Application of thermospray liquid chromatography-mass spectrometry to the simultaneous quantification of tracer concentrations of isotopically labelled carbamazepine epoxide and steady-state levels of carbamazepine and carbamazepine epoxide

A thermospray high-performance liquid chromatography-mass spectrometry method for the separation and quantification of tracer concentrations of isotopically labelled carbamazepine epoxide ([15N, 13C]CBZE) in the presence of steady-state levels of the anticonvulsant carbamazepine (CBZ) and its epoxide metabolite (CBZE) has been developed. The technique does not require derivatization, demonstrates little or no thermal degradation of the analytes, provides increased specificity not available from conventional high-performance liquid chromatography, and has a detection limit of 500 pg for CBZE on-column. The method, incorporating d4-CBZ and d4-CBZE as internal standards, allows precise and accurate determination of the analytes with good reproducibility and stability.     

Chiral liquid chromatography tandem mass spectrometry in the determination of the configuration of 2-hydroxyglutaric acid in urine

D-2-Hydroxyglutaric aciduria and L-2-hydroxyglutaric aciduria are two distinct inherited metabolic diseases. The accurate diagnosis of the exact disorder relies on the determination of the configuration of the enantiomers, either D-2-hydroxyglutaric acid or L-2-hydroxyglutaric acid excreted in excess in urine of patients. The enantiomeric chiral separation of 2-hydroxyglutaric acid was achieved using a ristocetin A glycopeptide antibiotic silica gel bonded column. The chiral column was interfaced with a tandem mass spectrometer for the purpose of specifically detecting the eluting 2-hydroxyglutaric acid. Tandem mass spectrometry was employed using an electrospray ion source in the negative ion mode. Three parent-to-daughter transitions under collision-induced dissociation conditions were used to detect only 2-hydroxyglutaric acid. The two forms of the compound were satisfactorily separated with almost baseline resolution at 4.95 and 5.5 min. Three known patients with 2-hydroxyglutaric aciduria were identified to have L-2-hydroxyglutaric aciduria. The method is simple, selective, rapid, and free from interference.     

Coordination compounds of hydrazine derivatives with transition metals. Part 27. Coordination chemistry of 4-amino-3-alkyl-5-thio-1,2,4-triazolines and 4-amino-5-oxo-3-thioxo-6-alkyl-2,3,4,5-tetrahydro-1,2,4-triazines

Summary Mono-, bis- and tris-ligand nickel(II) and cobalt(II) complexes with 4 amino-3-alkyl-5-thio-1,2,4-triazolines (HRL) (R=H, Me, or Et) and 4-amino-5-oxo-3-thioxo-6-methyl-2,3,4,5-tetrahydro-1,2,4-triazine (HL') have been prepared and characterized. In these complexes both HRL and HL' are in the neutral thione form. Nickel(II) and cobalt(II) complexes with mononegative thiolate ligands have been also isolated.The reaction of HL' with copper(II) salts in a molar ration of 11 results in the formation of [Cu(HL')X] (X=Cl or Br) and Cu(L')X (X=NO₃ or CH₃COO). However, in the presence of a large excess of HL' the reaction proceeds with partial reduction of Cu^II and both [Cu(HL')X₂] and [Cu(HL')₂]X have been isolated and characterized. The mechanism of copper(II) reduction by HL' is discussed.     

Synthesis of [1,5-A]Pyrimidinone Ring Derivatives

Cyclodehydrogenation of the benzalhydrazino derivatives 5 and 6 gave 6-cyano-7-(4-methoxyphenyl)- 2-phenyl-5-oxo-1,2,4-triazolo[1,5-a]pyrimidine (8) and 6-cyano-7-(4-methoxyphenyl)-4-methyl-2-phenyl- 5-oxo-1,2,4-triazolo[1,5-a]pyrimidine (9) respectively. Melhylation, acetylation and benzylation of 8 gave the corresponding N-methyl, acetyl and benzyl derivatives 10-12 . Methylation of 5 with dimethylsulfate gave 2-benzalhydrazino-5-cyano-3-methyl-6-(4-methoxyphenyl)-3,4-dihydropyrimidin-4-one (6) , of which the reaction with acetic anhydride in pyridine afforded the N-acetylbenzalhydrazino derivative 15 . The latter was also prepared from acetylation of 5 followed by medthylation with iodomethane. Acetylation of 5 with boiling acetic anhydride afforded the diacetyl derivative 16 , whereas its benzylation gave the mono-N-benzyl derivative 14 .     

