|Synthetic polymeric resins in downstream processing for food, fine chemicals and pharmaceuticals
|Fundamentals in Separation Science & Sample Prep
|Dr Benjamin Summers
|Dr Simona Serban
Dr Alessandra Basso
Abstract Information :
Solid phase extraction has developed into one of the more powerful tools for clean-up and concentration of very low levels of analytes from complex matrices, especially when paired with sensitive detection methods such as HPLC and MS technologies. An analytical method requires an extremely high degree of specificity in addition to the more universal requirements of sensitivity, precision, and linearity. The selection of resins used for Solid Phase Extraction, particularly in relation to their chemical and physical make-up, has a significant effect on the final results. By careful selection of solid phase extraction sorbents, paying attention to the polymer structure, the efficiency of clean-up and concentration activities can be improved well beyond the original capabilities of early methods.
A series of clean-up columns for reverse phase solid-phase extraction (SPE) were packed with various polymeric resins with different chemical structure, surface properties, hydrophobicity and porosity. These SPE columns were used for the isolation and concentration of paracetamol, haloacetic acids and polyaromatic hydrocarbons by reverse phase chromatography.
The highest yields in recovery or paracetamol are obtained with polymers with highly hydrophobic structures (polystyrene or divinylbenzene) and a low pore size. Haloacetic acid mixtures also show a strong effect of pore size, with diameters below 100 giving the best results. A high surface area, above 1000 m2/g also results in increased recovery. Polyaromatic hydrocarbons were also best recovered by low pore size resins and those with a high surface area.
Results have demonstrated a strong effect of pore size on the recovery, generally showing that smaller is better; this may be expected due to the low molecular mass of the organic compounds tested. The newly-developed Purolite PuroPhase™ Chromalite resins show good levels of recovery compared to other similar commercially available resins and confirm the effect of pore size on recovery of small organic molecules observed in previous works.
Synthetic polymer resins offer a significant improvement to some aspects of downstream processing for a wide range of industries. They offer higher solvent tolerance than silica-based resins when used in solid phase extraction procedures during product isolation and facilitate a customisable approach to chromatography, in which the required resin characteristics can be selected with little difficulty to provide the most suitable product for the most accurate results. Also observed is the link between pore diameter and recovery of small molecules: all tested molecules were recovered most efficiently by the resins with the smallest pore diameters tested. The increased hydrophobicity of the resins when compared to traditional silica and agarose-based resins enables improved separations, particularly of highly hydrophobic compounds that would otherwise prove challenging to successfully extract from their original solutions.