Integrated Ion Current Research Articles

Rapid Determination of Diethanolamine by Field Asymmetric Ion Mobility Spectrometry(FAIMS) Technique

The field asymmetric ion mobility spectrometry(FAIMS) technique was used for the rapid analysis of diethanolamine( DEA). The ion characteristic signal of DEA was acquired by FAIMS with the direct thermal desorption method for sampling,which was compared with the result of gas chromatograph-mass spectrometer(GC-MS). The concentration of DEA gas was controlled by the polytetrafluoroethene(PTFE) diffusion tube method. The DEA gas samples with different concentrations were detected by FAIMS technique. The dependence of the integrated ion current on DEA gas concentration was obtained,and the limit of detection for DEA gas is 0. 02 μg / L. This study has laid a foundation for the application of FAIMS technique to on-site rapid detection of DEA.

Ion current measurement in a homogeneous charge compression ignition engine

An ion current probe using a spark plug was applied to gasoline-fuelled homogeneous charge compression ignition (HCCI) combustion with hot residual gas in order to verify the possibility of using it as a combustion sensor. The ion current signal for single-cycle HCCI combustion had a simple profile and effectively one maximum value. There is a possibility that a similar ion current signal corresponding to the completed reaction can be obtained, depending on the location of the probe during HCCI combustion. The ionization reaction for HCCI combustion is affected by the chemical ionization reaction with heat release, and there is a possibility that the ion current can be used to detect heat release corresponding to the chemical ionization reaction. A strong correlation between the timing of the integrated ion current and the timing of the mass fraction burned is observed. The timing of the mass fraction burned is assumed from the timing of the integrated ion current, and the mass fraction burned (up to 70 per cent) can be determined, even if the engine driving condition changes within the scope of the test. There is a correlation between the timing of the maximum ion-current and the maximum rate of heat release, and there is a possibility that the maximum value of the rate of heat release can be inferred by detecting the timing of the maximum ion current. There is a correlation between the timing of the maximum ion current and the timing of the maximum pressure at each cycle. Therefore, it may be possible to monitor the variation of the HCCI combustion phasing.

Carbon stripper foil preparation by ion beam sputtering with 3.5 keV Kr ions

Heavy ion-beam sputtering with low beam voltage was found to be applicable for the preparation of long-lived carbon stripper foils. A test foil (25 μg/cm 2) made by this method survived an integrated ion current of 6213 mC/cm 2 corresponding a lifetime of about 200 times the best commercially available foil made by evaporation-condensation. The present method can be expected to be applicable to magnetron sputtering for mass production of carbon stripper foils.

Lignin analyzer based on pyrolysis‐mass spectrometry of pulp in hydrogen or helium

The lignin content of wood, paper, pulp, or other materials containing lignin (such as filter paper soaked in black liquor) is readily determined by flash pyrolysis of the sample at approximately 550 °C in a reducing atmosphere of hydrogen or in an inert atmosphere of helium followed by a rapid analysis of the product gas by a mass spectrometer. The heated pyrolysis unit as fabricated, comprises a small platinum cup welded to an electrically heated stainless‐steel ribbon with control units for programmed short duration (1.5 s, approximately) heating and for continuous flow of hydrogen or helium. The pyrolysis products enter an electron‐ionization‐mode mass spectrometer for spectral evaluation. Lignin content is obtained from certain ratios of integrated ion currents of many mass spectral lines, the ratios being linearly related to the Kappa number or Klason lignin. The Kappa number can be obtained from a few milligram sample in 3 min which is at least ten times faster than a Kappa number determination by the Standard Chemical Method. The present instrument can measure Kappa numbers in the whole range from 0 to 200 without any readjustments.

Measurement of endogenous leucine enkephalin in canine thalamus by high-performance liquid chromatography and field desorption mass spectrometry

A combination of high-performance liquid chromatography and field desorption mass spectrometry is used to quantify endogenous amounts of leucine enkephalin in canine thalamus tissue. Reversed-phase high-performance liquid chromatography effects rapid high resolution of brain neuropeptides using a triethylamine formate buffer. An internal standard, 2Ala-leucine-enkephalin, is used. Field desorption mass spectra of neuropeptides generally display only protonated molecular ions. (M + H) + ion currents of endogenous leucine enkephalin and internal standard were integrated by field desorption mass spectral-selected ion monitoring techniques. The ratio of the two integrated ion currents was used to calculate endogenous amount of leu-enkephalin in thalamus tissue extracts. Leucine enkephalin was determined in this structurally unambiguous fashion in canine thalamus tissue at 50 ng/g thalamus tissue, or the 50 part per billion level.

