Spirulina can be divided into feed-grade, food-grade, and types for special purposes based on its application. Feed-grade spirulina powder is typically used in aquaculture and livestock farming, while food-grade spirulina powder is used in health supplements and added to other foods for human consumption. Spirulina powder is produced by grinding spirulina into a fine powder. It is characterized by a dark green color and a smooth, slippery texture.
This study establishes a method for determining lead content in food-grade spirulina powder using graphite furnace atomic absorption spectrometry (GFAAS). The experimental results show that the linear correlation coefficient for lead exceeds 0.999. The method is precise, reliable, and highly sensitive, making it suitable for the detection of lead in food-grade spirulina powder.
Keywords: Atomic absorption, graphite furnace, spirulina powder, lead.
1.Experiment Method
1.1 Instrument Configuration
Table 1 Configuration List of Atomic Absorption Spectrophotometer
| No. |
Modular |
Qty |
| 1 |
AA2310 Atomic absorption spectrometer |
1 |
| 2 |
GF2310 Graphite furnace |
1 |
| 3 |
AS2310 Autosampler |
1 |
| 4 |
Circulating Water Chiller |
1 |
| 5 |
99.999% High purity argon |
1 |
| 6 |
Lead hollow cathode lamp |
1 |
1.2 Reagents and Experiment Materials
1.2.1 Lead standard solution: 1000mg/L
1.2.2 Nitric acid
1.2.3 Perchloric acid
1.2.4 Analytical balance with 0.0001g readability
1.2.5 Digital Hot Plate
1.2.6 Polytetrafluoroethylene crucible
1.3 Sample pretment
The analysis was performed in accordance with the standard GB 5009.12-2023 "National Food Safety Standard - Determination of Lead in Food". The sample pretreatment steps followed the wet digestion method as specified in Graphite Furnace Atomic Absorption Spectrometry, Method 1 of the standard.
2. Result and Discussion
2.1 Spectral Parameters for the Element
| Parameters |
Pb |
| Current (mA) |
5 |
| Spectral bandwidth (nm) |
0.4 |
| Characteristic wavelength(nm) |
283.3 |
| Background correction |
AA-BG |
| High pressure (V) |
350 |
| Injection volume (μL) |
10 |
| Graphite tube |
Pyrocoated graphite tube |
Temperature Program
| No. |
Temperature (°C) |
Time(s) |
Heating Method |
Sensitivity |
Gas |
Gas Path |
| 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 |
High |
Argon |
0.0 |
| 6 |
1900 |
3 |
STEP |
High |
Argon |
0.0 |
| 7 |
2100 |
2 |
STEP |
Low |
Argon |
1.0 |
2.2 Standard Curve Testing
| Concentration Table for the Calibration Standards |
| Concentration Level |
1 |
2 |
3 |
4 |
| Pb Standard Solution Concentration (μg/L) |
2 |
5 |
10 |
20 |
| Absorbance(abs) |
0.0280 |
0.0666 |
0.1260 |
0.2402 |
Lead Standard Curve
2.3 Test Result of A Sample
| Sample |
Sample Mass |
Measured Lead Concentration(μg/L) |
Actual Lead Content (mg/kg) |
| Spirulina Powder |
1.9956 |
12.2778 |
0.1538 |
3. Attention
The perchloric acid used in the experiment possesses strong oxidizing and corrosive properties, while nitric acid is highly volatile and corrosive. The preparation of reagents and digestion of samples must be conducted inside a fume hood. Appropriate personal protective equipment (PPE) must be worn as required to avoid inhalation or contact with the skin and clothing.
4. Conclusion
A method was established for the determination of lead in food-grade spirulina powder using graphite furnace atomic absorption spectrometry (GFAAS). The experimental results demonstrated a linear correlation coefficient for lead of greater than 0.999. The method proved to be precise, reliable, and highly sensitive, making it suitable for the determination of lead in food-grade spirulina powder.
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