ICP-MS

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.

The element selenium plays three distinct roles in biological processes, functioning in turn as a toxicant, a chemopreventive agent, and a heavy metal antagonist. This article discusses current research associated with each role, and how ICP-MS can be employed to better understand and utilize selenium's properties.

This report demonstrates that it is possible to meet and exceed EPA "statement of work" requirements using ICP-MS.

Elemental analysis in biological samples generally is achieved using flame atomic absorption spectrometry (AAS) and graphite furnace AAS (GFAAS). Flame AAS is fast, easy-to-use, and economical, but insufficiently sensitive for assays such as Se in serum and Pb/Cd in whole blood. These measurements require use of the more sensitive GFAAS. Inductively coupled plasma-mass spectrometry (ICP-MS), despite its low detection limit capabilities and wide elemental range, has had relatively little impact to date on biomedical analysis because of the popularly held conception that it is complex to use and expensive. In recent years, the instrumentation has been simplified and purchase, running, and maintenance costs have fallen. As a result, clinicians are becoming more interested in ICP-MS, although the perception that it is still much more expensive than GFAAS remains. This article provides a comparison of the costs of ICP-MS and GFAAS for biomedical sample analysis and illustrates the performance of ICP-MS for..

Plutonium is distributed globally in the Earth's surface environment as a result of atmospheric weapons tests, nuclear accidents, and nuclear fuel reprocessing. Mass spectrometry (MS), in particular, sector field ICP-MS, now is used widely to determine Pu activities and isotope ratios; 240Pu/239 is very useful in determining Pu origin. Determination of Pu by ICP-MS involves dissolution, column separation, and the MS determination; detection limits are 0.1–10 fg for each isotope. Applications of the determination of sector field ICP-MS to studies of environmental Pu include discerning sources of contamination near the Chernobyl reactor, and chronology of recent aquatic sediments.

Sample introduction can be a significant source of random and systematic error in the measurement of samples by inductively coupled plasma optical emission spectroscopy (ICP-OES) and ICP mass spectrometry (ICP-MS) systems.The considerations made in selecting a liquid introduction system include dissolved solids content, suspended solids presence, presence of hydrofluoric acid or caustic, detection limit requirements, precision requirements, sample load requirements, sample size limitations, and operating budget. The analyst is left with the task of choosing the best introduction components.This article discusses the key components of a typical liquid sample introduction system for inductively coupled plasma spectroscopy, and offers troubleshooting tips for problems commonly encountered by practitioners.

As the demand for accurate soil analysis increases, agriculturalists will need faster, less expensive analytical methods to determine the type and amount of fertilizer required for optimum crop growth. Today, inductively coupled plasma–optical emission spectroscopy (ICP-OES) is the most commonly employed technique for the determination of nutrient elements in fertilizers, while combustion analysis is used for nitrogen. Until recently, ICP-OES could not achieve the accuracy and precision necessary to measure nitrogen due to the elevated background effects caused by atmospheric nitrogen, as well as the inherent stability limitations associated with older instrument designs. This paper describes a new ICP-OES configuration and sample introduction system designed to greatly reduce nitrogen backgrounds and thereby facilitate nitrogen determinations by ICP-OES. Furthermore, the nitrogen determinations are carried out concurrently with the other nutrient elements previously reported by ICP-OES without..

Laser 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.

The potential for signal drift, matrix suppression, and spectral interference, in addition to demanding sample preparation, can make geological matrices some of the most difficult to analyze by conventional inductively coupled plasma-mass spectrometry.