Jinchuan Yang

• PhD
• Principal Investigator at Waters Corporation

Background Melatonin supplements are often used to alleviate jetlag and other sleep-depletion related disorders. Recent studies found large inconsistencies between labeled values and actual contents of melatonin within products, which has led to concerns over the quality of melatonin supplements. In order to facilitate the quality control testing o...

This work aimed to develop an analytical method for the screening of multiple aminoglycoside residues in foods of animal origin using an ethylene-bridged hybrid (BEH) particle-based sulfoalkylbetaine stationary phase. The effects of chromatographic conditions on the separation of 17 aminoglycosides have been systematically investigated. Sample prep...

Background: Baseline separation of nonivamide (NON) and capsaicin (CAP) has not been achieved by using the existing liquid chromatography (LC) methods for the capsaicinoid analysis. This could lead to large errors in the determination of capsaicinoids for capsicum products. Objective: The development of an ultrahigh-performance liquid chromatogr...

Recently, a novel hybrid surface technology (HST) has been developed to mitigate metal analyte adsorption in liquid chromatography. The HST provides a hybrid organic–inorganic surface on the metal fluidic path, from injection to detector and including the column frits and wall, to mitigate the interaction between analytes and metals. Here the impac...

An LC-MS method was developed for routine determination of lactose in low-lactose and lactose-free dairy products. The lactose was separated on an amide column under an isocratic elution condition. Baseline separation of lactose from common interferents, including epilactose, lactulose, and allolactose were achieved under this LC conditions. The la...

Background Bisphenol A (BPA) is a chemical of concern in food industry. There is need for sensitive analytical method for determination of BPA in beverages. Objective To develop a method for determination of BPA in carbonated, non-carbonated and non-alcoholic drinks. Methods Replicates of a carbonated soft drink, orange juice with pulp and a dair...

you can find the full SMPR on the AOAC web site:- http://www.aoac.org/aoac_prod_imis/AOAC_Docs/SMPRs/SMPR_2018_001.pdf

This AOAC Standard Method Performance Requirements (SMPR) is for authentication of Echinacea phenolic compounds in dietary ingredients and supplements. SMPRs describe the minimum recommended performance characteristics to be used during the evaluation of a method. The evaluation may be an on-site verification, a single-laboratory validation, or a m...

Vitamin D is a fat-soluble vitamin that promotes calcium absorption and maintains adequate serum calcium and phosphate concentrations [1]. The most common vitamin Ds are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol). Their structures are shown in Figure 1. Vitamin D can be produced endogenously when ultraviolet (UV) lig...

The quantification of allergens in food including baked food matrices is of great interest. The aim of the present study was to describe a non-immunologic method to quantify bovine β-casein using ultra performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-TQ-MS/MS) in multiple reaction monitoring (MRM) mode. Eight of te...

Pomegranate juices from various sources and whole fruit pomegranate were analysed using Ultra Performance Liquid Chromatography (UPLC) coupled with Quadrupole Time-of-flight (QTof) mass spectrometry and multivariate data analysis tools. Chlorogenic acid was identified in adulterated pomegranate juice samples and blends, but was absent from authenti...

End-tethered chains made of an adsorbed diblock copolymer of polystyrene (PS)−polyisoprene (PI) bearing an end-segment including a Ge atom are built by the Langmuir−Schaeffer technique. They are studied both in the dry state and in a good solvent for the PI chain using grazing incidence X-ray standing waves. The analysis of the signal provides a di...

This study investigates the structures of layers of amphiphilic diblock copolymers of poly(t-butyl styrene)-poly(styrene sulfonate) (PtBS-PSS) adsorbed on both the bare mica surface (hydrophilic) and an octadecyltriethoxysilane (OTE)-modified mica surface (hydrophobic). When the surface is rendered hydrophobic, the nonsoluble block exhibits stronge...

The influence of postadsorption relaxation processes has been evaluated in the adsorption behavior of block copolymer micelles comprised of asymmetric poly(tert-butylstyrene-b-sodium 4-styrenesulfonate) (PtBS−NaPSS) diblock copolymers as well as star-block copolymers of similar size and composition. The adsorptions were conducted from aqueous solut...

We present here oil-in-water microemulsions stabilized by charged diblock copolymers alone, along with their structural characterization by small-angle neutron scattering measurements. They consist of swollen spherical micelles containing small amounts of oil in their core, which is surrounded by a corona of stretched polyelectrolyte chains. Struct...

