CN110794086A - Method for determining purity of xylitol in granular xylitol - Google Patents

Abstract

The invention discloses a method for determining the purity of xylitol in granular xylitol, which comprises the following steps: accurately weighing 0.2g of a test sample, adding water to dissolve, diluting to 100mL, shaking up, accurately weighing 5mL of test sample solution, and placing in an iodine measuring flask; precisely adding 20mL of 0.02mol/L potassium periodate solution and 10mL of 0.5mol/L sulfuric acid solution, heating for 30min at 100 ℃ in a water bath, and cooling to room temperature; adding potassium iodide 1.5g, standing at room temperature in dark for 5min, adding 0.1mol/L Na₂S₂O₃Titrating the solution to light yellow, adding a proper amount of 1 wt% starch indicator solution, and continuing to use 0.1mol/L Na₂S₂O₃Titrating the solution until the blue color disappears; correcting the titration result by using a blank test; the xylitol purity is calculated according to a formula. The method can quickly measure the purity of the xylitol in the granular xylitol, saves time and reduces cost.

Description

Method for determining purity of xylitol in granular xylitol

Technical Field

The invention belongs to the technical field of food, and particularly relates to a method for determining the purity of xylitol in granular xylitol.

Background

In the field of food, granular xylitol is widely used as a raw material and processed into various products such as tablet candy and the like. The purity of xylitol in the raw materials has great influence on the hardness of the tablet sugar and the taste of food, and the purity of xylitol is an important index which needs to be detected by customers. Therefore, accurate, rapid and convenient methods for determining the purity of xylitol are needed.

The existing method for detecting the purity of xylitol mainly adopts gas chromatography or liquid chromatography. The gas chromatography takes erythritol as an internal standard substance to prepare an internal standard solution, xylitol, sorbitol, galactitol, mannitol and L-arabitol standard substance are weighed to prepare a standard solution, a proper amount of samples are weighed to prepare sample solutions, 1mL of each sample is taken, and detection is carried out under certain gas chromatography conditions. The liquid chromatography comprises weighing xylitol, sorbitol, galactitol, mannitol and L-arabitol standard substance to obtain standard solution, weighing appropriate amount of sample to obtain sample solution, and detecting under certain liquid chromatography condition. The main disadvantages of these methods are: a precise instrument needs to be configured, the cost is high, the sample pretreatment process is complex, and the detection time is too long.

Disclosure of Invention

The invention aims to provide a method for determining the purity of xylitol in granular xylitol so as to overcome the defects of the prior art.

The invention adopts the following technical scheme:

a method for determining the purity of xylitol in granular xylitol comprising the steps of:

step 1), precisely weighing 0.2g of a test sample, adding water to dissolve and dilute the test sample to 100mL of constant volume, shaking up, precisely weighing 5mL of test sample solution, and placing the test sample solution in an iodine measuring flask;

step 2), precisely adding 20mL of 0.02mol/L potassium periodate solution and 10mL of 0.5mol/L sulfuric acid solution into the iodine measuring flask in the step 1), heating the mixture on a water bath at 100 ℃ for 30min, and cooling the mixture to room temperature;

step 3), adding 1.5g of potassium iodide into the iodometric flask in the step 2), standing at room temperature in the dark for 5min, and adding 0.1mol/LNa₂S₂O₃Titrating the solution to light yellow, adding a proper amount of 1 wt% starch indicator solution, and continuing to use 0.1mol/L Na₂S₂O₃Titrating the solution until the blue color disappears;

step 4), correcting the titration result by using a blank test;

step 5), calculating the purity of the xylitol according to the following formula:

wherein, V_{Air conditioner}Consuming Na as a blank₂S₂O₃The number of mL of the solution,

V_{sample (A)}Consuming Na for the sample₂S₂O₃The number of mL of the solution,

1.902 is Na₂S₂O₃The conversion factor is a factor of the conversion,

0.1 is 0.1mol/L Na₂S₂O₃The value of the solution is determined by the value of the solution,

c is Na₂S₂O₃The concentration of the solution is mol/L,

m is the weight g of the sample,

1000 is a scaling factor for the number of bits,

5 precisely measuring the volume mL of the sample in the step 1),

100 is the constant volume mL of the sample in the step 1).

Further, the sample to be tested in the step 1) is weighed to be accurate to 0.001 g.

Further, 2mL of 1 wt% starch indicator solution was added in step 3).

Compared with the prior art, the invention has the following advantages:

1. the method can quickly measure the purity of the xylitol in the granular xylitol, saves time and reduces cost. The specific detection time and cost are shown in the following table:

2. compared with the national standard gas chromatography, the method of the invention has higher accuracy and can accurately determine the purity of xylitol in granular xylitol.

