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Chiral Analysis || Quantitative Chiral Analysis by Molecular Rotational Spectroscopy
摘要： This chapter presents early results from the emerging field of quantitative chiral analysis by molecular rotational spectroscopy. The focus is on the development of measurement techniques to solve the challenging analytical chemistry problem of determining the ratios of all stereoisomers for a chiral molecule. This analysis becomes particularly challenging as the number of chiral centers in the molecule increases. Furthermore, this area of spectroscopy has the goal of creating measurement techniques that can be used directly on complex chemical mixtures to perform chiral analysis without the need of chemical separation by chromatography. Examples of chemical samples that fall into this category include natural products like essential oils from plants that are a rich mixture of volatile species and reaction flask samples where stereospecific chemical reactions are performed and which contain unreacted reagents, desired and undesired reaction products, and solvents in the mixture.
关键词： stereoisomers,chiral tag,diastereomers,molecular rotational spectroscopy,chirality,enantiomers,three-wave mixing,analytical chemistry,quantitative chiral analysis
更新于2025-09-23 15:23:52
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Potential Application of Lasera??Induced Breakdown Spectroscopy (LIBS) Data for the Determination of Cation Exchange Capacity (CEC) of Agricultural Soils
摘要： The potential for Laser Induced Breakdown Spectroscopy (LIBS) technique to predict cation exchange capacity (CEC) values in agricultural soils, based on a partial least square (PLS) regression model, was investigated by analysing soils (N = 225) using a portable LIBS system. The prediction from the validation set was 0.75 and the RMSE was 5.4 cmol + /kg. Analysis of the PLS loading weights showed that emission lines that correlate with the exchangeable cations (Ca, Mg, K and Na) and clay (Al and Si) are significant. Good quality predictions could be obtained from the model as described by the ratio of performance to deviation (RPD) values calculated for calibration (RPDc = 1.99) and validation (RPDv = 2.02). The ratio of performance to interquartile distance (RPIQ) for calibration (RPIQc = 3.20) and validation (RPIQv = 3.32) indicated excellent prediction capability. It has been demonstrated that LIBS spectra coupled with multivariate data analysis could be used to predict CEC of agricultural soils which is considered fast and a chemical-free technique.
关键词： cation exchange capacity,agricultural soil,analytical chemistry,spectroscopic method,laser induced-breakdown spectroscopy
更新于2025-09-23 15:21:01
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Identification of Proteins Using Four Methods of Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry
摘要： An upper-division undergraduate- or graduate-level laboratory experiment, challenging students to identify bovine serum albumin, equine myoglobin, bovine calmodulin, and bovine cytochrome c, uses four methods of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS): linear positive, in-source decay, peptide mass fingerprint, and postsource decay. Individual hands-on experience with each method is provided in a three week experiment. The importance of sequencing proteins/peptides when identifying proteomic targets using MALDI-TOF MS is emphasized.
关键词： Mass Spectrometry,Hands-On Learning/Manipulatives,Upper-Division Undergraduate,Laboratory Instruction,Graduate Education/Research,Bioanalytical Chemistry,Biotechnology,Analytical Chemistry,Biochemistry
更新于2025-09-19 17:13:59
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Fiberoptic-Coupled Spectrofluorometer with Array Detection as a Process Analytical Chemistry Tool for Continuous Flow Monitoring of Fluoroquinolone Antibiotics
摘要： Nowadays, there is an increasing need for sensitive real-time measurements of various analytes and monitoring of industrial products and environmental processes. Herein, we describe a ?uorescence spectrometer in continuous ?ow mode in which the sample is fed to the ?ow cell using a peristaltic pump. The excitation beam is introduced to the sample chamber by an optical ?ber. The ?uorescence emitted upon excitation is collected at the right angle using another optical ?ber and then transmitted to the ?uorescence spectrometer which utilizes an array detector. The array detection, as a key factor in process analytical chemistry, made the ?uorescence spectrometer suited for multiwavelength detection of the ?uorescence spectrum of the analytes. After optimization of the experimental parameters, the system has been successfully employed for sensitive determination of four ?uoroquinolone antibiotics such as cipro?oxacin, o?oxacin, levo?oxacin, and moxi?oxacin. The linear dynamic ranges of four ?uoroquinolones were between 0.25 and 20 μg·mL? 1, and the detection limit of the method for cipro?oxacin, o?oxacin, levo?oxacin, and moxi?oxacin were 81, 36, 35, and 93 ng·mL? 1, respectively. Finally, the proposed system is carried out for determination of ?uoroquinolones in some pharmaceutical formulations.
