{"title":"Understanding and Employing (Non-)Linearities in Attenuated Total Reflection Spectroscopy.","authors":"Thomas G Mayerhöfer, Jürgen Popp","doi":"10.1177/00037028251317540","DOIUrl":"https://doi.org/10.1177/00037028251317540","url":null,"abstract":"<p><p>When Beer's law is interpreted through electromagnetic theory, it becomes clear that assuming a linear relationship between molar concentration and the imaginary part of the dielectric function is more accurate than using the absorption index function. A similar relationship holds true for attenuated total reflection (ATR) absorbance. When the negative logarithm of the reflectance is expanded into a series and truncated after the linear term, the approximation proves more accurate when based on the imaginary part of the dielectric function. Moreover, ATR correction schemes that utilize the low absorption approximation or the Bertie-Eysel formalism with this imaginary part, rather than the absorption index, tend to converge more quickly and provide more accurate results, particularly for stronger oscillators across an extended range of oscillator strength. Therefore, correction schemes for ATR spectra should prioritize the imaginary part of the dielectric function rather than the absorption index function when analyzing scalar and isotropic media.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"37028251317540"},"PeriodicalIF":2.2,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143405062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sai Eswar Jasti, Md Abrar Jamil, Chandru P Chandrasekaran, Suying Wei, Sylvestre Twagirayezu
{"title":"Continuous Monitoring of Sulfur Dioxide Removal Using K-Band Molecular Rotational Resonance Spectroscopy.","authors":"Sai Eswar Jasti, Md Abrar Jamil, Chandru P Chandrasekaran, Suying Wei, Sylvestre Twagirayezu","doi":"10.1177/00037028251317215","DOIUrl":"https://doi.org/10.1177/00037028251317215","url":null,"abstract":"<p><p>Sulfur dioxide (SO<sub>2</sub>), an air pollutant, poses significant threats to both public health and the environment. It is one of the six air pollutants regulated by the U.S. Environmental Protection Agency under the Clean Air Act. In efforts to determine the application of molecular rotational resonance (MRR) spectroscopy for monitoring SO<sub>2</sub> and its removal from point sources, a K-band MRR technique was evaluated. This method was applied to measure the products of heated mixtures of SO<sub>2</sub> and oxygen (O<sub>2</sub>) in the presence of ammonium metavanadate (NH<sub>4</sub>VO<sub>3</sub>) as a catalyst. The observed MRR spectrum revealed the presence of SO<sub>2</sub>, water vapor (H<sub>2</sub>O), and ammonia (NH<sub>3</sub>) due to the sensitivity of MRR to only polar species. SO<sub>2</sub> removal was further confirmed by the disappearance of SO<sub>2</sub> as NH<sub>3</sub> formed. The work presented here analyzed the measurements of SO<sub>2</sub> and validated K-band MRR for monitoring SO<sub>2</sub> removal. It was observed that the K-band MRR maintains its linearity and other polar species in the mixture did not interfere with MRR signature of SO<sub>2</sub>. The limit of detection, better than 1%, was determined by evaluating targeted K-band MRR signal response of SO<sub>2</sub> removal obtained at varying partial pressures of SO<sub>2</sub> in the mixture and using the MRR signal of pure SO<sub>2</sub> at 3 mTorr as a reference (100%). Additionally, the results showed that the accuracy and precision of K-band MRR for measuring SO<sub>2</sub> partial pressure were satisfactory.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"37028251317215"},"PeriodicalIF":2.2,"publicationDate":"2025-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143381481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Multichannel Dilution Analysis Using a Single Peristaltic Pump Tube.","authors":"Robbie M Huff, Willis B Jones, Bradley T Jones","doi":"10.1177/00037028251315753","DOIUrl":"https://doi.org/10.1177/00037028251315753","url":null,"abstract":"<p><p>Multi-channel dilution analysis (MCDA) is a novel, matrix-matched calibration method that automatically dilutes a standard solution using a tubing manifold to split a solution stream traveling between an autosampler and an analytical instrument. The manifold consists of separate tubing channels of various lengths, resulting in a stairstep of signal levels as different portions of