Source Mass Spectrometer Research Articles

A hybrid mesoporous material functionalized by 1,8-naphthalimide-base receptor and the application as chemosensor and absorbent for Hg 2+ in water

A novel hybrid material (SBA- P1) is prepared through the functionalization of mesoporous silica (SBA-15) with a 1,8-naphthalimide-based dye by sol–gel reaction. The characterization results of elemental analysis (EA), X-ray powder diffractometer (XRD) and spectroscopic methods demonstrate the fluorescence dye P1 is successfully grafted onto the inner surface of SBA-15 and the organized structure is preserved. SBA- P1 can detect Hg 2+ with high selectivity to Cu 2+, Zn 2+, Cd 2+, Pb 2+, Mn 2+, Ni 2+, Co 2+, Ag +, Cr 3+, and Mg 2+, Ca 2+, Li +, Na +, K + in water and sensitivity to environmentally relevant mercury in complex natural samples. The quenching fluorescence detection is also reversible by treating with EDTA/base. Furthermore, its fluorescence intensity keeps stable in the physiologically relevant pH range. The extraction ability of SBA- P1 is also estimated by inductively coupled plasma source mass spectrometer (ICP), showing that approximately 90% of the Hg 2+ ion is extracted. These results imply that the hybrid material has potential application for sensing and removing of Hg 2+ ions in waste water and working as toxicide for acute mercury poisoning.

Measurement of photoexcitation cross-sections of uranium by saturation method

We report the measurement of photoexcitation cross-sections of three first-step uranium transitions (0 → 16900.38 cm −1, 0 → 17361.89 cm −1 and 620 → 17361.89 cm −1) using saturation method. These measurements were performed on a resonance ionization mass spectrometry (RIMS) set-up consisting of Nd:YAG-pumped dye lasers, a reflectron time-of-flight mass spectrometer and high-temperature atomic vapour source. The uranium vapours were excited and photoionized by two-colour, three-photon photoionization scheme using Nd:YAG-pumped dye laser system. The resultant photoion signal was monitored as a function of dye laser fluence used for first step excitation to measure the excitation cross-section values. A new approach was adopted to overcome the large uncertainties associated with such measurements. With this approach the cross-section of transitions whose value is already reported in the literature was measured as a bench mark. By normalizing the measured value to the reported value, a scaling factor was derived. This scaling factor was used to scale up the cross-section values of other transitions measured by this method.

Symposium Report: The Waters Bioanalysis World Tour

Applied Pharmaceutical Analysis, Baltimore, MD, USA, 19 September 2010. As part of the Waters Corporation Bioanalysis World Tour [101] , an evening symposium was held at the Applied Pharmaceutical Analysis meeting in Baltimore (MD, USA) on 19 September 2010 [102,103] . The evening was chaired by Robert Plumb (Waters, MA, USA) and Christopher Evans (GlaxoSmithKline, PA, USA), and included three presentations from expert speakers. The talks covered diverse areas of bioanalysis unified by the theme of increasing sensitivity and data quality. Brian Hoffman (Advion, NY, USA) spoke about sample extraction plates for phospholipid depletion, Rand Jenkins (PPD Inc., VA, USA) discussed the use of 2D UPLC for enhancing the power and selectivity of UPLC-MS/MS bioanalysis, and Christopher Evans gave a presentation on increasing assay sensitivity for dried blood spot sample analysis, using a microfluidic chip-based column and a new mass spectrometer source. Following the presentations, all three speakers took to the stage again to respond to questions from the audience.

Improved Strategies for Rapid Identification of Chemically Cross-Linked Peptides Using Protein Interaction Reporter Technology

