Spectrophotometer Lab

Introduction

A spectrophotometer is used to measure the concentration or population density of liquid samples. Although it is an invaluable tool for scientists in multiple disciplines, many schools cannot afford it in their science classrooms. To address this problem, a cheaper, smaller spectrophotometer was built in by the lab which returns frequency values that relate to concentration. The purpose of this investigation is to test and calibrate the spectrophotometer against O.D. values of halobacteria samples returned by the regular lab spectrophotometer and various dilutions of a standard sample of Hawaiian Punch.

Hypothesis

The values returned by the device being tested will relate linearly with the standard O.D. values of the halobacteria and the relative concentrations of the Hawaiian Punch standard, as per Beer’s Law.

Procedure:

Results

Conclusion

As shown in the graphs, the Hawaiian Punch test displayed clearly the linear relationship as expected and resulted in a line of fit which closely correlated with the data. Using this graph, it is easy to map the frequency output of the device with percent concentration of Hawaiian Punch. However, the Halobacteria test resulted in noisy data, from which a clear relationship was difficult to discern. Although the data had clear direction it did not correlate well with the trend line. This could be a result of errors in preparation of the Halo cultures or in the spectrophotometer itself.