Method development for the determination of 1,1-dimethylhydrazine by the high-performance liquid chromatography-mass spectrometry technique

Unsymmetrical dimethyl hydrazine is highly toxic, carcinogenic compound, widely used for organic synthesis and drug development. Therefore, due to its high reactivity, direct analysis is problematic. Current study proposes to use derivatization reaction to increase selectivity and sensitivity of high-performance liquid chromatography-mass spectrometry method. Different derivatization agents were tested and optimal reaction media was found. Derivatization was performed by using small amounts of reagents to lower the cost of analysis. The full validation of the method was performed and it can be used in a routine control in pharmaceutical analysis. Method sensitivity is 0.15 ppm, and linearity range is 0.15-2.70 ppm.

Zwitterionic sulfonates as m/z shift reagents for 5-methylcytosine detection in deoxyribonucleic acids (DNA) using flow injection analysis and electrospray ionization mass spectrometry

5-Methylcytosine (5-MC) is an important epigenetic modification of DNA. Abnormally high concentrations of this substance appear because of the hypermethylation of cytosine. Therefore, the measurement of the quantity of this compound in mammals is of great importance. Recently, we reported that several imidazolium-based zwitterionic sulfonates form complexes with 5-MC in solution, which can be studied by electrospray ionisation mass spectrometry (ESI-MS). It is shown in this paper that such an association can be utilised for the detection of 5-MC in a DNA sample using high-throughput a flow injection analysis ESI-MS method. A variety of the sulfonate zwitterions have been tested as m/z shift reagents to increase the selectivity of the analysis. It is shown that either of the zwitterions can be used without the loss of sensitivity. The performance of the method was tested in terms of linearity range, sensitivity, intra- and between-day precision and accuracy, matrix effect and carryover. The method described is characterised by simplicity, a good limit of quantitation (1 pg injected) and low run times (at least 50 injections per hour). In addition, high-performance liquid chromatography and tandem mass spectrometry are not required. The possibility exists to widen the scope of the method to other amidine-containing compounds present in more complicated matrices.

Electrospray ionization mass spectrometry of non-covalent complexes formed between N-alkylimidazolium-containing zwitterionic sulfonates and protonated bases

This paper describes non-covalent complexes between zwitterionic 3-(1-alkyl-3N-imidazolio)- propane-1-sulfonates and different amines. Electrospray ionization (ESI) mass spectrometry and collision- induced dissociation were used to measure the stability of such complexes in solution and in the gas phase. Generally, zwitterionic sulfonates formed more abundant complexes with protonated 5-methylcytosine (5-MCH) than with aliphatic amines. The results show that the association constants and half-dissociation threshold energies of these complexes nonlinearly depend on the alkyl chain length of the zwitterion. It is shown that the complexes with the lowest stability exist in acetonitrile solution or in the gas phase. The factors responsible for this complicated behavior are discussed. The structure of the complexes was investigated by quantum chemical calculations using molecular mechanics and density functional theory. Hydrogen bonding is proposed as the main type of interaction responsible for the stability of ion-zwitterion complexes. In summary, the information obtained in this study could be used for the development of the new derivatization reagents for some compounds containing amidinium groups, like 5-MCH, to increase selectivity of ESI-based methods.

Positive and negative electrospray ionization-collision-induced dissociation of sulfur- containing zwitterionic liquids

The mass spectrometric properties of several (1,2-dimethyl-1H-imidazol-3-ium-3-yl)-alkane-1-sulfonates (alkane=ethyl, propyl and butyl) are investigated in this study. These substances, named zwitterionic liquids (ZILs), were synthesized using classical transformations and analyzed in positive and negative electrospray ionization mode using collision-induced dissociation (0-50 eV). We have also performed regioselective deuterium labeling of the alkyl chain of 3-(1,2-dimethyl-1H-imidazol-3-ium-3-yl)-propane-1-sulfonates. Thus, the mass spectra of isotopically-labeled compounds were used for the confirmation of fragmentation pathways of ZILs. Briefly, the data obtained in this study show that the fragmentation of ZILs is dependent on the alkyl chain length between the imidazolium ring and the sulfonate group. In positive electrospray mode, the main fragments are the imidazolium ring containing even electron ions. On the other hand, in negative electrospray mode, sulfur-containing radical-anions are dominant.

Collision-induced dissociation of imidazolium-based zwitterionic liquids

Fragmentation pathways of some imidazolium based zwitterionic liquids-3-(3-alkyl-1-imidazolio)- propane sulfonates and 3-(2-methyl-3-alkyl-1-imidazolio)-propane sulfonates -- have been studied by tandem electrospray mass spectrometry and collision-induced dissociation. The relative abundances of the lowest energy fragment ions depend on the length of the alkyl chain at the (II)N of the imidazolium ring and the cone voltage. The first fragment ions originate from the scission of C(non aromatic)-N bond of compounds investigated, but with increasing collision energy, scission of C-C bonds occurs. Aggregates of the general formula [(M + H)(x) + (M)(y)](+) (x;y = 1-2) formed. Methyl substituted zwitterionic liquids show higher molecular stability than 3-(3-alkyl-1-imidazolio)-propane sulfonates.

Potato (Solanum tuberosum) juice exerts an anticonvulsant effect in mice through binding to GABA receptors

Naturally occurring benzodiazepines have been identified in regular food such as wheat and potato, but there is still no evidence that potato extracts can affect CNS responses in vivo. Here we found that undiluted potato juice and potato juice diluted with saline 1 : 2 administered 10 min intracisternally ( I. C.) and 30 min per os before bicuculline exerted significant anticonvulsant activity in the bicuculline-induced seizure threshold test in mice. In vitro, potato juice from different harvests at dilution series from 10 % to 0.000001 %, diluted 100,000-fold, displaced 50 % of gamma-aminobutyric acid (GABA) receptor ligand [ (3)H]GABA and diluted 40-fold displaced 50 % of [(3)H]flunitrazepam from binding sites in mice forebrain membranes. The low content of diazepam (0.04 +/- 0.01 mg/kg) determined by HPLC and mass spectrometry in the potato extracts could not sustain the anticonvulsant activity of potato juice in vivo; therefore we hypothesized that potato juice might contain GABA (A) receptor GABA-site active compounds. The findings of this study suggest that potato juice as well as potato taken as food may have the capacity of influencing brain GABA-ergic activity.