Non-covalent binding and selective fluorescent sensing of dipyrone with a carbocyanine dye and cetyltrimethylammonium bromide.

The work is aimed at the search of selective fluorescent sensors without using specific artificial receptors, antibodies, enzymes etc. With this end in view, methods based on non-covalent binding of target analytes are sought. We observed dramatic changes in the emission spectrum of a carbocyanine dye in a micellar surfactant solution (cetyltrimethylammonium bromide, CTAB) in the presence of dipyrone (metamizol, analgin): the 480 nm band intensity increases with a simultaneous decrease in intensity in near-IR region (720 nm). MALDI and NMR-1H data show the intact molecules of dipyrone and the dye. The detection can be performed in the presence of other organic species and inorganic salts. Dipyrone testing is feasible within 5 × 10-7-5 × 10-4M with RSDs of 3.5% by using a visualizer instead of a spectrofluorimeter.

Letter: α,ω,N,N-Dimethylaminoalkylamines as possible derivatization agents for the analysis of small carbonyl compounds by low energy mass spectrometry.

Reaction with α,ω-N,N-dimethylaminoalkylamines (2-dimethylaminoethylamine, 3- dimethylaminopropylamine, 4-dimethylaminobutylamine) to form Schiff bases followed by quaternization of the N,N-dimethylamino group by alkyl (deuteroalkyl) halides to generate fixed-charge fragments is suggested for the characterization of carbonyl compounds by matrix-assisted laser desorption ionization (MALDI) mass spectrometry. As model objects, some aliphatic aldehydes and alicyclic and steroid ketones were involved in the modification. Using gas chromatography mass spectrometry, the first modification stage proved to be quantitative. Not only the MALDI conditions but also the nanostructurized target provided spectra that revealed peaks for the cationic parts of derivatives. It was shown that the use of deuterated alkyl halides allows one to prepare deuterium-labeled standards for possible quantitative analysis.

Reactive matrices for matrix-assisted laser desorption/ionization mass spectrometry of primary amines.

Some aromatic carbonyl compounds [2,4-dihydroxybenzaldehyde (2,4-DHBA), 2,5- dihydroxyacetophenone (DHAP), 2,3,5-trihydroxybenzaldehyde and 2,4-dinitrobenzaldehyde] were examined as potential reactive matrices for the analysis of mono-, di-, and polyamines by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Although all the above compounds readily and quantitatively react with primary amines to form Schiff bases (the completeness of the reactions was proved by gas chromatography MS of derivatized aliphatic amines), only DHBA and DHAP provide efficient desorption/ionization under MALDI conditions. This means that two these aromatic carbonyl compounds can simultaneously exhibit properties of both derivatization agents and efficient matrices for MALDI-MS analysis. The use of such reactive matrices eliminates the need to perform additional derivatization experiments. With the aid of DHBA and DHAP, it was confirmed that each individual oligomer of polypropylene glycols and co- polyethylene/propylene glycols contained two terminal amino groups. To calculate the number of NH2 groups, mass increments of the introduced groups and a difference in the masses of cations attached to the initial and derivatized amines were used. The suggested approach, involving the application of the same reactive matrices, was applied to the determination of a number of NH(2) groups in individual oligomers of branched polyethyleneimines (PEIs) by MALDI-MS. In this case, DHAP appeared to be the best reactive matrix. The dependence of the number of NH(2) groups on the quantity of monomeric units and branching of each individual PEI oligomer is shown.

Simple approach to derivatization of alcohols and phenols for the analysis by matrix(surface)-assisted laser desorption/ionization time-of-flight mass spectrometry.