Protein interaction reporter (PIR) technology can enable identification of in vivo protein interactions with the use of specialized chemical cross-linkers, liquid chromatography, and high-resolution mass spectrometry. PIR-cross-linkers contain labile bonds that are specifically fragmented under low energy collision or photodissociation conditions in the mass spectrometer source, thus releasing cross-linked peptides. Successful analysis of PIR-cross-linked proteins requires the use of expected mathematical relationships between cross-linked complexes and released peptides after fragmentation of the labile PIR bonds. Presented here is a next-generation software tool, BLinks, for use in the analysis and identification of PIR-cross-linked proteins. BLinks is an advancement beyond our previous efforts by incorporation of chromatographic profiles that must match between cross-linked complexes and released peptides to enable estimation of p-values to help filter true relationships from complex data sets. Additionally, BLinks was used to incorporate Mascot database searching results from subsequent MS/MS analysis of the released peptides to facilitate identification of cross-linked proteins. BLinks was used in the analysis of human serum albumin, and 46 interpeptide relationships were found spanning 30 proximal residues with a 2.2% false discovery rate. BLinks was also used to track peptides involved in multiple, coeluting relationships that make accurate identification of protein interactions difficult. An additional 10 interpeptide relationships were identified despite poor correlation using the profiling tools provided with BLinks. Additionally, BLinks can be used to globally map all interpeptide relationships from the data analysis and customize subsequent analysis to target specific peptides of interest, thus making it a useful tool for both discovery of protein interactions and mapping protein topology.

Identification of Glycyrrhiza Species by Direct Analysis in Real Time Mass Spectrometry

DART (Direct Analysis in Real Time)-MS is a novel mass spectrometric ion source, and allows the analysis of most compounds at ambient pressure and ground potential by producing [M+H]+ molecular ion species. Using this method, we examined the compounds characteristic of several kinds of licorices. For the analysis of Glycyrrhiza inflata Batalin, the peak at m/z 339 originates mainly from [M+H]+ of licochalcone A (LA), a species-specific compound. This peak was hardly detected in G. glabra Linné and G. uralensis Fischer. These results indicate that G. inflata can be differentiated from the other two species by detection of LA peaks using DART-MS analysis.

Achieving 50% ionization efficiency in subambient pressure ionization with nanoelectrospray.

Inefficient ionization and poor transmission of the charged species produced by an electrospray from the ambient pressure mass spectrometer source into the high vacuum region required for mass analysis significantly limits achievable sensitivity. Here, we present evidence that, when operated at flow rates of 50 nL/min, a new electrospray-based ion source operated at ∼20 Torr can deliver ∼50% of the analyte ions initially in the solution as charged desolvated species into the rough vacuum region of mass spectrometers. The ion source can be tuned to optimize the analyte signal for readily ionized species while reducing the background contribution.

Process methodology for the small scale production of m6N5 purity zinc using a resistance heated vacuum distillation system

Ultra high purity Zn (m6N5) was obtained through triple vacuum distillation using an m4N5 Zn as input material. High-volatile impurities were removed from the zinc matrix by vacuum evaporation, while traces having lower volatility than the matrix remained in the residual material after finishing of the entire purification process. The time required for the removal of the main high-volatile impurity (Cd) was monitored using a connected gas source mass spectrometer. During distillation the Zn vapor of the distillate was condensed on the cap of a glassy carbon crucible which was water cooled by a movable copper block. The temperatures were optimized for the removal of the volatiles and for the distillation process using vapor pressure data. High resolution glow discharge mass spectrometry was applied for the analysis and purity evaluation of the distilled and input zinc. The analysis confirmed the reduction of the metallic impurities from 43 mg kg −1 to 0.5 mg kg −1 (m6N5) after three consecutive vacuum distillations. An increase in the grain size and a decrease in the micro-hardness were observed for the purified Zn material.

Characterization of a third-generation Faraday-strip array detector coupled to a Mattauch-Herzog geometry mass spectrograph with a dc-glow discharge ionization source

A third-generation Faraday-strip array detector has been coupled to a Mattauch-Herzog mass spectrometer and dc glow-discharge ionization source. This combination offers simultaneous determination of multiple elements directly from solid samples and provides superior resolving power and improved limits of detection over previous generations of array detectors. With the third-generation detector array, resolving power is limited only by the mass spectrometer and not by the array. Because of this enhanced resolution, limits of detection, especially for higher mass-to-charge ratios, were improved. Isotope-ratio precision was found to be 0.07% RSD on average and quantitative response was linear over 5 orders of magnitude.

