Problem 3
A publication this year in the journal Yeast (who’d have thought!) by a Scottish group
described their development of a spectrometric procedure to monitor the concentration
of glucose, ethanol, biomass, and protein content in a vat during the production of
Baker’s yeast (Saccharomyces cerevisiae). They used near-infrared spectrometry to
perform this analysis. It is a particularly challenging matrix because the large yeast cultures
scatter so much of the light. (See Finn, Harvey, and McNeil, Yeast 23, 507-17
(2006).)
A standard addition method is used to determine the concentration of ethanol in an
unknown sample. Six 10 mL aliquots of the unknown are drawn from the processing
vat. An aqueous solution of ethanol is standardized to have 1.57 g/L. This standard is
pipetted to five of the aliquots in the following volumes: 5.00 mL, 10.00 mL, 15.00 mL,
20.00 mL, and 25.00 mL. Each of the six solutions is then diluted to a total volume of
50.00 mL. Three samples are taken from each of these solutions and the absorbance
spectrum in the ethanol region is measured and the relative area under the curve is reported.
This data is available in the accompanying Excel or pdf file.
Determine the concentration of ethanol in this unknown sample and provide the 95%
confidence limits for the answer.
For calculating the confidence limits, take n to be 3, the number of measurements of
the unknown by itself and let the number of degrees of freedom be 3-1 = 2 since the average
result is extracted from the data
I am unable to answer this question.
Could you please help me out.