NY/T 299-1995 Determination of total potassium in organic fertilizers NY/T299-1995 standard download decompression password: www.bzxz.net

Agricultural Industry Standard of the People's Republic of China
Determination of Total Potassium in Organic Fertilizers
1 Subject Content and Scope of Application
This standard specifies the determination of total potassium in organic fertilizers by sulfuric acid-hydrogen peroxide digestion and flame photometry. This standard is applicable to the determination of total potassium content in non-mud organic fertilizers. 2 Reference Standards
GB/T6682 Specifications and Test Methods for Water Used in Analytical Laboratories 3 Determination Principlewww.bzxz.net
NY/T 299-1995
Organic fertilizer samples are digested with sulfuric acid-hydrogen peroxide and diluted and then determined by flame photometry. Within a certain concentration range, the potassium concentration in the solution is in direct proportion to the luminescence intensity.
4 Reagents
Except for those specified, all reagents used are analytically pure. The experimental water meets the specifications of Grade 3 water in Chapter 5 of GB/T6682. 4.1 Sulfuric acid (GB/T625).
4.2 Hydrogen peroxide (GB/T6684).
4.3 Potassium standard stock solution: 1mg/mL
Weigh 1.907g potassium chloride (GB646) dried at 110℃ for 2h, dissolve it in water and make up to 1L. This solution contains 1mg potassium (K) in 1mL and is stored in a plastic bottle.
4.4 Potassium standard solution: 100μg/mL
Put 10.00mL potassium (K) standard stock solution 4.3) in a 100mL volumetric flask and make up to volume with water. This solution contains 100μg potassium (K) in 1mL.
5 Instruments and equipment
Usually use laboratory instruments and
5.1 Analytical balance: sensitivity 0.1mg.
5.2 Adjustable electric furnace: 1000W.
5.3 Flame photometer.
5.4 Kelvin flask: 50 or 100ml.
5.5 Volumetric flask: 50, 100, 1000mL.
5.6 Pipette: 5, 10mL.
5.7 Small curved funnel: $2cm.
5.8 Erlenmeyer flask with stopper: 150mL.
Approved by the Ministry of Agriculture of the People's Republic of China on November 23, 1995 and implemented on May 1, 1996
6 Preparation of test specimens
NY/T 299—1995
Take the air-dried laboratory sample, mix it thoroughly, and then reduce it to about 100g by quartering method, crush it, and let it all pass through a 1mm aperture sieve, and put it into a sample bottle for use.
7 Analysis steps
7.1 Preparation of sample solution
Weigh 0.5g of the sample (for liquid fertilizers such as urine or feces, weigh 1~~2g of liquid directly), accurately to 0.001g, and place it at the bottom of the Kelvin flask (5.4). Rinse the sample adhering to the wall with a small amount of water, add 5.0mL of sulfuric acid (4.1) and 1.5mL of hydrogen peroxide (4.2), and shake carefully. Place a small curved-neck funnel (5.7) at the mouth of the flask and leave it overnight. Slowly heat the flask on an adjustable electric stove (5.2) until the sulfuric acid smokes, remove it, add 15 drops of hydrogen peroxide (4.2) after it cools slightly, shake the Kelvin flask gently, heat for about 10 minutes, remove it, add 5~10 drops of hydrogen peroxide (4.2) in batches after it cools slightly, and boil it in batches until the solution becomes colorless or light yellow clear liquid, continue heating for 10 minutes, and remove the remaining hydrogen peroxide. Remove and cool slightly, carefully add water to 20-30mL, and heat to boiling. Remove and cool, rinse the bent-neck funnel with a small amount of water, and collect the washing liquid in the original Kelvin flask. Transfer the digestion solution to a 100mL volumetric flask, add water to the volume, let it stand to clarify or filter it with filter paper into a dry stoppered triangular flask (5.8) for use. Perform two parallel determinations with the sample.
7.2 Preparation of blank solution
Except for not adding the sample, the reagents and operating steps used are the same as 7.1. 7.3 Drawing of calibration curve
Put 0, 2.50, 5.00, 7.50, 10.00mL of potassium standard solution (4.4) into 5 50mL volumetric flasks respectively, add blank solution of the same volume as the sample solution, and make up to volume with water. This solution is a standard solution series containing 0, 5.00, 10.00, 15.00, 20.00μg of potassium (K) in 1mL. On the flame photometer, adjust the instrument zero point with the blank solution, and adjust the full scale to 80 divisions with the standard solution with the highest concentration in the standard solution series. Then measure other standard solutions from low concentration to high concentration in turn, and record the instrument indication. Draw a calibration curve or find a linear regression equation based on the potassium concentration and the instrument indication. 7.4 Determination
Pipette 5.00mL of the sample solution (7.1) into a 50mL volumetric flask and make up to volume with water. Determine on the flame photometer under the same conditions as the standard solution series, and record the instrument indication. The instrument must be calibrated with a potassium standard solution after measuring every 5 samples. 8 Expression of analytical results
Total potassium (K) content is expressed in g/kg and is calculated as follows: Total potassium (K) = ·V·D,
obtained from the calibration curve or obtained from the regression equation, ug/mL; where; c—
V—measurement volume, 50mL for this operation;
D-—division multiple, fixed volume/division volume, 100/5; m
-weighed sample mass, g
factor for converting from μg/g to g/kg.
The result should be expressed to two decimal places.
9 Tolerance
9.1The arithmetic mean of the results of two parallel determinations shall be taken as the determination result. 9.2 The allowable difference between the results of two parallel determinations shall meet the requirements of the following table: 430
Additional Notes:
K, g/kg
5.1~10. 0
NY/T299—1995
This standard is proposed by the National Soil and Fertilizer Station of the Ministry of Agriculture. Allowable difference, g/kg
This standard is drafted by the National Soil and Fertilizer Station of the Ministry of Agriculture and Changsha Soil and Fertilizer Testing Center. The main drafters of this standard are He Pingan, Su Yunhui, Liu Haihe, Du Yuanshen and Du Sen. 431
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