid concentration. This allows good estimates of ascorbic acid content to be made given the area under peak of interest for each sample. Table 1. Ascorbic acid concentration in samples prepared by Groups 10 to 18 Sample calculation for Group 11: Ascorbic acid concentration in diluted sample = = 116ppm Ascorbic acid concentration in original sample = 116ppm 5 = 581ppm = 58.1 mg / 100mL of juice Average ascorbic acid concentration in original sample = =58.0 mg / 100mL of juice The average retention time of the samples prepared by different groups was 2.557min (Table A3 in Appendix), which is highly similar to that of the ascorbic acid standard solutions was 2.559min (Table A2 in Appendix). This verifies that ascorbic acid was the component analysed. The average ascorbic acid concentration in the guava juice product determined experimentally was 58.0mg/100mL of juice. This was approximately 3.9 times higher than the amount indicated on the packaging (15mg/100mL). As mentioned earlier, As the expiration date is approached, ascorbic acid would be lost to different extents depending on the storage conditions (Kabasakalis, Siopidou, Moshatou, 2000). Manufacturers are known to add ascorbic acid to their products to improve their nutritional value and also to account for the ascorbic acid lost during the manufacturing and storage process (Ottaway, 2008). Since the experiment was conducted before the expiration date of the product (March 14, 2014), a higher ascorbic acid content would be expected. The original ascorbic acid concentration for group 14 was excluded from the calculation as it was almost double of other results and thus likely to be an outlier. A possible reason might be an error in dilution during the preparation of the sample. The other results were found to be precise with a low standard deviation (1.4) and a low coefficient of variation (2.5%). Conclusion The ascorbic acid content of commercial guava juice determined using RP-HPLC was 58.0mg/100mL of juice. References Arya, S. P., Mahajan, M., Jain, P. (2000). Non-spectrophotometric methods for the determination of Vitamin C. Analytica Chimica Acta, 417(1), 1-14. doi: http://dx.doi.org/10.1016/S0003-2670(00)00909-0 de Quirà ³s, A. R.-B., Fernà ¡ndez-Arias, M., Là ³pez-Hernà ¡ndez, J. (2009). A screening method for the determination of ascorbic acid in fruit juices and soft drinks. Food Chemistry, 116(2), 509-512. doi: http://dx.doi.org/10.1016/j.foodchem.2009.03.013 Eitenmiller, R. R., Landen, W. O., Ye, L. (2007). Vitamin Analysis for the Health and Food Sciences, Second Edition: Taylor Francis. Hernà ¡ndez, Y., Lobo, M. G., Gonzà ¡lez, M. (2006). Determination of vitamin C in tropical fruits: A comparative evaluation of methods. Food Chemistry, 96(4), 654-664. doi: http://dx.doi.org/10.1016/j.foodchem.2005.04.012 Kabasakalis, V., Siopidou, D., Moshatou, E. (2000). Ascorbic acid content of commercial fruit juices and its rate of loss upon storage. Food Chemistry, 70(3), 325-328. doi: http://dx.doi.org/10.1016/S0308-8146(00)00093-5 Ottaway, P. B. (2008). Food Fortification and Supplementation: Technological, Safety and Regulatory Aspects: Elsevier Science. Pisoschi, A. M., Danet, A. F., Kalinowski, S. (2008). Ascorbic Acid Determination in Commercial Fruit Juice Samples by Cyclic Voltammetry. Journal of Automated Methods and Management in Chemistry, 2008. doi: 10.1155/2008/937651 Appendix Table A1. Area under peak of interest for standard solutions Average area under peak for 40ppm = = 2197282 Table A2. Retention Times for standard solutions Table A3. Retention Times for samples prepared by Groups 10 to 18

