quantitative tests for reducing sugars Flashcards
why do we need standard solution of known concentrations of reducing sugar
they act as a standard to whi h to compare the unknown concentrations against
The comparison can be either
-visual
-measured through calorimetry and a calibration curve
-measured through the mass of a precipitate and a calibration curve
how do we form standard solutions of known concentrations
we carry out serial dilutions of an existing stock solution
is serial dilution a dilution factor is required.Is the dilution factor the same each time
yes
Describe how you would make five dilutions with a factor of 2 starting with initial glucose concentration of 40cM and 10cm3 volume
-line up 5 test tubes
-put 5 cm3 of distilled water in the test tubes
-draw up 5cm3 of the initial glucose concentration using a pipette and place it in the first test tube. Shake to mix.Now you
have 20cM of 10 cm 3 solution
-Repeat 3 more times to create 10cM,5cm and 2.5 cM solutions
how do you calculate how much of the existing stock solution you have to draw up
(desired concentration divided by stock concentration ) times that by the volume wanted
(DC/SC) x VW
describe how you would carry out a experiment to determine the concentration of reducing sugar within a sample using a colorimeter
-carry out serial dilutions of an existing stock solution to create standard solutions of known reducing sugar concentration
-add excess benedict reagent to each solution
-heat them in thermostatically et water bath or 5 min
-If reducing sugar is present a coloured precipitate will form
-Use a filter paper to filter out the precipitate from the solutions
-Left with the unreacted blue Cu2+ ions,the more blue the solution the less concentration of reducing sugar present
-Use the colorimeter to measure the blueness of a solution,the more blue thee solution the more unreacted Cu 2+ ions left meaning that the concentration of reducing sugar is low as it hasn’t fully reacted with the ions ,reducing them to Cu+ ions which form a coloured precipitate
-Place the leftover sample in a cuvette
-calibrate the colorimeter an dinsert the cuvette
-Shine a red light through the sample ,meaning the light absorbance,the more blue a solution ,the more light will be absorbed so the lower the concentration of reducing sugar present
-Recalibrate between reading
-Repeat for the solution of unknown reducing sugar c concentration
-Use the values from the known solution to plot a calibration curve of light absorbance against concentration
-Find out the concentration of the unknown sample by drawing an in tercepyt,from the light absorbance to the calibration curve an down to the concentration
-Wear gloves and protective glasses during the eexperiment
how do you use a colorimeter
-Shine red light through the sample
-recalibrate between readings
-use a cuvette
-calibrate before using a cuvette
describe an experiment to fin the concentration of reducing sugar present in a sample through measuring the mass of the precipitate
-carry out serial dilution of an existing stock solution to make solution of known reducing sugar concentration
-place excess of
Benedict reagent in solutions, heat them for 5 min in a thermostatically set water
bath.If a reducing sugar is present, coloured precipitate will form. Filter out the precipitate using a filter paper.
Dry it couple of times.
Zero the balance an weight it , make sure we are using at least 2 decimal places balance for higher accuracy
.Zero balance
between readings.Reweight the precipitate at least twice
Do the same for the sample of unknown reducing sugar concentration
-Us the values of the known concentration solution to plot a calibration curve of mass in grams against concentration
-Find out the concentration of the sample by drawing an intercept.
limitation of the mass experiment
the precipitate may not have been fully dry
what is a biosenser and how does it work
it is an analytical device that measures the concentration of a substance
uses a catalyst-enzyme to convert a biological response into an electrical signal, which is processed to find the concentration of a substance
what enzyme do blood glucose biosensors use
glucose oxidase
describe how blood glucose biosensors work
-uses the enzyme glucose oxidase
-glucose oxidase catalyses the breakdown of glucose at the electrodes,the reaction creates a charge
-the electrodes convert the charge into a electrical signal which is processed to determine the concentration of the substance
-then the blood glucose level is dispensed as a digital figure on the screen
who uses blood glucose biosensors and why
diabetics to check their blood glucose concentration
read notes for test strips
