Week 7: Calibration Curve

Our literature search revealed that protein concentration can be quantified by measuring absorbance at 280 nm.  Although considerable error can arise when measuring mixed protein samples, the concentration of pure proteins, such as bromelain, can be reliably and quickly determined via this method.  The goal for this week was to create a calibration curve for bromelain absorption at the reported peak of 280 nm.  

Based on the recommended dose of 200 mg bromelain per meal and the average volume of a human stomach (roughly 1 L), a maximum concentration of 0.2 mg/mL was determined.  A standard was created by adding 2 mg of bromelain to 20 mL of distilled water, and serial dilutions were performed to create four more solutions with concentrations decreasing by a factor of 10.  A 1 wt% sodium alginate standard solution and 0.5 wt% CaCl2 standard solution were also prepared for baseline tests.

Figure 1. Dan the pipetting expert

Figure 2. Mike inspecting samples

The group contacted a member of the chemistry department to gain access to a spectrophotometer.  However, on testing day, it was discovered that the Vernier SpectroVis spectrophotmeter could not test absorbance in the UV spectrum.  Reservations were made for next week to use a more sophisticated spectrophotometer.