Derivatization-based magnetic dummy molecularly imprinted polymers integrated with 4-plex stable isotope labeling derivatization strategy for specific and rapid determination of L-hydroxyproline in human serum.

The specific determination of L-hydroxyproline (Hyp) can serve as a potential indicator for early clinical diagnosis of liver fibrosis. In this work, an integrated strategy based on 4-plex stable isotope labeling derivatization combined with dummy magnetic molecularly imprinted polymers (QSILD-DMMIPs) was developed for specific extraction and rapid determination of Hyp in human serum by ultra high performance liquid chromatography tandem mass spectrometry. A new series of QSILD reagents d0/d1/d2/d3-6-N-methyl-rhodamine 6G-N-hydroxysuccinimidyl formate (d0/d1/d2/d3-MRSF) were designed, synthesized and applied for the high-throughput labeling of Hyp in serum samples. The structural analogue derivative of Hyp with 6-N-ethyl-rhodamine 6G-N-hydroxysuccinimidyl formate (ERSF-Hyp) was synthesized and used as a novel dummy template to prepare DMMIPs. The DMMIPs were well characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), fourier transform infrared spectroscopy (FTIR), Brunner Emmet Teller (BET) measurements, thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and adsorption experiments. All d0/d1/d2/d3-MRSF-Hyp derivatives were conveniently and specifically adsorbed by DMMIPs in magnetic dispersive solid phase extraction procedure before injection. Method validation results including linearity (0.2-100 ng mL-1), limits of detection and quantitation (0.05 and 0.2 ng mL-1), accuracy, precision, stability, matrix effect and derivatization efficiency were satisfactory. The analytical performances benefited from efficient integration of QSILD and specific DMMIPs extraction. The proposed strategy was successfully applied for Hyp determination in human serum of liver fibrosis patients and healthy controls, which was of great significance to early diagnosis.

Core-shell magnetic molecularly imprinted polymers used rhodamine B hydroxyproline derivate as template combined with in situ derivatization for the specific measurement of L-hydroxyproline.

In this work, a novel core-shell magnetic molecularly imprinted polymers (MMIPs) for the measurement of L-Hydroxyproline (Hyp) in dairy products was prepared. The derivative of Hyp using N-hydroxysuccinimidyl rhodamine B ester (RBS) as derivatization reagent was employed as template to prepare RBS-Hyp-MMIPs (Fe3O4@MIPs for RBS-Hyp). A new analytical procedure of in situ derivatization with MMIPs (ISD-MMIPs) has been developed for the specific extraction and determination of Hyp in dairy products by ultra high performance liquid chromatography tandem mass spectrometry. The RBS-Hyp-MMIPs was characterized by fourier transform infrared spectrometer and transmission electron microscopy, and evaluated by adsorption experiments. The adsorption process followed Langumuir adsorption isotherm with maximum adsorption capacity of RBS-Hyp on RBS-Hyp-MMIPs at 96 mg/g. In addition, RBS-Hyp-MMIPs showed a short equilibrium time (15.0 min), rapid magnetic separation (5 s) and high stability (retained 95.3% after six cycles). Under the optimized conditions, good linearity was observed with the limits of detection (S/N > 3) and limits of quantification (S/N > 10) at 0.1 and 0.5 ng/mL, respectively. On account of the specific extraction performance of RBS-Hyp-MMIPs, not any interference peak from real sample matrix was observed in the chromatograms of milk powder, liquid milk and milk drink. The proposed procedure was successfully applied for selective determination of Hyp from dairy products with satisfactory validation results, which is of great significance to food safety.

A new combined method of stable isotope-labeling derivatization-ultrasound-assisted dispersive liquid-liquid microextraction for the determination of neurotransmitters in rat brain microdialysates by ultra high performance liquid chromatography tandem mass spectrometry.

In this work, for the first time, a new hyphenated technique of stable isotope-labeling derivatization-ultrasound-assisted dispersive liquid-liquid microextraction has been developed for the simultaneous determination of monoamine neurotransmitters (MANTs) and their biosynthesis precursors and metabolites. The developed method was based on ultra high performance liquid chromatography tandem mass spectrometry detection using multiple-reaction monitoring mode. A pair of mass spectrometry sensitizing reagents, d0-10-methyl-acridone-2-sulfonyl chloride and d3-10-methyl-acridone-2-sulfonyl chloride, as stable isotope probes was utilized to facilely label neurotransmitters, respectively. The heavy labeled MANTs standards were prepared and used as internal standards for quantification to minimize the matrix effects in mass spectrometry analysis. Low toxic bromobenzene (extractant) and acetonitrile (dispersant) were utilized in microextraction procedure. Under the optimized conditions, good linearity was observed with the limits of detection (S/N>3) and limits of quantification (S/N>10) in the range of 0.002-0.010 and 0.015-0.040nmol/L, respectively. Meanwhile, it also brought acceptable precision (4.2-8.8%, peak area RSDs %) and accuracy (recovery, 96.9-104.1%) results. This method was successfully applied to the simultaneous determination of monoamine neurotransmitters and their biosynthesis precursors and metabolites in rat brain microdialysates of Parkinson's disease and normal rats. This provided a new method for the neurotransmitters related studies in the future.

