A comparison of the performance of a fundamental parameter method for analysis of total reflection X-ray fluorescence spectra and determination of trace elements,versus an empirical quantification procedure

The performance has been compared of two different quantification methods — namely, the commonly used empirical quantification procedure and a fundamental parameter approach — for determination of the mass fractions of elements in particulate-like sample residues on a quartz reflector measured in the total reflection geometry. In the empirical quantification procedure, the spectrometer system needs to be calibrated with the use of samples containing known concentrations of the elements. On the basis of intensities of the X-ray peaks and the known concentration or mass fraction of an internal standard element, by using relative sensitivities of the spectrometer system the concentrations or mass fractions of the elements are calculated. The fundamental parameter approach does not require any calibration of the spectrometer system to be carried out. However, in order to account for an unknown mass per unit area of a sample and sample nonuniformity, an internal standard element is added. The concentrations/mass fractions of the elements to be determined are calculated during fitting a modelled X-ray spectrum to the measured one. The two quantification methods were applied to determine the mass fractions of elements in the cross-sections of a peat core, biological standard reference materials and to determine the concentrations of elements in samples prepared from an aqueous multi-element standard solution.     

Negative Corona Discharge Ion Source Under Ambient Conditions with Mini Line-cylinder Electrodes

A novel ambient negative corona discharge ion source with mini line-cylinder electrodes is designed. The diameters of inner and outer electrode are 0.16 and 4 mm respectively. With a special assembly method, a perfect coaxiality of the two electrodes is obtained. An injection system utilizing a temperature control technique, achieves a constant and stable concentration of the sample, which is critical to the experiment. The formulas of the corona onset voltage of line-cylinder electrodes are also introduced. The experiment results show that negative substances such as formic acid and acetic acid can be ionized under ambient conditions. When combined with micro electrical mechanical system fabricationprocess, the volume of the ion source can be reduced dramatically, but there is an undesirable surface discharge. To solve the surface discharge problem, an improved structure was designed and tested. The simplicity of the interface of the ion source makes it suitable for mass spectrometer, micro mass spectrometer, ion mobility spectrometer, and high-field asymmetric waveform ion mobility spectrometer applications.     

Thermal analysis—mass spectrometer computer system and its application to the evolved gas analysis of green river shale and lunar soil samples

A thermal analysis—mass spectrometer system controlled by a computer has been developed and successfully used in the analysis of a wide variety of geochemical samples. The TA—MS computer system provides a very powerful analytical tool for the determination of volatile species released from samples over a very wide temperature and sample-size range. Use of a small laboratory computer and magnetic-tape storage units permits large quantities of analytical information to be handled and easily retrieved. The rapid scan capabilities of the quadrupole mass spectrometer operating under computer control are especially useful for following the rapidly changing composition of the evolved gases released from samples during heating under vacuum conditions. Samples of volatile-rich Green River shale and two lunar soils have been analyzed to show the utility of the TA—MS computer system.     

Quantitative analysis of crude plasma extracts by ion trap tandem mass spectrometry

The ion trap mass spectrometer is a tandem-in-time instrument that has promise as an extremely sensitive device for practical tandem mass spectrometry assays. An approach for the quantitative analysis of unknown drug levels in crude extracts, using combined capillary gas chromatography and the ion trap mass spectrometer in the tandem mode, is described. One-gram plasma samples were spiked with an anti-inflammatory drug at levels of 1–100 ng, and with 50 ng of a chemical analog internal standard. Crude extracts of the plasma samples are analyzed by using scan functions that utilize combined radiofrequency (rf) and de voltages. The need for combined rf- and de-voltage sequences for analysis of such extracts is demonstrated by comparison to attempted analyses using only rf voltages. Limitations of the method are: (1) the need for accurate calibration of ionization times to obtain linear calibration lines, and (2) the lack of automatic gain control for scans using combined rf and dc voltages to control and optimize parent ion populations and to allow a simpler analysis of “unknowns. ”     

Evaluation of Improved Ultrasonic Nebulizer for Miniature Simultaneous Microwave Plasma Torch Spectrometer

Introduction Forthelaboratoriesthatrequirerapidresultsor havehighsamplethroughput,analysisspeedispara mount.Tomeetthisrequirement,thedevelopmentof atomicspectrometershasgonethroughmanystages,fromsinglechannelsequentialscanningspectrometers,multichanneldir…     

