Unknown Amino Acid Lab Report

The aim of this experiment was to prepare a buffer for an unknown amino acid with the goal of identifying the unknown amino acid. The objective was to use the Henderson Hasselbalch equation to determine the buffer capacity, and to use the pKa values and molecular weight, to identify the unknown amino acid through acid-base titrations. Titration was done on the unknown amino acid with a strong acid and base while titration was done on NaCl, which acted as a blank for identifying the unknown amino acid and was used to find the true titration curve of the amino acid. The pka values were found to be 1.95 and 8.88, and the molecular weight 133.98 g/mol. Moles extrapolated from the titration curve were used to find the molecular weight of the unknown amino acid, along with the pkas and the pI. This information when compared to the literature values of Gly, L-ala, L-ser, and L-asp (of which the unknown was one of) led to the conclusion that the identification of unknown C was likely to be L-Aspartic Acid. The literature values agreed with some deviance from the experimental values, which were likely due to experimental errors. This showed that we can prepare a buffer using an amino acid and use the titration curve of that buffer to identify the unknown amino acid.

Results Data

Titration curve of NaCl and an unknown amino acid titrated with 2M HCl (blue), along with the NaCl blank (red). The graph shows the exact amount of HCl added in ml and the decrease of pH recorded during the titration. Figure 2: Titration curve of NaCl and an unknown amino acid titrated with 2M NaOH (blue), along with the NaCl titration with 2 M NaOH (red). The graph shows the exact amount of NaOH added in ml and the increase of pH recorded during the titration. It also shows that the same amount of NaCl base was used to titrate the blank. The pH of the solution and blank were taken initially before 2M NaOH was added and then taken corresponding to the increment of 2 M NaOH