Analytical Instrument Documents

Matrix assisted laser desorption/ionization (MALDI) combined with in-source decay (ISD) is a useful tool for doing top-down sequencing of intact proteins. In this work, we measured and compared the ISD fragment ions generated for several proteins by using both the high resolution MALDI-Spiral mode and the high sensitivity MALDI-Linear mode available on the JEOL SpiralTOF MALDI-MS system.

The SpiralTOF’s unique multi-turn ion optics package a very long (17-meter) flight path within a 1-meter space. Electric sectors and Matsuda plates provide perfect focusing to eliminate ion loss due to beam divergence. Post-source decay fragments occurring in the flight path are eliminated by the ion optics, providing a clean and artifact-free background.

Matrix assisted laser desorption ionization (MALDI) is a powerful and useful ionization technique that is commonly used for the analysis of biomolecules such as peptides and proteins. Typically, α-Cyano-4-hydroxycinnamic acid (CHCA) is the matrix used for MALDI peptide measurement. Recently, a new matrix “α-Cyano-4-chlorocinnamic acid (CClCA)” was investigated for peptide analysis [1]. In this study, we demonstrate the measurement of a BSA digest to evaluate the improvement in peptide sensitivity with CClCA in comparison with CHCA by using the JMSS3000 SpiralTOF MS system.

Matrix assisted laser desorption/ionization (MALDI) combined with in-source decay (ISD) is a useful tool for doing top-down sequencing of intact proteins. This technique can provide enough information to determine both N- and C-terminal sequences. In this work, we measured the ISD fragment ions generated for several peptides using the JEOL SpiralTOF MALDI-MS system.

High molecular weight polymers are often MS-silent due to their inherent high dispersity (ĐM) or detected in the high mass range with low resolving power. High-resolution mass spectrometry (HRMS) is indeed limited to the low mass range (< 3000 Da) for an unambiguous evaluation of the nature of repeating units and/or end-groups or the isolation of isobaric compounds. An “on-plate” alkaline degradation has thus been developed as a sample pre-treatment on the MALDI target with tenths of ng of polymer to cut long industrial polyester chains into short oligomers amenable to MALDI-HRMS [1]. The complexity of the associated mass spectra can be greatly reduced with the appropriate resolution-enhanced Kendrick mass defect (KMD) analysis using the “fraction base” option of msRepeatFinder to produce compositional maps.

High molecular weight polymers are often MS-silent due to their inherent high dispersity (ĐM) or detected in the high mass range with low resolving power. An “on-plate” alkaline degradation has thus been developed as a sample pre-treatment on the MALDI target with tenths of ng of polymer to cut long industrial polyester chains into short oligomers amenable to MALDI-HRMS [1]. The complicated mass spectrum of P3HB oligomers was analyzed by fraction base Kendrick mass defect (KMD) plot [2]. Fraction base KMD analysis has been developed from the regular KMD analysis to modify the aspect and separation capabilities of the KMD plots depending on a divisor (noted X) in addition to the base unit (noted R) via a fraction base R/X [3].

Industrial materials are often evaluated by surface analysis instruments that provide information on surface elements, bonding states, and functional groups. However, there are limited options for surface analysis techniques that provide molecular weight and molecular structure information for organic compounds present on surfaces. Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI-TOFMS) is a soft ionization technique that can be used to analyze surfaces in order to estimate elemental compositions with accurate mass measurements, obtain structural information by using MS/MS, and map surface compounds by using MS imaging. MALDI-TOFMS uses a high voltage on the target plate to accelerate the ions into the TOFMS analyzer. Therefore, the target plates are conductive and are typically made of stainless steel. MALDI imaging mass spectrometry is widely used for analyzing organic substances on frozen tissue sections. In this case, a frozen tissue section with a thickness of about 10 μm is placed on a conductive glass slide coated with an indium tin oxide (ITO) film. However, for the analysis of industrial products, the target organic compounds are on nonconductive substrates such as resins with millimeter thicknesses. MALDI-TOFMS surface measurements using nonconductive substrates lead to a reduction in mass resolution and a significant decrease in ion intensity due to surface charging. This problem can be solved by pretreating the surface with gold vapor deposition in order to change it from nonconductive to conductive. This method was previously shown to work well in MSTips No. 204 in which the gold vapor deposition method was applied to the MALDI-MS imaging analysis of inks on paper. In this report, we used gold vapor deposition to look at samples on the surface of a 1 mm thick acrylic plate.

Matrix assisted laser desorption ionization (MALDI) time-flight mass spectrometer (TOFMS) is a powerful tool to identify the repeat units and end groups of polymers. The mass spectra of polymers can be easily interpreted because MALDI can generate singly-charged ions over a wide mass range. MALDI is a soft ionization method that uses "matrix" compounds and “cationization agents” to assist the ionization process of polymers. Typically, sample, matrix and cationization agent are dissolved in the same solvent. These solutions are pre-mixed and placed drop-wise on the target plate to make cocrystals (dried droplet method). However, this procedure cannot be applied to polymers that are insoluble or only slightly soluble. To solve this problem, solvent-free methods have been developed [1-4] for these situations. In this report, we analyzed low molecular weight polyethylene by using a solvent-free method and then using a high mass-resolution MALDI-TOFMS “SpiralTOF™” system for the analysis.

Ethylene oxide (EO) – propylene oxide (PO) copolymers have been used as components of various functional materials. Detailed analyses of them, however, still remain challenging. As it turns out, it is difficult to detect all of the components by using mass spectrometry alone without chromatographic separation due to ion suppression effects. In this work we analyzed an EO-PO random copolymer by using an LC – MALDI-SpiralTOF MS system, with the expectation of detecting more components as a result of reduced ion suppression effects.

Recently, dioxin is being analyzed in a wide variety of materials. In addition to conventional environmental samples such as fly ash and exhaust gas, biological and water samples such as blood, breast milk, and tap water are being analyzed. Because the dioxin concentrations in these samples are extremely low, ultra high sensitivity is one of the critical features required for analytical systems. Higher sensitivity in analysis is obtained by improving the performance of the mass spectrometer as well as improving the injection techniques for the gas chromatograph. The PTV (Programmable Temperature Vaporizer) inlet is an example of such injection techniques. The PTV inlet selectively eliminates solvents at the sample injector, allows for large volume sample injection, and concentrates the compounds of interest onto the GC column.(1) However, the PTV inlet does not support solvents whose boiling point is higher than that of toluene because it is designed to separate solvents from compounds in question by controlling the injector temperature alone. Also, contamination builds up rapidly inside the injector. To address these problems, we investigated the analysis of dioxins by using a multi-dimensional gas chromatograph (MD-GC) with a large-volume injector as a high-sensitivity analytical method for dioxins.