August 15th 2024
A recent study examined the role of high-resolution mass spectrometry imaging in assessing environmental contaminants.
Application of Laser Ablation ICP-MS to the Analysis of Forensic Glass Samples
July 1st 2005Laser ablation ICP-MS enables identification and comparison of physical crime-scene evidence. Discriminating elemental and isotopic differences of solid samples directly at the parts-per-billion level provides forensic scientists with a powerful analytical tool.
Combining Confocal Raman with Atomic force Microscopy for High-Resolution Material Analysis
June 2nd 2005Confocal Raman microscopy can be useful when applied to all samples that are heterogeneous on the micrometer to millimeter scale and that generally can be investigated by Raman spectroscopy. This article presents examples of confocal Raman microscopy from various fields of application including pharmaceutical analysis and stress measurements in semiconductors.
A New Approach to Simultaneous Raman and IR Spectral Searches
June 2nd 2005A new system for multitechnique spectral searching is described that utilizes analysis of several hit lists resulting from spectral similarity searches performed simultaneously in reference databases for multiple complementary analytical techniques. This paper demonstrates the benefits of this multitechnique approach using the complementary techniques of IR and Raman spectroscopy.
Raman and EDXRF Chemical Imaging for Formulation Process Development and Quality Control
June 2nd 2005Compounds of magnesium and calcium are common components of pharmaceutical formulations. Spectroscopic imaging can provide a complete understanding of a formulation. This paper compares two spectral imaging techniques — energy dispersive X-ray fluorescence (EDXRF) microscopy and Raman microscopy.
Grating Corrected Laser Stabilization: A Case Study in Pharmaceutical Raw Material Identification
June 2nd 2005The authors present a novel technique for obtaining very high stability and reproducibility of a Raman spectrum, using grating corrected laser stabilization. An externally stabilized laser with a grating spectrometer provides exceptional quantum efficiency in the entire dynamic range. These components then are used to build a library of pharmaceutical raw materials and tested on samples of unknown material.
Reliable Substrate Technology for Surface-Enhanced Raman Spectroscopy
June 2nd 2005The acquisition of Raman spectra can be eased greatly through the use of surface-enhanced Raman spectroscopy (SERS). In this article, the authors discuss a new substrate technology that delivers reliable and consistent surface enhancement.
Detecting Bacillus Spores by Raman and Surface-Enhanced Raman (SERS) Spectroscopy
June 2nd 2005Raman spectroscopy has been employed to detect Bacillus cereus spores, an anthrax surrogate, collected from a letter as it passed through a mail sorting system. Raman spectroscopy also has the ability to identify many common substances used as hoaxes. A three-step method also is described for the detection of dipicolinic acid extracted from surface spores by SERS.
Comparing Standard CCD and Electron Multiplication CCD for Low Light Level Spectroscopy
June 2nd 2005This article compares different CCD platforms by outlining CCD and EMCCD noise sources as well as an explanation of the two calculations to arrive at the signal-to-noise ratio for each. The data presented will show that a liquid nitrogen-cooled CCD camera still is the proper choice for low light level applications, such as Raman spectroscopy.
The Baseline: The Solar Spectrum
June 1st 2005Spectroscopists separate light from the sun into spectra and look for the presence or absence of particular lines that give hints regarding its chemical composition. The same method can be applied to studying the composition of other matter in the universe.
AFM Measurement of Step Kinetics for the Growth and Dissolution of Crystallites
June 1st 2005This paper discusses two atomic force microscopy (AFM) techniques that have been used successfully to quantify step movement: direct and indirect measurement. The benefits and difficulties associated with each method are discussed.
