ICP-MS

One of the promises of array detector inductively coupled plasma (ICP) systems has been the ability to measure all elements in an unknown sample. Sometimes referred to as elemental fingerprinting, this capability can be extremely powerful for quality control (QC) and forensic applications. To take advantage of this capability, the ICP system employed must provide full wavelength coverage as well as the spectral data handling tools needed to do the "fingerprinting." This article will demonstrate some of the elemental fingerprinting capabilities of ICP.

The spectrometric techniques of inductively coupled plasma–optical emission spectrometry (ICP-OES) and inductively coupled plasma–mass spectrometry (ICP-MS) are compared for their applicability to regulatory water analyses, bearing in mind recent method approval changes. ICP-OES is found to be at its limit for confident detection of several elements for drinking water analysis, but is still suitable for many environmental water quality measurements. ICP-MS is the closest there is to a universally applicable technique for water analysis.

Assay sensitivity is the lowest concentration at which a targeted analyte can be measured and is often limited by chemical background or co-eluting interferences. FAIMS in combination with liquid chromatography (LC) and zero neutral loss tandem MS was used to remove chemical background and co-eluting interferences from the analysis of linoleic acid in cancer cell extracts. Concentration of endogenous linoleic acid was determined from back-calculation of standard calibration samples fortified with deuterium-labeled linoleic acid. No internal standard was used. LC–MS-MS analysis of the cancer cell extracts resulted in an increase in signal-to-noise ratio of 10-fold. The assay sensitivity was increased 10 times over the traditional LC–MS-MS experiment exclusively due to the new FAIMS technology.

More than 20 years passed after the introduction of Fourier transform–ion cyclotron resonance mass spectrometry (FT-MS) before advancements in electronics and computer technology enabled the development of practical, high-performance instruments. Modern analytical FT-MS instruments rely on sophisticated electronic circuitry and powerful computer software to achieve the dramatic resolving power and mass accuracy typical for the instrumentation. Here, the power of modern hybrid FT-MS instrumentation is discussed by demonstrating the capability of this instrumentation for selected applications such as the analysis of crude oil, intact protein, and fragile noncovalent complex samples.

Here we describe a new compact device for electron-capture dissociation (ECD) analysis of large peptides and posttranslational modifications of proteins, which can be difficult to analyze via conventional dissociation techniques such as collision-induced dissociation (CID). The new compact device realizes ECD in a radio frequency (RF) linear ion trap equipped with a small permanent magnet, which is significantly different than the large and maintenance-intensive superconducting magnet required for conventional ECD in Fourier-transform ion cyclotron resonance mass spectrometers. In addition to its compactness and ease of operation, an additional merit of an RF linear ion trap ECD is that its reaction speed is fast, comparable to CID, enabling data acquisition on the liquid-chromatography (LC) time scale. We interfaced the linear-trap ECD device to a time-of-flight mass spectrometer to obtain ECD spectra of phosphorylated peptides injected into a liquid chromatograph, infused glycopeptides, and intact small..

Metabolomics is a developing analytical approach that is growing rapidly in importance as a tool to improve diagnosis and treatment of disease, as well as to speed up the drug development process. Unlike genomics or proteomics, which only reveal part of what might be happening in a cell, metabolomic profiling can give an instantaneous snapshot of the entire physiology of that cell. This article describes the challenges associated with metabolomics research and new tools developed to overcome them.

The increased resolving power provided by comprehensive two-dimensional gas chromatography (GCxGC) extends the chromatographer's ability to rapidly detect and measure smaller components in complex mixtures beyond that which was possible previously, allowing for the identification of hazardous components in complex mixtures such as foodstuffs or emergency response samples. In target analysis, the increased numbers of peaks resulting from the sample matrix can be largely ignored during the review of data. However, when the nature of the analyte of interest is not entirely known, analysis of the samples might require screening through the entire peak table for compounds with specific chemical characteristics. For example, in the analysis of foodstuffs for pesticides (1,2), GCxGC coupled with a time-of-flight mass spectrometry (GCxGC–TOF-MS) can provide low detection limits for multiple analytes in these complex samples. Yet the question remains as to whether other toxic compounds, not included in the..

Reproducing analysis conditions is crucial to achieving consistent, accurate results in gas chromatography–mass spectrometry (GC–MS). Valid reproduction demands appropriate application of technique, solid method design, reliable and accurate equipment, and a dedicated team of well-practiced technicians and researchers. But even when all these conditions are met, users can be held back by the more subtle elements in GC–MS operations, such as cutting or changing a column, or setting up the same experiment on different equipment. Even getting the parameters of a test organized so that it can be reproduced elsewhere - in a laboratory across the hall, the country, or the world - can be daunting. Consistent GC–MS results depend upon retention-time reproducibility.

