Quantitation of trace components in liquid process streams by direct liquid sampling mass spectrometry

This paper describes the development of a liquid sampling approach for trace analysis by electron impact ionization magnetic sector mass spectrometry, with no chromatographic separation. Development of a liquid sample introduction interface based on the principle of Programmable Temperature Vaporizing (PTV) GC injection is shown. A univariate procedure for the analysis of trace (mg kg(-1)) propanoic acid in acetic acid was developed. Results from the laboratory-based analysis of acetic acid are presented and compared with conventional GC analysis. The detection limit was 16 mg l(-1) and the speed of analysis was employed to acquire 30 scans per minute thus reducing the confidence intervals of the results and potentially allowing production plants to run much closer to sales specifications. For the analysis of more complex samples where the analytes contained no unique ions, multivariate analysis was employed and up to three scans per minute were acquired. Results from the analysis of an ester for six trace impurities are shown. Calibration was by partial least squares regression. The detection limits for these components were 20-30 mg kg(-1), well within the required product specifications. The system proved to be robust and easy to operate, with analyses being carried out over a period of several months requiring no maintenance of the spectrometer and only cleaning of the injection liner of the PTV injector on a monthly basis.     

Mass spectrometry in trace analysis

This report is an opinion piece arising from the response to the 1996 ASMS Fall Workshop “Limits to Confirmation, Quantitation, and Detection.” The two subjects that generated the most heated discussion at the Workshop were the criteria for qualitative confirmation of target analytes and those for defining and measuring limits of detection and of quantitation. A reportorial account of the Workshop has been published previously (Baldwin, R.; et al. J. Am. Soc. Mass Spectrom. 1997, 8, 1180–1190). The purpose of the present work is to (1) attempt to reconcile the sometimes highly divergent views expressed by some of the invited Workshop speakers and (2) provide some impetus toward a consensus approach to the dual problems of analyte identification and operational definitions of limits of detection and quantitation for application to trace analysis using chromatography with mass spectrometric detection. In view of the wide range of analytical problems dealt with by modern mass spectrometrists and the varied contexts in which these activities are undertaken (including regulatory requirements and possible legal challenges), both issues are addressed using the concept of fitness for purpose. It is proposed that an appropriate goal is not to define a set of universally applicable criteria, but rather to recommend guidelines for establishing integrated analytical methods best suited to the particular purpose and context.     

NMR quantification of trace components in complex matrices by band‐selective excitation with adiabatic pulses

The use of band‐selective excitation with adiabatic pulses to rapidly obtain NMR spectra of trace components in the presence of strong signals is described, along with qualitative and quantitative examples from food matrices like olive oil and honey. Copyright © 2009 John Wiley & Sons, Ltd.     

Possibilities of multinuclear NMR in the chemistry of heteroorganic compounds

Results of multinuclear NMR studies of some heteroorganic compounds have been presented.According to a report at the conference «Current problems of organometallic chemistry» (May 8–13,1994, Moscow).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 614–616, April, 1994.     

Capillary electrophoresis inductively coupled plasma mass spectrometry combined with metal tag for ultrasensitively determining trace saxitoxin in seafood

As one of paralytic shellfish toxins, the saxitoxin (STX) in the aqueous environment can be accumulated by most shellfish, and thus harms human health through the food chain. Therefore, it is crucial to determine trace STX in seafood samples in order to ensure the safety of seafood consumption. In this study, we developed a novel indirect method for ultrasensitively determining trace STX in seafood by using CE‐ICP‐MS together with Eu³⁺ chelate labeling. We demonstrated that diethylenetriamine‐N ,N ,N ′,N ″,N ″‐pentaacetic acid (DTPA) can couple with STX and simultaneously chelate with Eu³⁺ to realize metallic labeling of STX, and thus realize the ultrasensitive quantification of trace STX with CE‐ICP‐MS. The proposed method has strong antiinterference ability, good stability, and extremely high sensitivity. It could be used to determine trace STX in seafood samples with an extremely low detection limit of 0.38 fmol (3.8×10⁻⁹ M, 100 nL sample injection) and a relative standard deviation (RSD, n = 5) <7%. The success of this study provides an alternative to precise quantification of ultra‐trace STX in seafood samples, and further expands the application of ICP‐MS.     

PFG NMR investigations of TPA-TMA-silica mixtures

Pulsed-field gradient (PFG) NMR studies of tetrapropylammonium (TPA)-tetramethylammonium (TMA)-silica mixtures are presented, and the effect of TMA as a foreign ion on the TPA-silica nanoparticle interactions before and after heating has been studied. Dynamic light scattering (DLS) results suggest that silica nanoparticles in these TPA-TMA systems grow via a ripening mechanism for the first 24 h of heating. PFG NMR of mixtures before heating show that TMA can effectively displace TPA from the nanoparticle surface. The binding isotherms of TPA at room temperature obtained via PFG NMR can be described by Langmuir isotherms, and indicate a decrease in the adsorbed amount of TPA upon addition of TMA. PFG NMR also shows a systematic increase in the self-diffusion coefficient of TPA in both the mixed TPA-TMA systems and pure TPA systems with heating time, indicating an increased amount of TPA in solution upon heating. By contrast, a much smaller amount of TMA is observed to desorb from the nanoparticles upon heating. These results point to the desorption of TPA from the nanoparticles being a kinetically controlled process. The apparent desorption rate constants were calculated from fitting the desorbed amount of TPA with time via a pseudosecond-order kinetic model. This analysis show the rate of TPA desorption in TPA-TMA mixtures increases with increasing TMA content, whereas for pure TPA mixtures the rate of TPA desorption is much less sensitive to the TPA concentration.     

