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The very fast separation and identification of isomeric small substances with a molecular weight under 800 Da is still a challenge for high-throughput analysis. Inadequate chromatographic or spectrometric separation hampers an unequivocal identification of isomers, which may be recorded as a sum parameter. Reversed-phase liquid chromatography can be considered a generic method for the separation of isomers. However, a separation is usually achieved within minutes and not milliseconds as is typical for ion mobility spectrometry. The aim of this study, therefore, was to investigate the potential of IMS to separate small isomeric compounds. Hence, 23 substances divided into 11 isomeric groups have been selected. Among them, cancer drugs, hormones, pain relievers and others are contained. Three ion mobility spectrometers with different separation principles were compared with respect to their resolving performance. These systems comprised a traveling wave ion mobility spectrometer, a differential ion mobility spectrometer and a differential mobility analyzer. For reference, the chromatographic resolution and peak capacity was determined by high-performance liquid chromatography using a reversed phase. [ABSTRACT FROM AUTHOR]

A novel reversed phase ion-pair micro HPLC system with on-line fluorescence detection has been developed systematically and studied for the determination of cadmium in its bio-available fractions of soil samples. In this system, a micro ODS column of 1.0 mm i.d.×150 mm length and a mobile phase containing 6 mmol L-1 8-hydroxyquinoline 5-sulphonic acid (HQS), 3 mmol L-1 cetyltrimethylammonium bromide (CTMABr), 10 mmol L-1 acetic acid-acetate buffer (pH 5.1) as well as 50% acetonitrile at 50 μL min-1 flow rate were employed to determine cadmium with a 2 μL flow cell through its fluorescence at 518 nm under 338 nm excitation. Furthermore, the composition of Cd-HQS chelate formed on the column was confirmed to be [Cd(HQS)2]2- through a log–log plot method, and then combined with the ion-pair reagent by the electrostatic force under the chromatographic condition proposed. With such a method, the detection limit of cadmium was 8.48 ng mL-1 (3σ) with 1 μL sample injection, and the linear range for the determination of cadmium was 30–800 ng mL-1 (R2=0.992). This method has been successfully applied to determination of cadmium in its bio-available fractions of BCR-483 and soil samples without interference from other coexistent metal ions. The RSD (n=6) was less than 7.3%. The results were in agreement with the indicative value for BCR-483 and those for the soil samples obtained by ICP-MS with a pretreatment of bis(1,1,3,3-tetramethylbutyl) phosphinic acid extraction. [ABSTRACT FROM AUTHOR]