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.     

Food safety measurement issues: way forward

Ensuring food safety (FS) is a persistent concern frequently faced by many countries. Safeguarding the quality of food that is fit for human consumption is the primary responsibility of the governmental regulatory agencies. For most part, agro-industries and food processors assume voluntary leadership for producing safe food. However, in the event of FS breach, the regulatory responsibility kicks into identify and rectify the situation. Notwithstanding whether it is the regulator or the industry that institutes the remedial action (e.g. improved hygiene and refined agricultural and manufacturing practices), the role of laboratory measurements is central in safeguarding the integrity of a functioning FS system. There are many analytical tools available to implement this task, such as validated analytical methods, natural matrix reference materials, field tested monitoring systems (proactive assessment) and effective surveillance systems (constant vigilance to prevent repeat safety violations). Way forward: existing FS tools are insufficient and should be strengthened with innovative approaches. Examples are: assembling swift intervention logistics to face FS breaches; rapid response systems including communication; robust metrology based measurement systems located at strategic locations in the country; and inter-disciplinary human resource to match the need for capacity development. These issues are discussed.     

Hydrocarbons and fuels analyses with the supersonic gas chromatography mass spectrometry--the novel concept of isomer abundance analysis

Hydrocarbon analysis with standard GC-MS is confronted by the limited range of volatile compounds amenable for analysis and by the similarity of electron ionization mass spectra for many compounds which show weak or no molecular ions for heavy hydrocarbons. The use of GC-MS with supersonic molecular beams (Supersonic GC-MS) significantly extends the range of heavy hydrocarbons that can be analyzed, and provides trustworthy enhanced molecular ion to all hydrocarbons. In addition, unique isomer mass spectral features are obtained in the ionization of vibrationally cold hydrocarbons. The availability of molecular ions for all hydrocarbons results in the ability to obtain unique chromatographic isomer distribution patterns that can serve as a new method for fuel characterization and identification. Examples of the applicability and use of this novel isomer abundance analysis (IAA) method to diesel fuel, kerosene and oil analyses are shown. It is suggested that in similarity to the "three ions method" for identification purposes, three isomer abundance patterns can serve for fuel characterization. The applications of the Supersonic GC-MS for engine motor oil analysis and transformer oil analysis are also demonstrated and discussed, including the capability to achieve fast 1-2s sampling without separation for oil and fuel fingerprinting. The relatively fast analysis of biodiesel is described, demonstrating the provision of molecular ions to heavy triglycerides. Isomer abundance analysis with the Supersonic GC-MS could find broad range of applications including petrochemicals and fuel analysis, arson analysis, environmental oil/fuel spill analysis, fuel adulteration analysis and motor oil analysis.     

In situ chemical ionization in ion trap mass spectrometry--the beneficial influence of isobutane as a reagent gas

We report a comparison of the ionization yields provided by the most common reagents (methane, ammonia, methanol, acetonitrile, isobutane) performing in situ chemical ionization with an ion trap mass spectrometer. Four molecules were chosen in the medical field to illustrate experimental results: alprazolam, diazepam, flunitrazepam and acetaminophen. Under usual operational conditions, relative abundances of protonated ions appreciably depend on the reagents. The greatest abundance of MH(+) ions was obtained with isobutane while observed intensities for MH(+) ions varied from 73% for methanol and ammonia to about 23% for acetonitrile and methane. Results were temptatively rationalized comparing energies of formation of the reagent ions and storage efficiency in the trapping field.     

Trace element detection by forward scattering using a continuum light source

It has been demonstrated that forward scattering is feasible using a continuum light source (high pressure Xe-lamp). Detection limits of 50 pg in the case of Cd (228.8 nm) and 0.2 ng for Pb (282.3 nm) have been achieved. The method is applicable to the trace detection of any element vaporisable in a graphite furnace. Since changing the light source is not required, there is good hope for a further development of this method for simultaneous multi-element detection.     