Radiolysis of 2-propanol in presence of 2-hexanoylfuran

2-hexanoyl-5-(2-hydroxy 2-propyl)furan (HHPF), has been investigated as the principal product of radiolysis of 2-hexanoyl-furan (HF) in 2-propanol. The effect of absorbed dose on the product yields has been examined. Possible mechanisms for the formation of radiolytic products are discussed.     

Radiolysis of 2-propanol in the presence of 1-(2-furanyl)-1-hexanone; The yields of hydrogen and methane

Hydrogen and methane produced during the -radiolysis of 2-propanol have been measured in the absence and presence of 0.1 and 0.01 M ketone (1-(2-furanyl)-1-hexanone) at different doses. In the absence of ketone at 100 kGy, the hydrogen and methane yields were found to be G(H₂)=5.1 and G(CH₄)=2.02. At lower ketone concentrations the hydrogen and methane yields were G(H₂)=4.35 and G(CH₄)=1.83, while higher concentrations decreased the above values to G(H₂)=2.95 and G(CH₄)=1.33, respectively. The radiolytic mechanism is discussed in detail.     

Selective determination of catechin, epicatechin and ascorbic acid in human urine using chiral capillary electrophoresis

Chiral CE was successfully applied to the separation and quantification of catechin, epicatechin and ascorbic acid in some commercial drinks and human urine. Analysis involved the separation of analytes in less than 5.0 min at 240 nm with an untreated fused-silica capillary under hydrodynamic injection mode. The running buffer consisted of 50 mM borate buffer with 3 mM beta-CD at pH 8.35. Detection limits for catechin, epicatechin and ascorbic acid were 0.028, 0.011 and 0.004 microg/mL, respectively. Linearity was investigated by selecting the ranges of calibration according to the amount of analytes in urine giving correlation coefficient percent (% r(2)) ranging between 99.4 and 99.6 at 99% confidence level. The maximum urinary excretion of catechin and epicatechin were noted at 2.0 and 4.0 h of the administrated dose. Unchanged catechin, epicatechin and ascorbic acid amounted to about 1.500, 8.696 and 0.003% of the administered dose in the 48.0 h urine collection. The proposed method achieved 99.2% completeness (n = 20) in urine media.     

Group analysis for natural convection from a vertical plate

The steady laminar natural convection of a fluid having chemical reaction of order n$n$ past a semi-infinite vertical plate is considered. The solution of the problem by means of one-parameter group method reduces the number of independent variables by one leading to a system of nonlinear ordinary differential equations. Two different similarity transformations are found. In each case the set of differential equations are solved numerically using Runge–Kutta and the shooting method. For each transformation different Schmidt numbers and chemical reaction orders are tested.     

Determination of catechin isomers in human plasma subsequent to green tea ingestion using chiral capillary electrophoresis with a high-sensitivity cell

A simple and reliable analytical electrophoretic method using chiral capillary electrophoresis (CCE) with a high-sensitivity cell of special design has been established for simultaneous determination of (+)-catechin (C) and (-)-epicatechin (EC) in aqueous and human plasma media. The application of a capillary with high-sensitivity cell has led to an improvement of 10-fold and 5-fold time-corrected peak area over a standard cell and a capillary with bubble cell, respectively. Analysis has involved the electrophoretic separation of C and EC in less than 4.0 min at 210 nm. The running buffer consist of 50.0 mmol L(-1) borate buffer with 1.0 mmol L(-1) beta-cyclodextrin at pH 8.5. CCE system has been proved for its intended use by applying procedure starting from calibration of CE instrument into validation of all experimental parameters. The resolution between catechin isomers under optimal conditions has been found to be more than 3.0. The detection limits of C and EC have been calculated to be 3.2 and 1.0 ng mL(-1), respectively. Good linearity has been obtained with correlation coefficient (r(2)) ranging between 0.995 and 0.996 at 99% confidence level (CL). Application of the proposed method to human plasma after ingestion of green tea has successfully been achieved and has statistically been proved. The unchanged amounts of C and EC in plasma were about 17.4 and 1.8% of the administered dose after 2 h of starting tea ingestion. The detection limits of C and EC in human plasma at 210 nm were 4.1 and 1.5 ng mL(-1), respectively.     

A novel assignment method in the 13C NMR spectroscopy of coumarins and furocoumarins

The signal shifts caused by replacing the carbonyl oxygen by sulphur represent a valuable method of assignment of the ¹³C NMR signals in coumarins and furocoumarins substituted at the benzoic and furanoic rings.