2024-10-22
Determination of Lead in White Wine by Atomic Absorption Spectrophotometry
In this paper, an analytical method is developed for the determination of lead elemental content in white wine by atomic absorption spectrophotometry. Lead showed good linearity in the concentration range of 1.0-40μg/L with linear correlation coefficients greater than 0.999. The RSD range for three injections is within 1.5%. The sample spiking recovery is 95.4%. The method is accurate, reliable and sensitive for the determination of lead in white wine.
Keywords: Atomic absorption, autosampler, white wine, lead
1. Experiment Method
1.1 Instrument Configuration
Table 1 Configuration List of Atomic Absorption Spectrophotometer
| No. | Modular | Qty |
| 1 | Atomic Absorption Spectrophotometer AA2310 | 1 |
| 2 | Graphite Furnace Power | 1 |
| 3 | Autosampler | 1 |
| 4 | Cooling Water Circulator | 1 |
| 5 | High Purity Argon | 1 |
1.2 Test Conditions
Wavelength: 283.3nm
Spectral Bandwidths: 0.4nm
Lamp Current: 5mA
Ignite: AA-BG
Injection Volume: 20μL
Temperature Program
| No. | Temperature (°C) | Time (s) | Heating Method | Sensitivity | Gases | Gas Circuit |
| 1 | 100 | 10 | RAMP | Low | Argon | 0.2 |
| 2 | 130 | 20 | RAMP | Low | Argon | 0.2 |
| 3 | 400 | 15 | RAMP | Low | Argon | 1.0 |
| 4 | 400 | 10 | RAMP | Low | Argon | 1.0 |
| 5 | 400 | 3 | RAMP | Low | Argon | 0.0 |
| 6 | 1900 | 3 | STEP | Low | Argon | 0.0 |
| 7 | 2100 | 2 | STEP | Low | Argon | 1.0 |
1.3 Reagents and Experiment Material
1.3.1 Nitric acid solution (1+99): Take 10mL of nitric acid and slowly add to 990mL of water and mix well.
1.3.2 Nitric acid solution (1+9): Take 50mL of nitric acid and slowly add to 450mL of water, and mix well.
1.3.3 Lead standard solution: 1000mg/L
1.3.4 One in ten thousand analytical balances
1.3.5 Digital display electric hot plate
1.3.6 Constant temperature drying oven
1.4 Sample Preparation
1.4.1 Lead standard intermediate solution
Pipette 0.1mL into 100mL volumetric flask, and fix the volume with 1% nitric acid, shaking well, prepared a concentration of 1mg/L of lead standard intermediate solution. Store under refrigeration at 0℃-4℃. Dilute with 1% nitric acid before use.
1.4.2 Lead Standard Working Solution
Pipette 400μL of lead standard intermediate solution in a 10mL volumetric flask, and fix the volume with 1% nitric acid, prepared a concentration of 40μg/L of lead standard solution, Prepare it when it will be used.
1.5 Sample Pre-treatment
Wet Digestion
Take 5.0mL of the liquid sample in a polytetrafluoroethylene crucible. The ethanol-containing samples are heated on a hot plate at a low temperature of 120°C to remove the ethanol firstly. Add 10mL of nitric acid and 0.5mL of perchloric acid, cover, and dissolve on a digital hot plate. (Reference conditions: 120 ℃/0.5 h~1 h; up to 180 ℃/2 h~4 h, up to 200 ℃~220 ℃). Open the lid and digest until white smoke is emitted and the digestion solution is colorless and transparent, drive the acid to nearly dry, stop dissolving, cool down and then dilute to 25 mL with water, mix well and spare. A reagent blank test was also done.
2. Result and Discussion
2.1 Standard Curve
Take 40μg/L lead standard working solution, according to the test conditions of 1.2 for injection and analysis, the autosampler selects the automatic dilution. Take concentration as the horizontal coordinate and absorbance as the vertical coordinate, and the external standard method is used to establish the working curve. The result is as shown Fig 1. The curve equation of lead in the concentration range of 1.0-40μg/L is y=0.008348*x+0.063430 with an R value of 0.9995, which has good linearity and meets the experimental requirements.
Fig 1 Lead Standard Curve
2.2 RSD of Standard Sample
The RSD value of 3 repeated injection of the standard is within 1.5%, and the stability of the instrument is in accordance with the experimental standards.
Fig 2 Overlap Chromatogram of Standard 32μg/L with 3 Repeated Injections
Table 2 Absorbance Data of Standard 32μg/L with 3 Repeated Injections
| Standard Point 5 | Absorbance | Background Absorbance | RSD (%) |
|
32μg/L |
0.3779 | 0.0051 |
0.65 |
| 0.3762 | 0.0040 | ||
| 0.3731 | 0.0044 |
2.3 Sample Spiking Rate
The digestion samples and sample blanks as well as spiked samples are injected and analyzed according to the test conditions of 1.2, and the sample chromatogram are shown in Fig. 3 and the spiked sample chromatogram are shown in Fig. 4. The data shows that the sample was not detected and the recoveries of the spiked samples were 95.4%. It meets the experimental requirements.
Fig 3 Sample Chromatogram
Fig 4 Sample Chromatogram
3. Conclusion
The curve equation of lead in the concentration range of 1.0-40μg/L was y=0.008348*x+0.063430 with an R value of 0.9995, which had a good linearity in accordance with the experimental requirements. The RSD range for three repeated injections was within 1.5%. The sample spiking recovery was 95.4%. The method is accurate, reliable and sensitive for the determination of lead in white wine.
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