the solution reach the instrument to be measured at different points in time. Multi-channel dilution analysis was initially developed on an inductively coupled plasma optical emission spectrometer (ICP-OES) equipped with a peristaltic pump with five channels, with three used to drive solution through individual tubes in the manifold and a fourth reserved for waste. The setup limited MCDA measurements from being realized on instruments that have fewer pump channels without employing an external pump. The use of a single peristaltic pump line to drive solution through the entire tubing manifold is proposed as a feasible way to overcome this hardware limitation and is applied to both ICP-OES and ICP mass spectrometry (ICP-MS). The method is validated through the analysis of certified reference materials, with recoveries for a suite of analytes ranging from 83% to 117%, with relative standard deviations on the order of 1%. The matrix matching capabilities of the method are demonstrated through the analysis of spiked matrices containing high concentrations of ethanol and calcium, and a comparison to traditional calibration techniques. In addition, the improvements in calibration statistics for ICP-MS measurements using MCDA are discussed.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"37028251315753"},"PeriodicalIF":2.2,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143254460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H Georg Schulze, Shreyas Rangan, Martha Z Vardaki, Michael W Blades, Robin F B Turner, James M Piret
{"title":"Demixing and Analysis of Complex Biological Raman Hyperspectra Based on Peak Fitting, Amplitude Trend Clustering, and Spectrum Reconstruction.","authors":"H Georg Schulze, Shreyas Rangan, Martha Z Vardaki, Michael W Blades, Robin F B Turner, James M Piret","doi":"10.1177/00037028241311296","DOIUrl":"https://doi.org/10.1177/00037028241311296","url":null,"abstract":"<p><p>To better interpret the Raman spectra from mammalian cells, it is often desirable to reduce their complexity by decomposing them into the spectral contributions from individual macromolecules or types of macromolecules. Diverse methods exist for demixing complex spectra, each with different benefits and drawbacks. However, some methods require a library of component spectra that might not be available, while others are hampered by noise and peak congestion that includes many proximal overlapping peaks. Through rapid fitting of individual peaks in every spectrum of a Raman hyperspectral data set, we have obtained individual peak parameters from which we determined the trends for all the peak amplitudes. We then grouped similar trends with <i>k</i>-means clustering. Then we used the peak parameters of all the peaks in a given cluster to reconstruct a spectrum representative of that cluster. This method produced spectra that were less distorted by unrelated overlapping peaks or noise, were less congested than those in the hyperspectral set, and thereby improved peak identification and macromolecule recognition. We have demonstrated the application of the method with Raman spectra from a perchlorate-polystyrene model system and extended it to complex spectra from methanol-fixed mammalian cells. We were able to recover independent spectra of perchlorate and polystyrene in the model system and spectra pertaining to individual macromolecular types (proteins, nucleic acids, lipids) from the mammalian cell data. We discuss how imperfections in spectral preprocessing and peak fitting can adversely affect the results. In summary, we have provided a proof-of-concept for a novel mixture resolution method with different attributes than extant ones.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"37028241311296"},"PeriodicalIF":2.2,"publicationDate":"2025-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143078516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tatiana Ap de Oliveira, Cibely S Martin, Rafael J G Rubira, Anerise de Barros, Italo O Mazali, Luiz P Zidoi, Augusto Batagin-Neto, Carlos J L Constantino
