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

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

Keywords: atomic absorption spectrometer; compound fertilizer;

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

Atomic Absorption Spectrometry

1. Scope and Field of Application

This standard specifies the determination of lead in compound fertilizers by atomic absorption spectrometry. It is applicable to samples where the lead concentration is less than 25μg/mL.

2. Reference Standards

GB 602 – Preparation of Standard Solutions for Impurities in Chemical Reagents

GB 6682 – Specifications and Test Methods for Analytical Laboratory Water

3. Method Summary

Lead in the sample solution is atomized in an acetylene-air flame. The resulting atomic vapor absorbs light at a characteristic wavelength (283.3nm) emitted from a lead hollow cathode lamp. The absorbance is proportional to the lead concentration in the flame.

4. Reagents and Materials

All reagents used should be analytical grade unless otherwise specified. The water must meet the standards of GB 6682 for secondary or tertiary grade water.

4.1 Hydrochloric Acid (GB 622): 0.5mol/L solution. Dilute 42mL of concentrated hydrochloric acid (density 1.19) to 1L with water.

4.2 Lead Standard Solution: 0.1mg/mL. Prepared according to GB 602, 1mL corresponds to 100μg of lead.

4.3 Acetylene: Use industrial-grade acetylene (GB 6819) or equivalent.

5. Equipment

Standard laboratory equipment including an AA-1800C Atomic Absorption Spectrophotometer equipped with an air-acetylene burner and a lead hollow cathode lamp.

6. Analysis Procedure

6.1 Working Curve Preparation

Prepare a series of lead standard solutions as shown in Table 1. Dilute each to 100mL with 0.5mol/L hydrochloric acid. Measure the absorbance at 283.3nm. Plot the absorbance against lead concentration to construct the working curve.

6.2 Determination

Analyse the test solution directly or after appropriate dilution with 0.5mol/L HCl. Ensure the lead concentration is below 25μg/mL. Measure the absorbance under the same conditions as the standard solutions and determine the lead concentration from the working curve.

7. Expression of Results

7.1 If no dilution is performed, calculate the lead content using formula (1).

7.2 If a portion of the test solution is diluted, use formula (2) to calculate the lead content.

8. Acceptable Difference

The average of parallel results is taken as the final result. The relative deviation between parallel measurements should not exceed the values in Table 2.

Table 2: Allowable Relative Deviation Based on Lead Content

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

0.005–0.0020 | < 25

0.0020–0.0001 | < 50

< 0.0001 | < 100

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