A microwave plasma cavity assembly for atomic emission spectrometry

Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading échelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.     

原位电离与小型质谱在公共安全领域的应用

质谱作为一种具有高准确度、高灵敏度、高选择性的检测仪器,在公共安全领域有着重要的应用前景。公共安全领域的需求主要涉及毒品、毒物、爆炸物等化学物质的现场快速检测,因其影响广泛,检测结果需非常准确。作为实验室分析仪器,质谱的准确性和速度能满足公共安全的应用需求,但作为现场快速检测的仪器仍需要一定改进。现场快速检测一方面要求检测仪器的小型化,另一方面要求样品前处理的简单化,以使整个检测流程可以无需专业人员来完成。对于检测仪器的小型化,小型质谱的开发在近20年得到了充分发展;对于样品前处理的简单化,研究者发明了原位电离技术,使得基质复杂的被分析物无需前处理即可进行质谱检测。该文首先介绍了原位电离技术的发展及其在公共安全领域的应用,特别是对解吸附电喷雾电离、实时直接分析电离、激光烧蚀电喷雾电离、纸喷雾电离与纸毛细管喷雾电离等典型原位电离技术的原理、性能及在公共安全领域的应用进行了详细介绍,并讨论了几种原位电离现场定量方法。然后,对原位电离小型质谱的发展进行了综述,从最初的小型化离子阱,到仅能检测可挥发有机物的小型质谱,再到可检测非挥发性物质的常规大气压电离源小型质谱,最后发展成为有原位电离源的小型质谱,历经20年的发展使得原位电离小型质谱得以出现和提升。并列举了原位电离小型质谱在毒品现场检测与吸毒人员排查、爆炸物现场侦察、食品安全之农用化学品检测、药物质量检查等公共安全领域的应用。最后,对原位电离小型质谱的发展进行了展望,指出原位电离与小型质谱相结合是小型质谱发展的必然趋势,未来需使用更加智能化的原位电离小型质谱,结合云数据平台,实现更方便广泛的应用。     

Full utilization of a mass spectrometer using on‐demand sharing with multiple LC units

The applicability of liquid chromatography–mass spectrometry (LC/MS) is often limited by throughput. The sharing of a mass spectrometer with multiple LCs significantly improves throughput; however, the reported systems have not been designed to fully utilize the MS duty cycle, and as a result to achieve maximum throughput. To fully utilize the mass spectrometer, the number of LC units that a MS will need to recruit is application dependent and could be significantly larger than the current commercial or published implementations. For the example of a single analyte, the number may approach the peak capacity to a first degree approximation. Here, the construction of a MS system that flexibly recruits any number of LC units demanded by the application is discussed, followed by the method to port a previously developed LC/MS method to the system to fully utilize a mass spectrometer. To demonstrate the performance and operation, a prototypical MS system of eight LC units was constructed. When 1‐min chromatographic separations were performed in parallel on the eight LCs of the system, the average LC/MS analysis time per sample was 10.5 s when applied to the analysis of samples in 384‐well plate format. This system has been successfully used to conduct large‐volume biochemical assays with the analysis of a variety of molecular entities in support of drug discovery efforts. Allowing the recruitment of the number of LC units appropriate for a given application, this system has the potential to be a plug‐and‐play system to fully utilize a mass spectrometer. Copyright © 2012 John Wiley & Sons, Ltd.     

High resolution electrospray ionization ion mobility spectrometry

Current commercially available ion mobility spectrometers are intended for the analysis of chemicals in the gas phase. Sample introduction methods, such as direct air sampling, a GC injector or a thermal desorber, are commonly an integral part of these instruments. This paper describes an electrospray ionization ion mobility spectrometer system that allows direct introduction samples in solution phase. This allows direct analysis of non-volatile organic and biological samples, and avoids decomposition of thermally liable samples, providing reliable chemical identification. In addition, the new ion mobility spectrometer allows mobility analysis with high resolving power. Commonly used commercial IMS systems provide resolving powers between 10 and 30; this new ion mobility spectrometer has resolving power greater than 60 for routine analysis. A high resolution instrument is necessary for many applications where a complex mixture needs to be separated and quantified. This paper demonstrates the advantages of using a high resolution ion mobility spectrometer and an electrospray ionization source for the analysis of non-volatile pharmaceuticals as well as dissolved explosive in solution phase.     