Development of a method to measure plasma and whole blood choline by liquid chromatography tandem mass spectrometry

Current gold standard markers for myocardial damage are troponins I and T, which are both sensitive and specific for the detection of myocardial infarction, but require up to 6 h to become reliably elevated in serum. Investigation into markers with potential to identify patients with early ischaemic changes is therefore intense. Choline is reported to be prognostic in patients presenting with acute coronary syndromes via its release from ischaemic cell membranes. Liquid chromatography tandem mass spectrometry was used to develop a method to quantitate choline in plasma and blood. The method involves addition of a deuterated internal standard to an aliquot of plasma or blood followed by organic solvent addition, which precipitates the proteins in the sample. Preparation was carried out directly into a 96-deep-well plate. Chromatography of choline used a strong cation exchange column and separation used a Waters Atlantis dC18 analytical column positioned directly before the mass spectrometer source, allowing on-line preanalytical clean up of the sample. The lower limit of quantitation was 0.38 micromol/L, linearity was observed up to 754 micromol/L, with a working concentration range of 0.38-224 micromol/L, inter- and intra-assay coefficients of variation were <6% and <4%, respectively. Samples were stable throughout five freeze-thaw cycles and recovery was between 94% and 114%. The assay was successfully validated in accordance with FDA guidelines and is suitable for quantitation of choline in research and clinical settings.

Rayleigh's distillation law and linear hypothesis of isotope fractionation in thermal ionization mass spectrometry

The relationship which exists between Rayleigh's distillation law and linear models of instrumental isotopic fractionation in thermal ionization mass spectrometry is shown. If the process of isotope fractionation in the mass spectrometer source occurs in terms of a Rayleigh's distillation, and, within the range of mass of isotopes of the element, the vapor/residue distribution coefficient is a linear function of mass with a slope which is sufficiently small in absolute value, then the linear hypothesis of isotope fractionation is fulfilled. The model shows that the fractionation factor per amu, defined as the instantaneous difference between the measured and true values of the isotope ratio, per unit of measured/true value and per unit of mass difference between the two isotopes which define the ratio, can be interpreted as a function of two parameters: the residual mass fraction of the sample on the filament, and the rate of change of the distribution coefficient with mass. These two parameters can be calculated and, in particular, the value of the residual mass fraction of the sample when the measured values of the isotopic ratios coincide with the actual values can be calculated as a function of the rate of change with mass of the distribution coefficient. A linear model of instrumental isotopic fractionation can be derived from the exponential hypothesis of fractionation, which can be also interpreted in terms of a Rayleigh's distillation process, but where mass is an exponential function of the distribution coefficient. Experimental results of instrumental isotopic fractionation (up to 1% amu −1) of strontium in NIST standard reference material 987, loaded as a nitrate on a single tungsten filament, can be interpreted in terms of the linear models of isotope fractionation (and therefore of Rayleigh's distillation law) within experimental error. They show: (i) changes in the vapor/residue distribution coefficient with mass in the range −0.006 to −0.004 amu −1; (ii) approximately constant rates of sample consumption in the range of residual mass fraction from ∼1 to ∼0.3–0.25, which are between 0.05 and 0.13% min −1; (iii) values of the residual mass fraction of the sample, when the measured values of the isotopic ratios coincide with the true ones, between 0.3668 and 0.3671, which correspond to sample consumption of 63.3%. Since the linear hypothesis of fractionation is fulfilled, the values of isotopic ratios of strontium in the standard material can be determined. The global weighted averages of the weighted averages of the results obtained in eleven runs in which 86Sr, 87Sr and 88Sr peaks were sampled are as follows: 86Sr/ 88Sr = 0.119445 ± 0.000053, 87Sr/ 86Sr = 0.71016 ± 0.00019, and 87Sr/ 88Sr = 0.084826 ± 0.000040.

On-line mass spectrometry: membrane inlet sampling.

Significant insights into plant photosynthesis and respiration have been achieved using membrane inlet mass spectrometry (MIMS) for the analysis of stable isotope distribution of gases. The MIMS approach is based on using a gas permeable membrane to enable the entry of gas molecules into the mass spectrometer source. This is a simple yet durable approach for the analysis of volatile gases, particularly atmospheric gases. The MIMS technique strongly lends itself to the study of reaction flux where isotopic labeling is employed to differentiate two competing processes; i.e., O2 evolution versus O2 uptake reactions from PSII or terminal oxidase/rubisco reactions. Such investigations have been used for in vitro studies of whole leaves and isolated cells. The MIMS approach is also able to follow rates of isotopic exchange, which is useful for obtaining chemical exchange rates. These types of measurements have been employed for oxygen ligand exchange in PSII and to discern reaction rates of the carbonic anhydrase reactions. Recent developments have also engaged MIMS for online isotopic fractionation and for the study of reactions in inorganic systems that are capable of water splitting or H2 generation. The simplicity of the sampling approach coupled to the high sensitivity of modern instrumentation is a reason for the growing applicability of this technique for a range of problems in plant photosynthesis and respiration. This review offers some insights into the sampling approaches and the experiments that have been conducted with MIMS.

