Micro-gel thin film molecularly imprinted polymer coating for extraction of organophosphorus pesticides from water and beverage samples.

Molecularly imprinted polymers (MIPs) have become an important class of materials for selective and efficient adsorption of target analytes. Despite versatility of MIPs for fabrication in numerous formats, these materials have been primarily reported as solid phase extraction packing materials. An effective thin film MIP prepared on stainless steel substrate is reported here for high throughput enrichment of organophosphorus pesticides (OPPs) from water and beverage samples followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The key factors controlling performance as well as best practices for optimized fabrication of thin film MIPs are presented. A pseudo-phase diagram is introduced to evaluate and predict the effect of the ratio of porogen (solvent, 1-octanol) volume to relative crosslinker mass on the desired polymer features (i.e., porosity, surface area, capacity, and selectivity). At low porogen ratios, a macroporous polymer with insignificant selectivity is formed, whereas at high porogen ratios a micro-gel polymer with superior selectivity towards targets is obtained. The porosity and morphology determined with nitrogen adsorption and scanning electron microscopy were attributed to specific regions in the pseudo-phase diagram. Other factors influencing selectivity and stability of the polymer, such as type of the template and its ratios with monomer (methacrylic acid) and crosslinker (ethylene glycol dimethacrylate) were optimized. The prepared thin film MIPs were characterized using adsorption isotherms and adsorption kinetics, and evaluated for matrix effects (high humic acid content) and cross-reactivity in presence of other pesticides and pharmaceuticals. The optimized method provided limits of quantitation (LOQs) ranged from 0.002 to 0.02 ng mL-1 in water and from 0.095 to 0.48 ng g-1 in apple juice. Regarding inter-device variability (CV∼10% without normalization), excellent linearity (R2 > 0.99), satisfactory accuracies (90-110%) and precisions (<15%) were obtained.

Thin film molecularly imprinted polymer (TF-MIP), a selective and single-use extraction device for high-throughput analysis of biological samples.

Enhancing selectivity, reducing matrix effects and increasing analytical throughput have been the main objectives in the development of biological sample preparation techniques. A thin film molecularly imprinted polymer (MIP) is employed for extraction and analysis of tricyclic antidepressants (TCAs) as a model class of compounds in human plasma for the first time to reach the abovementioned goals. The thin film MIPs prepared on a metal substrate can be used directly for extraction from biological matrices with no sample manipulation steps and no pre-conditioning. This method was validated with good linearity (R2 > 0.99 in 1.0-500.0 ng mL-1 range), excellent accuracy (90% -110%) and precision (RSD % value less than 15%) in pooled human plasma samples (N = 3). The limits of quantitation (LOQ) for TCAs in plasma samples were between 1.0-5.0 ng mL-1 which are lower than the therapeutic ranges of these drugs. Kinetic and isotherm studies showed the superior performance of MIP sorbent compared to a non-imprinted polymer (NIP) sorbent in extracting TCAs from a bovine serum albumin (BSA) solution. The optimized and validated method for pooled human plasma was utilized for monitoring the concentration of TCAs in three patient samples who had been prescribed TCAs. These selective single-use thin film extraction devices are promising for efficient and fast procedures for analyzing biological samples.

Optimized Oxidative Stress Protocols for Low-microliter Volumes of Mammalian Plasma.

Small blood volumes commonly obtained from small mammals during field studies are only sufficient for a single biochemical assay. In this study, we used blood collected from a population of wild eastern chipmunks (Tamias striatus) and developed modified methods to improve analytical selectivity and sensitivity required for measuring markers of oxidative stress using small blood volumes. Specifically, we proposed a modified malondialdehyde (MDA) analysis protocol by high performance liquid chromatography (HPLC) and also optimized both the uric acid independent ferric reducing antioxidant power (FRAP) and hypochlorous acid shock capacity (HASC) assays. We present methods in which a total volume of less than 60 µl of plasma is required to obtain a comprehensive portrait of an individual's oxidative profile.