ICP-MS

In this article, the author describes the components available for the "front end" of an inductively coupled plasma spectrometer and discusses the pros and cons of each.

Research regarding detection of chemical warfare agents has become vital for finding solutions that will help reduce the threat of these substances. This article looks at the use of collision cell ICP-MS for the analysis and detection of organophosphorus agents.

While inductively coupled plasma-mass spectrometry (ICP-MS) is capable of part-per-quadrillion (ppq) detection limits under ideal conditions, most applications do not require this level of sensitivity and do not justify the cost associated with achieving it. Practical sensitivity in ICP-MS is determined not by instrument signal-to-noise ratio, but rather by controlling interferences and matrix effects in real samples. Understanding the sources of these effects and their management is critical in determining the most practical way to achieve specific data quality objectives.

With electron ionization (EI) used in most gas chromatography–mass spectrometry (GC–MS) applications, the molecular ion typically is broken apart into multiple fragment ions during the EI process.

In drug discovery, determining information about the extent of metabolism and the elucidation of metabolite structures is a vital step for lead optimization and drug scaffold refinement. The identification and characterization of metabolites plays an important role in both the drug discovery and development phases, as unsuitable pharmacokinetics (bioavailability and drug distribution), toxicity, and adverse drug reactions might be linked to metabolic instability. Historically, metabolite identification was carried out after a compound had been chosen for drug development. However, to reduce candidate failures attributed to toxicity effects, many pharmaceutical companies now conduct these experiments in the earliest phases of candidate drug selection.

In this article, the authors evaluate the use of multiple mass defect filters on metabolite identification data from a hybrid mass spectrometer. The study also investigates the use of higher energy collisional dissociation for structural elucidation in metabolite identification experiments.

Specific purity requirements are set for water sources, whether we deal with waste, ground, surface, or drinking water. Water quality is key, and it is becoming a focal point for an increasing number of communities worldwide. Water quality determines the use of a body of water such as for manufacturing, farming, fishing, and human consumption. The reason to strive to maintain or improve a given body of water is to preserve or upgrade its quality, because once this quality degrades, so does its value.

The determination of inorganic elements in food substances is critical for assessing nutritional composition and identifying food contamination sources. The inorganic elements of interest can be divided into two classes: nutritional and toxic. It is important to determine the levels of both sets of elements accurately to assess both the nutritional and the harmful impacts of food substances. Nutritional elements such as Mg, P, and Fe are present at high levels (milligrams per kilogram), while toxic elements such as Pb, Hg, and Cd should be present only at trace levels (nanograms or micrograms per kilogram).

Detrimental health effects of a group of brominated flame retardants, polybrominated diphenyl ethers (PBDEs), have been recognized recently, but only after their wide usage and consequently, global dispersal. Of the possible 209 PBDE congeners, 39 (varying in degree of bromination from mono to deca) have been identified previously in the three common technical mixtures. Additional congeners, presumably debromination products of the fully brominated decabromodiphenyl ether (BDE-209), also have been reported in biotic and abiotic environments. However, costly analytical standards are needed to confirm their identification. In addition, the most widely used identification approach, electron ionization (EI) mass spectrometry (MS), primarily produces spectra indicating only homologue grouping (for example, hepta-BDE). Without specific compound identification, full assessment of toxicological consequences of PBDE burdens is impeded. It has been reported previously that electron-capture negative ionization (ECNI),..

Speciation analysis has grown rapidly and has expanded to a variety of markets, including environmental, clinical, food, nutraceutical, and bioanalytical. This growth has resulted from the realization that knowing the total amount of an element does not always provide adequate information for assessing health and environmental effects, but knowing which form of the element is present presents a much more comprehensive picture.

Gas chromatography and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC–TOFMS and GCxGC–TOFMS) were utilized to develop trace-level calibration curves in brewed green tea spiked with organochlorine and organophosphorus pesticide standards. A sensitive and robust calibration curve was developed from 10 to 500 parts per trillion (ppt), which allowed quantitative results to be determined for organochlorine–organophosphorus pesticides in brewed green tea. Exceptional limits of detection were achieved by GC–TOFMS and GCxGC–TOFMS at or below 10 ppt (solution concentration) for all but one of the pesticides. Stir bar sorption extraction (SBSE) was utilized to isolate the pesticide components from brewed green tea samples prior to analysis by GC–TOFMS and GCxGC–TOFMS. Different types of green tea were analyzed qualitatively by SBSE and GC–TOFMS with subsequent quantification for organochlorine–organophosphorus..

Beta-blockers are basic compounds that contain a secondary amino group in their structure. The amino substituents are typically an isopropyl group and a larger chain with a hydroxyl group in the beta position from the nitrogen atom (Table I). The simultaneous analysis of ?-blockers in biological samples is meaningful, and is made possible by the similarities in their structure. Gas chromatography (GC)–mass spectrometry (MS) has been the most used technique for their identification and quantification (4–6). However, most ?-blockers are nonvolatile and thus require derivatization via a cumbersome and time-consuming process before GC–MS analysis. In recent years, liquid chromatography (LC) coupled with mass spectrometric detection has evolved as the method of choice for drug analysis in the pharmaceutical, clinical, and forensic toxicology areas (4–8). In contrast to GC–MS, LC–MS-MS generally does not require derivatization and offers superior sensitivity. Moreover, due to the high specificity offered by LC–MS-MS, baseline chromatographic resolution often is not required, allowing for fast analysis in high-throughput environments.