Temperature-dependence of radical-trapping activity of phenoxazine,phenothiazine and their aza-analogues clarifies the way forward for new antioxidant design

The prediction and/or rationalization of diarylamine radical-trapping antioxidant (RTA) activity at the elevated temperatures where they are most useful presents a significant challenge, precluding the development of new technology. Whilst structure–activity relationships at ambient temperatures are well established, their predictive capacity at elevated temperatures is poor due to competing reactions. A striking example involves phenoxazine, which is a superior RTA relative to its sulfur analog phenothiazine at ambient temperature (e.g. k = 3.9 × 10⁷vs. 7.6 × 10⁶ M⁻¹ s⁻¹ at 37 °C, respectively), but is demonstrably inferior at elevated temperatures. Despite being inherently less oxidizable in electrochemical experiments and high-accuracy computations, phenoxazine is more rapidly consumed than phenothiazine in autoxidations at 160 °C – a result which we attribute to a lower reorganization energy barrier to oxidation. Given these observations, we surmised that incorporation of an electronegative N-atom into the phenoxazine ring system would decrease the driving force for oxidation and ‘rescue’ its activity. Indeed, this was found to be the case for nitrogen incorporation at any position, regardless of the impact on the inherent RTA activity. Analogous experiments were carried out on phenothiazines into which nitrogen atoms were incorporated, revealing little benefit at 160 °C. These results suggest that for highly reactive diarylamines (i.e. those with k > 10⁶ M⁻¹ s⁻¹), further enhancements in reactivity do not materially improve their ability to inhibit hydrocarbon autoxidation at elevated temperatures. Instead, their stability to one-electron oxidation determines their efficacy.

Studies of potent diarylamine antioxidants illustrate how their high-temperature activity can be limited by direct reaction with O₂, and how driving force and barrier to oxidation can be modulated for future antioxidant development.     

A new strategy for highly sensitive immunoassay based on single-particle mode detection by inductively coupled plasma mass spectrometry

A highly sensitive immunoassay is proposed based on time-resolved inductively coupled plasma mass spectrometry with nanoparticles as tags to antibody. Instead of using traditional integral mode detection, the transient signals induced by the flash of ions in the plasma torch from the ionization of nanoparticles tagged on antibody were recorded in a time-resolved mode. Since, under certain conditions, the frequency of transient signals is directly correlated to the concentration of nanoparticle tags, the concentration of nanoparticle-tagged antibodies can be quantified by the frequency of transient signals. With the present instrument setup, gold nanoparticle (Au-NP) tags, as small as about 15 nm in diameter, can be detected. This protocol is evaluated for a competitive immunoassay and the linear range for α-fetoprotein is 0. 016–6. 8 µg/L (between 20 and 80% inhibition). The limit of quantification is 0. 016 µg/L (20% inhibition, IC₂₀) with a relative standard deviation of 4.2% (20% inhibition, 4 replicates) for α-fetoprotein. The present strategy provides a sensitive readout method for nanoparticle tags, which is quite promising for numerous applications in immunoassay, DNA hybridization, and other biological analyses.     

Selenium speciation by HPLC with tandem mass spectrometric detection

An HPLC/MS-MS method was developed for the analysis of selenium species. Tandem mass spectrometry (MS-MS) was chosen as a detector to provide structural and molecular information allowing the identification of species, which are not commercially available as standards. A new separation method for selenium species was developed, based on porous graphitic carbon (PGC) as the stationary phase. The applicability of the optimized HPLC/MS-MS system was demonstrated by the analysis of a mixture containing Se-methyl-selenocysteine, selenomethionine, selenocystine, selenoethionine and selenocystamine. All peaks were baseline-resolved and eluted within 16 min. Positive ionization led to higher intensities than negative ionization. Signal suppression tests showed that electrospray ionization (ESI) is a more effective ionization method than atmospheric pressure chemical ionization (APCI) for selenium species in a matrix containing pentafluoropropionic acid, heptafluorobutyric acid or ammonium formate. Comparative experiments with a triple quadrupole mass spectrometer (Quattro LC) and a time-of-flight instrument (Q-Tof-2) showed a 20 fold higher mass resolution of the latter mass spectrometer (m/Am= 5000) and significantly lower intensities for analyte signals as well as background noise compared to the triple quadrupole instrument. MS-MS spectra of the investigated selenium species including characteristic fragmentation patterns are presented.     