Conscription in WW1 Essay

Were Australians against the introduction of conscription during WW1?As the war was happening people back home in Australia were starting to realise that the war was not as much about bravery and pride as they originally thought because very few men were returning, but the government needed young healthy men because of the amount of men on the front line dying and they needed to be replaced. Australian men werent volunteering so in November 1917 prime minister, Billy Hughes wanted to introduce conscription to Australia and ask the people are you in favour of the proposal of the commonwealth government for reinstating the Australian imperial forces overseas? Conscription was like the lottery, you would be randomly chosen to go to war because of the day that you were born. Australians were given the opportunity to vote for or against conscription and campaigns were made to support each point of view. Two referendums were held, the first on the 28th of October 1916 and the second on the 10th of December 1917, both referendums were lost, the second showed 1181747 votes against and 1015159 votes for conscription. Two referendums were held because men kept dying on the front line and the government were getting desperate. Both referendums ended with majority no votes, the first with 72446 votes against and the second with 1181747 votes against. Women were the main target for pro and anti conscription campaigns because they were seen as weak fragile and sensitive. Propaganda was largely aimed at women to intimidate women and target their emotions, either to make them feel like they were sending their husbands and sons to die or that it was their duty to send them to fight for their country. It was a hard decision deciding whether or not to vote for conscription. Some people thought they should vote yes because of pride and defending and protecting their country and coming back as a war hero and also because of loyalty to Britain because they were still part of their empire, voting yes or no also targeted Christian women because killing is a serious sin. Songs and posters were made to persuade Australia to vote yes or no. People were told that if you vote yes it is your fault they die but also that if you vote yes the country wont be taken over and that you could save Australia  from the enemy. A white feather was sent to the people who voted no to represent and parade that they are cowards and to embarrass them publicly. Conscription broke people apart and divided the country, it destroyed friendships and families because there is either yes or no and no in between. The way you voted reflected your character and the way you were thought of. Anti conscription appealed to woman and made them feel like killers but pro conscription also appealed to women making them feel like they were sacrificing men for the good of the country. Conscription divided Australia and turned their worlds upside down. People didnt want to be forced to go to war or force someone to go to war because they realised how bad it was. Australians voted no because they wanted freedom of choice and not to be conscripted as if it was just a game. bibliography:-shannon mckinnon ww1- class sheets

Native America and Astronomy

To a great degree, the reading point to an aspect of the study of astronomy that many people might not be entirely familiar. That aspect is, of course, the contributions of the Navajo to the study of astronomy. This contribution has been largely ignored by many in the established scientific community in large part due to the fact that the concept of Navajo astronomy is more based on interrelation of what is discovered as opposed to a categorizing approach that does not integrate the discovered with the discoverer. Consider the following: The concept of a dynamic integrated whole is important in Navajo cosmology and astronomy. The pattern of relationship is far more important than the identification, location and Greek or Arabic name of any individual star. The individual stars contribute to the significance of the whole. (Begay/Maryboy Navajo Astronomy) In other words, there is a concept of harmony and balance present in the concept of Navajo astronomy. The earth, stars, moon, etc are interwoven as parts of a whole known as the universe. In traditional approaches to astronomy, there is an almost centrist position that the earth is the center of the universe and that the moon and stars are dependent upon the earth. While this may sound like an odd ideology of exceptionalism, the reality is that this WAS the exact belief of astronomers at one point in history. Now, this does not mean that the barren moon is on equal parity of the earth, but it does acknowledge that the mere concept of earth centrist ideology can lead to a belief in pillaging the environment because there is limited acknowledgment that the other components of the universe help keep the earth in harmony. This is why it becomes important to read the more extensive work â€Å"Sharing the Skies† because it allows a more in depth look at the subject. Considering the complexity  of the subject, a lengthier work is required in order to develop a much more clear understanding. One of the more interesting aspects of â€Å"Sharing the Skies† is essentially the fact that the work points out that when one realizes that most astronomy is centered on a Western Civilization origin, one realizes that the concepts and definitions of astronomy lead directly to one culture. When one looks at different cultural explanations of astronomy, then an individual can gain an insight into the cultures of other peoples and nations. In Williamson’s â€Å"Native American Astronomy,† the reader discovers a bit more depth to the origins of Native American cosmology. It is important to present and define Native Astronomy in the manner that Williamson presents it because he re-establishes the fact that Native astronomy is a sphere of science and not the weird, New Age quasi-religion that it has become thanks to a number of hack writers who have flooded bookstores with dubious works. â€Å"Application to Astrology† ties much of the philosophy of Native Astronomy and earth studies into the component that conventional sciences ignore: the spiritual component. Again, this stresses the idea of interrelation between various parts of a whole. Since the spiritual can not be removed from the person and the person can not be removed from the earth, then it goes without saying that there is an interrelation between the human spirit and the earth. Both halves of the same idea compliment each other and compliment each other quite effectively. Bibliography Begay, David and Maryboy, Nancy C.Finding the Thunderbird in Navajo Astronomy. Bluff: Indigenous Education Institute, 2004. Begay, David and Maryboy, Nancy C. Sharing the Skies Bluff: Indigenous Education Institute, Date Unknown

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