Microplastics are becoming a global concern due to the potential risk to human health. This study focused on widely used polypropylene-based baby feeding bottles to develop a cost-effective protocol suitable for an MP study of many plastic products. This protocol provides the details of sample preparation, identification, and characterization.
It can substantially benefit future studies of microplastics released from plastic products. Microplastics released during formula preparation. Soak the baby feeding bottle in 95 degrees Celsius deionized water to sterilize the bottle.
To avoid the bottle floating, slightly press it using a stainless steel tweezer to ensure the whole bottle body is immersed in the water. After five minutes, take the bottle out and move it to a clean glass disk to await for air-drying. After air-drying, pour 180 milliliters of 70 degrees Celsius deionized water into the bottle.
Then cover the bottle immediately using a glass Petri dish and place it onto a shaking bed. To stimulate the formula mixing process, shake the bottle at a speed of 180 rpm for 60 seconds. After shaking, move the bottle to a clean glass plate and allow it to cool down.
Sample preparation for microplastics identification and quantification. Membrane filter is critical for microplastics capture, visualization, and detection. We used the gold coated polycarbonate membrane filter to capture microplastics.
Place a piece of membrane filter in the middle of a glass base. Then assemble the glass funnel and stainless steel clamp to fix the membrane filter and connect the glass filter with a vacuum pump after gently shaking the cooled water sample in the baby-feeding bottle. Then transfer a certain amount of water sample to the glass funnel using a glass pipette.
Switch on the vacuum pump to allow the water sample to filter through the membrane filter slowly. After filtering, wash the interior of the glass funnel using deionized water to ensure there are no particles sticking to the funnel. Disconnect the vacuum pump and disassemble the glass filter.
Then, carefully take out the membrane filter using a stainless steel tweezer and move it to a clean cover glass. Store the sample in a clean glass Petri dish immediately. Microplastics identification and quantification.
Carefully take out the sample from the glass Petri dish and place the filter sample in the middle of the Raman sample stage. Choose the representative spots in the membrane filter. Observe and photograph the particles on the surface of the membrane filter using an optical microscope.
Set up the Raman system and test these particles one by one using 532 nanometer excitation laser at 10%intensity. Compare the Raman spectrum obtained to referenced standard spectra. The AFM and Raman spectroscopy are assembled in one system.
Hence switch the system to AFM mode and test the topography of interesting microplastic particles. Microplastics test results. To validate this protocol, the standard polystyrene microplastics spheres were added to DI water and tested using the developed protocol.
The PS microplastics were successfully collected and detected. The particle inside the red box was confirmed as a typical polystyrene microplastic. Following the protocol, the microplastics recovery rate was 92 to 101%Hence, the developed protocol is reliable for the baby-feeding bottle test.
The protocol was used to test microplastics released from eight popular baby feeding bottle products, and found the microplastics released levels ranged from 1.3 million to 16.2 million particles per liter during formula preparation. The 3D topographic image further showed that the surface texture of the released microplastics is rich with nano sized bumps and valleys, which can substantially increase their absorption capacity.Conclusion. The study showed that plastic products that are used daily are very important sources for human microplastic exposure.
The protocol detailed here provides a reliable and cost-effective method for microplastics sample preparation and detection, which can substantially benefit future studies of microplastic release from plastic products.