Derivatization in mass spectrometry --7. On-line derivatisation/degradation

The review describes on-line derivatization/degradation methods employed in mass spectrometry to solve some structural and analytical problems. Advantages and applications of various positions of reaction systems connected mainly to a mass spectrometer or a gas chromatograph/mass spectrometer are considered. Among these are reaction systems connected directly to the mass spectrometer (reaction mass spectrometry, pyrolysis-mass spectrometry or direct pyrolysis-mass spectrometry); flash-heaters as reactors in gas chromatography/mass spectrometry (GC/MS); in-line chemical reactors located before the chromatographic column [pre-column derivatization/degradation with the use of catalytic reactions, pyrolysis (pyrolysis-GC/MS), degradation in elemental analyzers-isotope ratio mass pectrometry (EA-IRMS)]; on-column derivatization and deuteration; reactor located between the chromatographic column and a mass spectrometer [post-column catalytic derivatization, gas chromatograph-combustion-isotope ratio mass spectrometer (GC-c-IRMS)]. Post-column derivatization in high performance liquid chromatography/mass spectro-metry is briefly mentioned. Application of such on-line methodology to structure elucidation of low molecular mass compounds and polymers, to the determination of isotope ratios of the most common elements, to the investigation of catalytic reactions is discussed..     

Tungsten coil devices in atomic spectrometry: absorption, fluorescence, and emission.

In this work, tungsten coil (W-Coil) devices are used as atomizers for electrothermal atomization atomic absorption spectrometry (ETAAS), electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS), and electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). For most cases in ETAAS and ETA-LEAFS, limits of detection (LODs) using the W-Coil are within a factor of ten of those observed with commercial graphite furnace systems. LOD for Cd by W-Coil AAS is 10 pg, while LODs for As, Se, Cr, Sb and Pb by W-Coil LEAFS are 950, 320, 1400, 330, and 160 fg, respectively. The compact W-Coil device makes it an ideal atomizer for portable atomic spectrometry instrumentation, especially when coupled with a miniature charge coupled device spectrometer. Alternatively, the atomizer can be used as an inexpensive, modular add-on to an existing commercial ICP-AES system; and the thermal separation of Pb with interference elements Al, Mn, and Fe is demonstrated.     

Quantitative Fourier transform ion cyclotron resonance mass spectrometry--the determination of creatinine by isotope dilution mass spectrometry

Accurate quantitation has been demonstrated on many different types of mass spectrometer. However, quantitative applications of Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) have been limited. In this study, the quantitative potential of FTICRMS has been investigated using an exact matching isotope dilution method for the determination of creatinine in serum. Creatinine is an important clinical biomarker and its measurement is used as an assessment of renal function. The quantitation of creatinine was selected because a high-accuracy high-performance liquid chromatography/mass spectrometry (HPLC/MS) determination using a triple quadrupole mass spectrometer has already been successfully developed in-house. Therefore, a direct comparison of the quantitative capability of FTICRMS could be made against an established method. The accuracy of the quantitation of creatinine was found to be equivalent to that obtained using LC/MS. However, the expanded measurement uncertainty (k = 2) was larger, at 6%, when using FTICRMS compared with 1% when using HPLC/MS with the triple quadrupole mass spectrometer.     

Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) Imaging Source Coupled to a FT-ICR Mass Spectrometer

Mass spectrometry imaging (MSI) allows for the direct monitoring of the abundance and spatial distribution of chemical compounds over the surface of a tissue sample. This technology has opened the field of mass spectrometry to numerous innovative applications over the past 15 years. First used with SIMS and MALDI MS that operate under vacuum, interest has grown for mass spectrometry ionization sources that allow for effective imaging but where the analysis can be performed at ambient pressure with minimal or no sample preparation. We introduce here a versatile source for MALDESI imaging analysis coupled to a hybrid LTQ-FT-ICR mass spectrometer. The imaging source offers single shot or multi-shot capability per pixel with full control over the laser repetition rate and mass spectrometer scanning cycle. Scanning rates can be as fast as 1 pixel/second and a spatial resolution of 45 μm was achieved with oversampling.

