Aplicações

1. Princípio do método

After appropriate pretreatment, the sample is injected into a graphite tube atomizer. Lead ions are dissociated into atomic vapor at high temperatures within the graphite tube. The ground-state atoms of the target element absorb the resonance line emitted by a lead hollow cathode lamp, and the absorption intensity is proportional to the lead concentration within a certain range, enabling quantitative analysis of lead content.

1. Instrumentos e reagentes
2. Instruments and Equipment

– Detection Instruments:

– Temperature-controlled electric hot plate (room temperature–300°C)

– 10 mL colorimetric tubes

– Micropipettes (20μL–200μL, 100μL–1000μL, 1000μL–5000μL)

– 100 mL and 1000 mL volumetric flasks

– Pretreatment Equipment: Same as detection instruments, used for sample digestion and solution preparation.

2. Reagentes

– Key Reagents:

– MOS-grade nitric acid.

– 1+99 nitric acid solution: Add 10 mL of nitric acid to a 1000 mL volumetric flask containing a small amount of water, then dilute to the mark with water.

- Soluções padrão:

– Stock Solution: GBW(E)082818-2 lead standard stock solution, 1000 μg/mL.

– Intermediate Solution: 100 μg/mL (prepared by diluting 10.0 mL of stock solution to 100 mL with 1+99 nitric acid; stable for 1 week).

– Working Solution: 1.0 μg/mL (prepared by diluting 1.0 mL of intermediate solution to 100 mL with 1+99 nitric acid; freshly prepared before use).

– Standard Series: 0.00, 2.50, 5.00, 10.00, 20.00, 30.00, 40.00 μg/L (prepared by diluting the working solution).

Iii.

1. Preparação de amostras

– Pretreatment:

– Clear water samples can be directly measured.

– Samples with high suspended solids require acidification and digestion of organic matter (specific digestion steps not detailed).

– Standard Solution Preparation: Stepwise dilute the stock solution to prepare intermediate, working, and standard series solutions, all made up to volume with 1+99 nitric acid.

2. Teste de amostra

– Testing Conditions:

– Spectral Parameters:

– Wavelength: 283.3 nm

– Spectral bandwidth: 0.4 nm

– Element lamp current: 3.0 mA

– Background correction: Deuterium lamp

– Injection volume: 15 μL

– Graphite Furnace Heating Program:

– Drying: 110°C, 10 s ramp-up, 10 s hold, high internal gas flow.

– Ashing: 350°C, 10 s ramp-up, 10 s hold, high internal gas flow.

– Atomization: 1700°C, 0 s ramp-up, 3 s hold, internal gas flow off.

– Cleaning: 1900°C, 1 s ramp-up, 2 s hold, high internal gas flow.

– Measurement Steps: Inject reagent blank, standard series, and samples into the graphite tube to measure absorbance. Subtract the blank absorbance from each standard solution’s absorbance, plot a working curve with absorbance (ordinate) against lead concentration (abscissa), and determine the lead concentration of the sample from the curve.

3. Cálculo de resultados

Onde:

-ρ(Pb): Lead concentration in the water sample (μg/L);

-ρ1: Lead concentration of the sample obtained from the calibration curve (μg/L);

-V1 : Volume of the tested sample (mL);

– V: Volume of the original water sample (mL).

1. Parâmetros metodológicos
2. Minimum Detectable Mass Concentration

– Detection Limit: Calculated from 11 blank measurements. Standard deviation S₀ = 0.00044, calibration curve equation A = 0.0060C + 0.0013, correlation coefficient 0.99915. Detection limit: 0.22μg/L; minimum detectable mass concentration: 0.88μg/L.

2. Precisão

– Verification Results: Seven repeated measurements of the same sample yielded an average absorbance of 0.1509, standard deviation of 0.0046, and relative standard deviation (RSD) of 3.0%, meeting precision requirements.

3. Accuracy

– Standard Sample Testing:

– Sample 201237 (standard value: 42.0 ng/mL): Average measured value 42.425 ng/mL, within the expanded uncertainty (3.1 ng/mL).

– Sample 201236 (standard value: 152.0 ng/mL): Average measured value 147.85 ng/mL, within the expanded uncertainty (12 ng/mL).

4. Actual Sample Measurement

– Parallel measurements of three surface water samples showed relative errors of 3.62%–4.31%, meeting parallelism requirements.

1. Precauções

– Pretreat water samples with high suspended solids to eliminate organic interference.

– Prepare standard solutions via stepwise dilution to ensure concentration accuracy.

– Strictly control the graphite furnace heating program to avoid background interference and incomplete atomization.