A common endpoint for a biomarker discovery experiment is a list of putative marker proteins. The next step is then to perform targeted quantitative measurements of these proteins in an expanded patient population to assess their validity as markers. Analytical accuracy and precision are required for unambiguous quantitative analysis of targeted proteins from very complex mixtures. Wide dynamic range and high sensitivity are critical for detecting low-abundance proteins. Such an assay also is appropriate for "targeted discovery" experiments, where the goal is to quantitate a large number (up to hundreds) of known proteins in a complex sample.

The ability to perform accurate mass measurements in mass spectrometry (MS) for elemental composition determination (ECD, also known as formula identification) provides a powerful tool for assisting in the identification of unknown compounds. Recent advances in data processing methods have demonstrated the ability to obtain mass accuracy in the 5–10 ppm range on routine single- and tandem-quadrupole systems (1,2), sufficient to assist in the formula identification. However, even on more expensive high-resolution systems such as quadrupole time-of-flight (qTOF) or Fourier transform (FT)–MS instruments that are capable of routinely measuring mass accuracy in the 1–3 ppm range, the formula identification is not unique, particularly for higher molecular weight compounds. By calibrating instruments to obtain high spectral accuracy as well as mass accuracy, the ability to unambiguously identify the formula is improved substantially, particularly on low-resolution systems.

It makes intuitive sense - the higher the sensitivity of an inductively coupled plasma–mass spectrometry (ICP-MS) system, the lower the detection limit. But there are many factors that affect the detection limit for a given isotope in a given sample. These factors include sensitivity, background noise, and interferences.

Gas chromatography–mass spectrometry (GC–MS) and liquid chromatography (LC)–MS are widespread successful approaches, based on single-quadrupole MS, for the routine detection, identification, and quantitation of compounds. There has, however, been increasing interest in the use of tandem MS in more challenging, complex matrices such as those commonly found in food, environmental, and biological analyses. The combination of GC with tandem-quadrupole MS (MS-MS) is discussed, where the inherent increase in selectivity and sensitivity of the approach has enabled rapid, confident compound detection and quantitation for such demanding applications.

The 30-year history of advances in gas chromatography–mass spectrometry technology continues today. Recent improvements in hardware, electronics, and data analysis software have resulted in new levels of productivity and sensitivity that have broadened the potential applications for this laboratory mainstay.

Mass spectrometers are effective for identifying and quantifying unknown molecules, such as disease-related proteins and small molecules in pharmaceutical research and medical diagnosis. In addition, mass spectrometry (MS) can be particularly powerful when analyzing molecules with complex structures, such as posttranslationally modified proteins. Among various MS approaches, high-resolution multistep tandem MS (MS-MS) is an emerging methodology for accurate identification of complex molecules. In this article, we describe a new approach for mass analysis with enhanced quantitative capability combined with high-resolution multistep MS-MS, where the dynamic range of quantitation covers four orders of magnitude.

January 2007. Because of concerns over increasing levels of anthropogenic pollutants in the Great Salt Lake in Utah, the Utah Division of Water Quality recently conducted a roundrobin study of selenium in ambient and spiked Great Salt Lake waters to determine the most practical analytical technique for its detection. Of the techniques applied, only hydride generation atomic absorption and octopole reaction system ICP-MS provided acceptable results.

Mass spectrometry has long been a preferred tool for protein identification and biomarker discovery, but preparation of biological samples remains a challenge. Hindrances include the wide range of protein concentrations, sample complexity, and loss or alteration of important proteins due to sample handling. This article describes recent developments in sample fractionation technologies that are overcoming these challenges in interesting ways and are enabling in-depth proteomic studies that were not possible in the past.

Spectroscopy columnist Ken Busch once again brings readers his comprehensive list of common acronyms used in the field of mass spectrometry.

Serum protein profiling using mass spectrometry (MS) is one of the most promising approaches for biomarker identification. The authors adopted a nano liquid chromatography (nLC)–linear ion trap time-of-flight (LIT-TOF) MS system and newly developed software known as information-based acquisition (IBA) to identify biomarkers in human serum. IBA is a data processing protocol for repetitive MS analyses. Peptides selected for the first-pass MS-MS analysis are automatically excluded from the MS spectrum such that subsequent MS-MS analyses are performed on different peptides to minimize overlapping analyses, resulting in the identification of relatively low-abundant peptides.

Enabling targeted quantitative proteomics applications and hypothesis-driven inquiries will help researchers to understand how proteins function in living systems. The discovery and validation of small molecule and protein-based biomarkers, and the eventual translation of these discoveries from the research lab to the clinic, involves robust mass spectrometry (MS) systems and software that make it easier for technicians to perform routine sample analyses on liquid chromatography (LC)–MS-MS systems, which continue to be used in an increasing number of both protein and small molecule analysis applications.

