量子计算与超冷离子

通过介绍量子计算的基本概念和特点，并对比目前人们使用的计算机的计算方式，对于如何利用囚禁在离子阱中的超冷离子进行量子计算作了简要的叙述．     

Measurement of storage time, estimation of ion number and study of absorption line profile in a Paul trap

Europium (Eu⁺) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu⁺ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions. The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both experimentally and theoretically.     

A high-current electron beam ion trap as an on-line charge breeder for the high precision mass measurement TITAN experiment

The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and, hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap (EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear Physics in Heidelberg, Germany.     

小分子化合物在离子阱质谱中的分子离子反应研究

利用离子阱质谱的原理和特点，研究了小分子醇、醚、胺、醛、酮等有机化合 物（分子量小于200）在离子阱里的分子离子反应，总结了反应特点和规律，并把 它归类为自身化学电离（SCI）反应。以丁酮、丙烯醇为例，采用FTMS对反应产物 离子进行准确质量测定，验证了它们各自的分子离子反应结果。另外，把该类化合 物（30个）SCI反应的质谱图与NIST98库中的标准EI质谱图进行了比较，建立了 SCI质谱图库，提高了在离子阱质谱上对这类小分子化合物定性分析的准确率。     

Addressing the metabolic activation potential of new leads in drug discovery: a case study using ion trap mass spectrometry and tritium labeling techniques

Metabolic activation of drug candidates to electrophilic reactive metabolites that can covalently modify cellular macromolecules may result in acute and/or idiosyncratic immune system-mediated toxicities in humans. This presents a significant potential liability for the future development of these compounds as safe therapeutic agents. We present here an example of an approach where sites of metabolic activation within a new drug candidate series were rapidly identified using online liquid chromatography/multi-stage mass spectrometry on an ion trap mass spectrometer. This was accomplished by trapping the reactive intermediates formed upon incubation of compounds with rat and human liver microsomes as their corresponding glutathione conjugates and mass spectral characterization of these thiol adducts. Based on the structures of the GSH adducts identified, potential sites and mechanisms of bioactivation within the chemical structure were proposed. These metabolism studies were interfaced with iterative structural modifications of the chemical series in order to block these bioactivation sites within the molecule. This strategy led to a significant reduction in the propensity of the compounds to undergo metabolic activation as evidenced by reductions in the irreversible binding of radioactivity to liver microsomal material upon incubation of tritium-labeled compounds with this in vitro system. With the efficiency and throughput achievable with such an approach, it appears feasible to identify and address the metabolic activation potential of new drug leads during routine metabolite identification studies in an early drug discovery setting.     

Repeatability and pattern recognition of bacterial fatty acid profiles generated by direct mass spectrometric analysis of in situ thermal hydrolysis/methylation of whole cells

Direct CI mass spectrometry profiling of fatty acid methyl esters (FAMEs) from in situ thermal hydrolysis/methylation (THM) of whole bacterial cells with tetramethylammonium hydroxide (TMAH) has been demonstrated as a potential method for real time and fieldable detection/identification of microorganisms. Bacillus anthracis (Ames), Yersinia pestis (Nair. Kenya), Vibrio cholerae (E1 Tor), Brucella melitensis (Abortus wild) and Francisella tularensis (LVS vaccine) were profiled by this method during a 10-month period. Repeatability of the in situ FAME data was calculated using one-way analysis of variance (ANOVA) and a t-test. Artificial neural network (ANN) and multivariate statistics of the FAME profiles were also compared for bacterial identification/classification. Equivalent results were obtained with a multivariate rule building expert system (MuRES) and the ANN. However, the ANN analysis required much less computer time and was deemed the best choice for this application. In situ THM FAME profiles of the bacterial samples provided comparable results with those obtained from the Microbial Identification System (MIDI) (Newark, DE) wet chemistry-gas chromatographic based system.     

Fast screening of anabolic steroids and other banned doping substances in human urine by gas chromatography/tandem mass spectrometry

A fast and sensitive method for the comprehensive screening of anabolic agents and other banned doping substances using gas chromatography/tandem mass spectrometry (GC/MS/MS) with an external ionization ion trap mass spectrometer is presented. The method takes advantage of the resolving power of MS/MS to eliminate background interferences, thus speeding up the chromatographic analysis. For each compound, different fragmentation reactions were studied and their collision energies optimized to obtain the best sensitivity in terms of their signal-to-noise ratio (S/N). A dramatic reduction in overall analysis time was achieved compared with other common approaches. More than 50 substances could finally be monitored in less than 7.4 min with detection limits (S/N >3) lower than 0.5 ng ml(-1) for most of the compounds with special sensitivity requirements according to the International Olympic Committee (IOC). A validation procedure for qualitative analysis was performed. The selectivity of the method showed that no interfering peaks were observed at the retention time of the analytes. Good intermediate precision, below 25% for most of the compounds, and robustness were observed. The optimized method was successfully applied to analyse more than 100 real human urine samples with optimum sensitivity and specificity rates.     

Comparison of purge and trap GC/MS and spectrophotometry for monitoring petroleum hydrocarbon degradation in oilfield produced waters

Results of using a field spectrophotometer and its appropriate protocols as a surrogate method for an oilfield produced water treatment process is presented. Methylene chloride extractions of the produced water before and after treatment maintained a yellow color pigment that was directly proportional to the hydrocarbon concentration. From this, an absorption spectrum and standard curve were developed. A resultant linear plot of the standard curve indicated that there is an excellent correlation (r²=0.9847) between the varying concentrations and the associated absorbance values at a wavelength of 400 nm. Total n-alkane concentration comparisons between the laboratory GC/MS analysis and the spectrophotometry analysis generated data of similar accuracy and precision at concentrations ranging from 1 to 137 mg/l (alpha=0.05). Linear comparisons between GC/MS and spectrophotometric coefficients were near unity, with the constant being near zero, with a correlation coefficient (r²) of 0.99. Based on this study, spectrophotometry is a complimentary method to GC/MS for determining total n-alkane concentrations in oilfield produced water samples.     

用原子捕获技术提高火焰原子吸收光谱法的灵敏度

采用简易的石英原子捕获器，使Ｃｕ，Ａｇ，Ａｕ，Ｚｎ，Ｃｄ，Ｐｂ，Ｓｂ，Ｂｉ等易挥发元素在空气－乙炔火焰原子吸收光谱法中的灵敏度提高了３～５倍，并有较好的精密度，相对标准偏差在１％左右，方法中用此技术测定了标准物质中Ｐｂ、Ｃｄ的含量，获得了满意的结果，它较之石墨炉原子吸收光地具有快速，简便的特点，具有较大的实用价值。