A guaianolide pigment from a deep sea gorgonian

Yellow pigment 3 is one of the minor constituents of a deep sea gorgonian, Placogorgia sp.     

HPLC-CHIP coupled to a triple quadrupole mass spectrometer for carbonic anhydrase II quantification in human serum

A method for carbonic anhydrase II (CA II) absolute quantification in human serum is presented. This method is based on high-performance liquid chromatography (HPLC)-Chip microfluidic device incorporating a nanoelectrospray source interfaced to a triple quadrupole mass spectrometer. The fraction containing CA II was isolated by preparative reversed-phase HPLC, and peptides obtained from the tryptic digest of the protein mixture were separated by the HPLC-Chip system. The multiple-reaction monitoring acquisition mode of a selected suitable CA II peptide and peptide internal standard allowed the selective and sensitive determination of a CA II. Absolute recovery of the method was 52 ± 12%, while analytical recovery was 81 ± 10%. For the eight samples analyzed, the matrix effect was found to be only −14 ± 6%. A comparison among three regression lines type which were obtained by external calibration, matrix-matched calibration, and standard addition method, respectively, demonstrated that the first one is adequate in obtaining good accuracy and precision. Method quantification limit for CA II in serum was estimated to be 2 fmol/mL. CA II mean concentration in sera from eight healthy subjects was found to be 56 pmol/mL (relative standard deviation 24%).     

Laser multiphoton ionization in a time-of-flight mass spectrometer: vibronic/mass spectra of triethylenediamine from 425 to 560 nm

Resonance-enhanced multiphoton ionization (REMPI) fragmentation patterns are obtained as a function of laser wave-length using a new, computer-controlled, high-resolution time-of-flight laser mass spectrometer system. REMPI mass spectra for triethylenediamine show extensive fragmentation, the pattern dependent upon the particular two-photon resonance (doorway state) selected.     

Quantification and evaluation of ion transmission efficiency in two-stage vacuum chamber miniature mass spectrometer

Miniature mass spectrometer is more compact and portable than traditional commercial mass spectrometry, with more potential for application outside the laboratory. However, a miniature mass spectrometer is less sensitive than a commercial instrument, limiting its application scenarios. The ion transmission efficiency of the instrument is an essential factor affecting the sensitivity. Still, there are few works of literature on the quantitative study of the ion transmission efficiency of each component from a systematic perspective. In this paper, the Faraday cup coupled with a microcurrent signal testing instrument was used to measure the ions generated by nanoelectrospray ionization (nano-ESI), which have successfully gone through several components. Then the ion transmission efficiency of each component was quantified. Results showed that the front lens had the highest ion transmission efficiency of 39.7%, whereas the inlet and skimmer had the lowest ion transfer efficiency of 0.8% and 17.1%. Next, the influence of control parameters on ion transmission efficiency of critical components was investigated. If optimized, the ion funnel and the skimmer had the potential to improve their transmission efficiency by 120% and 79%, respectively. This paper shows the decreasing intensity distribution of ions in the whole transmission process and the transmission efficiency of each component, which can guide for improving the sensitivity of the miniature mass spectrometer.     

Analytical performance of a triple quadrupole mass spectrometer compared to a high resolution mass spectrometer for the analysis of polybrominated diphenyl ethers in fish