Polarization induced electrospray ionization mass spectrometry for the analysis of liquid,viscous and solid samples

In this study, a polarization‐induced electrospray ionization mass spectrometry (ESI‐MS) was developed. A micro‐sized sample droplet was deposited on a naturally available dielectric substrate such as a fruit or a stone, and then placed close to (~2 mm) the orifice of a mass spectrometer applied with a high voltage. Taylor cone was observed from the sample droplet, and a spray emitted from the cone apex was generated. The analyte ion signals derived from the droplet were obtained by the mass spectrometer. The ionization process is similar to that in ESI although no direct electric contact was applied on the sample site. The sample droplet polarized by the high electric field provided by the mass spectrometer initiated the ionization process. The dielectric sample loading substrate facilitated further the polarization process, resulting in the formation of Taylor cone. The mass spectral profiles obtained via this approach resembled those obtained using ESI‐MS. Multiply charged ions dominated the mass spectra of peptides and proteins, whereas singly charged ions dominated the mass spectra of small molecules such as amino acids and small organic molecules. In addition to liquid samples, this approach can be used for the analysis of solid and viscous samples. A small droplet containing suitable solvent (5–10 µl) was directly deposited on the surface of the solid (or viscous) sample, placed close the orifice of mass spectrometer applied with a high voltage. Taylor cone derived from the droplet was immediately formed followed by electrospray processes to generate gas‐phase ions for MS analysis. Analyte ions derived from the main ingredients of pharmaceutical tablets and viscous ointment can be extracted into the solvent droplet in situ and observed using a mass spectrometer. Copyright © 2015 John Wiley & Sons, Ltd.     

Novel multichannel plasma-source mass spectrometer

A novel mass spectrometer system for elemental analysis is described. The instrument combines an inductively coupled plasma (ICP) ion source with a Mattauch-Herzog mass spectrometer and multichannel ion detector. Ion detection is simultaneous and an elemental mass spectrum (20–230 μ) can be acquired in <10 ms. The instrument can be used with either Ar or He plasma sources. The speed of the system makes it well suited for acquisition of fast (10–100-ms duration) transient signals, such as those generated by pulsed laser ablation sample introduction. Preliminary system performance characteristics, which include detection limits, stability, and measurement accuracy, obtained with an Ar ICP are presented. The application of the instrument to the analysis of solid samples by laser ablation is discussed.     

The characterization of closely related polymeric materials by thermogravimetry—mass spectrometry

The potential of a new technique in forensic science, thermogravimetry—mass spectrometry, is illustrated by its application to the examination of acrylic fibres and white alkyd gloss paints, small samples of which are difficult to differentiate even by a combination of current techniques. A simple interface allowing the coupling of a magnetic sector mass spectrometer to a thermobalance is described. This combination allows up to five experimental parameters to be determined simultaneously either for classification of the material under investigation or for the detailed direct comparison of samples. The thermobalance allows the temperatures at which weight losses occur and their relative proportions to be determined; the basic parameter obtained from the mass spectrometer is the total ion current trace. From this, single qualitative mass spectra may be chosen for examination and ions, whose presence or absence may be diagnostic or which vary characteristically throughout the analysis, can be selected. The variations of these ions may then be examined by computer-generated mass thermograms (analagous to mass chromatograms in g.c.—m.s.) or, if computer facilities are not available, by multiple ion detection. The residue from the analysis can be used for trace element analysis, e.g. by energy-dispersive x-ray fluorescence spectrometry.     

Multisample probe for fast-atom bombardment / mass spectrometry

An inexpensive multisample fast-atom bombardment (FAB) probe assembly was designed for high-throughput analysis of samples on a VG ZAB-SE mass spectrometer. The system consists of a vacuum lock system and a FAB probe whose tip contains five or more sample wells. The probe enters the mass spectrometer source region perpendicular to the secondary ion beam axis, The probe is maintained at high voltage on contact with a spring clip attached to the screen plate of the source block. Sample throughput with the multisample probe is twice that of a coaxial probe, with about twice the sensitivity and no sample cross contamination.     