Fractionation and mixing in a thermal ionization mass spectrometer source: Implications and limitations for high-precision Nd isotope analyses

We present a large dataset of normal Nd standard analyses to evaluate the adequacy of commonly used “laws” to correct for the mass dependent isotope fractionation introduced in a thermal ionization mass spectrometer (TIMS) source, and to assess if the assumption of homogenous sample evaporation and ionization from one sample domain on the filament can be considered valid when obtaining high precision (better than 5 ppm, 2 σ) 142Nd/ 144Nd ratios for studies in geo- and cosmochemistry. The exponential law is fully adequate to correct for the mass fractionation at the current level of obtainable precision and surprisingly performs better than the Rayleigh law. Our modelling shows that the observed correlations in the isotope ratios that remain after data have been corrected using the exponential law are a consequence of correlated uncertainties in counting statistics. These correlations are therefore not from residuals resulting from inadequate correction. Application of the exponential law, however, assumes evaporation from a single homogenous domain on the filament—a condition which was impossible to maintain even under optimal sample loading and heating conditions. While a majority of samples showed an increase in heavy/light isotope ratio with time (normal fractionation), many samples showed the reverse trend (reverse fractionation) indicating evaporation and mixing from variably depleted domains on the filament. Our modelling suggests that up to 50% of the calculated external reproducibility (=standard deviation of the population, σ p of n independent measurements) can be explained by the ion emission from multiple domains of somewhat different isotopic composition on the filament. The fractionation behaviour of a sample is not necessarily a good indicator of the extent of domain mixing as mixing effects in data collected during reverse fractionation are similar to those of data collected during normal fractionation before and after periods of reverse fractionation. Domain mixing effects in 142Nd/ 144Nd isotope ratios can be assessed by examining variations in stable 148Nd/ 144Nd and 150Nd/ 144Nd ratios. The 148Nd and 150Nd data from recent reports of 142Nd deficits in terrestrial samples suggest that the 142Nd anomalies are likely produced from domain mixing during analysis rather than from the decay of short-lived 146Sm during the early history of the earth. It is imperative to measure all the isotopes of Nd to the utmost possible precision and to examine domain mixing effects by normalizing the data using multiple isotope pairs.

Inter-annual stability of oligopeptide patterns of Planktothrix rubescens blooms and mass mortality of Daphnia in Lake Hallwilersee

During mass developments of Planktothrix rubescens, the biomass of this cyanobacterium was collected over a period of four consecutive years (2002–2005) from Lake Hallwilersee, Switzerland. To avoid any shifts in analytical separation and sensitivity, the biomasses were extracted with 60% aqueous methanol at the end of the investigation period and were analysed within 1 week by LC-ESMS. A new mass spectrometric method to quantify oligopeptides was introduced. The sum of all major molecular species (quasi-molecular ion, double charged ion, adducts, dimers and molecular ions that had lost a water molecule) rather than just the signal of the quasi-molecular ion was used to determine the total abundance of oligopeptides. This procedure has become necessary because the variable presence of inorganic ions and the varying conditions of the mass spectrometric source strongly affect the formation of the different molecular species. Several anabaenopeptins, oscillapeptins and planktocyclins were found. [Asp 3, Dhb 7]microcystin-RR was the major microcystin. The oligopeptide patterns were relatively stable over the investigation period of 4 years. In June 2005, a mass mortality of Daphnia was observed. The dead Daphnia, which floated on the surface of the lake, were collected and analysed for oligopeptides. Planktocyclin and planktocyclin sulfoxide, which belong to the major cyclic peptides in P. rubescens, were found in the carcasses of Daphnia, but microcystins were missing. Live zooplankton of the epilimnion was represented by both Daphnia and copepods, while the patches of dead zooplankter on the lake surface were free of copepods and contained only Daphnia. Protease inhibitors rather than microcystins are discussed as the major bioactive compounds for grazer defence of P. rubescens.

