title: Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of partially depolymerised carboxymethyl cellulose.
abstract: Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) of partially depolymerised carboxymethyl cellulose (CMC) have been investigated. The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised CMC were collected from size-exclusion chromatography (SEC) and further investigated by MALDI-TOFMS. 2,5-Dihydroxybenzoic acid was used as matrix, dissolved in H(2)O due to the poor solubility of CMC in suitable organic solvents. The samples were dried by two methods, in ambient atmosphere and at reduced pressure. Under reduced pressure the sample spot homogeneity increased. This drying method, however, produced additional adduct peaks in the mass spectra originating from ion exchange on the CMC oligomers. Analysis of CMC could be performed in both negative and positive ion modes. Mass discrimination and variation in ionisation efficiency were demonstrated by comparing mass spectra with SEC data. Measurements of the degree of substitution (DS) were performed on three CMCs with different DS values, which were depolymerised in trifluoroacetic acid. The three CMCs were easily distinguished from one another, but the obtained DS values deviated from the values supplied by the manufacturer.
authors.affiliation: Division of Technical Analytical Chemistry, Lund University, PO Box 124, S-221 00 Lund, Sweden.
authors.forename: Dane
authors.initials: D
authors.lastname: Momcilovic
authors.forename: Bengt
authors.initials: B
authors.lastname: Wittgren
authors.forename: Karl-Gustav
authors.initials: KG
authors.lastname: Wahlund
authors.forename: Johan
authors.initials: J
authors.lastname: Karlsson
authors.forename: Gunnar
authors.initials: G
authors.lastname: Brinkmalm
mesh_terms: D016477:Artifacts; D001704:Biopolymers / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D002266:Carboxymethylcellulose Sodium / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D001704:Biopolymers; D002266:Carboxymethylcellulose Sodium