Spherical polyelectrolyte block copolymer micelles were investigated as a function of added NaCl salt concentration using Small-Angle Neutron Scattering (SANS) and Light Scattering (LS). The micelles are formed by the self-association of charged-neutral copolymers made of a long deuterated polyelectrolyte moiety (NaPSSd)251 and a short hydrophobic...

We have performed neutron reflectivity measurements on a monolayer of charged diblock copolymers in a Langmuir trough, and determined precise density profiles of the polyelectrolyte brush at different densities. We obtain profiles in good agreement with existing self-consistent field computations, both for the osmotic and the salted brush regime. W...

Poly( l -caprolactone) was characterized by size exclusion chromatography on-line with a right-angle laser-light scattering photometer and a four-capillary bridge design differential viscometer (SEC/RI/RALLS/DV) in tetrahydrofuran (THF) at 25°C. The dependence of intrinsic viscosity and radius of gyration of poly( l -caprolactone) on molecular weig...

Polyelectrolyte brushes were formed at the interface between hydrophobized mica and water by adsorbing amphiphilic diblock copolymers consisting of a hydrophobic and a charged block. We measured force−distance profiles with the surface force apparatus (SFA) for several polyelectrolyte brushes of different lengths as a function of aqueous 1:1 electr...

A series of sodium poly(styrene sulfonate)-block-poly(4-tert-butylstyrene) (NaPSS-b-PtBS) copolymers and related homopolymers were characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The homopolymers included polystyrene (PS), poly(4-tert-butylstyrene) (PtBS), sodium poly(4-styrene sulfonate) (NaP4...

Thesis (Ph. D.)--University of Alabama at Birmingham, 2001. Includes bibliographical references.

Nanoparticles of improved stability against long-term aggregation were prepared using poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) star-block copolymer architectures. The star-block copolymers, physically resembling diblock copolymer micelles, were synthesized by anionic polymerization and coupling with ethylene glycol dimethacrylate. They con...

We report force measurements in thin liquid films containing charged diblock copolymers (poly(tert-butylstyrene)−poly(styrenesulfonate)) adsorbed at the film surfaces. Although the film surfaces are likely to be covered by copolymer layers with a brush structure, the observed features, both film ordering and force ranges, cannot be explained within...

Water soluble diblock copolymers composed of a long poly(styrene sulfonate) chain (between 200 and 400 monomers) and a short poly(ethylene propylene) or poly(tert.-butylstyrene) hydrophobic end (20-50 monomers) are highly associative and form micelles in aqueous solution. The micelles are composed of a small hydrophobic core and a polyelectrolyte c...

Adsorbed and spread charged diblock copolymer layers are studied at flexible interfaces. In both cases, equilibrium situations can be reached and the structure and fluctuations in height of the interface are examined by different experimental means. In particular, buckled deformations of the air–water interface are evidenced by optical and X-ray sc...

In this work, we describe the synthesis and characterization of gold nanoparticles from tetrachloroauric acid (HAuCl4) in block copolymer micelles and star graft block copolymers. In order to achieve complete control of the nanoparticles' properties, as required for several important applications, it is necessary to obtain samples that are as close...

The counterion distribution within a spherical polyelectrolyte sparse brush was measured by small-angle X-ray scattering using contrast variation with different counterions by means of ion dialysis. The brush was made by self-association of charged diblock copolymers. Thanks to the contrast variation method, we were able to separate the signal due...

Matrix-assisted laser desorption/ionization time-of-flight mass spectra (MALDI/TOF/MS) of sodium poly(styrenesulfonate)-block-poly (tert-butylstyrene) (NaPSS-b-PtBS) and polystyrene-block-poly (tert-butylstyrene) (PS-b-PtBS) diblock copolymers were obtained. MALDI/TOF/MS of NaPSS-b-PtBS directly yields molecular weights and polydispersities of thes...

We report the results of small-angle neutron scattering (SANS) studies on aqueous solutions of spherical polyelectrolyte micelles formed by association of charged-neutral diblock copolymers. The neutral moieties are found to self-assemble into small dense spheres (cores of the micelles) whose sizes are independent of the polymer concentration c. In...

An experiment was conducted on a series of block copolymers (di-, tri-, star-) of poly(t-butylstyrene)-sodium-co-poly(styrene sulfonate) with different molecular weights, percentage sulfonation, and copolymer architecture in terms of their adsorption behavior to hydrophobically modified surfaces. Quartz crystal microbalance (QCM) was used to measur...

Asymmetric diblock copolymers made of a short hydrophobic part and a long charged part self-assembled in water under the form of spherical micelles. Neutron and X-ray scattering are able to probe selectively the three main components of this system: the charged corona, the hydrophobic core, and the counterions. The charged corona is similar to a sp...