Development and validation of an isotope-dilution electrospray ionization tandem mass spectrometry method with an on-line sample clean-up device for the quantitative analysis of the benzene exposure biomarker S-phenylmercapturic acid in human urine

An isotope-dilution electrospray ionization tandem mass spectrometry (ESI-MS/MS) method with an on-line sample clean-up device, for the quantitative analysis of human urine for the benzene exposure biomarker S-phenylmercapturic acid (SPMA), was developed and validated. The sample clean-up system was constructed from an autosampler, a reversed-phase C18 trap cartridge, a two-position switching valve, and controlling computer software and hardware. The sample clean-up system was interfaced via 1/20 splitting to the ESI source of a triple-quadrupole mass spectrometer using negative ion mode and multiple reaction monitoring for SPMA and the isotope-labeled internal standard. A strategy was adopted to acquire pooled blank urine matrix and quality control samples spiked with standards. Validated procedures and data on method specificity, detection limits, standard curves, precision and recovery, sample storage stability, and inter-laboratory comparison are presented. The analytical system was fully automated. No tedious manual sample clean-up procedures are required. With the selectivity and the sensitivity provided by ESI-MS/MS detection, the analytical system can be used for high-throughput and accurate determination of SPMA levels in human urine samples, as a biomarker for environmental as well as occupational benzene exposure.     

A computer system for the spectrometric analysis of high alloyed steel

Summary Experiences with a computer controlled analyser system for production control in a steel plant are reported. The analyser system consists of a direct reading vacuum spectrometer, a digital computer and a data transmission system. The computer system is responsible for the control of the spectrometer as well as for the transformation of measured values into element concentration values and their transmission into the plant internal teleprinter network. A great disadvantage of spectrometers is the fact that matrix effects occur. To solve the problems arising from that — especially in the case of analyses of an extended alloying program — either numerous special calibration curves for all the different types of alloyed steels can be established or one can use only one calibration curve and eliminate the matrix effects by calculation of the line coincidences and the third element influences. The combination of a spectrometer and a digital computer permits rapid determination of the chemical composition of samples by following the second procedure and makes the automatic transmission and documentation of data possible. The composition and working method of such an equipment is described, some selected examples for the used method of calibration are given. The principle of the digital computer program for the calculation of the chemical composition from measured intensity values is demonstrated, and the means of automatic transmission of results are shown. The main advantages of the system and also its limits are discussed.     

Application of headspace-mass spectrometry for differentiating sources of olive oil

In the present work we propose the use of headspace-mass spectrometry (HS-MS) for the characterisation of monovarietal olive oils, an issue of interest when the origin of an oil has to be determined. The HS-MS procedure involves the direct introduction of the sample into a vial, headspace generation and automatic injection of the volatiles into a mass spectrometer. The results were compared with those obtained using more conventional approaches, including chromatographic, spectrophotometric and other types of analysis. Linear Discriminant Analysis (LDA) was applied to the data obtained with both analytical methodologies to achieve the differentiation of the three types of samples. The proposed method is faster and cheaper than those usually employed for edible oil analysis and no sample preparation is required. Additionally, the measuring process is simple and the results obtained from chemometric treatment are 100% correct as regards classification and prediction, making it an appropriate method for routine control.     

Development of a toolkit for early precision immunochromatographic diagnosis

A device is developed for automated immunochromatographic assay, designed for one-time tests at the place of occurrence of a disease. The device comprises a turntable platform for up to five strips placed simultaneously, a unit for sample collection and microdosing to a test strip, a detection unit, and a microprocessor control system. A manual, semiautomatic, or automatic operation mode may be selected. Colloidal quantum dots with a luminescence peak from the visible to near-infrared spectral region (600–800 nm) are used as fluorescent labels. A UV-LED or a laser at 365–480 nm can be used as an excitation system; the detection device is a spectrometer with an operation range of 500–800 nm, based on a CCD series of TCD1304DG sensors (Toshiba). RFID tags of samples can re read and the analysis results can be sent to an external computer. The device is made in a plastic case for carrying.     

红外光谱仪模拟空间原位分析表征系统的研制

对现有傅里叶红外光谱仪进行拓展开发,空间模拟试验系统通过法兰与外置原位真空池及光谱仪相连接,实现样品推送机构的建立.分析单元与主真空室之间采用双闸板阀联用实现双向密封,可独立对材料表面进行快速原位分析.摩擦试样可通过样品精密传送和定位装置移动至分析单元进行表征,实现了模拟空间环境下摩擦表面的原位分析功能,将润滑材料的空间摩擦学行为与其表面及化学状态准确关联,避免环境对摩擦表面的污染,为设计新型空间润滑材料提供可靠的试验依据.     