3. The method is simple and convenient to operate, and the purity of the xylitol in the granular xylitol can be quickly measured in the process of checking and accepting raw materials.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention adopts an oxidation-reduction titration method to determine the purity of xylitol in granular xylitol, and the principle is as follows:

CH₂OH-(CHOH)₃-CH₂OH+5IO₄ ^-+2H⁺→2HCHO+3HCOOH+5IO₃ ^-+2H₂O

IO₄ ^-+7I^-+8H⁺→4I₂+4H₂O

IO₃ ^-+5I^-+6H⁺→3I₂+3H₂O

I₂+2Na₂S₂O₃→2NaI+Na₂S₄O₆

the method specifically comprises the following steps:

step 1), precisely weighing 0.2g (precisely to 0.001g) of a test sample, adding water to dissolve and dilute the test sample to 100mL, shaking up, precisely weighing 5mL of test sample solution, and placing the test sample solution in an iodine measuring flask.

Step 2), precisely adding 20mL of 0.02mol/L potassium periodate solution and 10mL of 0.5mol/L sulfuric acid solution into the iodine measuring flask in the step 1), heating the mixture on a water bath at 100 ℃ for 30min, and cooling the mixture to room temperature.

Step 3), adding 1.5g of potassium iodide into the iodometric flask in the step 2), standing at room temperature in the dark for 5min, and adding 0.1mol/LNa₂S₂O₃The solution is titrated to light yellow, 2mL of 1 wt% starch indicator solution is added, and 0.1mol/L Na is continuously used₂S₂O₃The solution titrated until the blue color disappeared.

Step 4), correcting the titration result by using a blank test.

Step 5), calculating the purity of the xylitol according to the following formula:

wherein, V_{Air conditioner}Consuming Na as a blank₂S₂O₃The number of mL of the solution,

V_{sample (A)}Consuming Na for the sample₂S₂O₃The number of mL of the solution,

1.902 is Na₂S₂O₃The conversion factor is a factor of the conversion,

0.1 is 0.1mol/L Na₂S₂O₃The value of the solution is determined by the value of the solution,

c is Na₂S₂O₃The concentration of the solution is mol/L,

m is the weight g of the sample,

1000 is a scaling factor for the number of bits,

5 precisely measuring the volume mL of the sample in the step 1),

100 is the constant volume mL of the sample in the step 1).

0.1mol/L of Na per 1mL₂S₂O₃The solution corresponded to 1.902mg of C₅H₁₂O₅。

Example 1

The method for determining the purity of xylitol and the method for determining the content of xylitol by using the gas chromatography in appendix A.3 of the national standard GB1886.234 are respectively used for determining the purity of xylitol in the following 6 granular xylitol samples, and the results are shown in the following table:

item	Sample 1	Sample 2	Sample 3	Sample No. 4	Sample No. 5	Sample No. 6
							The method of the invention	99.74	99.78	99.76	99.79	99.80	99.72
National standard gas chromatography	99.79	99.81	99.73	99.84	99.86	99.75
							Deviation of	-0.05	-0.03	+0.03	-0.05	-0.06	-0.03

From the above table, it can be seen that the xylitol purity measured by the method of the invention is basically consistent with the detection result of the national standard gas chromatography, and the deviation is within 0.1.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (3)

1. A method for determining the purity of xylitol in granular xylitol, which is characterized by comprising the following steps:

step 1), precisely weighing 0.2g of a test sample, adding water to dissolve and dilute the test sample to 100mL of constant volume, shaking up, precisely weighing 5mL of test sample solution, and placing the test sample solution in an iodine measuring flask;

step 2), precisely adding 20mL of 0.02mol/L potassium periodate solution and 10mL of 0.5mol/L sulfuric acid solution into the iodine measuring flask in the step 1), heating the mixture on a water bath at 100 ℃ for 30min, and cooling the mixture to room temperature;

step 3), adding 1.5g of potassium iodide into the iodometric flask in the step 2), standing at room temperature in the dark for 5min, and adding 0.1mol/LNa₂S₂O₃Titrating the solution to light yellow, adding a proper amount of 1 wt% starch indicator solution, and continuing to use 0.1mol/L Na₂S₂O₃Titrating the solution until the blue color disappears;

step 4), correcting the titration result by using a blank test;

step 5), calculating the purity of the xylitol according to the following formula:

wherein, V_{Air conditioner}Consuming Na as a blank₂S₂O₃The number of mL of the solution,

V_{sample (A)}Consuming Na for the sample₂S₂O₃The number of mL of the solution,

1.902 is Na₂S₂O₃The conversion factor is a factor of the conversion,

0.1 is 0.1mol/L Na₂S₂O₃The value of the solution is determined by the value of the solution,

c is Na₂S₂O₃The concentration of the solution is mol/L,

m is the weight g of the sample,

1000 is a scaling factor for the number of bits,

5 precisely measuring the volume mL of the sample in the step 1),

100 is the constant volume mL of the sample in the step 1).

2. The method of determining the purity of xylitol in granular xylitol according to claim 1, wherein the sample to be tested in step 1) is weighed to the nearest 0.001 g.

3. The method for determining the purity of xylitol in granular xylitol according to claim 1, wherein 2mL of 1% by weight starch indicator solution is added in step 3).