Determination of lead in tap water and surface water by graphite furnace atomic absorption method

Summary

This experiment is from the official website of College of Chemistry, Qingdao University of Science and Technology.

Operation method

Determination of lead in tap water and surface water by graphite furnace atomic absorption method

Principle

Lead is a harmful substance to human body, the lead content of drinking water is an important indicator for monitoring and control by environmental protection department, and the test means are spectrophotometry, enrichment flame atomic absorption method, graphite furnace atomic absorption method and ICP-MS method, etc. The graphite furnace method, also known as the electrothermal atomic absorption method, is a method of generating high temperatures (up to 3000℃) through the heating of graphite tubes (commonly known as graphite furnaces) by a high-power power supply, through high temperatures and carbon (graphite) cleavage and reducibility to make its metal salts into metal atoms and thus absorb its characteristic spectral lines. High temperature and carbon (graphite) cleavage and reducibility, so that its metal salts into metal atoms and thus absorb the characteristic spectral lines of the analytical method of the method has the advantage of high sensitivity, than the flame sensitivity is 3-5 orders of magnitude higher. The disadvantage is that the atomization process produces smoke, serious background absorption, poor measurement accuracy. Graphite furnace heating generally have four steps, drying, ashing, atomization, heat in addition to residue, the heating method is divided into slope and step a drying temperature of about 100 ℃, the role of the solution solvent evaporation, the liquid into a solid two ashing temperature of 300 ℃ or more, the role of the complex material into a simple matter, the elimination of organic matter, the volatile material to be driven away to reduce the absorption of molecular and low-boiling point inorganic matrix. Boiling point inorganic substrate interference, convert complex salts into oxides III Atomization First cleave oxides or salts, then use high temperature carbon (graphite) to reduce metal ions to atoms. Thermal Removal Remove the original sample from the graphite tube using high temperature burning and a large air flow for the next sample measurement

Materials and Instruments

TAS-990AFG Atomic Absorption Spectrometer Microfeed Tube Working Software Lead Marker Solution Matrix Improver Nitric Acid (Superior Purity) Secondary Deionized Water Pipette Volumetric Bottle)

Move

1 Turn on the Atomic Absorption Graphite Furnace section, etc., for 15-30 minutes of preheating according to the Appendix. 2 Set the graphite furnace heating program.

Step Temperature Rising time Holding time Gas volume

Drying 140°C 10 20 Medium

Ashing 700℃ 10 25 Medium

Atomization 1800℃ 0 5 Off

Thermal Removal of Residue 2400℃ 0 5 Large

3 Standard Series Formulation

Working fluid 500ppb

Take six 25ml volumetric flasks and add working solution 0 0.25 0.5 1 1.5 2ml 5 drops per day 1:1 HNO3 with secondary water to the scale.

4 Water sample

Take 20ml tap water in a 25ml volumetric flask, add 5 drops of 1:1 HNO3 and the matrix improver to the scale with secondary water.5 Measurement

Pipette 10μl of solution (first standard and then sample) into the graphite furnace, start the heating program, repeat twice for each point.

Note: The vessel is susceptible to adsorption and should only be used to store concentrated solutions.

Prepare the standard solution as soon as it is used and leave it for no more than 4 hours.

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