Complementary use of hyphenated purge-and-trap gas chromatography techniques and sensory analysis in the aroma profiling of strawberries (Fragaria ananassa).

The aroma compositions of Fragaria ananassa varieties are assessed by purge-and-trap high-resolution gas chromatography. Gas chromatography/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy allow the identification of 93 components from which 21 are for the first time described as constituents of strawberry aroma. Despite the complexity of the aroma, sensory properties are assigned to 40 components as perceived by three independent testers by application of a sniffing technique to the chromatographic effluent. The data are used for comparative sensory characterization of strawberry varieties by means of principal component analysis.

Bioequivalence assessment of diltiazem preparations by means of discriminant analysis of data from solid-phase extraction and liquid chromatography.

A solid-phase extraction technique for sample clean-up coupled with a new LC procedure is reported for the assay of diltiazem in plasma. The use of disposable cartridges provides selective extraction and easy automation. A new LC system based on LiChrospher RP 60 Select B columns is described. For routine analysis, the procedure provides a rapid simultaneous clean-up of several samples prior to chromatography and reproducible recoveries over a concentration range of 10-800 ng. The procedure was used to analyse the plasma samples from a bioequivalence study of three commercial diltiazem preparations. The pharmacokinetic parameters in 12 healthy male volunteers were determined and the assessment of bioequivalence was conducted by discriminant analysis.

[Bioavailability of 3 formulations of diltiazem]. / Estudo da biodisponibilidade de três formulações de diltiazem.

The plasma concentration profiles of diltiazem were determined in three series of twelve male volunteers to whom a single doses of 60 mg of diltiazem was administered. Three commercial diltiazem preparations, labelled A, B and C were evaluated. The plasmas were analysed for diltiazem concentration by a new HPLC technique and from the data on concentration profiles, the pharmacokinetic parameters, Cmax, Tmax, T1/2, AUC0-12 and AUC0-infinity were calculated from the function derived by computerized curve fitting and integration. Computerized Pattern Analysis was used for product comparison, based on the plasmatic concentration and the calculated pharmacokinetic data. Differences observed between the three products regarding plasmatic levels and pharmacokinetic, were within the range values defined by individual variation, and were similar to the ones described in the literature for single doses of diltiazem - 60 mg. However, the multiparametric analysis showed that the studied preparations formed two distinct groups: preparation B was different from preparations A and C. This means that preparation B was not bioequivalent to preparations A and C, both considered as bioequivalent.

Capillary gas chromatography of amino acids, including asparagine and glutamine: sensitive gas chromatographic-mass spectrometric and selected ion monitoring gas chromatographic-mass spectrometric detection of the N,O(S)-tert.-butyldimethylsilyl derivatives.

Amino acids and the amino acid amides glutamine and asparagine can be simultaneously derivatized to the corresponding N,O(S)-tert.-butyldimethylsilyl derivatives in a one-step reaction with N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide in acetonitrile. The solution is used directly for gas chromatography (GC). Losses due to evaporation steps are avoided. Except for the more basic amino acids, derivatization occurs at room temperature. Lysine, arginine and histidine require additional heating at 150 degrees C for 2.5 h in order to complete derivatization. The derivatization has high reproducibility. The response factors relative to norvaline or cycloleucine lie between 0.40 and 1.30. Arginine is the most difficult amino acid to derivatize. The size of the tert.-butyldimethylsilyl (TBDMS) group prevents multiple silylation of the nitrogen atoms. Only a single peak is observed for each compound. Twenty-seven amino acid (and glutamine and asparagine) derivatives were simultaneously chromatographed and well separated in a single run on a 25 m X 0.20 mm I.D. glass capillary column coated with OV-1. The TBDMS derivatives possess very characteristic EI mass spectra at 70 eV, with intense diagnostic ions. This makes them very appropriate for GC-mass spectrometric (MS) work and selected ion monitoring GC-MS at the picomole level. The detection limit for arginine as the TBDMS derivative is less than 0.3 ng. The usefulness of the method is illustrated by the detection of amino acids in a peptide hydrolysate obtained from 1 microgram of bovin insulin B-chain.