Gas chromatography/isotope-ratio mass spectrometry method for high-precision position-dependent 15N and 18O measurements of atmospheric nitrous oxide

We describe an automated gas chromatography/isotope-ratio mass spectrometry (GC/IRMS) method for the determination of the (18)O and position-resolved (15)N content of nitrous oxide at natural isotope abundance. The position information is obtained from successive measurement of the isotopic composition of the N(2)O(+) ion at m/z 44, 45, 46 and the NO(+) fragment ion at m/z 30, 31. The fragment ion analysis is complicated by a non-linearity in the mass spectrometer that has to be taken into account. Evaluation of the absolute peak areas allows for a simultaneous determination of the N(2)O mixing ratio for atmospheric samples. Samples with mixing ratios ranging from a few nmol/mol up to the percent level can be analyzed using different sample inlet systems. The high concentration inlet system provides an easy and quick method to carry out various diagnostic tests, in particular to perform realistic linearity tests. A gas chromatographic set-up with a split column and a backflush possibility improves analytical precision and excludes interferences by substances with long retention times from preceding runs. We also describe a new open split interface that uses only a single transfer capillary to the mass spectrometer for sample and reference gas.     

Automation of a Fourier transform ion cyclotron resonance mass spectrometer for acquisition, analysis, and e-mailing of high-resolution exact-mass electrospray ionization mass spectral data

A system has been designed to automatically acquire high-resolution (>50,000 FWHM), exact-mass (mass measurement error ≤3 mmu) electrospray ionization mass spectra with a commercial Fourier transform ion cyclotron resonance mass spectrometer equipped with a high-field (9.4 tesla) superconducting magnet and a commercial autosampler. Upon the injection of each individual sample, the autosampler transmits a contact closure signal to the previously tuned and calibrated mass spectrometer to initiate data acquisition. A software package was designed to run off-line and to accept a sample list with input information for each of the samples. Then for each of the samples, the software automatically processes the acquired data, interprets the exact-mass data by correlating the observed masses with predicted masses computed from proposed elemental formulas, and then finally prints the spectra, peak lists, and exact-mass reports, and e-mails the exact-mass reports to the submitting chemists. With this automation package, large numbers of samples can be run unattended while obtaining exact masses for all the abundant ions in the spectra. Sample turnaround times are reduced with a corresponding increase in sample throughput. The performance of the system was evaluated with nearly 700 samples with a precalibrated instrument, without the presence of an internal standard. The system was found to be reliable and robust with a fitted standard deviation of 0.32 mmu and a small average systematic mass error of ?0.28 mmu. Typical data acquired with the system have resolving powers >50,000 (FWHM) and mass errors <1.0 mmu.     

Tritium isotope fractionation between ammonia,methylamine, dimethylamine and n-butane thiol

An automatic gamma-ray spectrometer equipped with a micro-robot for sample changing has been developed and constructed. The facility is comprised of a commercially available micro-robot, sample changer for up to 36 samples, personal computer programmed in BASIC language, input/output devices, detector and multichannel analyzer. This paper describes the components, software and effective uses of the above facility.     

高纯四氯化锗测试样品的采集和制备方法研究

针对光纤级高纯四氯化锗(99.999999%)中痕量含氢杂质吸收峰红外透过率检测(FTIR)用试样的采集,以及痕量金属杂质的电感耦合等离子体质谱法(ICP-MS)测定用试样的制备方法进行了系统研究。设计开发了用于检测痕量含氢杂质吸收峰红外透过率的样品采集实验装置,实现了含氢杂质(如—OH、—CH、HCl等)吸收峰的红外透过率在线连续测试,试样采集过程全密闭进行,避免了采样过程的二次污染,采样过程流程简短,操作简便;实验优选了在制备ICP-MS法测定痕量金属杂质用的试样过程中消除四氯化锗基体干扰、防止砷等易挥发杂质损失以及防止样品处理过程污染试样的制样方法,实现了试样制备过程二次污染源的有效控制,制样过程试剂消耗量少,制备时间短,待测元素无损失。