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The capabilities of two-dimensional separation using a high irradiance laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) were demonstrated in this paper. Ions were separated via their initial kinetic energy in one dimension and their mass-to-charge ratios in the other dimension. Investigation of the transient ion profiles after laser pulses revealed that the separation of analyte ions from multiply charged ions and gas species ions was achieved. Comparison of mass spectra in the normal accumulation mode and in the two-dimensional separation mode indicated that the relative sensitivity coefficients are stable and close to their true values in the two-dimensional separation mode, especially for trace elements that are prone to interference. 10.1021/ac902981j

The simultaneous determination of nonmetallic elements in solid samples is difficult owing to their discrepant physical and chemical properties. We developed a high-irradiance laser ionization orthogonal time-of-flight mass spectrometry (LI-O-TOFMS) system and applied it for the determination of nonmetallic elements in solids. Helium was used as the buffer gas at 250 Pa in the source chamber; the laser irradiance was about 7 x 1010 W/[cm.sup.2]. A series of artificial standards containing B, C, N, O, F, Si, P, S, CI, As, Br, Se, I, and Te were used. Explicit spectra were obtained with only a little interference from gas species and doubly charged matrix ions. Standardless semiquantitative analysis could be accomplished with a novel sampling methodology to obtain near-uniform sensitivity coefficients for different elements. Limits of detection (LOD) at microgram per gram level and a dynamic range of 6 orders of magnitude were achieved for most nonmetallic elements. 10.1021/ac9026912

A newly developed high irradianee laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) was employed for the elemental analysis of residues, which were prepared by evaporating mixed salt solutions. The residues were first characterized in terms of shape and elemental distribution. In TOFMS detection, all of the metal elements in the residue can be observed in the spectra. Relative sensitivity coefficients for different elements were within 1 order of magnitude, which meets semiquantitative analysis criteria. By calculating the individual masses from the ablated area due to a single laser shot, the absolute detection limit reached 7 x [10.sup.-15], g fur most metal elements. The results indicate that LI-O-TOFMS is capable of performing ultratrace elemental qualification and quantification, with an absolute limit of detection and an absolute limit of quantitation at the femtogram level. 10.1021/ac901615k

A compact high-irradiance laser ionization time-of-flight mass spectrometry system has been developed for the multielemental analysis of solids. Helium was introduced into the ion source as a buffer gas to cool high kinetic energy ions and suppress the interference of multicharged ions. A special pulse train repelling mode was used to achieve explicit spectra. Two quantitative methods are described for the laser ionization mass spectrometry in this paper. The first of these is the routine calibration curve quantitation, in which various matrix-matched standards are required; the second method, which is based on the uniform correlation between the signal and elemental concentration of different samples, is more convenient and covers a typical dynamic range of 6 orders. All the investigations and results indicate satisfactory performance of the newly developed instrument and its applicability for simultaneous multielemental analysis of solid samples.

Laser desorption laser postionization time-of-flight mass spectrometry (L2MS) was applied for unambiguous discrimination of pigment-based inks in blue, black, and red gel pens and molecular imaging of equivocal documents in a quasi-non-destructive way. In comparison to laser desorption mass spectrometry (LD-MS), additional discriminatory information on ink components is acquired uniquely, facilitating the distinct differentiation of various pigmented gel inks. More importantly, diversified images of additional characteristic ions achieved using L2MS offer reliable support to discriminate forged documents and decipher important hidden contents. Apart from minimized matrix effect and maximized ionization yield, direct and confirmatory identification of forged documents is achieved successfully without solvent or matrix involved, not only eliminating unwanted damage and contamination to the samples but significantly shortening the overall analysis time. In addition, L2MS is a minimally destructive approach with tiny analyte consumption. With these appealing qualities, L2MS imaging is poised to be a powerful tool for confirmatory surface analysis of complex pigment-based samples.Weight and see: Highly distinct and comprehensive images of counterfeit documents with blue-pigmented gel inks are achieved successfully, due to the high sensitivity and increased ion yield of laser desorption laser postionization time-of-flight mass spectrometry. The hidden important contents of the obliterated documents are visually deciphered with the help of the additional chemical information. [ABSTRACT FROM AUTHOR]