The following articles are the most accessed digital object identifier (DOI) manuscripts for Spectroscopy and LCGC International during the month of September 2026. Nine articles are individually ranked here by DOI page views; the third-highest entry (186 views) was recorded against the bare journal-level DOI rather than an individual article and is therefore not attributable to a single manuscript.
Each article has been selected based on the number of successful DOI page views by readers as reported by reports@crossref.org. The articles showcase key developments and insights in spectroscopy and chromatography. Spectroscopy covers the main topics of electronic spectroscopy, vibrational spectroscopy, magnetic resonance, imaging techniques, atomic spectroscopy, and data analysis and integration. LCGC covers most aspects of liquid and gas chromatography, mass spectrometry, and related technical aspects of separation science.
This month's ranking is led by Howard Mark and Jerome Workman, Jr.'s examination of decimal versus binary number representation, which drew 556 DOI views—nearly three times the next-ranked article. Brian C. Smith's Infrared Spectroscopy of Polymers series again features prominently with four of the nine individually ranked spots, joined by strong reader interest in Raman spectroscopy for forensic drug identification and protein structure, miniaturized handheld near-infrared sensing, and LC–MS/MS determination of mutagenic nitrosamine impurities from Spectroscopy and LCGC International.
1.
Authors: Howard Mark and Jerome Workman, Jr.
This article examines a practical problem that arises when computers, which store numbers internally in binary form, exchange numerical data externally in decimal notation. The authors show that truncating the number of decimal digits used during data transfer—particularly for spectral data exported in the JCAMP-DX format—can introduce precision loss that compromises downstream chemometric calculations such as calibration modeling. Drawing on the structure of IEEE 754 floating-point representation, they recommend exporting at least nine significant decimal digits to preserve the full information content of the original binary values.
Authors: Ling-yu Zhao, Guo-ping Wu, and Yuan-zhao Wu
Fluorescence from cutting agents and other additives frequently masks the Raman signal of illicit drugs, limiting the usefulness of portable Raman instruments in the field. In this study, the authors analyzed 43 seized drug samples with both a shifted-excitation Raman difference spectroscopy (SERDS) instrument and a conventional portable Raman spectrometer, confirming all identifications against gas chromatography–mass spectrometry (GC–MS) results. SERDS suppressed fluorescence interference effectively and achieved a detection rate of 93.0%, compared with 53.3% for the conventional instrument, although the conventional spectrometer resolved the components of multi-component mixtures more accurately. The authors conclude that the two techniques are complementary and that using them together can speed and strengthen the screening of seized drugs.
3. Not attributable to a single manuscript (186 views): this entry was recorded against the bare journal-level DOI,
4.
Author: Brian C. Smith
Polyethylene remains one of the most important commercial polymers and serves as an excellent model system for learning polymer infrared spectroscopy. This article continues the discussion of polyethylene spectral interpretation, showing how synthesis methods affect polymer morphology and spectroscopic behavior. Particular attention is given to crystalline splitting and methylene rocking vibrations, illustrating how subtle spectral changes reveal structural differences in polyethylene materials.
5.
Author: Brian C. Smith
This article examines the infrared spectroscopy of polyurethanes, comparing their spectral behavior to the structurally related polyamides. Polyurethanes contain secondary urethane linkages that combine ester- and amide-like character around a shared carbonyl group, and the discussion reviews the resulting N–H stretching, carbonyl, and C–O vibrations. A key diagnostic point is that urethane C=O stretches appear at higher wavenumbers than those of amides, helping distinguish the two polymer classes. The article also covers the diisocyanate precursors used in polyurethane synthesis, which display an intense, broad N=C=O asymmetric stretch near 2277 cm⁻¹.
6.
Authors: Fang Ou, Anne van Klinken, Kaylee D. Hakkel, Maurangelo Petruzzella, Don M.J. van Elst, Petar Ševo, Chenhui Li, Francesco Pagliano, Rene P.J. van Veldhoven, and Andrea Fiore
Moving near-infrared (NIR) spectroscopy into portable devices, consumer appliances, and eventually smartphones requires sensors that are small, inexpensive, and robust against vibration. The authors describe a handheld NIR spectral sensing module operating from 850 to 1700 nm that is built around a fully integrated multipixel detector array with a footprint of roughly 2 × 2 mm². The module was evaluated in two applications: quantifying the fat content of raw milk, achieved with a root mean square error of prediction of 0.14%, and classifying plastic types, achieved with 100% prediction accuracy on unknown samples. These results demonstrate the feasibility of the direct, chip-based NIR sensing approach for a wide range of field and consumer applications.
