Pirjo Kuronen

Reversed-phase liquid chromatographic separation and simultaneous profiling of steroidal glycoalkaloids and their aglycones

Improved and simplified reversed-phase liquid chromatographic conditions for the separation and simultaneous profiling of both steroidal glycoalkaloids and their aglycones, having solanidane- or spirosolane-type structures, are described. The most reproducible retention behavior for these ionizable compounds on C18 columns was achieved under isocratic and gradient elution conditions using acetonitrile in combination with triethylammonium phosphate buffer at pH 3.0, when basic functional groups of solutes and silanol groups on the silica are fully protonated minimizing ionic interactions. Gradient elution was the only feasible approach for the simultaneous separation of steroidal glycoalkaloids and their aglycones. A Zorbax SB C18 column, specially designed for low-pH separations, showed good performance in critical separations. The impurities of the commercial tomatine and tomatidine standards were studied and confirmed using mass spectrometric, liquid chromatographic and thin-layer chromatographic methods.

High-performance liquid chromatographic screening method for mycotoxins using new retention indexes and diode array detection

A reversed-phase high-performance liquid chromatographic (RP-HPLC) screening method for the determination of mycotoxins has been developed. The toxins were characterized by retention indexes and on-line UV spectra produced with a diode array detector (DAD). Retention indexes of mycotoxins exhibiting a wide range of polarities and chemical structures were determined during linear gradient elution with an acetonitrile/ water solvent system. The retention index scale was based on the use of a new homologous series of 1-[4-(2,3-dihydroxypropoxy)phenyl]-1-alkanones (D-compounds) as internal standards. The mycotoxins studied were: five trichothecenes of group A: T-2 toxin (T-2), HT-2 toxin (HT-2), diacetoxyscirpenol (DAS), neosolaniol (NEO), and an isomer of neosolaniol (NEO isomer); three trichothecenes of group B: nivalenol (NIV), deoxynivalenol (DON), and fusarenon-X (FUS-X); four aflatoxins: B1, B2, G1, and G2; and five other mycotoxins: sterigmatocystin (STE), zearalenone (ZEA), ochratoxin A (OCH A), citrinin (CIT), and patulin (PAT).

High-performance liquid chromatographic separation and isolation of the methanolic allomerization products of chlorophyll a

Abstract Isocratic normal-phase HPLC on a silica column with diode-array detection provided a powerful means for the analytical separation and preparative isolation of seven methanolic allomerization products of chlorophyll a. Diastereomeric selectivity was achieved for 132(R,S)-hydroxychlorophyll a, 132(R,S)-methoxychlorophyll a and the Mg complex of 31,32-didehydro-151-hydroxy-151(R,S)-methoxyrhodochlorin-15-acetic acid δ-lactone 152-methyl 173-phytyl ester. The Mg complex of 31,32-didehydrorhodochlorin-15-glyoxylic acid 131,152-dimethyl 173-phytyl ester was also isolated in high purity. Reversed-phase HPLC did not result in an acceptable separation in spite of using several different brands of reversed-phase C18 columns and mobile phase compositions. The identification of the allomerization products was based on UV-Vis and 1H NMR spectra, retention times and co-elution with authentic samples. The observed formation of small amounts of numerous side-products is interpreted as further evidence for the free-radical mechanism of the allomerization.

Comparison of commercial solid-phase extraction sorbents for the sample preparation of potato glycoalkaloids.

In this study five different commercial sorbents C18, SCX, CN, Certify and Oasis HLB were compared for the solid-phase extraction of potato glycoalkaloids. The recoveries were determined using alpha-solanine, alpha-chaconine and alpha-tomatine, which contained dehydrotomatine as an impurity, as standard compounds. The samples were analysed by reversed-phase liquid chromatography under gradient elution conditions using a Zorbax Rx-C18 column and acetonitrile-25 mM triethylammonium phosphate buffer (pH 3.0) as the mobile phase. The highest recovery (approximately 100%) was achieved with Oasis HLB (60 mg) cartridges. An acetic acid extract of wild Solanum brevidens leaf material was used for the testing of a clean-up procedure. The SCX proved to be the most selective and efficient for removing the undesired components from the leaf extract.

Use of 1-[p-(2,3-dihydropropoxy)phenyl]-1-alkanones as retention index standards in the identification of trichothecenes by liquid chromatography—thermospray and dynamic fast atom bombardment mass spectrometry

Abstract A homologous series of 1-[ p -2,3-dihydroxypropxy)phenyl]-1-alkanones (D-standards) were used as retention index standards in the detection of trichothecenes by reversed-phase (RP) gradient elution liquid chromatography—mass spectrometry (LC—MS). Thermospray (TSP) and dynamic fast atom bomabardment (dynamic FAB) were used as LC—MS interfaces. The retention indices provide independent identification of compounds, improving the reliability of the identification by LC—MS. The TSP and dynamic FAb mass spectra of the D-standards and trichothecenes are presented.

Reversed-phase high-performance liquid chromatographic screening method for serum steroids using retention index and diode-array detection

A multisteroid screening method has been developed based on the use of 1-[4-(2,3-dihydroxypropoxy)phenyl]-1-alkanones as retention index standards and UV absorbance spectra recorded on-line with a diode-array detector using reversed-phase high-performance liquid chromatographic gradient elution with acetonitrile and water. The effect of chromatographic conditions on retention indices of steroids were studied. The method was tentatively applied to profiling of steroids in serum samples.