Molecularly Imprinted Polymers (SupelMIP)

By careful design of the imprinting site, either by molecular modeling, experimental design, or screening methods, the binding cavities can be engineered to offer multiple interaction points with the analyte(s) of interest. This leads to a stronger interaction between the sorbent and the analyte(s). As a consequence, harsher wash conditions can be tolerated during SPE methodology resulting in cleaner extracts. Because extraction selectivity is significantly improved, lower background is observed allowing analysts to achieve lower detection limits.

Superior selectivity results in lower detection limits. Clenbuterol was extracted from 5 mL urine using SupelMIP SPE – Clenbuterol, and compared against 3 different mixed-mode SPE phases. High background and misleading responses were observed on the mixed-mode chemistries whereas the SupelMIP phases offered superior sample cleanup and lower detection limits.

Sample preparation is often the rate-limiting step within the analytical process, and can often take up to 10 times as long as the analysis in itself. It is therefore critical for analysts to develop simple, robust, and rapid extraction techniques that are selective enough to achieve sensitivity, precision, and accuracy limits required of the assay. In this application example, MIP Technologies AB in collaboration with Bernhardt et al. developed an extraction method for the carcinogenic tobacco-specific NNAL or nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) from urine samples¹. Total urinary NNAL is a valuable biomarker for monitoring exposure to carcinogenic TSNAs in smokers and non-smokers exposed to second-hand smoke. However, measuring the low concentrations of NNAL present in urine is challenging and typically involves multiple extraction steps that can take over one day to perform². Using SupelMIP SPE – NNAL, even in the presence of nicotine, lower limits of quantitation were achieved, and reproducibility was increased.

MIPs are highly cross-linked polymers that maintain stability when exposed to a broad range of organic solvents, can withstand high temperatures, and can be used over broad pH ranges, without loss of selectivity. Furthermore, they can be stored at room temperatures for prolonged periods of times. This is extremely advantageous over immunoaffinity based products.

Mass spectrometry is a powerful quantitative tool that has been introduced into most clinical and research laboratories in recent years. When coupled to HPLC (LC-MS), the technique offers sensitivity, speed, and specificity.

Ion suppression is a common and problematic phenomenon that occurs when analyzing trace levels of analyte(s) in complex matrixes such as biological fluids. As analytical runtimes are reduced, ion suppression can often become more prevalent manifesting as poor assay accuracy and precision. Because ion suppression is often caused by the co-elution of matrix components with analyte(s) of interest, improved selectivity/sample cleanup during sample preparation is critical. Because selectivity is tailor-made during the design and production of a SupelMIP SPE phase, ion suppression is often reduced when compared to more conventional SPE phases.