The nanoLC LIT-TOF approach combines multiple capabilities that improve the ability to characterize complex protein mixtures significantly.

The usefulness of liquid chromatography–mass spectrometry–mass spectrometry (LC–MS-MS) methods for the unambiguous identification and quantification of pesticides in complex matrix samples is well known. Triple-quadrupole systems have proven to be useful for this task because of their high specificity in MS-MS mode and their low detection limits. However, working in MS-MS mode makes any MS system blind to other compounds of interest.

Because it is extremely rapid, biomarker discovery and identification using liquid chromatography–mass spectrometry (LC-MS), including both ion-trap and triple-quadrupole LC–MS, is well established. Fractionation of complex samples before LC–MS-MS analysis might be necessary to identify the proteins, greatly increasing the number of analyses required. In this case, there is ongoing debate regarding knowing whether the protein is identified correctly, knowing how much prior fractionation is needed to reduce complexity to the point where low-abundance proteins can be detected reliably, and balancing specificity with sensitivity.

Although not currently used in U.S. or European aquaculture, malachite green (MG) is still an effective and inexpensive fungicide that is used in other countries, particularly in Asia. During metabolism, MG reduces to leucomalachite green (LMG) (Figure 1), which has been shown to accumulate in fatty fish tissues. Trace levels of MG and LMG residues continue to be found in fish products. In a 2005 report, MG was found in 18 out of 27 live eel or eel products imported from China to Hong Kong local market and food outlets, resulting in a government recall and destruction of all remaining products (1).

The implementation of ICP-MS as a detection system for reversed-phase HPLC was proven to be a useful technique for the investigation of pharmaceutical molecules containing the heteroatoms sulfur, phosphorus, bromine, and chlorine, as well as organometallic compounds containing a transition metal such as cobalt.

Inductively coupled plasma (ICP) spectroscopy is an important optical emission technique, with strong applications in environmental testing and related areas. The basic principle of ICP involves the introduction of a liquid sample into an argon plasma torch, which provides the excitation energy required to stimulate atomic emission in the sample. The geometry of the torch with respect to the optical components provides one source of control over the analysis. The axial mode, with the optics directed toward the plasma jet, provides better detection levels, although the radial (side-on) mode generally is less problematic.

In this month's installment, columnist Ken Busch addresses the molecular applications of inductively coupled plasma linked with mass spectrometry (ICP-MS), and how those applications have developed.

Mass spectrometry has become a fundamental tool for compound identification or confirmation by virtue of its ability to obtain elemental composition determination (formula identification) by accurate mass measurements. The speed, sensitivity, and ease of interfacing the technique with gas chromatography and liquid chromatography make it the technique of choice for many applications. However, accurate mass measurements must be made with care, and sometimes they can require careful calibration procedures and validation methods. In addition to accurate mass measurements, the isotope abundance distribution also provides information unique to a given chemical formula. However, the mass spectral accuracy required for accurate isotope modeling has not been easy to obtain previously. More recent approaches (1–3) that calibrate the spectral line-shape show promise in obtaining the necessary level of spectral accuracy but still require careful calibration methods with the use of known standards. This article..

Today's ion traps use advanced scanning techniques such as automatic gain control, axial modulation, and triple resonance scanning, resulting in efficient control of both ionization and optimal storage of ions in the trap during analysis. These instruments provide excellent sensitivity and quantitative data, even in "dirty" samples.

Root diseases caused by soilborne plant pathogens are responsible for billions of dollars of losses annually in food, fiber, ornamental, and biofuel crops. The use of pesticides often is not an option to control plant diseases because of economic factors or potential adverse effects on the environment or human health. For this reason, many Americans are now buying pesticide-free organic foods. Organic agriculture has few options for controlling pests and thus must make full use of natural microbial biological control agents in soils that suppress diseases.

Mass spectrometry (MS) has advanced to analyze ever-larger biomolecules with the invention of soft ionization techniques like electrospray ionization (ESI). Although ESI has provided a method of generating ions of high mass, mass spectrometers generally suffer both lower sensitivity and lower resolution as the mass-to-charge ratio of an ion increases. To extend the mass range of ionized macromolecules beyond the limits of MS, macroion mobility spectrometry utilizes ion mobility sizing to characterize charge-reduced ESI-generated macroions from >5 kDa to beyond megadalton masses. One prominent application of macroion mobility spectrometry, highlighted here, is the high sensitivity analysis of intact proteins, antibodies, and conjugates in which molecular masses range from antibody light-chain fragments to high mass immunoglobulin multimers.