A small high‐irradiance laser ionization time‐of‐flight mass spectrometer

A small high‐irradiance laser ionization time‐of‐flight mass spectrometer (LI‐TOFMS) with orthogonal sample introduction was described. High irradiance of 6 × 10¹⁰ W/cm² at 532 nm from a Nd : YAG laser was applied in the experiment to get a high ionization degree in plasma and to dissociate the interferential polyatomic ions. Meanwhile, the interferential multiply charged ions resulted by high‐irradiance were nearly eliminated in the spectrum by utilizing helium as the buffer gas in the ion source due to three‐body recombination, which resulted in a relatively clean background. Improved signal stability was obtained by automated step moving of the sample stage in short time intervals. By using two sets of Einzel lens in transport system, nearly uniform relative sensitivity coefficients (RSCs) were achieved for most of metal elements including light ions which were detected in extremely low sensitivity in previous hexapole transportation instrument. The resolving power reaches 2200, and the detection limits (DLs) are 10^?6 g/g for metal elements in the steel standard. Copyright © 2009 John Wiley & Sons, Ltd.     

Further investigation of a peptide extraction method with mesoporous silica using high‐performance liquid chromatography coupled with tandem mass spectrometry

Mobil Composition of Matter No. 41 (MCM‐41) was the most frequently used mesoporous silica material to extract peptides from complex biological samples. However, there were confusing extraction conditions and large extraction efficiency variance among related reports, which resulted from unclear understanding about the interaction between the material and peptides. In this study, the extraction mechanism was investigated with one set of tryptic peptides by using high‐performance liquid chromatography coupled with triple quadrupole mass spectrometry. Generally, hydrophobic interaction and electrostatic attraction were two major driving forces for extraction of peptides, while electrostatic repulsion greatly weakened the interaction between the material and peptides with isoelectric points below the pH. With most peptides positively charged and MCM‐41 slightly negatively charged, most efficient extraction was obtained at pH 3, and it was proved that electrostatic and hydrophobic interaction acted in synergy for extraction of all the peptides. A mixed solution of acetonitrile with buffers of high pH or ion strength was demonstrated to be favorable for elution, which performed much better than the commonly used eluate (mixture of acetonitrile with 0.1% trifluoroacetic acid). Finally, under optimum conditions, it was found that extraction efficiency of MCM‐41 for protein digest and human serum was greatly improved.     

Comparison between a high‐resolution single‐stage Orbitrap and a triple quadrupole mass spectrometer for quantitative analyses of drugs

The capabilities of a high‐resolution (HR), accurate mass spectrometer (Exactive‐MS) operating in full scan MS mode was investigated for the quantitative LC/MS analysis of drugs in patients' plasma samples. A mass resolution of 50 000 (FWHM) at m/z 200 and a mass extracted window of 5 ppm around the theoretical m/z of each analyte were used to construct chromatograms for quantitation. The quantitative performance of the Exactive‐MS was compared with that of a triple quadrupole mass spectrometer (TQ‐MS), TSQ Quantum Discovery or Quantum Ultra, operating in the conventional selected reaction monitoring (SRM) mode. The study consisted of 17 therapeutic drugs including 8 antifungal agents (anidulafungin, caspofungin, fluconazole, itraconazole, hydroxyitraconazole posaconazole, voriconazole and voriconazole‐N‐oxide), 4 immunosuppressants (ciclosporine, everolimus, sirolimus and tacrolimus) and 5 protein kinase inhibitors (dasatinib, imatinib, nilotinib, sorafenib and sunitinib). The quantitative results obtained with HR‐MS acquisition show comparable detection specificity, assay precision, accuracy, linearity and sensitivity to SRM acquisition. Importantly, HR‐MS offers several benefits over TQ‐MS technology: absence of SRM optimization, time saving when changing the analysis from one MS to another, more complete information of what is in the samples and easier troubleshooting. Our work demonstrates that U/HPLC coupled to Exactive HR‐MS delivers comparable results to TQ‐MS in routine quantitative drug analyses. Considering the advantages of HR‐MS, these results suggest that, in the near future, there should be a shift in how routine quantitative analyses of small molecules, particularly for therapeutic drugs, are performed. Copyright © 2012 John Wiley & Sons, Ltd.     