Analytical plasma ion sources for elemental mass spectrometry: where are we coming from–where are we going to?

The invention of mass spectrometry at the beginning of the 20th century has had a very important impact on science and technology. In the early days of mass spectrometry a combination of electric and magnetic sector fields was used to separate ions according to their mass to charge ratio and as an ion source a reduced pressure plasma has been applied. Nowadays, plasma source mass spectrometers have become the most powerful instrumentation for inorganic analytical chemistry. The history of plasma source mass spectrometry will be discussed in this article highlighting our own contribution and presenting a personal vision of future application where instrumentation with high mass resolving properties will still play the most important role as to get the highest possible elemental coverage.

Letter: New Fragment Ion Production Method Using Super Cold Electrons in Electron Cyclotron Resonance Plasma

We examined the fragmentation and ionization of molecules by low-temperature electrons generated by electron cyclotron resonance (ECR) plasma. We examined several types of metallocene compounds comprising a metal and 1,3-cyclopentadienes as ligands. We performed analyses using an ECR ion source (ECRIS) mass spectrometer. Consequently, we succeeded in ionizing fragments of an organometallic compound by adjusting the input power of the microwave introducing a super high-frequency plasma. Moreover, we succeeded in dynamically generating a significant quantity of fragment ions by continuously varying the input power. Information on the structure of a molecule may be acquired from this operation. Moreover, a molecule that could not be easily ionized thus far may now be ionizable when soft ionization is performed with this technique.

Evaluating the status of uranium isotope ratio measurements using an inter-laboratory comparison campaign

The REIMEP 18 (Regular European Inter-laboratory Measurement Evaluation Programme) campaign for the measurement isotopic ratios of uranium in nitric acid solution was completed in December 2006. The task for all participating laboratories was to measure the uranium isotopic composition of four uranium samples ranging from depleted to slightly enriched uranium. With 71 participating laboratories REIMEP 18 has become the largest nuclear isotopic measurement campaign organized by IRMM so far. Participation in this kind of measurement campaign is an integral part of the external quality control required for nuclear safeguards laboratories worldwide. For the first time also a significant number of academic laboratories, mainly from the geochemistry area was included. Certification measurements were carried out at IRMM using state-of-the-art mass spectrometric methodology. A MAT511 UF 6-gas source mass spectrometer (GSMS) was used to determine the n( 235U)/ n( 238U) ratios and a TRITON thermal-ionization mass-spectrometer (TIMS) for the minor isotope ratios n( 234U)/ n( 238U) and n( 236U)/ n( 238U). Verification measurements on ampouled samples were performed successfully prior to sample shipping and showed good agreement with the certified ratios. The results of the REIMEP 18 campaign confirm in general the excellent capability of nuclear safeguards and scientific laboratories in measuring isotopic abundances of uranium, although some problems were discovered for the measurements of the minor isotope ratios n( 234U)/ n( 238U) and n( 236U)/ n( 238U) and the calculation of measurement uncertainties for isotope ratios in general. This paper describes the outcome of the REIMEP 18 campaign. It includes a graphical evaluation and discussion of the results, an evaluation of the applied measurement and calibration techniques and a discussion of conclusions and actions to be taken.

Silicon Isotopic Fractionation by Banana (Musa spp.) Grown in a Continuous Nutrient Flow Device