The use of a sample-independent standard for direct insertion mass spectrometric quantitations

Methyl stearate was tested as an internal standard for the mass spectrometric quantitation of six structurally different compounds because of the limited availability of sample-like standards (labelled analogues, etc.). Based on the selected ion monitoring and integrated ion current techniques, satisfactory (correlation coefficient >0.99) calibration curves were obtained in all cases by plotting the log ratio of evaporated weights vs the log ratio of integrated ion currents (sample to standard). This indicates that the use of sample-independent standards instead of compounds closely related to the sample, provides a versatile and generally applicable quantitation technique with a precision better than ± 15% at the ng level.

Analysis of complex mixtures by computer controlled high resolution mass spectrometry: I—application to atmospheric aerosol composition

Techniques are described for the computer reduction and identification of complex high resolution mass spectrometric data to yield qualitative and quantitative data for one hundred or more components in a complex mixture. The procedures described have been applied to direct insertion probe separations coupled with high resolution mass spectrometry. Two mass spectrometer computer systems are described in this paper. The basic techniques were developed at the University of Washington utilizing an A.E.I. MS-9 high resolution mass spectrometer, which was interfaced with a PDP-12 digital computer. The most recent system utilizes a Nova II computer interfaced to a Varian MAT 311 mass spectrometer. Programs were developed which were capable of determining the accurate mass (± 3 millimass) of up to 1000 ions per scan. High accuracy limited mass searches were first used to reduce the data. A correlation program was developed to resolve pure mass spectra from the composite mass spectral data using data obtained from the limited mass searches. A library search program was developed which used up to four major identifying masses and their relative abundances in addition to relative volatilization temperatures (probe) or relative retention times (gas chromatographic) for obtaining qualitative data. Quantitative data for each compound were obtained by comparing the total integrated ion current of one ion fragment to that of an internal standard. Instrumental and computer parameters are discussed with respect to the accuracy of the quantitative work. Final computer results gave compound identification and concentrations in μg/m3 or ppm. The use of this analytical technique for the analysis of complex mixtures of pollutants present in atmospheric aerosols is described.

Absolute, unambiguous ultramicroanalysis of metabolites present in complex biological extracts.

THE analysis of substances of biogenic interest is usually difficult and often ambiguous because the metabolite of interest is usually present at low concentration in a complex mixture. Quantitation usually proceeds via pre-fractionation (organic solvent extraction, ion exchange or absorption), chromatographic separation and then a relatively specific chromogenic or fluorogenic reaction either directly on the chromatogram or, after elution, in solution. The certainty of identification using these, or variants of these, procedures is limited. This is particularly so in the field of biochemical psychiatry where over the past few years there have been numerous examples of chromatographically separated chromogenic factors which have meant different things to different people (further details in ref. 1). We present here preliminary data on the use of a new technique—the so-called “integrated ion current (IIC) technique”—involving the high resolution double focusing mass spectrometer (in our case, the MS9 manufactured by Associated Electrical Industries).

Mass spectrometric and chromatographic techniques for determination of polycyclic compounds

Abstract

Application of the integrated ion-current technique to the study of rare-earth chelates

Several substituted acetylacetones have been prepared and reacted with holmium to give tris chelates of the form HoL 3. One of these chelates has been converted to a tetrakis chelate of the form NaHoL 4. The mass spectra of these compounds have been studied and the integrated ion currents at significant m/e values have been related to the amounts of metal chelates evaporated into the ion source of the mass spectrometer. The shape of the integrated ion-current curve is shown to give information about the nature of the evaporation process. When the β-diketone (L) is asymmetrical as in the case of 1,1,1-trifluoro-5,5-dimethylhexan-2,4-dione, the existence of geometrical isomers of the chelate, HoL 3, is reflected in the shape of the integrated ion-current curve, which shows fine structure. The results of mass spectrometric studies are compared with those of the sublimation and gas chromatographic behaviour of the metal chelates.

The mass spectrometry of metal chelates—IIOxinates of common metals

The mass spectra of the oxinates of zinc, iron(III), manganese(II), nickel, cobalt, aluminium, copper and magnesium have been measured. Concentrations of several of these chelates have been related to the integrated ion currents recorded at a significant m/e value during evaporation of the sample in the source of an A.E.I. M.S.9 mass spectrometer. The structural significance of some of the mass spectra is discussed.

Mass spectrometry of metal chelates—I: Detection on the picogram scale

A method has been developed for the detection and estimation of metals in the form of chelates in amounts down to 10 −12 g. The chelate is evaporated into the source of a mass spectrometer and a continuous record of the ion current at a significant mass number is made. The integrated ion current is directly proportional to the concentration of metal chelate.

Chemical Analysis by Means of Mattauch-Herzog Type Double Focusing Mass Spectrograph III.

Three different methods have been examined to express the densities of spectrograms recorded on an Ilford Q2plate in our Mattauch-Herzog type mass spectrograph. The exposures have been decided by the integrated ion currents measured by the monitor electrode, thus their fluctuations have been eliminated without any internal standard. As examples, the isotopic abundances of Cu and Zn have been measured with appropriate calibration curves . The precision and accuracy of the measurements have been briefly discussed.