I. A. Rodin

Transformations of asymmetric dimethylhydrazine in soils

High-performance liquid chromatography and mass spectrometry were used to find that the decomposition of asymmetric dimethylhydrazine (I) in soils occurred with the formation of dimethylamine, formaldehyde dimethylhydrazone, methylhydrazine, trimethylhydrazine, N-nitrosodimethylamine, 1-methyl-1,2,4-triazole, formic acid dimethylhydrazide, 1,5,5-trimethylformazane, 1-methyl-1,6-dihydro-1,2,4,5-tetrazine, N,N-dimethylaminoguanidine, and several other products. High-reliability structure identification was achieved using independent methods, including gas chromatography-mass spectrometry, 1H and 13C NMR, and UV spectroscopy, and by measuring retention times and spectral characteristics after the counter-synthesis of the suggested structures. The products of the decomposition of I potentially capable of forming initial I and characterized by high migration mobility in soils were identified.

Spectrophotometric and fluorometric methods for the determination of hydrazine and its methylated analogues

The review considers the main approaches used for the determination of hydrazine and its derivatives by spectrophotometric and fluorometric methods. Examples of their determination in real samples are presented. The advantages and disadvantages of the proposed analysis scenarios are discussed and the trends of the method development are considered.

1-Formyl-2,2-dimethylhydrazine as a new decomposition product of 1,1-dimethylhydrazine

A new decomposition product of 1,1-dimethylhydrazine (UDMH), 1-formyl-2,2-dimethylhydrazine (FDMH), was found in water and soil samples. The formation of FDMH was confirmed by LC-MS and NMR studies. The possibility of FDMH conversion to initial UDMH by alkaline hydrolysis was shown.

Determination of the products of the transformation of unsymmetrical dimethylhydrazine in soils using chromatography/mass spectrometry

An approach is proposed for the simultaneous determination of formic acid N,N-dimethylhydrazide and 1-methyl-1-H-1,2,4-triazole (ecotoxicants formed upon the oxidative transformation of unsymmetrical dimethylhydrazine) in soils in the concentration range 0.05–50 mg/kg using gas chromatography/mass spectrometry. The conditions for the quantitative extraction of the components by continuous periodic extraction with methanol have been found. The adsorption of formic acid N,N-dimethylhydrazide and 1-methyl-1-H-1,2,4-triazole from solutions by soils of different types has been studied and a method has been proposed for preparing uniform model soil samples with the required contaminant concentrations.

Determination of the products of the oxidative transformation of unsymmetrical dimethylhydrazine in soils by liquid chromatography/mass spectrometry

Procedures are developed on the basis of liquid chromatography/mass spectrometry for determining the transformation products of unsymmetrical dimethylhydrazine in soils: formic acid dimethylhydrazide (1-formyl-2,2-dimethylhydrazine, analytical range 0.01–20 mg/kg), 1-methyl-1,2,4-triazole (analytical range 0.05–100 mg/kg), 1,1-dimethylguanidine (analytical range 0.05–100 mg/kg), and dimethylamine (analytical range 0.25–250 mg/kg). The measurements were performed in the mode of chemical ionization under atmospheric pressure followed by the registration of positive ions corresponding to the protonated forms of the components to be determined. A version of ion chromatography was elaborated for separation. For sample pretreatment, the use of extraction with methanol (for 1-formyl-2,2-dimethylhydrazine) and ultrasonic extraction with a weakly alkaline buffer solution (for other substances) was proposed.

A validated LC-MS/MS method for rapid determination of methotrexate in human saliva and its application to an excretion evaluation study

A sensitive and simple method for the methotrexate quantification was developed using aminopterin as internal standard. Methotrexate is an anticancer agent that is widely used in a variety of human cancers including primary central nervous system lymphoma. The compound was quantified by liquid-chromatography coupled to electrospray ionization (positive ion-mode) low-energy collision dissociation-tandem mass spectrometry. Quantitative detection was by multiple reaction monitoring of the transitions of the [M+H]+ ion of MTX to its common product ion at m/z 308.4 and of aminopterin at m/z 441.2→m/z 294.0. The method demonstrated linearity over at least three orders of magnitude and had a detection limit of 1ng/ml for methotrexate. A run time of less than 8.0min for each sample made it possible to analyze a large number of human saliva samples per day. Application of this procedure was demonstrated to a saliva excretion study of methotrexate on the samples obtained after an intravenously administration of 1mg/kg/dose of methotrexate to six patients with acute lymphoblastic leukemia.

Combination of HPLC-MS and QAMS as a new analytical approach for determination of saponins in ginseng containing products.

