NY/T 1972-2010Water-soluble fertilizers - Determination of sodium, selenium, silicon content (English PDF)

3.1 Flame photometric method

3.1.1 Principle

The sodium atoms in the sample solution are excited by the thermal energy

of the flame; when the excited electron is transited from a higher energy level

to a lower energy level, it can release a certain energy, which will generate

the spectral line of a fixed wavelength; USE the optical system to measure

the radiant energy, in order to obtain the sodium content.

3.1.2 Reagents and materials

WEIGH 0.2 g ~ 3 g sample (accurate to 0.0001 g); PLACE it into a 250mL

volumetric flask; USE water to make it reach to constant volume; MIX it

uniformly; dry FILTER it; DISCARD the first few milliliters of filtrate; USE the

rest filtrate for measurement.

3.1.4.3 Drawing of working curve

Respectively PIPETTE 0 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL,

6.00 mL, AND 7.00 mL of sodium standard solution (3.1.2.2) into eight 100

mL volumetric flasks; USE water to make it reach to constant volume; MIX it

uniformly. The sodium's mass concentration of this standard series solution

is respectively 0 µg/mL, 1.00 µg/mL, 2.00 µg/mL, 3.00 µg/mL, 4.00 µg/mL,

5.00 µg/mL, 6.00 µg/mL, AND 7.00 µg/mL. On the flame photometer of

selected working conditions, based on the sodium concentration of the

solution to be tested, SELECT six points from the standard series solution;

USE the 0 µg/mL standard solution to adjust the zero point of the instrument;

from low concentration to high concentration, respectively MEASURE the

emission intensity of each standard solution. USE the sodium's mass

concentration of each standard series solution (µg/mL) as the abscissa AND

the corresponding emission intensity as the ordinate; DRAW the working

curve.

3.1.4.4 Measurement

USE the sample solution OR the solution which is diluted to certain ratio,

under the same conditions of the standard series solution for measurement

purposes, to measure the emission intensity of sodium; from the working

curve, FIND the corresponding mass concentration of the sodium (µg/mL).

3.1.4.5 Blank test

Except for not adding of sample, the rest steps are same as the sample

solution measurement.

3.1.5 Analysis result presentation

The sodium (Na) content w1 is expressed in mass fraction (%), AND

calculated in accordance with the equation (1).

Where.

rho – The sodium's mass concentration of the sample solution as found from

the working curve, in the unit of micrograms per milliliter (µg/mL);

3.2.2.2 Cesium chloride solution. rho (CsCl) = 4 g/L. WEIGH 4 g of cesium

chloride and DISSOLVE it in water; USE water to dilute it to 1 L; MIX it

uniformly.

3.2.2.3 High purity argon.

3.2.3 Instruments

3.2.3.1 Ordinary laboratory instruments;

3.2.3.2 Horizontal reciprocating oscillators OR oscillators with equivalent

functions.

3.2.3.3 Plasma emission spectrometer.

3.2.4 Analysis procedures

3.2.4.1 Sample preparation

With respect to the solid samples, after multiple times of splitting, TAKE out

about 100 g; rapidly GRIND it to the grain which can all pass the 0.50 mm

pore size sieve (if the sample is wet, it shall pass through the 1.00 mm pore

size sieve); MIX it uniformly; PLACE it in a clean AND dry container; after the

liquid sample is subject to multiple times of shaking, quickly TAKE out about

3.2.4.2 Sample solution preparation

3.2.4.2.1 Solid sample

WEIGH 0.2 g ~ 3 g of sample (accurate to 0.0001 g); PLACE into a 250 mL

volumetric flask; ADD 150 mL of water; PLACE it into the (25 ± 5) °C

oscillator; under the oscillating frequency of (180 ± 20) r/min, OSCILLATE it

for 30 min; TAKE it out; USE water to make it reach to constant volume; MIX

it uniformly; dry FILTER it; DISCARD the first few milliliters of filtrate; USE the

rest filtrate for measurement.

3.2.4.2.2 Liquid sample

WEIGH 0.2 g ~ 3 g sample (accurate to 0.0001 g); PLACE it into a 250mL

volumetric flask; USE water to make it reach to constant volume; MIX it

uniformly; dry FILTER it; DISCARD the first few milliliters of filtrate; USE the

rest filtrate for measurement.

3.2.4.3 Drawing of working curve

3.2.6 Allowable difference

The relative difference of the parallel measurement results is not more than

10%;

The relative difference between the measurement results from different

laboratories is not more than 30%.

When the measurement result is less than 0.15%, the relative difference of

the parallel measurement results AND the measurement results from

different laboratories will not be considered.

3.3 Atomic absorption spectrophotometric method

3.3.1 Principle

USE the flame emission method of atomic absorption spectrophotometer to

measure the sodium content. DO not use the sodium hollow cathode lamp.

Under the effect of air – acetylene flame, the sodium in the sample solution is

converted into gaseous atom, AND the atom's outer layer electrons are

further excited; when the excited electrons are transited from the higher

energy level to the lower energy level, the atom will release the excess

energy to produce the spectral line of characteristic emission; within the

certain range, the emission spectral line intensity is directly proportional to

the sodium atom concentration; through measuring the 330.2 nm emission

spectral line intensity, MEASURE the sodium content of the sample.

3.3.2 Reagents and materials

The preparation of the reagents, water and solution which are used in this

standard shall, unless otherwise indicated of specifications AND preparation

methods, be in accordance with the provisions of HG/T 2843.

3.3.2.1 Sodium standard solution. rho (Na) = 1 mg/mL.

3.3.2.2 Dissolved acetylene.

3.3.3 Instruments

concentration range, the fluorescence intensity is directly proportional to the

selenium content of the sample solution.

4.2.1 Potassium hydroxide solution. rho (KOH) = 5 g/L.

4.2.2 Potassium borohydride solution. rho (KBH4) = 20 g/L. WEIGH 10.0 g of

potassium borohydride; DISSOLVE it into the 500 mL of potassium hydroxide

solution (4. 2.1); MIX it uniformly.

4.2.3 Potassium ferricyanide solution. rho {K3[Fe(CN)6]} = 20 g/L.

4.2.4 Hydrochloric acid solution. phi (HCl) = 3 %.

4.2.5 Hydrochloric acid solution. phi (HCl) = 50 %.

4.2.6 Selenium standard solution. rho (Se) = 1000 µg/mL.

4.2.7 Selenium standard solution. rho (Se) = 10 µg/mL. Accurately PIPETTE

10.00 mL of selenium standard solution (4.2.6); USE hydrochloric acid

solution (4.2.4) to make its volume reach to 1000 mL; MIX it...

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