The determination of the plant-induced Si-isotopic fractionation is a promising tool to better quantify their role in the continental Si cycle. Si-isotopic signatures of the different banana plant parts and Si source were measured, providing the isotopic fractionation factor between plant and source. Banana plantlets (Musa acuminata Colla, cv Grande Naine) were grown in hydroponics at variable Si supplies (0.08, 0.42, 0.83 and 1.66 mM Si). Si-isotopic compositions were determined on a multicollector plasma source mass spectrometer (MC-ICP-MS) operating in dry plasma mode. Results are expressed as delta Si-29 relative to the NBS28 standard, with an average precision of +/- 0.08 parts per thousand (+/- 2 sigma(D)). The fractionation factor (29)epsilon between bulk banana plantlets and source solution is -0.40 +/- 0.11 parts per thousand. This confirms that plants fractionate Si isotopes by depleting the source solution in Si-28. The intra-plant fractionation Delta Si-29 between roots and shoots amounts to -0.21 +/- 0.08 parts per thousand. Si-isotopi c compositions of the various plant parts indicate that heavy isotopes discrimination occurs at three levels in the plant (at the root epidermis, for xylem loading and for xylem unloading). At each step, preferential crossing of light isotopes leaves a heavier solution, and produces a lighter solution. Si-isotopic fractionation processes are further discussed in relation with Si uptake and transport in plants. These findings have important implications on the study of continental Si cycle.

Pretreatment Method for Determination of Trace Elements in Seawater Using Solid Phase Extraction Column Packed with Polyamino-Polycarboxylic Acid Type Chelating Resin

A pretreatment method of Al, Mn, Fe, Ni, Cu, Zn, Mo, Cd, Pb, and U in seawater has been investigated using the solid phase extraction column packed with polyamino-polycarboxylic acid type chelating resin. The dependence of pH on the recovery differed in each analytes. However, all analytes were simultaneously extracted at pH 5.5. Hence the optimum condition was decided at pH 5.5. Na, K, Ca, and Mg, which are major components in the seawater were not extracted at pH 7 and below. After the column was cleaned with 10 ml of pure water, the optimum concentration of nitric acid as eluate was 3 M. The analytes concentration in standard reference materials (Seawater NRC-CNRC, CASS-4) pretreated by the presented method was measured with the ion source mass spectrometer and the analytical values were well agreed with the certified values and the reference values without the interference of major components. Moreover, in the analysis of the analytes in the coastal sea water sample, a high recovery of 93∼107% was obtained.

Silicon isotope abundance ratios and atomic weights of NBS-28 and other reference materials

The silicon isotope abundance ratios and atomic weights of NBS-28 and several other silicon isotope reference materials were determined in this study. For the calibration of the measurement procedure, two new synthetic isotope mixtures were prepared gravimetrically from highly enriched silicon isotope materials in the form of SiO 2. All materials were converted into SiF 4 gas and subsequently their silicon isotope ratios were measured on the SiF 3 + species by using a gas source mass spectrometer MAT-253. The calibrated isotope abundance ratios of NBS-28 are 0.0507446 (26) for 29Si/ 28Si and 0.0341465 (15) for 30Si/ 28Si. The corresponding isotopic abundances are 92.17515(28)% for f( 28Si), 4.67739(24)% for f( 29Si) and 3.14746(14)% for f( 30Si). The silicon molar mass of NBS-28 is determined to be 28.08653(11), which is 0.001 larger than previously reported values. In the meanwhile, the 29Si/ 28Si and 30Si/ 28Si isotope abundance ratios and atomic weights of SRM-990, IRMM-017, IRMM-018, GBW-04421 and GBW-04422 are also calibrated. These new calibrated data can improve the reliability and comparability of silicon isotope results using above calibrators.

Silicon isotope fractionation between plant parts in banana: In situ vs. in vitro

We recently showed that silicon isotopic fractionation in banana ( Musa acuminata Colla, cv Grande Naine) was related to phytolith production, and therefore to silica content in plant. The present study focuses on isotopic fractionation between the different plant parts. Silicon isotopic compositions were measured using a Nu plasma multicollector plasma source mass spectrometer (MC–ICP–MS) operating in dry plasma mode. The results are expressed as δ 29Si relatively to the NBS28 standard, with an average precision and accuracy of ± 0.08‰ (± 2 σ). On mature banana ( Musa acuminata Colla, cv Grande Naine) from Cameroon, δ 29Si ranged from + 0.13‰ in the petiole to + 0.49‰ in the lamina, yielding to a 0.36‰ change towards heavier isotopic composition in the upper parts of the plant. This strongly accords with results obtained on in vitro banana plantlets cultivated in hydroponics, where the δ 29Si increase from pseudostems to lamina is 0.26‰. These preliminary results on in situ banana show a trend of intra-plant fractionation comparable with that of in vitro hydroponics banana plantlets and with previous data obtained on bamboo.