Recent progress in the analysis of sugar monomers from complex matrices using chromatography in conjunction with mass spectrometry or stand-alone tandem mass spectrometry

Analysis of trace levels of carbohydrate monomers in complex matrices requires excellent discrimination of the peaks of interest from background noise. Minimizing contaminating peaks introduced during sample preparation and chromatography is extremely important. However, the exquisite selectivity of the mass spectrometer is essential as a chromatographic detector in this regard. Traditionally gas chromatography-mass spectrometry (GC-MS) has been the method of choice for trace analysis of derivatized carbohydrates. Recent improvements in commercial tandem mass spectrometers (MS-MS) are encouraging the use of GC-MS-MS for improved specificity in trace analysis. There has also been an explosion in applications of electrospray ionization (ESI) for sensitive introduction of polar molecules (including sugars) into the mass spectrometer. This has encouraged ongoing developments in high-performance liquid chromatography-mass spectrometry (LC-MS) and MS-MS of underivatized carbohydrates. This has the potential to dramatically simplify sample preparation. However, as yet LC-MS and MS-MS do not match the sensitivity of GC-MS or GC-MS-MS. Developments in analysis of sugar monomers from complex matrices using chromatography (GC/LC) in conjunction with mass spectrometry (MS, MS-MS) or stand-alone MS-MS are discussed.     

Current Developments in Optical Emission Spectrometry with High-Frequency and Microwave Induced Plasmas

The state-of-the-art and trends of development with the inductively coupled plasma (ICP) and microwave induced plasmas (MIP) as radiation sources for optical emission spectrometry arc presented. Especially techniques for sample introduction are discussed. Here special reference is given to the use of spark ablation as well as 10 direct sample insertion and slurry atomization for the direct analysis of powder samples. The development in MIP optical emission Spectrometry is shown to center on the improvement of the plasma sources, their characterization and their tailoring to various sampling techniques. Results of the use of pneumatic nebulization of liquids and electrothermal evaporation of dry solution residues will be presented.     

Direct analysis of volatile organic compounds in foods by headspace extraction atmospheric pressure chemical ionisation mass spectrometry

Rationale

The rapid screening of volatile organic compounds (VOCs) by direct analysis has potential applications in the areas of food and flavour science. Currently, the technique of choice for VOC analysis is gas chromatography/mass spectrometry (GC/MS). However, the long chromatographic run times and elaborate sample preparation associated with this technique have led a movement towards direct analysis techniques, such as selected ion flow tube mass spectrometry (SIFT‐MS), proton transfer reaction mass spectrometry (PTR‐MS) and electronic noses. The work presented here describes the design and construction of a Venturi jet‐pump‐based modification for a compact mass spectrometer which enables the direct introduction of volatiles for qualitative and quantitative analysis.

Methods

Volatile organic compounds were extracted from the headspace of heated vials into the atmospheric pressure chemical ionization source of a quadrupole mass spectrometer using a Venturi pump. Samples were analysed directly with no prior sample preparation. Principal component analysis (PCA) was used to differentiate between different classes of samples.

Results

The interface is shown to be able to routinely detect problem analytes such as fatty acids and biogenic amines without the requirement of a derivatisation step, and is shown to be able to discriminate between four different varieties of cheese with good intra and inter‐day reproducibility using an unsupervised PCA model. Quantitative analysis is demonstrated using indole standards with limits of detection and quantification of 0.395 μg/mL and 1.316 μg/mL, respectively.

Conclusions

The described methodology can routinely detect highly reactive analytes such as volatile fatty acids and diamines without the need for a derivatisation step or lengthy chromatographic separations. The capability of the system was demonstrated by discriminating between different varieties of cheese and monitoring the spoilage of meats.     

