溪水中孔雀石绿的痕量检测
AN-RS-018
2020-06
zh
用 Misa 保护消费者安全
孔雀石绿（MG）是一种纺织品染料，具有有效的杀菌特性，但它有剧毒，其代谢物会在鱼肉和哺乳动物体内存留，对人类食物链构成威胁。欧盟认为，孔雀石绿含量高于 2 μg/g MG 的受污染食品会对健康构成威胁，一些国家已禁止将孔雀石绿用作水产养殖添加剂。尽管监管严格，但受孔雀石绿污染的海鲜产品仍不断流入消费者手中。使用 Misa（瑞士万通即时 SERS 分析仪）确保食品安全，以简便的检测形式实现了对孔雀石绿的快速、高灵敏度检测。
Malachite green (MG) is a dye used widely as a textile colorant and biological stain. It was also a remarkably effective fungicide used in aquaculture operations until the turn of the 21st century. MG is acutely toxic to fish and mammals, and it and its metabolites persist in the flesh, making it a threat to the human food chain. The EU has concluded that contaminated foods containing levels higher than 2 μg/g MG constitute a credible health risk, and several countries have banned malachite green as an aquaculture additive. Despite tight regulation, seafood products contaminated with MG continue to find their way to consumers from illegal operations that evade strict oversight procedures and health safety standards.
Using Misa (Metrohm Instant SERS Analyzer) to ensure food safety, the rapid and highly sensitive detection of malachite green is achieved in a facile assay format.
Many food matrices require complicated sample digestion and extraction procedures. This application note describes a very simple water test that can be performed directly at the aquaculture site, to determine if malachite green is being illegally used as a fungicidal treatment.
To establish a reference spectrum for MG, a pure standard in water is first analyzed using gold nanoparticles (Au NPs). This unique SERS spectrum (Figure 1) can be used to create a library entry for MG.
Simulated testing of MG in aquaculture media was conducted by spiking stream water samples with a range of analyte concentrations (10 and 1 μg/mL, 100, 10, and 1 ng/mL). Test samples were prepared by pipetting 0.1 mL of each analyte concentration (at pH 7.0) into vials containing 0.8 mL of Au NPs and 0.1 mL of 500 mmol/L NaCl. After thorough mixing, samples were inserted into the Misa vial attachment for the acquisition of SERS spectra.
| Instrument | Acquisition | ||
|---|---|---|---|
| Firmware | 0.9.33 | Laser Power | 5 |
| Software | Misa Cal V1.0.15 | Int. Time | 1 s |
| Misa Vial Attachment | 6.07505.040 | Averages | 10 |
| ID Kit - Au NP | 6.07506.440 | Raster | ON |
Overlaid spectra in Figure 2 at each MG concentration show clear detection down to 1 ng/mL.
Detection of malachite green in the field
Fill a clean vial halfway full with Au NPs. Using pipettes, add 2 drops each of aquaculture medium and NaCl solution to Au NPs, then cap and shake the vial gently to mix. Insert into vial attachment on Misa for measurement.
| ID Kit - Au NP | 6.07506.440 |
|---|---|
| includes: | Gold nanoparticles (Au NP) |
| Scoop | |
| Disposable pipettes | |
| 2 mL glass vials | |
| Reagents | |
| NaCl solution | 3 g NaCl in 100 mL water |
| Test settings | Use ID Kit OP on MISA |
The highly sensitive detection of MG in a potentially difficult test matrix is reduced to a very simple assay with Misa and Au NPs. This analysis requires minimal user training and can be performed on-site for rapid, high-throughput test applications. The lower limit of MG reported here is accurate even below the threshold for permissible levels in contaminated foods, and compares favorably with the detection limit recently reported for MG in commercial aquaculture media.
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