Determination of sodium in imported fertilizer by atomic absorption spectrophotometry - Master's thesis - Dissertation

Determination of sodium in imported fertilizer by atomic absorption spectrophotometry

Key words: atomic absorption spectrophotometry; content of imported chemical fertilizer sodium;

;

This standard specifies methods for determining the sodium content of imported fertilizers.

1

Scope of application

Suitable for potassium chloride and the like.

2

Method summary

The sample is dissolved in water and used in an aqueous solution.

Atomic absorption spectrophotometer

At wavelength

589.0nm

With air

-

The absorbance of sodium was determined by acetylene flame.

3

instrument

AA-1800

Atomic absorption spectrophotometer: with air

-

Acetylene burner and sodium hollow cathode lamp.

The atomic absorption spectrophotometer used should meet the following criteria:

Minimum sensitivity: the highest concentration standard of the equivalence concentration standard solution has an absorbance reading not lower than

0.2

.

Working curve linearity: the difference between the absorbance readings of the two highest concentration standard solutions in the equivalence concentration standard solution, not less than the difference between the lowest concentration standard solution and the zero concentration solution absorbance reading

0.8

Times.

Minimum stability: the absorbance reading obtained by multiple measurements of the highest concentration standard solution and the zero concentration solution, the coefficient of variation of the average value of the absorbance reading of the highest concentration standard solution should be no more than

1.5

%with

0.6

%

(

See Appendix

A)

.

Working conditions of atomic absorption spectrophotometer: see appendix

B

.

4

Reagent

4.1

Potassium chloride

(1

%

)

: weighing

1g

Sodium chloride-free reference potassium chloride, soluble

100mL

In the water.

4.2

Sodium standard solution

(1mg/mL)

: Accurately weigh the spectrum of pure sodium chloride

2.544g

in

200mL

In the beaker, dissolve in water, move in

1L

In a volumetric flask, dilute to the mark with water, mix and store in a plastic bottle. This solution

1mL

Contain

1mg

sodium.

4.3

Sodium standard solution

(100?g/mL)

: Accurately draw

50mL

Sodium standard solution

(4.2)

Placed

500mL

In the volumetric flask. Dilute to the mark with water, mix, this solution

1mL

Contain

100?g

sodium.

5

Operating procedure

5.1

Test solution preparation

Weigh sample

1g (

Accurate to

0.001g)

in

250mL

In the beaker, add

50mL

Water, heat at low temperature, let the sample dissolve completely, move in

100mL

In a volumetric flask, dilute to the mark with water, mix and place for a while to clarify or dry filter.

5.2

Determination of sodium absorbance

draw

5mL

Solution

(

Or filtrate

) (5.1)

in

100mL

In a volumetric flask, dilute to the mark with water and mix. On an atomic absorption spectrophotometer, wavelength

589.0nm

Turn to the burning head

30

°, in the air

-

In the acetylene flame, the water is adjusted to zero with the standard solution series, and the absorbance of sodium is measured, and the corresponding amount of sodium is detected from the working curve.

5.3

Drawing of the working curve

Accurate absorption

0

,

1

,

2

,

3

,

4mL

Sodium standard solution

(4.3)

Group

100mL

In the volumetric flask, join

1mL

Potassium chloride solution

(4.1)

Dilute to the mark with water, mix well, adjust to zero with water, and measure the absorbance of sodium. The working curve is plotted with the concentration of sodium as the abscissa and the absorbance as the ordinate.

6

Result calculation

The percentage of sodium is calculated as follows:

In the formula:

c

─ Find the concentration of sodium from the sodium work curve,

?g/mL

;

V

─ the volume of the sample at the time of measurement,

mL

;

m

──

V

The mass of the sample contained in the milliliter test solution,

g

.

appendix

A

Calculation of minimum stability coefficient of variation

(

Supplement

)

The formula for calculating the coefficient of variation of the absorbance readings of the highest concentration standard solution and the zero concentration solution is as follows:

................................................

(A1)

................................................

(A2)

In the formula:

Sc

─ the percent coefficient of variation of the absorbance reading of the highest concentration standard solution;

So

─ percent change coefficient of absorbance reading of zero concentration solution;

─ the average of the absorbance readings of the highest concentration standard solution;

C

─ absorbance reading of the highest concentration standard solution;

─ the average of the absorbance readings of the zero concentration solution;

O

─ zero concentration solution absorbance reading;

n

─ The number of measurements.

appendix

B

Instrument working conditions

(

Reference piece

)

use

AA-1800

The reference working conditions for the determination of sodium by atomic absorption spectrophotometer are as follows:

Analysis line:

589.0nm turn

30

°;

Slit width:

0.5;

Lamp current:

8mA;

Air flow:

45L/min;

Acetylene flow:

20L/min.

Key words: atomic absorption spectrophotometry; content of imported chemical fertilizer sodium;

;