{"title":"Gold Nanorod Surface-Enhanced Raman Spectroscopy Substrate for l-DOPA Detection: Experimental and Theoretical Approaches.","authors":"Tatiana Ap de Oliveira, Cibely S Martin, Rafael J G Rubira, Anerise de Barros, Italo O Mazali, Luiz P Zidoi, Augusto Batagin-Neto, Carlos J L Constantino","doi":"10.1177/00037028251315208","DOIUrl":"https://doi.org/10.1177/00037028251315208","url":null,"abstract":"<p><p>Experimental efforts aimed at detecting levodopa (l-DOPA) using surface-enhanced Raman scattering (SERS) face a persistent challenge in obtaining a SERS signal with negatively charged nanoparticles. This challenge stems from the repulsion between deprotonated l-DOPA in aqueous solution and the charged surface of the nanoparticles, revealing dependencies on time and concentration to achieve the SERS signal. This study explores the adsorption mechanism of l-DOPA on the surface of gold nanorods (AuNRs) covered with a cetrimonium bromide (CTAB) bilayer as a colloidal solution, subsequently dried onto a solid substrate such as glass, silicon, and Au substrate. Experimental findings are supported by density functional theory theoretical calculations. The comparison between experimental and theoretical results highlights that the SERS profile can be attributed to the adsorption of l-DOPA via the catechol ring, leading to the formation of anionic and dianionic species.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"37028251315208"},"PeriodicalIF":2.2,"publicationDate":"2025-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied SpectroscopyPub Date : 2025-02-01Epub Date: 2024-09-23DOI: 10.1177/00037028241279328
Yanru Li, Keming Yang, Bing Wu
{"title":"Feature Selection and Spectral Indices for Identifying Maize Stress Types.","authors":"Yanru Li, Keming Yang, Bing Wu","doi":"10.1177/00037028241279328","DOIUrl":"10.1177/00037028241279328","url":null,"abstract":"<p><p>This study aims to identify different types of stress on maize leaves using feature selection and spectral index methods. Spectral data were collected from leaves under heavy metal, water, fertilizer stress, as well as under normal healthy conditions. Preprocessing steps such as continuum removal (CR), standard normal variable (SNV) transformation, multiple scattering correction (MSC), detrend correction (DT), and first-order derivative (FOD) were applied to the raw spectra. Various feature selection methods including ReliefF, chi-square test, recursive feature elimination (FRE), mutual information (MI), random forest (RF), and gradient boosting tree (GBT) were employed to determine the importance scores of different spectral bands, thus identifying sensitive spectral features capable of distinguishing various stress types. Spectral indices for stress type differentiation were constructed using label correlation method. Classification models were built using support vector machine (SVM), K-nearest neighbors (KNN), Gaussian naive Bayes (GNB), extreme gradient boosting (XGBoost), RF, and adaptive boosting (AdaBoost) algorithms. Results indicate that the characteristic spectral bands for differentiating stress types are primarily distributed around the red edge (near 700-800 nm) and water absorption valley (near 1900 nm). Spectral indices constructed using combinations of spectral bands around the near-infrared plateau absorption valley (near 1185 nm) and water absorption valley (near 1460 nm) effectively differentiate maize stress types. Among the modeling classification algorithms, RF and AdaBoost algorithms exhibited optimal performance, demonstrating high classification accuracy on both training and validation sets. These findings hold promise for providing new technical support for maize stress monitoring and diagnosis in agricultural production.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"306-319"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142279786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied SpectroscopyPub Date : 2025-02-01Epub Date: 2024-09-28DOI: 10.1177/00037028241285150
Kailun Zhang, Ruike Bi, Johan Tidholm, Jakob Ängeby, Mattias Richter, Andreas Ehn
{"title":"Detection of Nickel Atoms Released from Electrodes in Spark Discharges Using Laser-Induced Fluorescence.","authors":"Kailun Zhang, Ruike Bi, Johan Tidholm, Jakob Ängeby, Mattias Richter, Andreas Ehn","doi":"10.1177/00037028241285150","DOIUrl":"10.1177/00037028241285150","url":null,"abstract":"<p><p>The reduction of greenhouse gas emissions and the effort of carbon neutrality require the improvement of spark-ignition engines in terms of efficiency and capability to operate on renewable fuels. The electrode wear of spark plugs, used for ignition of novel fuels and lean mixtures, emerges as a significant challenge in this transition. Understanding the physical