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants used globally in many consumer products and industrial applications. Traditionally, gas chromatography–high resolution mass spectrometry (GC–HR-MS) is the method of choice for analysis of PBDEs in environmental samples because it offers high sensitivity and selectivity, resulting in less interferences. However, the specificity offered by gas chromatography-triple quadrupole tandem mass spectrometry (GC–QQQ-MS/MS), operated in selected reaction monitoring mode, provides a more affordable alternative to GC–HR-MS for the analysis of PBDEs in complex environmental samples. In this study, an analytical method was developed for the analysis of 41 PBDE congeners in fish using GC–QQQ-MS/MS. Results from the analysis of three fish species [lake trout (Salvelinus namaycush), yellow perch (Perca flavescens), and round goby (Neogobius melanostomus)] using GC–QQQ-MS/MS were compared with those obtained by GC–HR-MS. These species were selected because they represent varying levels of lipid-rich matrix and contaminant loads. Instrumental limits of detection for the GC–QQQ-MS/MS ranged from 0.04 pg to 41 pg, whereas those for the GC–HR-MS ranged from 5 pg to 85 pg. The PBDE values obtained from these two methods were highly correlated, R² values >0.7, for all three fish species, supporting the suitability of GC–QQQ-MS/MS for analysis of PBDEs in fish with varying fat content.     

Reactions in the source of a mass spectrometer: The mass spectrum of 1-chlorobenzotriazole

The mass spectrum of 1-chlorobenzotriazole contains ions derived from benzotriazole, a product of an exchange reaction with water in the source of the mass spectrometer. Relatively intense ions derived from iodine, iodine monobromide and other inter-halogen compounds are also observed. These species are produced by oxidation of involatile halide coatings in the source region by 1-chlorobenzotriazole. It is suggested that anomalous peaks produced by oxidation-reduction reactions in the source may be expected in the spectrum of any organic oxidant.     

Evaluation of a differential mobility spectrometer/miniature mass spectrometer system

A planar differential mobility spectrometer (DMS) was coupled to a Mini 10 handheld rectilinear ion trap (RIT) mass spectrometer (MS) (total weight 10 kg), and the performance of the instrument was evaluated using illicit drug analysis. Coupling of DMS (which requires a continuous flow of drift gas) with a miniature MS (which operates best using sample introduction via a discontinuous atmospheric pressure interface, DAPI), was achieved with auxiliary pumping using a 5 L/min miniature diaphragm sample pump placed between the two devices. On-line ion mobility filtering showed to be advantageous in reducing the background chemical noise in the analysis of the psychotropic drug diazepam in urine using nanoelectrospray ionization. The combination of a miniature mass spectrometer with simple and rapid gas-phase ion separation by DMS allowed the characteristic fragmentation pattern of diazepam to be distinguished in a simple urine extract at lower limits of detection (50 ng/mL) than that achieved without DMS (200 ng/mL). The additional separation power of DMS facilitated the identification of two drugs of similar molecular weight, morphine (average MW = 285.34) and diazepam (average MW = 284.70), using a miniature mass spectrometer capable of unit resolution. The similarity in the proton affinities of these two compounds resulted in some cross-interference in the MS data due to facile ionization of the neutral form of the compound even when the ionic form had been separated by DMS.     

Development of a palm portable mass spectrometer

A palm portable mass spectrometer (PPMS) has been developed with a weight of 1. 48 kg (3 lb) and a size of 1.54 L (8.2 × 7.7 × 24.5 cm³) that can be operated with an average battery power of 5 W. A miniaturized ion trap has been used as a mass analyzer that consists of four parallel disks with coaxial holes. A rf voltage of 1500 V _p-p at 3.9 MHz has been used for scanning ion mass of up to m/z 300. An ion-getter pump serves for high vacuum of the PPMS. Sample gas was introduced in pulse mode. An embedded microcomputer has been developed for system control. Detection of organic gases diluted in the air has been demonstrated up to 6 ppm for toluene and 22 ppm for dimethyl methylphosphonate (DMMP). Performance results suggest usefulness of the PPMS as a personal mobile device for detection/identification of chemical warfare agents in the field.     

N,N-dimethylamino-3-guaiazulenylmethane from a deep sea gorgonian

A naturally occurring nitrogeneous azulene derivative (4) has been isolated from a deep sea gorgonian collected by minisubmersible at -350 m.     