两种微波等离子体炬质谱测定水中铅的对比研究

建立了一种新型的能够灵敏分析水中痕量铅的质谱方法,以微波等离子体炬(MPT)为离子源,可无需样品预处理而直接分析水样。样品经雾化和去溶后由MPT的中心管道引入等离子体,离子由国产的四极杆质谱仪(Q-MS)检测,得到铅的MPT特征质谱。定量结果表明,该方法的检出限为20 ng/L,线性范围为200~1 000 ng/L,相对标准偏差(RSD)为5.3%;所得定量指标优于相同条件下商用的线性离子阱质谱(LTQ-MS)测试结果,且四极杆质谱仪上所得的铅离子特征质谱信号更简单、易归属,无需复杂的多级串联质谱加以确认。这种MPT可与国产质谱仪器相结合发展成为一种低成本的现场检测铅的质谱仪器,在环境监控、饮用水检验等方面具有一定的应用价值。     

Miniaturized system of a gas chromatograph coupled with a Paul ion trap mass spectrometer

Miniature gas chromatography (GC) and miniature mass spectrometry (MS) instrumentation has been developed to identify and quantify the chemical compounds present in complex mixtures of gases. The design approach utilizes micro-GC components coupled with a Paul quadrupole ion trap (QIT) mass spectrometer. Inherent to the system are high sensitivity, good dynamic range, good QIT resolution, low GC flow-rates to minimize vacuum requirements and the need for consumables; and the use of a modular approach to adapt to volatile organic compounds dissolved in water or present in sediment. Measurements are reported on system response to gaseous species at concentrations varying over four orders of magnitude. The ability of the system to deal with complicated mixtures is demonstrated, and future improvements are discussed. The GC/QIT system described herein has a mass, volume and power that are, conservatively, one-twentieth of those of commercial off-the-shelf systems. Potential applications are to spacecraft cabin-air monitoring, robotic planetary exploration and trace-species detection for residual gas analysis and environmental monitoring.     

Bioavailability of nanoparticles in nutrient and nutraceutical delivery

The field of nanoparticle delivery systems for nutrients and nutraceuticals with poor water solubility has been expanding, almost exponentially, over the last five years, and some of these technologies are now in the process of being incorporated in food products. The market projections for these technologies suggest a multifold increase in their commercial potential over the next five years. The interest in the pharmaceutical and food-related applications of these technologies has sparked tremendous developments in mechanical (top-down) and chemical (bottom-up) processes to obtain such nanoparticle systems. Mechanical approaches are capable of producing nanoparticles, typically in the 100–1000 nm range, whereas chemical methods tend to produce 10–100 nm particles. Despite these technological developments, there is a lack of information regarding the basis of design for such nanoparticle systems. Fundamental thermodynamic and mass transfer equations reveal that, in order to generate a broad spectrum delivery system, nanoparticles with 100 nm diameter (or less) should be produced. However, experimental data reveal that, in some cases, even nanoparticles in the 100–1000 nm range are capable of producing substantial improvement in the bioavailability of the active ingredients. In most cases, this improvement in bioavailability seems to be linked to the direct uptake of the nanoparticle. Furthermore, direct nanoparticle uptake is controlled by the size and surface chemistry of the nanoparticle system. The use of this direct nanoparticle uptake, in particular for soluble but poorly absorbed ingredients, is one of the areas that needs to be explored in the future, as well as the potential side effects of these nanoparticle carriers.     

A review of direct liquid introduction interfacing for LC/MS Part I: Instrumental aspects

Summary Considerable progress has been made in the coupling of liquid chromatography and mass spectrometry over the past ten years. Three interfaces tend to dominate the LC/MS market: transport systems, direct liquid introduction, and the thermospray interface. In this paper the developments in direct liquid introduction interfacing for LC/MS will be reviewed. The paper will be published in two parts. Mass spectrometry and applications will be discussed in the second part. This first part of the review concentrates on the various instrumental aspects of direct liquid introduction, such as the design of vacuum systems, the interface probes and the desolvation chambers.     