Solid‐phase microextraction with fast GC combined with a high‐speed triple quadrupole mass spectrometer for targeted and untargeted food analysis

The present contribution is focused on the evaluation of a high‐speed triple quadrupole mass spectrometer, carried out under moderately fast GC conditions (analysis time: 16.6 min). The mass spectrometric instrument can be operated under high‐speed GC conditions, in both full‐scan (maximum scan speed: 20 000 amu/s) and multiple reaction monitoring (MRM) modes (minimum dwell time: 0.01 s). Additionally, the mass spectrometric system can generate full scan and MRM information, simultaneously and rapidly. A headspace solid‐phase microextraction with fast GC coupled to triple quadrupole MS approach was developed for the: (i) qualitative untargeted analysis of brewed tea volatiles, and (ii) MRM qualitative and quantitative analysis of targeted volatiles (also in brewed tea), namely 30 phytosanitary contaminants. The performance of the triple quadrupole instrument was satisfactory both for identification and quantification purposes. Furthermore, the method sensitivity was more than sufficient for the requirements of current legislation. Method validation, related to the MRM analysis, was performed considering: precision of quantification data (maximum coefficient of variation value: 12.0%) and quantification/qualification ion ratios (maximum coefficient of variation value: 14.4%), along with limits of detection (4 parts per trillion–5 parts per billion range) and quantification (14 parts per trillion–16 parts per billion range).     

A gas-inlet system coupled with a Knudsen cell mass spectrometer for high-temperature studies

A gas-inlet system coupled with a Knudsen effusion mass spectrometer has been developed to study at high temperature the interaction of solids and vapors with reactive permanent gases, such as H(2) and O(2), directly introduced into the cell from external low-pressure reservoirs (pressure range: 10(-4) < p < 1 bar). By selecting the gas flow from the external reservoir the pressures of the gases inside the Knudsen cell can be quantitatively controlled over three orders of magnitude, approximately from 10(-8) to 5.10(-5) bar. Mixtures of two different gases can be introduced into the cell, controlling their partial pressures independently. The capabilities of the device have been tested with four gas-solid systems: PbO(s) + O(2)(g), GeO(2)(s) + O(2)(g), Ga(s) + H(2)(g) and Au(s) + H(2)(g), by studying the relevant high-temperature equilibria. The results obtained for the dissociation energies of the diatomic molecules PbO(g), GeO(g), GaH(g), and AuH(g) compare well with the literature data giving confidence in the reliability and versatility of the method. Preliminary experiments on the in situ formation of H(2)O(g) in the Knudsen cell by the introduction of controlled gaseous H(2)/O(2) mixtures are also presented.     

Isotopic analysis of ethanol: study on 18O/16O measurement using a high‐temperature pyrolysis system coupled to an isotope ratio mass spectrometer

The original article to which this Erratum refers was published in Rapid Commun. Mass Spectrom. 20 ; 2006, 937–940.     

On-line capillary supercritical fluid chromatography-inductively coupled plasma mass spectrometry for the analysis of organometallic compounds

Supercritical fluid chromatography with inductively coupled plasma-mass spectrometric detection is a new and useful technique for the analysis of organometallic compounds. An interface has been developed for coupling these techniques. The interface is compact, easy to assembel, and causes minimal disruption to either instrument. A series of organotin, organoarsenic, and organorion compounds has been used to evaluate the interface and ICPMS as a detector for SFC. The effect of analyte concentration and restrictor temperature on peak intensity has been investigated and the effect of the mobile phase on the plasma has also been studied to assess background interference from changes in the plasma.     

