Returning to nature: use of pollen grains for solid phase extraction

If you are interested in green analytical chemistry, this is an article for you. Researchers from the Wuhan University at China have recently proposed the use of pollen grains as sorbent in hydrophilic interaction solid phase extraction (1). These grains are characterized by a high superficial area (close to 20 m2/g), a high hydrophilic surface due to the presence of residual hydroxyl groups and particle size in the medium micrometer range. The selection of the proper variety of pollen to be used for analytical purposes is a critical issue according to the authors. They prefer pine pollen to bee pollen grains since the first one is more homogeneous from the chemical point of view and therefore it leads to more reproducible results. In addition, this type of pollen is available at higher amounts allowing the fabrication of many extraction cartridges for sample extraction.

Figure 1. Pollen from a variety of common plants
(Public domain image from wikipedia)

Pollen grains cannot be directly used, a previous treatment being necessary. A simple cleaning process by Soxhlet extraction is required to remove fatty compounds, some pigments and carbohydrates. After that treatment the pollen grains are dried and they can be packed into a conventional cartridge.

The authors have used this natural material for the isolation of 16 plant growth regulators from fruits and vegetables. The polar surface of pollen grains makes them an excellent alternative to perform hydrophilic interaction solid phase extraction. After the activation of the sorbent with a mixture of acetonitrile and water, an enrich water layer is formed on the grains surface. A plant extract in acetonitrile, obtained after a solid-liquid extraction of fruit and vegetables samples, is finally passed through the cartridge in order to isolate the target analytes. The analytes are finally eluted with a combination of solvents before the final UHPLC-MS/MS analysis. The excellent results include limits of detection in the range of 0.01-1.1 µg/Kg and relative standard deviations lower than 14%.

The article presents some useful information and we encourage you its reading. The complete chemical and physical characterization of the pollen grains, the optimization of the extraction protocol and the interesting application are some aspects to highlight.

Reference

(1) Using pollen grains as novel hydrophilic solid-phase extraction sorbents for the simultaneous determination of 16 plant growth regulators. Link to the article