how would an error in preparing a spectrophotometer blankexplain an upside-down absorbance trend?
in a lab analzying the effect of temperature and pH onenzyme-catalyzed reaction rate, we used a spec 20 to measureabsorbance of potato-extract (containing catacholase aka potatopolyphenol oxidase) and added subtrate (catechol) -- the reactionforms benzoquinone, which is visible in browning. Absorbance wasmeasured after 5 minutes in 4 different temperature solutions(4deg, 25deg, 37deg, 65deg -- C). Expected absorbance peak wouldhave been room temp 25deg, low would have been 65deg (re: enzymesare proteins, proteins denatured at higher temps). Instead we hadabsorbance PEAK at 65deg, LOW at 25deg. I did not prepare orobserve the preparation of the blank or the calibration of the spec20 or the preparation of the potato extract itself (this was a4-person, 4-part lab and I was working on a ph-dependent relatedexperiment while the extract and blanks were created).
What kind of error would explain these results that appear to beexactly opposite of the expected trends? Incorrect blank? Improperratios or temperature in potato extract (theoretically made from aroughly 2:1 volume ratio of cold water to peeled potato, blended,strained over a beaker in ice and spun at 2000rpm for 2 min, andthen kept in tubes over ice until the start of the experiment)?
Any (and as detailed as possible) suggestions would be greatlyappreciated. I have a lab report due on this, the data makes nosense, and my lab partners are oblivious.
Temperature (C) Absorbance 4 0.469 25 0.436 37 0.474 65 0.493
how would an error in preparing a spectrophotometer blankexplain an upside-down absorbance trend?
in a lab analzying the effect of temperature and pH onenzyme-catalyzed reaction rate, we used a spec 20 to measureabsorbance of potato-extract (containing catacholase aka potatopolyphenol oxidase) and added subtrate (catechol) -- the reactionforms benzoquinone, which is visible in browning. Absorbance wasmeasured after 5 minutes in 4 different temperature solutions(4deg, 25deg, 37deg, 65deg -- C). Expected absorbance peak wouldhave been room temp 25deg, low would have been 65deg (re: enzymesare proteins, proteins denatured at higher temps). Instead we hadabsorbance PEAK at 65deg, LOW at 25deg. I did not prepare orobserve the preparation of the blank or the calibration of the spec20 or the preparation of the potato extract itself (this was a4-person, 4-part lab and I was working on a ph-dependent relatedexperiment while the extract and blanks were created).
What kind of error would explain these results that appear to beexactly opposite of the expected trends? Incorrect blank? Improperratios or temperature in potato extract (theoretically made from aroughly 2:1 volume ratio of cold water to peeled potato, blended,strained over a beaker in ice and spun at 2000rpm for 2 min, andthen kept in tubes over ice until the start of the experiment)?
Any (and as detailed as possible) suggestions would be greatlyappreciated. I have a lab report due on this, the data makes nosense, and my lab partners are oblivious.
| Temperature (C) | Absorbance |
| 4 | 0.469 |
| 25 | 0.436 |
| 37 | 0.474 |
| 65 | 0.493 |