Hyphenation and hypernation the practice and prospects of multiple hyphenation

In the past two decades, combining a chromatographic separation system on-line with a spectroscopic detector in order to obtain structural information on the analytes present in a sample has become the most important approach for the identification and/or confirmation of the identity of target and unknown chemical compounds. In most instances, such hyphenation can be accomplished by using commercially available equipment. For most (trace-level) analytical problems encountered today, the combination of column liquid chromatography or capillary gas chromatography with a mass spectrometer (LC–MS and GC–MS, respectively) is the preferred approach. However, it is also true that additional and/or complementary information is, in quite a number of cases, urgently required. This can be provided by, for example, atomic emission, Fourier-transform infrared, diode-array UV–vis absorbance or fluorescence emission, or nuclear magnetic resonance spectrometry. In the present review, the various options are briefly discussed and a few relevant applications are quoted for each combination. Special attention is devoted to systems in which multiple hyphenation, or hypernation, is an integral part of the setup. As regards this topic, the relative merits of various combinations—which turn out to include a mass spectrometer as one of the detectors in essentially all cases—are discussed and the fundamental differences between GC- and LC-based systems are outlined. Finally, the practicability of more extensive hypernation in LC, viz. with up to four spectrometers, is discussed. It is demonstrated that, technically, such multiple hyphenation is possible and that, from a practical point of view, rewarding results can be obtained. In other words, further research in this area is certainly indicated. However, in the foreseeable future, using several separate conventional hyphenated systems will be the commonly implemented solution in most instances.     

Recent developments of miniature ion trap mass spectrometers

The recent development of miniature ion trap mass spectrometer systems in the last ten years is reviewed in this paper. These instruments adopt different atmospheric pressure interfaces (APIs), which are membrane inlets (MIs), discontinuous atmospheric pressure interface (DAPI) and continuous atmospheric pressure interface (CAPI).     

Improved detection of low vapor pressure compounds in air by serial combination of single-sided membrane introduction with fiber introduction mass spectrometry (SS-MIMS-FIMS)

The use of two methods in tandem, single-sided membrane introduction mass spectrometry (SS-MIMS) and fiber introduction mass spectrometry (FIMS), is presented as a technique for field analysis. The combined SS-MIMS-FIMS technique was employed in both a modified commercial mass spectrometer and a miniature mass spectrometer for the selective preconcentration of the explosive simulant o-nitrotoluene (ONT) and the chemical warfare agent simulant, methyl salicylate (MeS), in air. A home-built FIMS inlet was fabricated to allow introduction of the solid-phase microextraction (SPME) fiber into the mass spectrometer chamber and subsequent desorption of the trapped compounds using resistive heating. The SS-MIMS preconcentration system was also home-built from commercial vacuum parts. Optimization experiments were done separately for each preconcentration system to achieve the best extraction conditions prior to use of the two techniques in combination. Improved limits of detection, in the low ppb range, were observed for the combination compared to FIMS alone, using several SS-MIMS preconcentration cycles. The SS-MIMS-FIMS response for both instruments was found to be linear over the range 50 to 800 ppb. Other parameters studied were absorption time profiles, effects of sample flow rate, desorption temperature, fiber background, memory effects, and membrane fatigue. This simple, sensitive, accurate, robust, selective, and rapid sample preconcentration and introduction technique shows promise for field analysis of low vapor pressure compounds, where analyte concentrations will be extremely low and the compounds are difficult to extract from a matrix like air.     

Automated in-line gel filtration for native state mass spectrometry

Characterization of protein-ligand complexes by nondenaturing mass spectrometry provides direct evidence of drug-like molecules binding with potential therapeutic targets. Typically, protein-ligand complexes to be analyzed contain buffer salts, detergents, and other additives to enhance protein solubility, all of which make the sample unable to be analyzed directly by electrospray ionization mass spectrometry. This work describes an in-line gel-filtration method that has been automated and optimized. Automation was achieved using commercial HPLC equipment. Gel column parameters that were optimized include: column dimensions, flow rate, packing material type, particle size, and molecular weight cut-off. Under optimal conditions, desalted protein ions are detected 4 min after injection and the analysis is completed in 20 min. The gel column retains good performance even after >200 injections. A demonstration for using the in-line gel-filtration system is shown for monitoring the exchange of fatty acids from the pocket of a nuclear hormone receptor, peroxisome proliferator activator-delta (PPARdelta) with a tool compound. Additional utilities of in-line gel-filtration mass spectrometry system will also be discussed.