post lab discussion: exp. 6 Flashcards
Sweet, sticky, yellowish food made by bees from nectar collected from flowers
honey
- good source of carbs which gives our bodies strength and energy
- 69% glucose _ fructose; substitute for sugar
what are the enzyme content of honey
diastase
catalases
B-glucosidase
what type of sugar that fructose is belonged to
ketohexoses
- fructose in a 6C sugar w a ketone grp
test in distinguishing ketoses and aldoses
seliwanoff’s test
positive result: cherry-red colored complex formed - fr ketoses
(fr aldoses - faint pink color)
reagent of seliwanoff’s test
resorcinol and conc. HCI
deals with the production, measurement, and interpretation of spectra arising from the interaction of electromagnetic radiation (light) with matter.
spectroscopy
- there are diff spectroscopic methods
spectroscopy utilizing radiation in the UV–Vis range
UV-Vis spectroscopy
what is the ranges in wavelength of the elecromagnetic radiation in the UV-Vis portion of the spectrum
~200 nm to ~700nm
(Note: In other literature, the wavelength range for UV-Vis may be somewhat higher or lower, hence the symbol ~)
what is the
UV range:
Vis range:
UV range:
200 to 350 nm
Vis range:
350 to 700 nm
- UV range is colorless to the human eye
- diff wavelengths in the visible range each have a characteristics color (ROYGBIV)
instrument used for this experiment
UV-Vis Spectrophotometers
Sample models of UV-Vis spectrophotometer
it shld be chosen after the general spectral region to be used in a spectrophotometric measurement has been determined.
sample holding cell or cuvettes
what shld the composed material for sample holding cell shld be
a material that does not absorn radiation in the spectral region being used
the cells meeting this requirement for measurements is composed of what in the
UV range:
Vis range:
UV range:
quartz or fused silica
Vis range:
silicate glass are appropriate
plastic cells - inexpensive and available for some applications
why shld we not touch the clear/ transparent sides of the cuvette
to not interfere and not cause unnecessary absorption
contaminating the clear sides of the cuvette with fingerprints
particles from wiping tissues
other contaminant that can affect the reading
what happens if the cuvette gets wet outside during filling
wipe the cuvette clean and dry with soft facial tissue to avoid scratching the surface
how much do u fill the cuvettes
3/4 full with your prepared standard soln and sample will be done in the lab
what us the r/s bten absorbance and conc
Under appropriate conditions, absorbance is directly proportional to the concentration of the absorbing species in the solution. In general, this relationship is applicable only to dilute solutions, up to approximately 10mM for most analytes.
why? cos u had to diltue the honey sample
Note: Since the concentration of fructose in your honey sample is unknown, you had to find the appropriate dilution by preparing a series of 10-fold dilution (1:10, 1:100, 1:1000) to determine which one falls within the range of the standard curve.
In principle, the concentration range covered by the standard solutions must include that expected for the unknown – very important for accurate measurement.
standard -
sample -
standard - fructose
sample - honey
A calibration curve can be used to determine the?
concentration of unknown sample solution by measuring its absorbance.
The calibration curve is used to establish
the relationship between analyte concentration and absorbance.
- This relationship is established experimentally by analyzing a series of samples of known analyte concentration (standards).
y axis -
x axis -
y axis - absorbance
x axis - corresponding conc
- under appropriate conditions, it shld be linear
how to find the conc of fructose from the calibration curve
use the eqn of the line
x = y - b / m
x is the conc.
y is the absorbance
