Challenge For Chemical Analysis Research Articles

Ion Transport in Intelligent Nanochannels: A Comparative Analysis of the Role of Electric Field.

This research delves into investigating ion transport behavior within nanochannels, enhanced through modification with a negatively charged polyelectrolyte layer (PEL), aimed at achieving superior control. The study examines two types of electric fields─direct current and alternating current with square, sinusoidal, triangular, and sawtooth waveforms─to understand their impact on ion transport. Furthermore, the study compares symmetric (cylindrical) and asymmetric (conical) nanochannel geometries to assess the influence of overlapping electrical double layers (EDLs) in generating specific electrokinetic behaviors such as ionic current rectification (ICR) and ion selectivity. The research employs the finite element method to solve the coupled Poisson-Nernst-Planck and Navier-Stokes equations under unsteady-state conditions. By considering factors such as electrolyte concentration, soft layer charge density, and electric field type, the study evaluates ion transport performance in charged nanochannels, investigating effects on concentration polarization, electroosmotic flow (EOF), ion current, rectification, and ion selectivity. Notably, the study accounts for ion partitioning between the PEL and electrolyte to simulate real conditions. Findings reveal that conical nanochannels, due to improved EDL overlap, significantly enhance ion transport and related characteristics compared to cylindrical ones. For instance, under ηε = ηD = 0.8, ημ = 2, C0 = 20 mM, and NPEL/NA = 80 mol m-3 conditions, the average EOF for conical and cylindrical geometries is 0.1 and 0.008 m/s, respectively. Additionally, the study explores ion selectivity and rectification based on the electric field type, unveiling the potential of nanochannels as ion gates or diodes. In cylindrical nanochannels, the ICR remains at unity, with lower ion selectivity across waveforms compared to conical channels. Furthermore, rectification and ion selectivity trends are identified as Rf,square > Rf,DC > Rf,triangular > Rf,sinusoidal > Rf,sawtooth and Ssawtooth > Ssinusoidal > Striangular > SDC > Ssquare for conical nanochannels. Our study of ion transport control in nanochannels, guided by tailored electric fields and unique geometries, offers versatile applications in the field of Analytical Chemistry. This includes enhanced sample separation, controlled drug delivery, optimized pharmaceutical analysis, and the development of advanced biosensing technologies for precise chemical analysis and detection. These applications highlight the diverse analytical contributions of our methodology, providing innovative solutions to challenges in chemical analysis and biosensing.

NMR based metabolomic approach for evaluation of Vietnamese honey

AbstractHoney represents a natural, agricultural product endowed with valuable nutritional and pharmacological functions. Therefore, the classification and evaluation of honey has always been a challenge for chemical analysis, especially when honey adulteration is increasing. The traditional methods for quality control of honey is currently based on physicochemical methods, which is often relatively high cost and time‐consuming. NMR based metabolomics is a metabolomic fingerprinting approach for NMR data using chemometric tools. This combined approach can be apply in food analysis for origin discrimination, biomarker discovery and authenticity screening. The present study demonstrated the capability of the 1H NMR based metabolomics for evaluation of 27 NMR spectra of 09 selected honey samples from Viet Nam. 1H NMR analysis was conducted immediately on collected honey samples, without extraction. Unsupervised PCA multivariate data analysis, applied on 1H NMR experimental data, used to characterize and classify honey samples according to their origin and quality. Different metabolites specific for each botanical origins of honey samples also determined. The obtained results of the demonstration suggests that this combined approach could be useful to develop generally applicable metabolomic approaches to valuate honey products as well as other agricultural products.

Chemistry Puts Herbal Supplements To The Test

Some 3,000 species of plants are sold as herbal supplements in this country in as many as 50,000 different products, the American Herbal Products Association estimates. Figuring out if what's inside any particular package corresponds to the contents on the label is far from simple, according to Joseph M. Betz, director of the dietary supplements methods and reference materials program at NIH. is the only means of determining the quality of the material, Betz last week told a symposium on challenges in chemical analysis of herbal supplements sponsored by the Division of Agricultural & Food Chemistry at the ACS meeting in Anaheim, Calif. Betz's program supports research aimed at clearing the confusion in the marketplace by validating analytical methods and developing reference materials. The need for reliable, reproducible tests was reinforced by data from Mingfu Wang, research assistant professor at Rutgers University. His team found that the contents of ...