7.
Author: Fran Adar
In this installment of her Raman column, Adar reviews the band assignments of protein Raman spectra and explains why knowing those assignments helps researchers use Raman data to probe protein structure and function. Using the spectrum of a fingernail (α-keratin) as a representative example, the article works region by region through the CH–NH stretching region and the more variable fingerprint region, including the amide I and amide III bands that arise from coupled vibrations of the peptide backbone and reflect secondary structure. The discussion also addresses band fitting as a means of estimating relative amounts of secondary structure, while noting that published amide band assignments do not always agree.
8.
Author: Brian C. Smith
This installment of Smith's polymer series examines pendant ester polymers, such as cellulose acetate, and polycarbonates. The article explains that acetate esters produce a distinctive, high-wavenumber C–C–O stretching peak near 1240 cm⁻¹, then turns to organic carbonates and shows how polycarbonates such as Lexan display three characteristic peaks arising from carbonyl, O–C–O, and O–C–C stretching vibrations. The discussion concludes by demonstrating how infrared spectroscopy can distinguish between different carbonate types and differentiate carbonates from esters based on peak position.
9.
Author: Brian C. Smith
This is the third installment in Smith's ongoing series on polymer infrared spectroscopy, building on the earlier discussion of polyethylene to examine two additional hydrocarbon polymers: polypropylene and polystyrene. The article provides detailed analysis of how these materials' infrared spectra differ from one another and from polyethylene, demonstrating how characteristic absorption bands distinguish among hydrocarbon polymer types. The discussion serves as both a practical materials-identification resource and an educational review of infrared spectral interpretation technique.
10.
Authors: Matthew James and Tony Edge
Since N-nitrosodimethylamine (NDMA) was detected in a batch of valsartan in 2018 at levels exceeding ICH acceptable intake limits, nitrosamine analysis has become a major focus for the pharmaceutical industry. The authors review how the nitrosamine story and its regulatory landscape developed, discuss potential origins of nitrosamine contamination in drug substances, and describe the development of a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for a series of nitrosamines named by regulatory authorities. Starting from a proposed USP method for nitrosamines in sartans, the optimized method separates the nitrosamines from the active pharmaceutical ingredient, cuts overall cycle time by 50%, and delivers the sensitivity, accuracy, and precision needed to quantify these impurities at the low parts-per-billion levels required by regulators.
References
1. Mark, H.; Workman, J., Jr. Decimal Versus Binary Representation of Numbers in Computers. Spectroscopy 2022, 37 (10), 13–20.
2. Zhao, L.-Y.; Wu, G.-P.; Wu, Y.-Z. Evaluation of Shifted-Excitation Raman Difference Spectroscopy and Comparison to Ordinary Portable Raman Spectroscopy in Identification of Seized Drugs. Spectroscopy 2023, 38 (8), 12–21.
3. DOI:
4. Smith, B. C. The Infrared Spectra of Polymers II: Polyethylene. Spectroscopy 2021, 36 (9), 24–29.
5. Smith, B. C. Infrared Spectroscopy of Polymers XIII: Polyurethanes. Spectroscopy 2023, 38 (7), 14–16.
6. Ou, F.; van Klinken, A.; Hakkel, K. D.; Petruzzella, M.; van Elst, D. M. J.; Ševo, P.; Li, C.; Pagliano, F.; van Veldhoven, R. P. J.; Fiore, A. Spectral Sensing Using a Handheld NIR Module Based on a Fully Integrated Sensor Chip. Spectroscopy 2022, 37 (S11), 34–38.
7. Adar, F. Interpretation of Raman Spectrum of Proteins. Spectroscopy 2022, 37 (2), 9–13, 25.
8. Smith, B. C. Infrared Spectroscopy of Polymers, IX: Pendant Ester Polymers and Polycarbonates. Spectroscopy 2022, 37 (11), 16–19, 31.
9. Smith, B. C. The Infrared Spectra of Polymers III: Hydrocarbon Polymers. Spectroscopy 2021, 36 (11), 22–25.
10. James, M.; Edge, T. Low-Level Determination of Mutagenic Nitrosamine Impurities in Drug Substances by LC–MS/MS. LCGC Europe 2021, 34 (7), 267–276.