The mass detector: A new detection system for carbohydrate and lipid analyses

Summary The mass detector was investigated as an alternative to RI detection for carbohydrate and lipid analyses with high pressure liquid chromatography. The instrument was found to be more sensitive than most RI detectors and, as gradient elution could also be carried out, the resulting chromatograms showed improved resolution.     

Improvement of the power of detection in ICP/OES by a new way of sample introduction (hydraulic high-pressure nebulization)

Summary During an ICP-/OES procedure, the application of an aerosol solely created by a very high hydraulic pressure (1000 to 5000 psi) is employed for sample introduction (HHP-nebulization). The BEC-values achieved are lower by a factor of 1.7 to 3.6 in comparison to pneumatic nebulization.

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Steigerung des Nachweisvermögens in der ICP/OES durch eine neue Art der Probeneinführung (hydraulische Hochdruck-Zerstäubungstechnik)

     

A new way of synthesizing steroids

Summary A new method for the synthesis of steroids has been found which is based on the Michael condensation of 2-(-ketobutyl)-3-vinyl-²-cyclohexanone (V) with 2-methyldihydroresorcinol followed by a double cyclization of the tetraketone (VI).     

西地那非的合成

西地那非 (ｓｉｌｄｅｎａｆｉｌ,商品名 :Ｖｉａｇｎａ)是美国辉瑞公司于 1 997年开发上市的新型磷酸二酯酶 5型(ＰＤＥ5 )抑制剂 ,化学名为 5 〔2 乙氧基 5 (4 甲基哌嗪 1 磺酰基 )苯基〕 1 甲基 3 正丙基 1 ,6 二氢 7Ｈ 吡唑并〔4,3 ｄ〕嘧啶 7 酮。作者对文献[1- 3] 的合成路线及合成方法进行了改进 :在中间体 4 氨基 1 甲基 3 正丙基吡唑 5 甲酰胺制备中 ,采用水合肼作还原剂 ,收率达 91 5 % ,且后处理方便 ,易于操作 ,安全简单 ,产品质量稳定。ＨＮＭＲ谱 ,元素分析结果与对照品完全一致。在环合反应中使用表面活性剂十二…     

Synchronous multielement detection by forward scattering in a transverse magnetic field (SYNFO)

Forward scattering in a transverse magnetic field is a sensitive method for the detection of low concentrations of elements. It has a large dynamic range in comparison to atomic absorption spectroscopy and is a “zero-method”. The application for $\text{syn}$chronous multielement detection by $\text{for}$ward scattering (SYNFO) is described. A continuous light source and a vidicon camera as detection system are used. In contrast to emission spectroscopy the spectra are easy to identify because they only consist of the few resonance lines.Different light sources were tested and detection limits and dynamic ranges of resonance lines of Tl, Fe, Pb, Zn, and Cd in a wavelength range between 260 and 335 nm were synchronously determined.     

Simultaneous detection of attomolar pathogen DNAs by Bio-MassCode mass spectrometry

A general method is described to analyze pathogen DNAs in homogenous solution by a novel Bio-MassCode probe, using a small organic (namely disulfide) "reporter mass" that self-assembled in oligonucleotide-modified gold nanoparticles. With conventional MALDI TOF MS, the assay simultaneously detected DNAs for HIV, HBV, HCV, and TP with extraordinarily high sensitivity in the low attomolar (10(-18) M) range without any other amplification.     

A new naphthimidazole derivative for saccharide labeling with enhanced sensitivity in mass spectrometry detection

A series of saccharides, including maltoheptose, blood type B antigen, pullulan and the glucan of Ganoderma lucidum, are easily converted into the naphthimidazole (NAIM) derivatives in high yields by the iodine‐promoted oxidative condensation. The NAIM‐labeled saccharides, without further purification, show enhanced signals in matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). The combined use of NAIM derivatization and MALDI‐TOFMS analysis thus provides a rapid method for identification of saccharides even in less than 1 pmol of saccharide in the sample. Characterization of the biologically active saccharides and complex polysaccharides is also achieved through the NAIM‐derivatization method. This study can be further applied to facilitate the isolation and analysis of novel saccharides. Copyright © 2009 John Wiley & Sons, Ltd.