Enhanced cleanup efficiency hydroxy functionalized-magnetic graphene oxide and its comparison with magnetic carboxyl-graphene for PRiME pass-through cleanup of strychnine and brucine in human plasma samples.

An enhanced cleanup efficiency hydroxy functionalized-magnetic graphene oxide (EH-Mag-GO) fully covered porous nano-titania as coating has been designed and synthesized. It has been evaluated in PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure for human plasma prior to analysis of strychnine and brucine by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Comparing with the magnetic carboxyl-graphene (Mag-CG), EH-Mag-GO is much more effective for the removal of matrix effect resulted from blood phospholipids. Under optimal conditions, the results show higher cleanup efficiency of EH-Mag-GO with recoveries in the range of 89.4%-118%. The limits of quantification (LOQs) for strychnine and brucine are 0.088 µg/L and 0.092 µg/L, respectively. Especially, the EH-Mag-GO is also evaluated for reuse (20 times) without much sacrifice of the cleanup efficiency. Validation results on linearity, specificity, accuracy and precision, as well as on the application to analysis of strychnine and brucine in six cases of suspected semen strychni poisoning demonstrate the applicability to clinical studies.

Fast determination of catecholamines in human plasma using carboxyl-functionalized magnetic-carbon nanotube molecularly imprinted polymer followed by liquid chromatography-tandem quadrupole mass spectrometry.

A novel, simple and sensitive method based on the use of dispersive micro-solid-phase extraction (d-µ-SPE) procedure combined with ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) for the determination of catecholamines, i.e., dopamine (DA), norepinephrine(NE) and epinephrine (E), was developed and validated. The novel catecholamines molecularly imprinted polymer (MIP) on the surface of carboxyl-functionalized magnetic-carbon nanotube (CF@m-CNTs-MIP) was synthesized and characterized by vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The CF@m-CNTs-MIP was used as the d-µ-SPE sorbent to extract catecholamines from human plasma samples. The obtained results demonstrated the higher extraction capacity of CF@m-CNTs-MIP with recoveries between 87.5-110%. The limits of quantification (LOQs) for NE, E and DA were 76 ng/L, 18 ng/L and 10 ng/L, respectively. Validation results on linearity, specificity, accuracy, precision and stability, as well as on application to the analysis of catecholamines in 120 healthy volunteers demonstrated the applicability to clinical studies.

Rapid determination of memantine in human plasma by using nanoring carboxyl-functionalized paramagnetic molecularly imprinted polymer d-µ-SPE and UFLC-MS/MS.

A novel, simple, and sensitive method based on the use of dispersive micro-solid-phase extraction (d-µ-SPE) procedure combined with ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) for the determination of memantine (ME) was developed and validated over the linearity range 0.05-10.0 µg/L with 100 µL of human plasma using memantine-D6 (ME-D6) as the internal standard. The novel nanoring carboxyl-functionalized paramagnetic molecularly imprinted polymer (NR-CF-Mag-MIP) was synthesized by ultrasound-assisted suspension polymerization, using ME as a template molecule, methacrylic acid as a functional monomer, and divinylbenzene as a cross-linking agent. The NR-CF-Mag-MIP was used as the d-µ-SPE sorbent to extract ME from human plasma samples. The obtained results demonstrated the higher extraction capacity of NR-CF-Mag-MIP with recoveries between 97.6 and 101%. The limits of quantification (LOQs) for ME was 0.015 µg/L. Validation results on linearity, specificity, accuracy, precision, and stability, as well as on application to the analysis of samples taken up to 480 h after oral administration of 20 mg (two 10 mg capsules) of ME in healthy volunteers demonstrated the applicability to bioequivalence studies.