Matrix-Assisted Laser Desorption/Ionization (MALDI) is used for soft ionization of macromolecular analytes, for subsequent analysis by Mass Spectrometry. The analyte is first co-crystallized into a laser energizable matrix and then bombarded with laser pulses to induce desorption and ionization of matrix and analyte molecules. Infinita Lab, USA, offers this test to clients in the USA and across the world, through its vast laboratory network.
Matrix-Assisted Laser Desorption/Ionization (MALDI) is a technique used for ionizing macromolecular analytes without fragmenting them, for subsequent analysis by Mass Spectrometry. MALDI utilizes the assistance of laser energizable matrix molecules, to perform Laser Desorption/Ionization of a prepared sample containing the analyte.The sample is prepared by co-crystallization of analyte and matrix molecules from a solution and deposition onto a target plate, for excitation by laser energy. The co-crystallized matrix is then bombarded by laser pulses, inducing localized desorption and gas-phase ionization of co-crystallized molecules. The analyte ions are then identified and quantified by Mass Spectrometry. MALDI usually employs UV lasers, though occasional use of Infrared lasers has been reported.
Suitable matrix compounds display low mass relative to the analyte and high laser energy absorbance, generally in the UV range. They typically have ‘conjugated pi-bond’ structures for UV absorbance, polar functional groups to form aqueous solutions with analyte and acidic groups to facilitate deprotonation. Proven combinations of analytes and matrix compounds are used for MALDI analysis. MALDI requires a very low concentration of analyte, which is mostly dispersed in the interstices of the crystallized matrix. For example, Cinnamic Acid derivatives, which display high absorbance of UV radiation, co-crystallized with polypeptide analytes can desorb/ionize one picomole of analyte for detection. Modern MALDI techniques and instrumentation, can detect molecular masses upto 350,000 Da.
Since MALDI causes minimal break-up of macromolecules, it is used for analysis of a range of biopolymers such as peptides, proteins, oligonucleotides, carbohydrates as well as synthetic macromolecules.
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Common Uses of Matrix-Assisted Laser Desorption/Ionization (MALDI)
In Biochemistry, for Peptide mass fingerprinting
Determining molar mass distribution or degree of polymerization of synthetic polymers
Identification and molecular mass determination of biopolymers
In Microbiology, for the identification of microorganisms
Advantages of Matrix-Assisted Laser Desorption/Ionization (MALDI)
Sensitive, with high mass accuracy
Small quantity of analyte is sufficient
Limitations of Matrix-Assisted Laser Desorption/Ionization (MALDI)
The Matrix assisted ionization produces limited analyte ions, leading to lower mass sensitivity
Suitable sample preparation is needed
Soft ionization not effective for all molecules
Industrial Applications of Matrix-Assisted Laser Desorption/Ionization (MALDI)
ASTM E572 test method covers the analysis of stainless and alloy steels by Wavelength Dispersive X-ray Fluorescence Spectrometry (WDXRF). It provides rapid, multi-element determinations with sufficient accuracy to assure product quality.
The ASTM D2674 is a standard test method for the analysis of sulfochromate etches solution used in the surface preparation of aluminum. The ASTM D2674 standard specifies a method for determining the efficacy of an etchant used to prepare the surface of aluminum alloys for subsequent adhesive bonding.
An immunological method for quantization of Hevea Natural Rubber (HNRL) proteins using rabbit anti-HNRL serum. Rabbits immunized with HNRL proteins react to the majority of the proteins present, and their sera have the capability to detect most if not all the proteins in HNRL.
ASTM G65 measures the resistance of metallic materials to abrasion using the dry sand/rubber wheel apparatus. The quality, durability, and toughness of the sample are determined using this test. Metallic materials are ranked in their resistance to scratching abrasion under a controlled environment.
ASTM E2141 test methods provide accelerated aging and monitoring of the performance of time-dependent electrochromic devices (ECD) integrated in insulating glass units (IGU). This test helps to understand the relative serviceability of electrochromic glazings applied on ECD.
ASTM C724 test method is used in analyzing the quality and ease of maintenance of a ceramic decoration on architectural-type glass. This test method is useful in the acknowledgment of technical standards.
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