关键词： Fluoroquinolone antibiotics,Fiberoptic-coupled spectrofluorometer,Process Analytical Chemistry,Continuous flow monitoring,Array detection
更新于2025-09-19 17:13:59
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Analytical Methods for Monitoring the Degradation of Plasmonic Nanoparticles in Solution: An Instrumental Analysis Laboratory Exercise
摘要： Nanoparticles are an increasingly important in chemistry research, but currently there are few opportunities for chemistry students to work with nanoparticles in undergraduate analytical courses. In this exercise, designed for an analytical or instrumental analysis lab course, students have the opportunity to work with solutions of silver nanoparticles and analyze them with two instrumental techniques. UV?vis spectrophotometry is utilized to monitor the optical behavior of silver nanoparticles over the course of the experiment. ICP-OES analysis determines the concentration of total silver species present in solution based on storage conditions. This exercise also introduces students to the concept of localized surface plasmon resonance and its role in producing the vivid colors often associated with plasmonic nanoparticles embedded in stained glass.
关键词： Upper-Division Undergraduate,Instrumental Methods,Collaborative/Cooperative Learning,Laboratory Instruction,Analytical Chemistry,Nanotechnology,Problem Solving/Decision Making
更新于2025-09-19 17:13:59
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Structural characterization of Argania spinosa Moroccan wooden artifacts during natural degradation progress using infrared spectroscopy (ATR-FTIR) and X-Ray diffraction (XRD)
摘要： The present work is focused on spectroscopic study of four samples of Argan wooden artifact pertaining to the 17th, 18th, 20th and 21st centuries. The objective is to characterize their unknown structures by the study of their non degraded parts and to investigate changes occurred in their degraded parts due to the natural degradation process. Attenuated total re?ectance Fourier transform infrared spectroscopy gauges the presence of many functional groups related to cellulose I and/or II (OH, C–O–C and –CH2), hemicelluloses (particularly C?O (cid:2)1), and lignin (OH phenolic, Car-O and C?Car) and provides qualitative information on the state of wood alteration by informing on the evolution of new former C?O bands. The degree of conversion to carbonyl group, especially quinone or p-quinone at 1650 cm (cid:2)1, is correlated to lignin degradation, while the absence of the C?O acetoxy absorption is ascribable to occurred deterioration in hemicelluloses, and (cid:2)1. X-ray diffraction determines the presence of two forms of cellulose; amorphous cellulose at 18.5(cid:3) 2θ and predominant crystalline cellulose Iβ at 2θ ? 22.6(cid:3) which characterized by an intense peak. The decrease of crystallinity index values con?rms the deterioration level and obvious changes in crystallinity level. However, the microcrystalline structure appears unaltered because no signi?cant changes were observed for calculated cristallite seize. The obtained results depend on the prolonged time of ageing, natural deterioration phenomena, and wood part (internal or external) that is exposed to degradation. The combination of these two methods is useful for an accurate estimation of the degradation level of argan wood.
关键词： Chemistry,Argan wood artifact,XRD,Analytical chemistry,Natural product chemistry,Materials Chemistry,Natural degradation,Archaeology,ATR-FTIR spectroscopy,Crystallinity,Lignocelluloses,Structural characterization,Materials Science,Organic chemistry
更新于2025-09-12 10:27:22
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Detecting and Quantifying Microplastics in Bottled Water using Fluorescence Microscopy: A New Experiment for Instrumental Analysis and Environmental Chemistry Courses
摘要： Microplastics (MPs) are small plastic particles (<5 mm in size) that are ubiquitous in the environment and have even been detected in bottled water. In this laboratory experiment, suited for instrumental or environmental chemistry classes, students detect and quantify MPs in bottled water by filtering and staining them with Nile red dye prior to utilizing fluorescence microscopy. Instrumental concepts in fluorescence spectroscopy are reinforced as students build a low-cost fluorescence microscope and use it to collect images of the fluorescing MPs for counting purposes and assessing morphology. The exercise introduces students to MP pollution, an emerging field of chemical research, and motivates and engages them helping to form connections beyond the classroom. Each group detected MPs in their bottled water, and many were surprised by how many they found. Overall, the hands-on experiment received positive feedback from students, and postexperiment assessments showed marked improvement in their understanding of the principles of fluorescence and of the growing problem of MP pollution.
