Characterisation of riverine particulate organic matter by pyrolysis-gas chromatography-mass spectrometry.

Particulate matter samples were collected in the mountainous section and river mouth at the Tech River basin, south France, during flood (December 1996) and summer (September 1997) periods. Suspended material was analysed by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and 23 identified pyrolysis products were divided into five main fractions: aminosugars, aromatic hydrocarbons, polysaccharides, phenols and nitrogenous compounds. Analysis of relative amounts of these fractions revealed neither significant spatial nor temporal changes in the particulate organic matter composition. Nevertheless, their specific composition showed that during flooding there is a certain homogeneity in the composition of the riverine particulate organic matter, with more degraded material of pedogenic (allochthonous) character, and during the summer the results suggest the presence of two components, allochthonous and autochthonous.

Rotavirus associated diarrhoea during infancy in the city of S. Luís (MA), Brazil: a two-year longitudinal study.

A total of 479 diarrhoeic children and 337 children without diarrhoea (controls) less than 5 years old were investigated in a two-year study in the city of S. Luís (MA), with the purpose to determine the incidence, the age distribution and the seasonality of rotaviruses, as well as to establish the severity of the disease in this region between the North and the Northeast of Brazil. rotavirus incidence was highest in children of the 1st. year of life, showing an average of 25% per year among the diarrhoeic patients attending the two main hospitals and three health units at the periphery of the city. It was shown that rotaviruses are significant enteropathogens in children less than 18 months old. Frequency of rotaviruses dropped in diarrhoeic patients 18 to 23 months old to only 4%, the same percentage observed in children of the control group. A typical seasonal distribution of rotaviruses was not seen during the two years of study. There was a peak in the incidence of rotaviruses in 1986, during the rainy season, and two peaks in 1987, one in the rainy season and one in the dry season. It was also shown that severity of diarrhoea in rotavirus positive cases was higher than in the negative cases. Rotavirus diarrhoeic patients had more loose stools per day, and higher frequencies of vomiting and fever, resulting more often (> 2 times) in moderate or severe dehydration. Finally, it is concluded that the introduction of immunoprophylaxis may reduce significantly the high mortality rates in early childhood observed in S. Luís.

Kinetic disposition of (+)-S- and (-)-R-sotalol enantiomers in cardiac patients with tachyarrhythmias using an improved HPLC-fluorescence stereoselective method.

Since the enantioselective pharmacokinetic profiles of R,S-sotalol in cardiac patients are controversial, the present investigation aimed to study the kinetic disposition of sotalol enantiomers in patients with tachycardia. Thirteen cardiac patients, who gave their written consent, were included (6F/7M; 53 +/- 12 yrs, 66 +/- 13 kg, 163 +/- 8 cm height). They had tachycardia, normal renal function and had been chronically treated with tablets of sotalol 160 mg b.i.d. The patients were submitted to blood samples collection at zero, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10 and 12 h after drug administration. The quantitation of sotalol enantiomers were performed by a stereoselective HPLC method with fluorescence detection previously published. A one open compartment model was applied and the main pharmacokinetic parameters obtained for R-/S-sotalol were, respectively (Mean +/- SD): CSSMAX = 1007 +/- 307/1040 +/- 340 ng/mL; TMAX = 1.82 +/- 0.6/1.83 +/- 0.6 h; AUCSST = 6959 +/- 2153/7388 +/- 2563 ng.h/mL; CISSr/F = 2.7 +/- 1.2/2.5 +/- 1.2 mL/min/kg and VdSS/F = 1.9 +/- 0.9/2.0 +/- 1.0 L/kg. The pharmacokinetic parameters of R,S-sotalol were within the published range and the kinetic parameters for the isomers were grouped as two independent samples and statistically compared. In conclusion, stereoselective pharmacokinetic for sotalol was not observed in cardiac arrhythmic patients, i.e., both R- and S-sotalol enantiomers have the same pharmacokinetic profile.

An improved HPLC-fluorescence stereoselective method for analysis of (+)-S- and (-)-R-sotalol enantiomers in plasma sample.

A simplified high performance chromatographic method (HPLC) was performed for sotalol enantiomers in plasma samples for purposes of investigation of the kinetic disposition of racemic sotalol in cardiac arrhythmic patients under multiple dose and multidrug therapy regimens. After addition of NaCl:Na2CO3 (4:1) and plasma protein precipitation by acetonitrile:methanol mixture (1:1) the supernatant was evaporated. The residue containing sotalol racemate was submitted to derivatization reaction with (-)-menthylcloroformate to R(-)- and S(+)-sotalol diastereoisomers. The diastereoisomers were resolved in HPLC, by a C18 column with fluorescent detection under lexcitation = 235 nm and lemission = 310 nm. The retention times for R- and S-sotalol were 20 and 22 minutes while that of internal standard S(-)-atenolol, was 17 minutes. The detection limit for each enantiomer was 12.5 ng/mL and intra-day/inter-day coefficients of variation were less than 10% for each enantiomer within a concentration range of 200 and 2000 ng/mL. The method was appropriate for the objective proposed.