Graphical abstract Figure. No Caption available. HighlightsWe developed a novel HPLC–MS‐QAMS approach for characterization of ginsenosides.Single ion monitoring mode for sapogenin‐type characteristic ions was suggested.HPLC–MS and HPLC‐UV with both QAMS and external standard methods were compared.Several quality control parameters were evaluated using the approaches developed. ABSTRACT Conventional liquid chromatographic methods coupled with ultraviolet detection with low‐wavelength range are lacking selectivity and sensitivity to determine both polar and less polar ginsenosides. Also the lack of standard substances for such quality control methods is leading to development of the approaches using single standard for quantitative analysis of multi‐component system (QAMS). The objective of present study was to establish and compare for the first time liquid chromatography–ultraviolet detection and liquid chromatography–mass spectrometry QAMS methods for the simultaneous determination of protopanaxatriol‐type and protopanaxadiol‐type ginsenosides in a variety of ginseng products. Sixteen polar and less polar ginsenosides were separated on a reversed‐phase C18‐column (150mm × 2.0 mm, 2.2 &mgr;m) with a mobile phase consisting of 0.1% formic acid in water and acetonitrile. Components were then detected by means of ultraviolet and mass spectrometry detection. Characteristic sapogenin fragmentation signals with m/z 423 and 425 for two major groups of ginseng saponins allowed their simultaneous determination in a single chromatographic run, while the use of ultraviolet detection tends to give overvalued results. Structural correlation between the relative response factors and saponin structure was demonstrated. The method was linear (R2 >0.999) and sensitive (LODs, 0.01–0.03 mg/mL) within the concentration range tested. Concentrations of individual ginsenosides and several quality control parameters were determined in ginseng root extracts and commercial ginseng products of different types (root slices, tablets and tea samples), and results showed that ginsenoside content can be successfully measured by means of QAMS approach.

RAPID METHOD FOR THE DETECTION OF METABOLITE OF SULFUR MUSTARD 1,1′-SULFONYLBIS[2-S-(N-ACETYLCYSTEINYL)ETHANE] IN PLASMA AND URINE BY LIQUID CHROMATOGRAPHY-NEGATIVE ELECTROSPRAY-TANDEM MASS SPECTROMETRY

A method for detection of an important biological marker, 1,1′-sulfonylbis[2-S-(N-acetylcysteinyl)ethane] (SBSNAE) of sulfur mustard agent [bis-(2-chloroethyl)sulfide] (HD) in human plasma and rat urine to quantify HD exposure, is presented. It employs solid-phase extraction sample preparation, followed by liquid-chromatography-negative ion-electrospray ionization-tandem mass spectrometry. The method limit of detection (LOD) for SBSNAE is 0.05 ng/mL for rat urine samples with relative standard deviations of less than 10%. Application of this procedure was demonstrated in the HD animal exposure model. Rats were exposed intravenously to 5 mg/kg HD, and SBSNAE levels in urine samples were analyzed for 22 days post-exposure.

Lewisite metabolites detection in urine by liquid chromatography–tandem mass spectrometry

A sensitive and simple method for the quantification and for the detection of 2-chlorovinylarsonous (CVAA) and 2-chlorovinylarsonic (CVAOA) acids was developed. CVAA and CVOA are important biological markers in human and rat urine specific to lewisite (chlorovinylarsonous chloride compounds) exposure. The developed assay was based on the use of solid-phase extraction (SPE) followed by liquid-chromatography coupled to electrospray ionization (negative ion-mode) low-energy collision dissociation-tandem mass spectrometry (ESI-CID-MS/MS). The method demonstrated linearity over at least three orders of magnitude and had a detection limit (LOD) of 0.5 ng/ml for CVAA and 3 ng/ml for CVAOA. The relative standard deviations for the quality control samples ranged from 6 to 11%. Application of this procedure was demonstrated in the lewisite animals exposure model. Rats were exposed intravenously by no lethal doses of lewisite and markers levels in urine samples were analyzed for 21 days post-exposure.

Use of ion and ion-pair chromatography with mass spectrometric detection to determine unsymmetrical dimethylhydrazine and its transformation products

The conditions of the simultaneous determination of unsymmetrical dimethylhydrazine (UDMH) and products of its transformation in aqueous solutions with ion and ion-pair chromatography and mass-spectrometric detection in the electrospray ionization mode have been selected. It has been shown that up to seven components may be determined within the limits of detection at the μg/L level. The application of the developed methods to the analysis of solutions with an initial UDMH concentration of 500 mg/L that had undergone spontaneous oxidation by atmospheric oxygen has been demonstrated. The accumulation of formic acid dimethylhydrazide, 1-methyl-1,2,4-triazole and dimethylamine has been found.