The Felin reagent method determines total sugar.

related topics . First, the experimental purpose
to master the principles and methods of
total sugar by
reagent method of ferrin reagents.II, Experimental Principle
Reduced sugar refers to monosaccharies containing free aldehyde (e.g. glucose) or ketones (e.g., fructose) and certain glycosaccharies (e.g. lactose, maltose). In alkaline solutions, reduced sugars can restore metal ions (Cu2 plus, Hg2 plus, Ag plus, etc.), while the sugar itself is oxidized into
a variety of
acid
.
is often used for the qualitative and quantitative determination of sugar. In this experiment, the heat titration method of ferrin reagent was used, and the ferrin reagent was an oxidant, consisting of two solutions, A and B. Melphate contains ketones and submethyl blues (redox indicators); When A and B solutions are mixed, copper sulfate reacts with sodium hydroxide to produce sky-blue copper hydroxide precipitation. In alkaline solutions, potassium saline sodium and precipitated copper hydroxide act to form soluble enses.
Feiling reagents are alkaline solutions containing Cu2 plus that oxidize sugars with free or ketone-based properties, which in themselves are reduced to red or yellow Cu2O (due to the different precipitation speeds, the resulting particle sizes are different, the particles are large red and the small ones are yellow).
III, instruments and reagents
instruments
acid titration tube (25mL), suction tube (5,10mL), capacity bottle (100mL), electric furnace, conical bottle (250mL), dropper, drip board.
reagents
.1. Ferin Reagents (quantitative)
Ferin meth liquid 15g copper sulfate and 0.05g methyllanin dissolved in 1000mL water;
Ferin ethyl fluid called 50g potassium citrate sodium, 54g sodium hydroxide and 4g potassium iron cyanide dissolved in 1000mL water.
2. The standard glucose solution is called taking glucose (pre-dried at 105 degrees C, constant weight) 1g, dissolved with a small amount of distilled water and added 8mL of thick hydrochloric acid (to prevent the growth of
microorganisms
), and then with distilled water to 1000mL.
6mol/L hydrochloric acid solution
.4. 10% sodium hydroxide
5. 85% ethanol
6. Phenol indicator
7. Iodine reagents (potassium iodide - iodine solution) 4, operating steps
(i) blank Assay
accurately absorb 5mL each of the Ferin meth and distilled water 5mL into a 250mL conical bottle, and then add a quantitative standard glucose solution with a titration tube, mix it well and place it on the asbestos network
heat
, the solution in the bottle should be boiled within 2min, at a rate of 4 to 5s per drop of glucose dripping from the titration tube until it disappears blue. The sum of the amount of standard glucose solution added before boiling and the amount of standard glucose solution used for titration after boiling is the number of standard glucose liquid mL (V1) used to determine the blank.
titration process must be carried out quickly in a boiling state and should generally be completed within 3min. Therefore, in addition to controlling the titration speed, a portion of the standard glucose solution needs to be added before titration. The amount of the liquid added should be determined at the time of the preparatory titration test prior to formal titration, while the operating conditions are exercised.
(ii) Reduction sugar determination
accurately called potato powder 4g into a 250mL conical bottle, add 85% ethanol 50mL, in 50 degrees C
rout temperature
water bath immersion 30min, and often stir.
filter
the filter and collect the filter. The filter residue was treated twice with 85% ethanol, filtered, and the residue was washed with 85% ethanol at 50 degrees C. Combine the above filter and washing liquid, steam off ethanol, move into a 100mL capacity bottle, with distilled water to the scale, that is, to determine the reduction of sugar sample fluid.
Apply ethanol (80% to 85%) to extract the reduced sugar of the sample under test, because when extracted with water (even ice water) or thin ethanol (10%), soluble starch can dissolve with the reduced sugar, resulting in a high reduced sugar content and low starch content. If the insoluble starch in the sample to be tested (in the case of iodine is blue), the reduced sugar can be extracted from water. The use of 85% ethanol extraction is assumed to be
dyer
the sample, if the sample water content is high, the ethanol concentration needs to be increased accordingly.
Accurately absorb the sample liquid 5mL placed in a 250mL conical bottle, add Ferin A liquid, B liquid each 5mL, heat to boil on the electric furnace, and then according to the blank measurement of the titration speed dripped into the standard glucose liquid until the blue disappeared, note the titration of the number of mL (V2). Oxidation is closely related to temperature, boiling time, solution concentration and acidity, and should be strictly operated in addition to accurate reagents. When titration the sample, it should be as consistent as possible with the operating conditions of the blank determination.
(iii) total sugar determination
accurately named potato powder 1g, add 6mol/L hydrochloric acid 10mL, distilled water 15mL, mixed well. After heating 30min in the boiling water bath, take out a few drops of hydrolyte with potassium iodide-iodine solution to check whether the hydrolysalization is complete, if it has been hydrated completely, it does not appear blue. After cooling, add phenolic indicator 1 drop, with 10% sodium hydroxide to the solution is slightly red, filtration, filter solution to 100mL, accurate absorption of the solution 10mL, moved into the 100mL capacity bottle and fixed to the scale, that is, to determine the total sugar sample solution.
Accurately absorb the sample amount of 5mL put in a 250mL conical bottle, add Ferin A liquid, B liquid each 5mL, mix well, and then according to the determination of reduced sugar the same operation for titration, recorded in the consumption of standard glucose mL (V2). , calculate V1 - the standard glucose volume (mL) consumed to determine blanks.
V2 - the volume (mL) of standard glucose consumed to determine reduced sugar or total sugar.
.