This standard specifies the gravimetric determination of formic acid content in fruits, vegetables and their products. This standard applies to the determination of formic acid content in fruits, vegetables and their products. GB/T 15664-1995 Gravimetric determination of formic acid content in fruits, vegetables and their products GB/T15664-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of formic acid content in fruits, vegetables and their products--Gravimetric method
Fruit, vegetable and their products--Determination of formic acid content-Gravimetric method
GB/T15664-1995
This standard is equivalent to the international standard ISO6638-1:1985 "Determination of formic acid content in fruit and vegetable products" Part 1: Gravimetric method.
1 Subject content and scope of applicationbzxz.net
This standard specifies the gravimetric determination of formic acid content in fruits, vegetables and their products. This standard is applicable to the determination of formic acid content in fruits, vegetables and their products. 2 Principle
The formic acid in the sample is distilled out and absorbed by barium carbonate (or calcium carbonate) to generate barium formate (or calcium formate). Barium formate (or calcium formate) quantitatively reduces mercuric chloride to mercurous chloride, and then the amount of formic acid is calculated based on the mass of mercurous chloride. 3 Reagents and solutions
All reagents used in this standard are analytically pure, and the water used is deionized water or distilled water. 3.1 Barium carbonate (GB654) or calcium carbonate (HG3-1066); 3.2 Mercuric chloride, sodium fluoride mixture:
Weigh 100g mercuric chloride (HG3-1068) and 30g sodium chloride (GB1266) and dissolve them in water and dilute to 1L. 3.3 Sodium acetate solution:
Weigh 500g sodium acetate (GB693) and dissolve them in water and dilute to 1L. 3.4 Hydrochloric acid (GB622) solution: 10% (m/m). 3.5 Tartaric acid (GB11294).
3.6 95% ethanol (GB679).
Ether (HG 3-1002).
4 Instruments and Equipment
Analytical balance, sensitivity 0.0002g.
4.2 Steaming filling device See figure:
Approved by the State Administration of Technical Supervision on August 18, 1995, 200
Implemented on June 1, 1996
Steam generator, volume 5I.
GB/T15664-1995
Distillation device diagram (4.2)
Long-necked flasks A, B, volume 0.5L, neck length 12cm. 4.2.3 Condenser, length 50cm.
Conical flask, volume 1L.
4.2.5 Adjustable electric furnace: 500~1000W.
Electric furnace: 2000W.
4.3 Crucible filter, 1G4.
Dryer.
4.5 Oven, 100±2℃.
4.6 Stirrer.
4.7 Conical flask, volume 0.5L.
4.8 Rapid quantitative filter paper, 15cm.
4.9 Bent-neck funnel.
4.10 Water bath.
Suction filter.
5 Analysis steps
5.1 Sample preparation
After removing the inedible parts (such as fruit kernels, hard seed shells, etc.), the sample is mashed and mixed with a stirrer (4.6). Frozen samples must be thawed in a sealed container before the sample and liquid are mashed and mixed. 5.2 Sampling
5.2.1 Liquid samples
Use a pipette to draw 2550 mL of liquid sample (formic acid content is less than 0.15 g) and add it to flask A (4.2.2) and add water to a total volume of 100 ml (this step can also be done by weighing the mass to an accuracy of 0.01 g). 5.2.2 Viscous and solid samples
Weigh 25 to 50 g of sample to an accuracy of 0.01 g, transfer it to flask A (4.2.2) (formic acid content is less than 0.15 g) and add water to a total volume of 201
GB/T15664--1995
100 mL. If necessary, soak the sample in water for 1 to 2 hours. 5.3 Distillation
5.3.1 Add 0.5~1.0g of tartaric acid (3.5) to flask A, weigh 2g of barium carbonate (or calcium carbonate) (3.1) to flask B (4.2.2) and add water to 100mL.
5.3.2 Connect flasks A and B between the steam generator (4.2.1) and the condenser (4.2.3) as shown in the figure, and heat the steam generator (4.2.1) and flasks A and B at the same time.
Control the temperature of the electric furnace and the amount of steam in the distillation apparatus so that the volume change of the solution in flasks A and B does not exceed 10mL. Collect 1000mL of the distillate in a conical flask (4.2.4) and discard. 5.3.3 Use a fast quantitative filter paper (4.8) to filter the hot solution in flask B into a 0.5L conical flask (4.7), and wash flask B 3 to 4 times with hot water. Pour the washing liquid into the filter paper each time. The final solution in the conical flask is about 250mL. Place the conical flask in an electric furnace to heat and evaporate until the solution in the flask is about 100mL. 5.3.4 Take 10mL of sodium acetate solution (3.3), 2mL of hydrochloric acid solution (3.4) and 25mL of mercuric chloride and sodium chloride mixture (3.2) into a conical flask (4.7), cover it with a bent-neck funnel (4.9), keep it in a water bath (4.10) at 100±2℃ for 2h, take it out and cool it (barium formate quantitatively reduces mercuric chloride to form mercurous nitride precipitation). Wash the crucible filter (4.3), dry it, balance it in a desiccator for 0.5h, and weigh it to an accuracy of 0.0002g. Wash all the precipitate with cold water into the crucible, filter it with suction, and wash the precipitate with 95% ethanol (3.6) and ether (3.7) respectively. 5.3.5 Dry the crucible filter containing the mercurous chloride precipitate in an oven at 100±2℃ for 1 hour, take it out and put it in a desiccator to cool, and weigh it to the nearest 0.0002g.
6 Expression of analysis results
6.1 Calculation method and formula
When measured by volume, the formic acid content (X,) is expressed in g/100 mL and is calculated according to formula (1): a.
X, = (m2 = -m) × 0. 097 5 × 100V
When measured by mass, the formic acid content (X,) is expressed in g/100g and is calculated according to formula (2): b.
X = (m2 = mi) × 0. 097 5 × 100mo
Sample volume, mL;
Wherein: V-
mass of the crucible filter, g
-mass of the crucible filter plus mercurous chloride precipitate, g: m2
m. Sample weight, g;
0.0975——conversion factor, one gram of mercurous chloride is equivalent to grams of formic acid. 6.2 Repeatability
·(2)
Each sample is measured twice in parallel, and the arithmetic mean is taken as the measurement result. The result is rounded to three decimal places. The error should meet the following requirements: when the formic acid content is less than 0.010g/100mL (liquid) or 0.010% (solid), the relative difference between the two parallel measurement results is not more than 15%;
When the formic acid content is 0.010～0.100g/100mL (liquid) or 0.010%~0.100% (solid), the relative difference between the two parallel measurement results is not more than 10%;
When the formic acid content is greater than 0.100g/100mL (liquid) or 0.100% (solid), the relative difference between the two parallel measurement results is not more than 2%.
Additional Notes:
T15664—1995
This standard was proposed by the Ministry of Agriculture of the People's Republic of China. This standard is under the jurisdiction of the National Agricultural Analysis Standardization Technical Committee. This standard was drafted by the Agricultural Testing Center of the Hubei Academy of Agricultural Sciences. The main drafters of this standard are Wang Fuhua, Long Renjun, Mai Ming203
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