Rapid and sensitive determination of phytosterols in functional foods and medicinal herbs by using UHPLC-MS/MS with microwave-assisted derivatization combined with dual ultrasound-assisted dispersive liquid-liquid microextraction.

In this work, a hyphenated technique of dual ultrasound-assisted dispersive liquid-liquid microextraction combined with microwave-assisted derivatization followed by ultra high performance liquid chromatography tandem mass spectrometry has been developed for the determination of phytosterols in functional foods and medicinal herbs. Multiple reaction monitoring mode was used for the tandem mass spectrometry detection. A mass spectrometry sensitive reagent, 4'-carboxy-substituted rosamine, has been used as the derivatization reagent for five phytosterols, and internal standard diosgenin was used for the first time. Parameters for the dual microextraction, microwave-assisted derivatization, and ultra high performance liquid chromatography tandem mass spectrometry were all optimized in detail. Satisfactory linearity, recovery, repeatability, accuracy and precision, absence of matrix effect, extremely low limits of detection (0.005-0.015 ng/mL) and limits of quantification (0.030-0.10 ng/mL) were achieved. The proposed method was compared with previously reported methods. It showed better sensitivity, selectivity, and accuracy. The matrix effect was also significantly reduced. The proposed method was successfully applied to the determination of five phytosterols in vegetable oil (sunflower oil, olive oil, corn oil, peanut oil), milk and orange juice (soymilk, peanut milk, orange juice), and medicinal herbs (Ginseng, Ganoderma lucidum, Cordyceps, Polygonum multiflorum) for the quality control of functional foods and medicinal herbs.

Determination of dopamine, serotonin, biosynthesis precursors and metabolites in rat brain microdialysates by ultrasonic-assisted in situ derivatization-dispersive liquid-liquid microextraction coupled with UHPLC-MS/MS.

This paper, for the first time, reported a simple, rapid, sensitive and environmental friendly ultrasonic-assisted in situ derivatization-dispersive liquid-liquid microextraction (in situ UAD-DLLME) method followed by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for the simultaneous determination of dopamine (DA), serotonin (5-HT) and their biosynthesis precursors and metabolites in rat brain microdialysates. In this work, a commercial reagent, Lissamine rhodamine B sulfonylchloride (LRSC), was proposed as a derivatization reagent. The ionization efficiency of neurotransmitters was greatly enhanced through the introduction of a permanent charged moiety of LRSC into their derivatives during electrospray ionization MS (ESI-MS) analysis. Parameters of in situ UAD-DLLME and UHPLC-MS/MS conditions were all optimized in detail. The optimum conditions of in situ UAD-DLLME were found to be as follows: a mixture of 150µL of acetonitrile (dispersant) containing LRSC (derivatization reagents) and 50µL of low toxic bromobenzene (extractant) was rapidly injected into an aqueous sample containing 30µL of microdialysate and 800µL of NaHCO3-Na2CO3 buffer solution (pH 10.5) at 37°C. After ultrasonication for 3min and centrifuging for 2min, the sedimented phase was conveniently injected for UHPLC-MS/MS analysis. Under the optimized conditions, good linearity was observed with the limits of detection (LODs, S/N>3) and limits of quantification (LOQs, S/N>10) in the range of 0.002-0.008 and 0.015-0.040nmol/L, respectively. Meanwhile, it also brought good results of precision (3.2-13.0%, peak area RSDs %), accuracy (86.4-112%), recovery (73.9-105%), matrix effect (86.2-105%), and stability (3.1-8.8%, peak area RSDs %). The developed method was successfully applied for the simultaneous determination of multiple neurotransmitters, their precursors and metabolites in brain microdialysates of normal and L-DOPA induced dyskinesias (LID) rats.

[Determination of four phenolic endocrine disruptors in environmental water samples by high performance liquid chromatography-fluorescence detection using dispersive liquid-liquid microextraction coupled with derivatization].

To achieve accurate, fast and sensitive detection of phenolic endocrine disruptors in small volume of environmental water samples, a method of dispersive liquid-liquid microextraction (DLLME) coupled with fluorescent derivatization was developed for the determination of bisphenol A, nonylphenol, octylphenol and 4-tert-octylphenol in environmental water samples by high performance liquid chromatography-fluorescence detection (HPLC-FLD). The DLLME and derivatization conditions were investigated, and the optimized DLLME conditions for small volume of environmental water samples (pH 4.0) at room temperature were as follows: 70 microL chloroform as extraction solvent, 400 microL acetonitrile as dispersing solvent, vortex mixing for 3 min, and then high-speed centrifugation for 2 min. Using 2-[2-(7H-dibenzo [a, g] carbazol-7-yl)-ethoxy] ethyl chloroformate (DBCEC-Cl) as precolumn derivatization reagent, the stable derivatives of the four phenolic endocrine disruptors were obtained in pH 10.5 Na2CO3-NaHCO3 buffer/acetonitrile at 50 degrees C for 3 min, and then separated within 10 min by HPLC-FLD. The limits of detection (LODs) were in the range of 0.9-1.6 ng/L, and the limits of quantification (LOQs) were in the range of 3.8-7.1 ng/L. This method had perfect linearity, precision and recovery results, and showed obvious advantages and practicality comparing to the previously reported methods. It is a convenient and validated method for the routine analysis of phenolic endocrine disruptors in waste water of paper mill, lake water, domestic wastewater, tap water, etc.