[Class Name]
Aim/Objectives
The aim of this experiment is to quantify the how much salicylic acid is collected between three different urine samples. A control sample, samples taken from subjects taking sodium bicarbonate to make the urine more basic, and samples from subjects taking ammonium chloride to make the urine more acidic. Using the assays provided, we will attempt to quantify the amount of salicylic present in the urine sample by the concentration and pH level since the ionization of salicylic acid is dependent on urinary pH.
Abstract/Introduction
Salicylic acid, a major component of Aspirin, is a compound used to ease aches and pains, and reduce fevers. Aspirin is easily hydrolyzed, and in the body the salicylic acid will be excreted via the kidneys. Due to the fact that Salicylic acid is a weak acid, the ionization of it is dependent on the pH of the liquid that it is in. This makes the balance between the ionized and unionized forms of Salicylic acid dependent on the pH of the urine excreted from the body. From this, we can quantify the amount of the acid in the body due to the pH of the urine.
Method
Results
In tables and graphs below are the results of the assay and experiments. Table One includes the calibration data for the individual assays. Table 2, Table 3, and Table 4 have the data for the individual assays as well as the quantities of the salicylic acid as it compares tot he pH of the urine. Table 5 is the cumulative excretion table. In Graph 1 we have the calibration graph and Graphs 2, 3, 4 are the cumulative excretion graphs.
Discussion
Determining the amount of salicylate in biological fluids is a widely researched topic (Brodie et al 1944). After completing the lab we found a couple of interesting things. First we found out that the more time that the urine had to sit, the more salicylic acid it produced. We also found that the pH levels in both the control and the acidic solution were about the same, which was a minor fluctuation between 4.5 and 6.5. However during hours 4 and 5, the NH4Cl and Aspirin made the pH of the urine slightly acidic at a pH level and 4.6 and 4.9. This was also the time when the amount of salicylic acid was concentrated. The control group had the most cumulative excretion amount, which means that there was more observed in the urine sample of the controls versus the basic or acidic urine solutions. In the NaHCO3 (basic) urine solution the concentration was mostly during the hours of 5 and 6, which means it was delayed versus the control and acidic urine solutions. What we see here and what we see in other experiments is that “urinary alkalinization increases salicylate elimination, although the mechanisms by which this occurs have not been elucidated,” (Proudfoot et al 2003). It also may be worth it to note that at the 20th hour in the basic solution that there was actually a negative concentration, which may have been due to human error.
Since the ionization constant of the process of alkalization of the urine is a logarithmic function, the calibration graph was used to find the concentration of the different samples (Harrison et al 1980). It being a log function, any small deviation in the pH will have a disproportionately effect on the quantity of salicylate in the samples as seen when the pH is basic or acidic.
The control group excreted the most amount of salicylic acid, followed by the basic solution, followed by the acidic solution. This means that the more acidic solution, the less salicylate was excreted. In a pH of 7 or greater, the amount of salicylate excrement increases and in a more acidic solution it decreases.
Conclusion
Although we do not know the complete mechanism as to why elimination of salicylic acid by the kidneys is increased substantially in alkaline urine (Proudfoot et al 2003) it is still significant to see how little changes in alkalinity of the urine affects the quantity of the salicylate excretion. This is extremely helpful in the design of drugs and the industry of pharmacokinetics (Proudfoot 2003). We conducted this study to determine the changes that alkalinity had on the excretion quantity of salicylate. This is extremely helpful for biological processes because different organs have different pH levels (Trinder 1954). For example, the stomach usually has a pH of around 5 (can fluctuate between 1 and 5) and the intestines usually have a pH from about 6 to 7.8. This is extremely helpful for further research and to see which medicines will be excreted into the bloodstream and at what time the uptake may happen. Since Salicylic Acid is a component used for fever reducing and pain relief, it is extremely helpful to see how much would be in the bloodstream by quantifying how much of the salicylic acid is excreted in the urine. It has been shown that only about 1/5 of the salicylic acid is absorbed in the body, and the rest is excreted (Kapp et al 1942). All of this information is extremely helpful in discovering the processes of the human body.
SOURCES
Brodie, B. Bernard; Udenfriend, Sidney; Coburn, Alvin F.; “The Determination of Salicylic Acid in Plasma” Journal of Pharmacology and Experimental Therapeutics 80.1 (1944): 114-117.
Harrison, L. I., M. L. Funk, and R. E. Ober. "High‐pressure liquid chromatographic determination of salicylsalicylic acid, aspirin, and salicylic acid in human plasma and urine." Journal of pharmaceutical sciences 69.11 (1980): 1268-1271.
Kapp, Eleanor M., and Alvin F. Coburn. "Urinary metabolites of sodium salicylate." Journal of Biological Chemistry 145.2 (1942): 549-565.
Proudfoot AT, Krenzelok EP, Brent J, Vale JA. “Does urine alkalinization increase salicylate elimination? If so, why?” Toxicol Rev. 2003;22(3):129-36.
Trinder. P. “ Determination of Salicylate in Biological Fluids.” Biochem J. 1954 June; 57(2): 301–303.