NMR stereotopic induced shifts in epimeric mixtures

The proton NMR spectra of epimeric mixtures of menthone ( 1 ), carvomenthone ( 2 ), carquejone ( 3 ), 2,5-dimethyl-1,4-cyclohexanedione ( 4 ) and piqueridione ( 5 ) were studied using the chemical shift reagent Eu(DPM)₃. The results allow quantifications of the epimers and some conformational assignments to be made.     

Determination of minor components in mixtures using EXAFS

An EXAFS spectrum, obtained by taking the difference between a weighted absorptivity spectrum of a known compound and that of a mixture containing this compound, contained information mainly on the remaining phase(s) in the mixture. The optimum weighting factor was that which gave the minimum value of the definite integral of the radial distribution function (RDF). The efficacy of this technique was demonstrated by the easy identification of Cu₂O, after removal of the CuO contribution, from the spectrum of a mixture of 5% Cu₂O in a ca. 1 + 1 mixture of CuO and ZnO. The method was also used to probe the minor component(s) of a CuO and ZnO calcined catalyst precursor; these showed features consistent with copper dissolved in the ZnO lattice.     

Possibilities of powder X-ray diffraction methods in determining structural characteristics of carbon materials

The possibilities of using powder X-ray diffraction methods in the study of carbon materials are discussed. To determine the phase composition of the crystalline materials the X-ray phase analysis is employed; the real structure is established by the harmonic analysis of diffraction profiles; the structural features and phase composition of the nanomaterials are found by the radial electron density distribution function.     

Possibilities of micro X-ray fluorescence spectrometry of solutions with preconcentration

Results of investigations in energy-dispersive X-ray fluorescence analysis aimed at the development of a high-sensitivity method of microanalysis of solutions are presented. A combined scheme of analysis of one drop of solution of the volume several microliters is proposed and tested. The scheme includes a new preconcentration method based on the drop evaporation in the presence of a micrograin of a hydrophilic adsorbent followed by the microanalysis of the solid phase on the portable device with a polycapillary lens with a focal spot of 10 μm designed at the Institute of Physical Optics. Analytically meaningful X-ray fluorescence spectra are obtained using DETATA (grain diameter about 100 μm) and SAC8 (50 μm) adsorbents and individual drops of model solutions containing Mn, Fe, Co, Ni, Cu, and Zn (0.2 mg/L and higher) and analytical characteristics of the proposed approach are demonstrated.     

Inorganic trace analysis by mass spectrometry

Mass spectrometric methods for the trace analysis of inorganic materials with their ability to provide a very sensitive multielemental analysis have been established for the determination of trace and ultratrace elements in high-purity materials (metals, semiconductors and insulators), in different technical samples (e.g. alloys, pure chemicals, ceramics, thin films, ion-implanted semiconductors), in environmental samples (waters, soils, biological and medical materials) and geological samples. Whereas such techniques as spark source mass spectrometry (SSMS), laser ionization mass spectrometry (LIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), glow discharge mass spectrometry (GDMS), secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) have multielemental capability, other methods such as thermal ionization mass spectrometry (TIMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS) have been used for sensitive mono- or oligoelemental ultratrace analysis (and precise determination of isotopic ratios) in solid samples. The limits of detection for chemical elements using these mass spectrometric techniques are in the low ng g⁻¹ concentration range. The quantification of the analytical results of mass spectrometric methods is sometimes difficult due to a lack of matrix-fitted multielement standard reference materials (SRMs) for many solid samples. Therefore, owing to the simple quantification procedure of the aqueous solution, inductively coupled plasma mass spectrometry (ICP-MS) is being increasingly used for the characterization of solid samples after sample dissolution. ICP-MS is often combined with special sample introduction equipment (e.g. flow injection, hydride generation, high performance liquid chromatography (HPLC) or electrothermal vaporization) or an off-line matrix separation and enrichment of trace impurities (especially for characterization of high-purity materials and environmental samples) is used in order to improve the detection limits of trace elements. Furthermore, the determination of chemical elements in the trace and ultratrace concentration range is often difficult and can be disturbed through mass interferences of analyte ions by molecular ions at the same nominal mass. By applying double-focusing sector field mass spectrometry at the required mass resolution—by the mass spectrometric separation of molecular ions from the analyte ions—it is often possible to overcome these interference problems. Commercial instrumental equipment, the capability (detection limits, accuracy, precision) and the analytical application fields of mass spectrometric methods for the determination of trace and ultratrace elements and for surface analysis are discussed.     