mechanism and influence of spark operation parameters of the wear process is thus important. Compared to the conventional methodology of performing long-term wear tests, laser-based optical diagnostics methods are capable of assessing electrode wear during one single or a few spark discharges. In this work, the necessary initial steps required for performing optical investigations using laser-induced fluorescence (LIF) are presented. Several excitation pathways of nickel atoms were investigated, and 336.96 nm was identified as the optimal one. This excitation approach yielded emissions between 338.75 and 353.58 nm, effectively avoiding the major interference from N<sub>2</sub> plasma emission in spark discharges. Additionally, a linear relationship in fluorescence signal intensity with excitation energy up to 400 µJ was observed. These findings indicate the potential of LIF for in situ diagnostics of electrode wear, contributing to engine development in both efficiency and compatibility with sustainable fuels.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"281-288"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11823277/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142340055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied SpectroscopyPub Date : 2025-02-01Epub Date: 2024-09-26DOI: 10.1177/00037028241280722
Sergei V Bykov, Sanford A Asher
{"title":"Solid State Vanadate Laser and 213 nm Rayleigh Rejection Filter Enable Miniaturized Deep Ultraviolet Raman Spectrometers.","authors":"Sergei V Bykov, Sanford A Asher","doi":"10.1177/00037028241280722","DOIUrl":"10.1177/00037028241280722","url":null,"abstract":"<p><p>A combination of a highly efficient 213 nm Rayleigh rejection filter (RRF) and a miniaturized 213 nm neodymium-doped vanadate laser enables portable deep ultraviolet (UV) Raman spectrometers. We demonstrate the high efficiency of 213 nm RRF manufactured by Green Optics Co., Ltd. by utilizing our compact 213 nm vanadate laser to measure high signal-to-noise ratio UV Raman spectra of Teflon and UV resonance Raman (UVRR) spectra of solid ammonium nitrate. We also demonstrate UVRR detection of trace amounts of ammonia formed during ammonium nitrate UV photolysis. We roughly estimate the ammonia UVRR detection limit of ∼10 ng under our experimental conditions.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"345-348"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142340057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Advertising and Front Matter.","authors":"","doi":"10.1177/00037028251318118","DOIUrl":"https://doi.org/10.1177/00037028251318118","url":null,"abstract":"","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":"79 2","pages":"235-240"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143405209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied SpectroscopyPub Date : 2025-02-01Epub Date: 2024-06-11DOI: 10.1177/00037028241257267
Cobey L McGinnis, Jesse A Frantz, Jasbinder S Sanghera, Kenneth J Ewing
{"title":"Biomimetic Optical-Filter Sensor System for Discrimination of Infrared Chemical Signatures Against a Cold Sky Background.","authors":"Cobey L McGinnis, Jesse A Frantz, Jasbinder S Sanghera, Kenneth J Ewing","doi":"10.1177/00037028241257267","DOIUrl":"10.1177/00037028241257267","url":null,"abstract":"<p><p>Passive infrared (IR) systems enable rapid detection of chemical vapors but are limited by size, weight, cost, and power. Previously, the authors reported a novel passive sensor that utilizes multiple IR filter/detector combinations to discriminate between different chemical vapors based on their unique IR absorption spectra in the same manner the human eye uses to generate colors. This approach enables a very small, compact, and low-power sensor system with the capability to discriminate between chemical vapors of interest and background chemicals. All previous work showed the capability of this sensor system in discriminating chemical vapors against a hot blackbody in a laboratory environment. Now the authors demonstrate the ability of this sensor system to discriminate between the chemical vapor agent simulant dimethyl methylphosphonate and ethanol against the cold sky in an outdoor environment.</p>","PeriodicalId":8253,"journal":{"name":"Applied Spectroscopy","volume":" ","pages":"260-264"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141299876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}