关键词： Analytical Chemistry,Upper-Division Undergraduate,Collaborative/Cooperative Learning,Water/Water Chemistry,Instrumental Methods,Environmental Chemistry,Hands-On Learning/Manipulatives
更新于2025-09-12 10:27:22
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Quantitative Analysis of Cerium-Gallium Alloys Using a Hand-Held Laser Induced Breakdown Spectroscopy Device
摘要： A hand-held laser-induced breakdown spectroscopy device was used to acquire spectral emission data from laser-induced plasmas created on the surface of cerium-gallium alloy samples with Ga concentrations ranging from 0–3 weight percent. Ionic and neutral emission lines of the two constituent elements were then extracted and used to generate calibration curves relating the emission line intensity ratios to the gallium concentration of the alloy. The Ga I 287.4-nm emission line was determined to be superior for the purposes of Ga detection and concentration determination. A limit of detection below 0.25% was achieved using a multivariate regression model of the Ga I 287.4-nm line ratio versus two separate Ce II emission lines. This LOD is considered a conservative estimation of the technique’s capability given the type of the calibration samples available and the low power (5 mJ per 1-ns pulse) and resolving power (λ/?λ = 4000) of this hand-held device. Nonetheless, the utility of the technique is demonstrated via a detailed mapping analysis of the surface Ga distribution of a Ce-Ga sample, which reveals signi?cant heterogeneity resulting from the sample production process.
关键词： LIBS,plasma spectroscopy,analytical chemistry,nuclear forensics,nuclear chemistry,lanthanide spectroscopy
更新于2025-09-12 10:27:22
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Process Analytical Technology for Online Monitoring of Organic Reactions by Mass Spectrometry and UV–Vis Spectroscopy
摘要： Process analytical technologies (PATs) are used in the pharmaceutical and other industries to monitor chemical processes in real-time with analytical instrumentation. Each PAT analyzer brings its own advantages and disadvantages to the process, and multiplexing PAT analyzers can be advantageous as they can provide confirmatory measurements and increase the overall confidence of the analysis. In a pedagogical setting, online reaction monitoring enables the instructor to explain the fundamentals of instrumental techniques while highlighting pertinent real-world applications. Here we present a teaching laboratory exercise in which students monitor an amide bond formation reaction by flow UV?vis spectroscopy and by mass spectrometric analysis. The coupling of these two specific instruments allows students to investigate two instruments in one laboratory exercise, to explore the fundamentals behind each, and to contemplate the advantages and disadvantages of these instrumental methods. The coupling of the two instruments was aided by 3D printing which allowed students to explore how rapid prototyping can enable the development of innovative procedures.
关键词： Organic Chemistry,Mass Spectrometry,UV?Vis Spectroscopy,Laboratory Instruction,Instrumental Methods,Hands-On Learning/Manipulatives,Upper-Division Undergraduate,Analytical Chemistry,Reactions
更新于2025-09-04 15:30:14
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A critical review of flexible and porous SERS sensors for analytical chemistry at the point-of-sample
摘要： For decades surface enhanced Raman spectroscopy (SERS) has been intensely investigated as a possible solution for performing analytical chemistry at the point of sample origin. Unfortunately, due to cost and usability constraints, conventional rigid SERS sensors and microfluidic SERS sensors have yet to make a significant impact outside of the realm of academics. However, the recently introduced flexible and porous paper-based SERS sensors are proving to be widely adaptable to realistic usage cases in the field. In contrast to rigid and microfluidic SERS sensors, paper SERS sensors feature (i) the potential for roll-to-roll manufacturing methods that enable low sensor cost, (ii) simple sample collection directly onto the sensor via swabbing or dipping, and (iii) equipment-free separations for sample cleanup. In this review we argue that movement to paper-based SERS sensors will finally enable point-of-sample analytical chemistry applications. In addition, we present and compare the numerous fabrication techniques for paper SERS sensors and we describe various sample collection and sample clean-up capabilities of paper SERS sensors, with a focus on how these features enable practical applications in the field. Finally, we present our expectations for the future, including emerging ideas inspired by paper SERS.
关键词： flexible sensors,paper-based sensors,SERS,porous sensors,point-of-sample,analytical chemistry
更新于2025-09-04 15:30:14