Monitoring trace anion contamination in disk drive components

Ion chromatography was used to determine trace anionic contamination on the surface of hard disk drive components. These contaminants can have a detrimental effect on device reliability and yield. Disk drive components were soaked in deionized water and these extracts were analyzed for anions. The anions fluoride, acetate, formate, acrylate, methacrylate, chloride, nitrite, bromide, nitrate, benzoate, sulfate, oxalate, phthalate and phosphate were separated on a high-performance anion-exchange column and determined at concentrations less than 1 microg/l with suppressed conductivity detection. The extract solutions were analyzed either by injecting 1 ml or by preconcentrating 5 ml. We evaluated the performance of both methods.     

Laser ionization mass spectrometry in inorganic trace analysis

Summary Among the different spectrometric techniques for trace analysis Laser Ionization Mass Spectrometry (LIMS) is well established as a trace analytical method. With the LIMS technique the sample material is evaporated and ionized by means of a focused pulsed laser in a laser microplasma, which is formed in the spot area of the irradiated sample. All chemical elements in the sample materials are evaporated and ionized in the laser plasma. The ions formed are separated according to their mass and energy by a time-of-flight, quadrupole or double focusing mass spectrometer. In this review the characteristics and analytical features, some recent developments and applications of laser ionization mass spectrometry in inorganic trace analysis are described.     

Solid-surface derivative room-temperature luminescence spectrometry of mixtures

Derivative solid-surface room-temperature fluorescence and phosphorescence were combined for the identification of components in binary and ternary mixtures of nanogram amounts of nitrogen heterocycles. Direct, and first and second derivative room-temperature phosphorescence excitation, room-temperature fluorescence and room-temperature phosphorescence spectra were used in the identification of the components in the mixtures by matching spectral wavelengths from mixtures with spectral wavelengths from standards. The criteria for matching wavelengths, subtracting background signals and obtaining derivative spectra at the 0.5-ng level are discussed.     

Selective drug trace detection with low-field NMR

Advances with para-hydrogen induced polarization open up new fields of applications for portable low-field NMR. Here we report the possibility of tracing drugs down to the micromolar regime. We could selectively polarize nicotine quantities similar to those found in one cigarette. Also less than 1 mg of harmine, a drug used for treatment of Parkinson's disease, and morphine extracted from an opium solution were detectable after polarization with para-hydrogen in single-scan (1)H-experiments. Moreover, we demonstrate the possibility to selectively enhance and detect the (1)H-signal of drug molecules with PHIP in proton rich standard solutions that would otherwise mask the (1)H NMR signal of the drug.     

Analysis of trace components in gases by gas chromatography

Summary Relationships are derived describing how the detection limit of a chromatographic system depends on the minimum detectable limit of the detector and the chromatographic parameters such as column length, efficiency, carrier gas flow rate and the capacity factor. Performance data of detectors developed in the last 25 years at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences are given and a few selected application examples are listed. These include trace analysis by preconcentration and by direct analysis and the utilization of multidimensional gas chromatography with two columns, two detectors, a 12-port valve, and a catalytic conversion reactor.     

A fluorometric method for determining trace quantities of phosphate

Summary A method has been developed for the determination of microgram quantities of phosphate based upon fluorescence quenching by phosphate of the aluminum-morin chelate. A variety of other metal-chelates of aluminium, gallium, and zirconium with morin, 3-hydroxyflavone, and quercetin were examined but none proved as satisfactory as the aluminummorin for the determination of phosphate.

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Zusammenfassung Ein Verfahren zur Bestimmung von Mikrogrammengen Phosphat wurde entwickelt. Es beruht auf der Fluoreszenzlöschung von Aluminmm-Morin-Chelat durch Phosphat. Eine Reihe anderer Chelate des Aluminiums, Galliums und Zirkons mit Morin, 3-Hydroxyflavon und Quercetin erwies sich für diesen Zweck nicht geeignet.

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Résumé On a mis au point une méthode pour le dosage des phosphates en quantités de l'ordre du microgramme; elle repose sur l'extinction de la fluorescence du chélate aluminium-morin par les phosphates. On a examiné divers autres chélates métalliques de l'aluminium, du gallium et du zirconium avec le morin, l'hydroxy-3 flavone et la quercétine, mais aucun d'entre eux ne s'est montré aussi satisfaisant que le système aluminium-morin pour le dosage des phosphates.

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The opinions or assertions contained in this paper are the private ones of the authors and are not to be construed as official or reflecting the views of the Naval Service at large.     

A fluorometric method for determining trace quantities of fluoride

Summary A very selective method has been developed for the determination ofg quantities of fluoride based on the fluorescence quenching by fluoride of the zirconium-flavonol chelate. The fluorescence intensity is read at 460 nm. The reduction in fluorescence intensity caused by the fluoride is a measure of the fluoride concentration present.

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Zusammenfassung Eine sehr selektive Methode zur Bestimmung von Mikrogrammengen Fluorid mittels Fluoreszenzlöschung von Zirkonium-Flavonol-Chelat wurde ausgearbeitet. Die Messung erfolgt bei 460 nm. Die Herabsetzung der Fluoreszenzintensität entspricht der Fluoridkonzentration.