Uranium and plutonium containing particles in a sea sediment sample from Thule, Greenland

Particles composed of radioactive materials and probably originating from US nuclear weapons were identified in sea sediment samples collected from Thule, Greenland, in 1997. The weapons were destroyed close to the Thule Air Base in 1968 in an aeroplane crash, which dispersed radioactive materials in the environment. The presence of particulate radioactive materials in the sediment samples was revealed by combining gamma-spectrometry and autoradiography. Isolation and separation of a radioactive particle from a bulk sample were performed using autoradiography, phosphor plate imaging and scanning electron microscopy. Using X-ray microanalysis as well as alpha and beta activity analysis, U and weapons-grade Pu were detected in the granular, brittle particle.     

Chip-based CE coupled to a quadrupole TOF mass spectrometer for the analysis of a glycopeptide

A novel approach using sheath flow chip-based CE coupled to a quadrupole TOF mass spectrometer was developed and applied to the analysis of an O-glycopeptide. The method provided good separation and sensitive analysis of the glycopeptide and its beta-elimination product. The beta-elimination reaction of the glycopeptide with ammonia or dimethylamine was adapted for changing the glycopeptide into deglycosylated form and for specifying the site of glycosylation. MS/MS analysis of the native peptide, glycopeptide and beta-elimination product enabled the identification of the glycosylation site through the comparison of the fragmentations and peptide sequence analysis.     

Analysis of the low molecular weight serum peptidome using ultrafiltration and a hybrid ion trap-Fourier transform mass spectrometer

Advances in proteomics are continuing to expand the ability to analyze the serum proteome. In recent years, it has been realized that in addition to the circulating proteins, human serum also contains a large number of peptides. Many of these peptides are believed to be fragments of larger proteins that have been at least partially degraded by various enzymes such as metalloproteases. Identifying these peptides from a small amount of serum/plasma is difficult due to the complexity of the sample, the low levels of these peptides, and the difficulties in getting a protein identification from a single peptide. In this study, we modified previously published protocols for using centrifugal ultrafiltration, and unlike past studies did not digest the filtrate with trypsin with the intent of identifying endogenous peptides with this method. The filtrate fraction was concentrated and analyzed by a reversed phase-high performance liquid chromatography system connected to a nanospray ionization hybrid ion trap-Fourier transform mass spectrometer (LTQ-FTMS). The mass accuracy of this instrument allows confidence for identifying the protein precursors by a single peptide. The utility of this approach was demonstrated by the identification of over 300 unique peptides with 2 ppm or better mass accuracy per serum sample. With confident identifications, the origin and function of native serum peptides can be more seriously explored. Interestingly, over 34 peptide ladders were observed from over 17 serum proteins. This indicates that a cascade of proteolytic processes affects the serum peptidome. To examine whether this result was an artifact of serum, matched plasma and serum samples were analyzed with similar peptide ladders found in each.     

The development of a high resolution mass spectrometer: A reminiscence

This article is a review of the events leading to the development of the double-focusing tandem mass spectrometer system, which is sometimes called the Johnson-Nier geometry. An essential feature of the geometry is that it eliminates second-order angular aberration, enhancing the sensitivity, without a loss in resolution. Flexibility in the choice of ion source and collector designs is assured because both are outside of regions of electric and magnetic fields. The vacuum housing permits high-temperature baking, ensuring ultrahigh vacuum conditions. Although introduced initially for the purpose of determining precise atomic masses, the design has found its greatest application in studies of structure of heavy molecules, making use of the high resolution to identify fragments. In many cases the composition of a molecule, or fragment, can be deduced from its exact mass by utilizing the known atomic masses of likely constituent atoms.     

Construction of a new multi-turn time-of-flight mass spectrometer

A new type of multi-turn time-of-flight mass spectrometer was constructed, consisting of four cylindrical electric sectors and 28 electric quadrupole lenses, the size of the vacuum chamber being 60 x 70 x 20 cm. It was demonstrated that the mass resolution can be increased according to the number of cycles of the ions through the ion optical system.