Determination of lead in compound fertilizer by AA-1800 atomic absorption spectrometry - Master's thesis - Dissertation

Determination of Lead in Compound Fertilizer by AA-1800 Atomic Absorption Spectrometer

Key words: atomic absorption spectrometer; compound fertilizer; lead analysis

This standard outlines the procedure for determining lead content in compound fertilizers using atomic absorption spectrometry.

The method involves atomizing the sample in an acetylene-air flame and measuring the absorption at a wavelength of 283.3 nm using a lead hollow cathode lamp.

The absorbance is directly proportional to the concentration of lead in the sample.

1. Scope and Application

This method is suitable for determining lead content in compound fertilizers where the lead concentration is less than 25 μg/mL.

2. Reference Standards

GB 602 – Preparation of standard solutions for impurity determination in chemical reagents

GB 6682 – Specifications and test methods for analytical laboratory water

3. Principle of the Method

Lead in the sample solution is atomized in an acetylene-air flame. The atomic vapor absorbs light emitted by a lead hollow cathode lamp at 283.3 nm. The amount of absorbed light is proportional to the lead concentration in the flame.

4. Reagents and Materials

Use high-purity reagents unless otherwise specified. Water should meet the requirements of GB 6682 (second or third grade).

4.1 Hydrochloric acid (c=0.5 mol/L): Dilute 42 mL of concentrated HCl (density 1.19) to 1 L with distilled water.

4.2 Lead standard solution (0.1 mg/mL): Prepared according to GB 602.

4.3 Acetylene gas: Use pure acetylene or equivalent.

5. Equipment

AA-1800C Atomic Absorption Spectrophotometer with air-acetylene burner and lead hollow cathode lamp.

6. Procedure

6.1 Preparation of Working Curve

Prepare a series of lead standard solutions (0, 5, 10, 15, 20, 25 μg/mL) by diluting the lead standard solution with 0.5 mol/L hydrochloric acid. Measure the absorbance at 283.3 nm and plot the working curve.

6.2 Sample Analysis

Prepare the sample solution as described in GB/T 14539.1, section 5.2. Measure the absorbance under the same conditions as the standard solutions. Determine the lead concentration from the working curve.

7. Expression of Results

7.1 If no dilution is required, calculate the lead content (X5) using the formula: X5 = (c × 200) / m

Where c = concentration of lead (μg/mL), m = mass of the sample (g), 200 = total volume of the solution (mL).

7.2 If the sample is diluted, use the formula: X5 = (c × 200 × V1) / (m × V2)

Where V1 = volume of sample taken (mL), V2 = total volume of the diluted solution (mL).

8. Acceptable Deviation

The relative deviation between parallel determinations should not exceed the values given in Table 2.

Table 2: Allowable Relative Deviation

Lead Content (%) | Allowable Relative Deviation (%)

0.005–0.0020 | < 25

0.0020–0.0001 | < 50

< 0.0001 | < 100