This article demonstrates the improved robustness of a liquid chromatography–tandem mass spectrometry assay achieved by utilizing the combined selectivity of high-field asymmetric waveform ion mobility spectrometry and highly selective reaction monitoring.

Ultrahigh performance liquid chromatography (LC)–time-of-flight mass spectrometry –(TOF-MS) and gas chromatography (GC)–TOF-MS are powerful approaches for screening target compounds and identifying or characterizing nontarget compounds in complex mixtures. The combination of accurate mass data and newly developed software enables truly generic screening methods with TOF-MS, and the confident detection, identification, and confirmation of small molecules in a range of application areas.

Accurate determination of trace Cl, Br, and I is important in industries such as petrochemical refining, chemical manufacturing, biomedical and nutritional supplement manufacturing, and environmental analysis. Until recently, it was thought that the halogen elements could not be determined effectively by inductively coupled plasma–optical emission spectroscopy (ICP-OES); however, with recent advances in spectrometer and detector design, these elements are now readily determined. In fact, ICP-OES offers many advantages for the measurement of Cl, Br, and I. These include ease-of-use and the ability to test for other elements simultaneously, along with good sensitivity, precision, and accuracy. This article describes the measurement of chlorine in tissue and oil samples as well as the measurement of bromine in plastics and electronic materials where the solids were sampled using laser ablation.

Interactive dedicated tools have been developed to facilitate the use of multiline analysis in inductively coupled plasma–atomic emission spectroscopy (ICP-AES) with emphases on multiline selection and on statistics for rejection of possible outliers. The aim is to take full benefit of the available information when using a charge-coupled device (CCD) detector–based instrument and to enhance the accuracy of the results. Determination of Cu in steel will be used to illustrate the potential of the tools.

The use of fertilizers is important to increase crop yields in soils that are being used for agricultural purposes. However, in order to maximize plant growth, it is also absolutely essential to know how the crops are using the nutrients in the soil. This process is commonly referred to as a fertility management program, where many soil samples are taken over a predefined area of the land and analyzed for various components such as pH, organic matter, and trace element nutrients. This article describes how a soil testing laboratory in the midwest has developed a method to analyze up to 3500 soil samples per day for 11 trace metals, using inductively coupled plasma–optical emission spectroscopy. It will focus on the soil sampling procedure together with the sample preparation requirements for this high workload environment. The instrumental analytical procedure will be described in greater detail, particularly how the measurement protocol and sampling process are optimized to cope with such extreme..

The analysis of edible oils and fats by inductively coupled plasma–optical emission spectroscopy (ICP-OES) utilizing direct injection after dilution with kerosene is described. Sample preparation was performed according to EN ISO 661 (1) and ISO 10540-3 (2). The accuracy was investigated using the AOCS reference sample, "Trace Metals in Soybean Oil" (3) and by spike recovery measurements using commercial sunflower oil. The analysis requirements for sensitivity, precision, and accuracy were met. This article includes line selection, detection limits, and accuracy studies.

Although inductively coupled plasma–mass spectrometry (ICP-MS) has rapidly attained acceptance as the choice in trace metal analysis, most commercially available instruments are equipped with quadrupole-based mass analyzers. Quadrupole mass spectrometers have been available commercially for ICP since the early 1980s. Modifications and advances in these types of instruments predominantly have been in the sample introduction and ion optic areas, leaving the quadrupole mass spectrometer untouched.

Fertilizers are used to provide major plant nutrients (N, P, and K), secondary plant nutrients (Ca, S, and Mg), and micronutrients such as B, Mn, Fe, Cu, Zn, Mo, and Se. Accurate determination of the composition of fertilizers is essential so that the correct dose can be applied to the soil. An insufficient application of a fertilizer can result in poor crop yield, and an excessive application can result in environmental damage such as eutrophication by dissolved phosphates and nitrates entering water courses or land contamination from nonnutrient elements within the fertilizers. Inductively coupled plasma (ICP) spectroscopy offers cost-effective analysis of fertilizers because of its multielement capabilities. Complex torch designs and sparging systems have been employed in the past to determine nitrogen by ICP spectroscopy, but these additions to ICP instrumentation are costly and prolong analysis time.

Here, the authors discuss a multielement method for the simultaneous determination of inorganic As, Cr, and Se species in potable waters using a HPLC system coupled to a dynamic reaction cell indusctively coupled plasma mass spectrometer.

In this article, the authors discuss the basic premises that underlie the science of spectrochemistry, which has been humorously referred to as a "black art" by some.