A High-Volume, High-Throughput LC–MS Therapeutic Drug Monitoring System
June 1st 2005Therapeutic drug monitoring is performed routinely by liquid chromatography–mass spectrometry (LC–MS) using instrumentation and methods originally developed and systematically configured for the high-volume, high-throughput analysis of drugs of abuse. An example of LC–MS monitoring of the drug clozapine and its metabolite, desmethylclozapine, is detailed along with a description of the overall system architecture, workflow, and maintenance routines that support a large-scale clinical therapeutic drug monitoring program. The relative advantages of LC–MS over immunoassay and LC–UV, the current standard techniques for therapeutic drug monitoring, are discussed in the light of these results.
Using FT-MS to Detect Indoor Chemical Contamination
May 2nd 2005A transportable miniature Fourier-transform ion cyclotron resonance mass spectrometer is used to identify chemical species and remove isobaric interferences in gas analysis. Experimental results use real time direct analysis without the need for additional separation.
GC–MS Analysis on Titan Mission
May 2nd 2005The European-built Huygens probe made history on January 14 by becoming the first spacecraft to land on Saturn's largest moon. The Huygens gas chromatography–mass spectrometry team concluded that methane rain occurs on the moon, and GC–MS can distinguish between two isotopic forms of carbon — carbon-12 and carbon-13. By comparing the carbon-12/13 ratios it might be possible to pin a biological source to the methane arising from the interior of Titan.
Time-of-Flight Mass Spectrometry for Proteomics Research
May 2nd 2005Time-of-Flight (TOF) is rapidly becoming the most popular method of mass separation for proteomics and conventional analytical chemistry. The development of very high temporal resolution ion detectors and low-cost high-speed digitizers has rendered this technique easily deployed and able to produce very high mass resolution. The performance of a TOF mass spectrometer is dependent upon a number of critical components. This article will focus on the ion detector.
A Mathematical Approach to Error Reduction in Mass Spectrometry
May 2nd 2005The exploding field of proteomics has highlighted the need to improve the performance of mass spectrometry, both quantitatively and qualitatively. These needs have led instrument manufacturers to produce instruments of increasingly higher quality, but little work has been done to address the fundamental errors inherent in the measurement technique itself. This paper examines these errors and demonstrates that the appropriate mathematical correction of MS data can significantly improve the performance of both low- and high-resolution instruments.
On-line and Off-line 2-D LC–ESI MS-MS Methods in Proteomic Analysis
May 2nd 2005Off-line 2-D LC–MS-MS represents a powerful alternative to on-line methodologies for protein identification from complex proteomes, improving the chromatographic resolution of digest peptide mixtures, even for low-abundance proteins. Here, the authors provide a detailed comparison of the two techniques.
Theoretical and Experimental Investigation of the Electronic Spectra of Antitumor Compounds
May 1st 2005Time-dependent density functional theory and ZINDO/S methods have been used to compute and analyze the electronic spectra of benzazoles, 2-phenylbenzazoles, and 2-(4-aminophenyl)benzazoles. The observed spectra of the studied antitumor drugs are diffuse and highly solvent-dependent. Spectral analysis of the charge density distributions and relative polarities of the ground and excited states have enabled understanding of the observed solvent effects.
Photonic Bandgap Fibers in Gas Detection
April 1st 2005Photonic crystal fibers are novel optical waveguides that offer promising alternatives for various sensing applications. This article describes an experiment in which the absorption spectrum of acetylene was measured to demonstrate the effectiveness of photonic bandgap fibers for high sensitivity gas detection. Methane also was studied to determine the same capability in weakly absorbing gases.
Characterization of Archaeological Findings by FT-IR Spectroscopy
April 1st 2005The authors describe their work characterizing archaelogical ceramics by means of Fourier-transform infrared (FT-IR) absorption. Semiquantitative analyses using the technique can identify the main components and trace elements constituting the ceramics. An accurate knowledge of the chemical composition of the samples gives useful information for their classification.
Tech Note: Diffractive MEMS in Spectroscopy
April 1st 2005MEMS are small, microfabricated devices that are finding application in a variety of industries in both analytical and manufacturing settings. This paper reviews the properties of diffractive MEMS devices and examines their application in chemical spectroscopy.