Pilar Arias Abrodo

Experimental design applied to the analysis of volatile compounds in apple juice by headspace solid-phase microextraction.

A simple and fast method based on solid-phase microextraction (SPME) followed by fast gas chromatography (Fast GC) has been developed for the analysis of volatile compounds in Asturian apple juices employed in the cider production. Three different fiber coatings have been checked (PDMS, PDMS-DVB and CAR-PDMS) and PDMS-DVB has been presented to be the most suitable one. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The use of Fast GC allowed the separation of 14 compounds (esters, aldehydes and alcohols) in approximately 4 min, clearly reducing the analysis time when compared to conventional GC. Good linearity, recoveries and repeatability of the solid-phase microextraction were obtained with r(2) values, recoveries and relative standard deviations ranging from 0.9822 to 0.9998, 83.2 to 109.8% and 0.5 to 11.7%, respectively, using standard solution.

A novel method for the determination of total 1,3-octanediols in apple juice via 1,3-dioxanes by solid-phase microextraction and high-speed gas chromatography

In this work, a novel, simple and fast method based on solid-phase microextraction (SPME) followed by high-speed gas chromatography (HSGC) was developed for the analysis of total 1,3-octanediols in apple juices by means of derivatization reaction to volatile 1,3-dioxanes. The derivatization reaction, SPME conditions, glycosidically bound fraction and 1,3-nonanediol as a surrogate standard were studied. The formation of 1,3-dioxanes from 1,3-diols was confirmed by GC-MS. The method was validated obtaining a regression coefficient (r(2)) of 0.9996, precisions between 0.3 and 9.8%, extraction recoveries in the range 94.7-112.2% and LOD of 2.9 microg l(-1). Experimental design has been employed in the optimization of extraction factors and robustness assessment. The method was applied to the analysis of 21 Asturian apple varieties finding a double reciprocal relationship between the concentrations of saturated and unsaturated 1,3-octanediol.

Fluorimetric determination of calcium by ion-pair extraction with cryptand 2.2.1 and eosin

A fluorimetric study on the extraction of calcium into 1,2-dichloroethane as an ion-pair, formed between the cryptand 2.2.1-calcium complex and the eosinate anion, is described. Optimum conditions for extraction are established and a new fluorimetric determination of ultratraces of calcium is proposed. A linear working range from 1.5 ng ml−1 (detection limit) to 100 ng ml−1 of calcium and a relative standard deviation of ± 2.9% at the 70 ng ml−1 level are obtained. The equilibrium constants involved in the extraction process have been calculated and refined by the Letagrop-DISTR program. The proposed method has been tested for the direct determination of calcium in sugars.

Ion-pair extraction and fluorimetric determination of ultratraces of strontium with cryptand 2.2.2 and eosin

A highly sensitive and selective fluorimetric determination of strontium is proposed, based on solvent extraction of the ion-pair formed between the cationic complex of Sr2+ with cryptand 2.2.2 and eosinate as counter ion. A linear working range from 0.7 ng/ml (limit of detection) to 500 ng/ml of strontium and a relative standard deviation of 3.5% at the 100 ng/ml level are obtained. The metal: ligand: counter ion molecular ratio in the extracted mononuclear ion-pair is 1 ∶ 1 ∶ 1. The equilibrium constants involved in the extraction process were calculated.

Modification of a Conventional High Performance Liquid Chromatograph for Use in High Speed Liquid Chromatography

Abstract A practical procedure is described for the modification of a conventional HPLC system to a set‐up compatible with high speed HPLC requirements. A number of experimental parameters, such as extra‐column volume, extra‐column band broadening, effectiveness, and dwell volume, were examined to characterize and demonstrate the suitability of the modified system for use in high speed HPLC applications. In addition, an injector bypass is presented as an alternative to reduce the pressure damage suffered by short columns packed with microparticles.

High Speed Liquid Chromatography for In-Process Control of Sultamicillin

Abstract A fast HPLC method has been developed for simultaneous determination of sultamicillin and its synthesis precursors. The analytes are separated in 2.5 min by means of a Kromasil 100 C18 column (50 mm × 2.1 mm i.d., 3.5 µm) at 25°C. The mobile phase (A: 5 mM KH2PO4 and 20 mM KCl adjusted to pH 6.0 with H3PO4 plus 1% THF and B: acetonitrile with 1% THF) was pumped at a flow rate of 0.5 mL min−1 according to the fast gradient mode: 0–0.9 min, 40% B; 0.9–1.0 min, 85% B; 1.0–2.5 min, 85% B; 2.5–2.6 min, 40% B, 2.6–4.0 min, 40% B. Detection was by ultraviolet absorbance at 205 nm. The method was validated in accordance with the International Conference on Harmonisation (ICH) guidelines, good accuracy, intermediate precision (≤3.8%), and linearity being observed for all compounds. This method is sensitive (limits of detection ranged between 0.1–1.1 mg l−1) and selective for quantifying sultamicillin and its synthesis precursors and could be used for in-process control.