RATIONALE: Direct analysis of hydroxyl-containing compounds by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) methods is not always possible due to the neutral character of analytes. The suggested fixed-charge derivatization may increase the ionization efficiency for various alcohols and phenols in specific matrix- and surface-activated LDI conditions. METHODS: Aliphatic and steroid alcohols, as well as chlorophenols, were converted into various ammonioacetyl derivatives, containing a covalently bonded charged group, by reaction with bromoacetyl chloride and amine-type compounds such as triethylamine, pyridine or quinoline. The derivatives are suitable for MALDI-time-of-flight (TOF)MS analysis. RESULTS: Triethylammoniumacetyl, pyridyliumacetyl and quinoliniumacetyl derivatives were prepared from aliphatic alcohols, some sterols and chlorinated phenols in one stage with quantitative yields. The derivatives produced characteristic MALDI and SALDI mass spectra. CONCLUSIONS: The suggested derivatization approach for the modification of alcohols is simple and does not require any expensive reagents. The derivatives include a fixed charge and produce intense signals in MALDI (preferentially non-acidic matrices) and matrix-free SALDI (nanostructured target) conditions. Corresponding mass spectra are suitable for the determination of molecular mass and profiling of alcohols.

Characterization of low-molecular weight iodine-terminated polyethylenes by gas chromatography/mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with the use of derivatization.

Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, in conjunction with various derivatization approaches, have been applied to structure determination of individual oligomers and molecular-mass distributions (MMD) in low-molecular mass polyethylene having an iodine terminus. Direct GC/MS analysis has shown that the samples under investigation composed of polyethyelene-iodides (major components) and n-alkanes. Exchange reaction with methanol in the presence of NaOH gave rise to methoxy-derivatives and n-alkenes. Electron ionization mass spectra have shown that the former contained terminal methoxy groups indicating the terminal position of the iodine atom in the initial oligomers. MMD parameters have been determined with the aid of MALDI mass spectrometry followed by preliminary derivatization-formation of covalently bonded charge through the reaction of iodides with triphenylphosphine, trialkylamines, pyridine or quinoline. The mass spectra revealed well-resolved peaks for cationic parts of derivatized oligomers allowing the determination of MMD. The latter values have been compared with those calculated from GC/MS data.

Matrix effect in matrix-assisted laser desorption/ionization mass spectra of derivatized oligomeric polyols.

RATIONALE: Herein we describe a strong matrix effect observed in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectra of silylated glycerol alkoxylates and manifested in the loss of the silyl groups in the presence of carboxyl-containing matrices. METHODS: Commercially available glycerol alkoxylates containing three end OH groups as well as three matrices - 2,5-dihydroxybenzoic acid (DHB), 3-indoleacrylic acid (IAA) and 1,8,9-anthracenetriol (dithranol) - were chosen for the investigation. N,O-Bis(trimethylsilyl)trifluoroacetamide containing 1% trimethylchlorosilane, acetic anhydride and a formylation mixture (formic acid/acetyl chloride) were used for derivatization. Initial oligomers and derivatized products were analyzed by MALDI-ToF-mass spectrometry (MS) on an Autoflex II instrument, equipped with a nitrogen laser (λ 337 nm), in positive ion reflectron mode. RESULTS: Only [M + Na](+) ions were observed for underivatized polymers and for completely derivatized polymers in the presence of DHB and dithranol, respectively. In the case of IAA the mass spectra revealed sets of peaks for underivatized, and for partially and completely derivatized oligomers. No similar 'matrix effect' was observed in the case of acylated glycerol alkoxylates (acyl = formyl, acetyl): only peaks for completely derivatized oligomers were obtained in all matrices: DHB, IAA and dithranol. Using 1,9-nonandiol, we showed that the 'matrix effect' was due to trans-silylation of carboxyl-containing matrices (DHB and IAA) during co-crystallization of silylated oligomers and matrices. CONCLUSIONS: The obtained results show that matrix molecules can participate as reactive species in MALDI-ToF-MS experiments. The matrix should be carefully chosen when a derivatization approach is applied because the analysis of spectra of the completely derivatized products is particularly desirable in the quantitative determination of functional end-groups.

Derivatization aids in the determination of end groups in poly(alkylene glycol)s by matrix-assisted laser desorption/ionization mass spectrometry.

A method for end-group characterization by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry following preliminary derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and capryloyl chloride is described and applied to poly(alkylene glycol)s. The MALDI mass spectra of the products revealed peaks of sodiated derivative cations, whose shift by the respective increments allowed the determination of the number of end functional groups with active hydrogens. This approach is particularly efficient for the distinction of cyclic and linear dehydration products among minor components.