Investigation of potential toxic components based on the identification of Genkwa Flos chemical constituents and their metabolites by high‐performance liquid chromatography coupled with a Q Exactive high‐resolution benchtop quadrupole Orbitrap mass spectrometer

Genkwa Flos, a famous traditional Chinese medicine has been reported to have significant hepatotoxicity. A high‐throughput and reliable method was established to explore potential toxic components by high‐performance liquid chromatography coupled with a Q Exactive high‐performance benchtop quadrupole‐Orbitrap mass spectrometer. A total of 68 compounds including 22 chemical components and 46 metabolites were tentatively identified based on the accurately measured mass value, retention time, and fragmentation pattern. Besides, the metabolic pathways of main components in Genkwa Flos were also illustrated. The results indicated that hydroxylation, demethylation, methylation, glucuronidation, sulfation, cysteine conjugation, and glutathione conjugation participated in the metabolic reactions of Genkwa Flos. Moreover, 12 Genkwa Flos chemical components and 26 metabolites were detected in cell lysate, which were considered as the bound components to HL‐7702 cells. In view of cell affinity theory, these compounds were preliminarily deduced to be potential toxic ingredients for the hepatotoxicity induced by Genkwa Flos. The results demonstrated that the developed method was a very feasible and efficient approach for the components identification even in the complex matrix. In conclusion, this study will provide a deep insight into the toxic substances of Genkwa Flos and lay a chemical basis for in‐depth toxic studies on Genkwa Flos hepatotoxicity.     

Fast and sensitive analysis of beta blockers by ultra‐high‐performance liquid chromatography coupled with ultra‐high‐resolution TOF mass spectrometry

This paper presents a method for the determination of acebutolol, betaxolol, bisoprolol, metoprolol, nebivolol and sotalol in human serum by liquid–liquid extraction and ultra‐high‐performance liquid chromatography coupled with ultra‐high‐resolution TOF mass spectrometry. After liquid–liquid extraction, beta blockers were separated on a reverse‐phase analytical column (Acclaim RS 120; 100 × 2.1 mm, 2.2 μm). The total run time was 6 min for each sample. Linearity, limit of detection, limit of quantification, matrix effects, specificity, precision, accuracy, recovery and sample stability were evaluated. The method was successfully applied to the therapeutic drug monitoring of 108 patients with hypertension. This method was also used for determination of beta blockers in 33 intoxicated patients.     

Determination of organometallic compounds by capillar gas chromatography – inductively coupled plasma mass spectrometry

The separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC-ICP-MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC-ICP-MS has been extended considerably beyond that possible in earlier studies (retention indices up to 3400).     

Quantitation of hepcidin in serum using ultra‐high‐pressure liquid chromatography and a linear ion trap mass spectrometer

Hepcidin is a peptide hormone that functions as a key regulator of mammalian iron metabolism. Biological levels are increased in end‐stage renal disease and during inflammation but suppressed in hemochromatosis. Thus hepcidin levels have diagnostic importance. This study describes the development of an analytical method for the quantitative determination of the concentration of hepcidin in clinical samples. The fragmentation of hepcidin was investigated using triple quadrupole and linear ion trap mass spectrometers. A standard quantity of a stable isotopically labelled hepcidin internal standard was added to serum samples. Extraction was performed by protein precipitation and weak cation‐exchange magnetic nanoparticles. Chromatography was carried out on sub 2 µm particle stationary phase, using ultra‐high‐pressure liquid chromatography and a linear ion trap for quantitation. The lower limit of quantitation was 0.4 nmol/L with less than 20% accuracy and precision. The mean hepcidin concentration in sera for controls was 4.6 ± 2.7 nmol/L, in patients with sickle cell disease, 7.0 ± 8.9 nmol/L; in patients with end‐stage renal disease, 30.5 ± 15.7 nmol/L; and patients with penetrant hereditary hemochromatosis, 1.4 ± 0.8 nmol/L. Copyright © 2010 John Wiley & Sons, Ltd.