Chiral Nano-Liquid Chromatography and Dispersive Liquid-Liquid Microextraction Applied to the Analysis of Antifungal Drugs in Milk

Abstract

A novel chromatographic application in chiral separation by using the nano-LC technique is here reported. The chiral recognition of 12 antifungal drugs was obtained through a 75 µm I.D. fused-silica capillary, which was packed with a CSP-cellulose 3,5-dichlorophenylcarbamate (CDCPC), by means of a lab-made slurry packing procedure. The mobile phase composition and the experimental conditions were optimized in order to find the optimum chiral separation for some selected racemic mixtures of imidazole and triazole derivatives. Some important parameters, such as retention faction, enantioresolution, peak efficiency, and peak shape, were investigated as a function of the mobile phase (pH, water content, type and concentration of both the buffer and the organic modifier, and solvent dilution composition). Within one run lasting 25 min, at a flow rate of approximately 400 nL min−1, eight couples of enantiomers were baseline-resolved and four of them were separated in less than 25 min. The method was then applied to milk samples, which were pretreated using a classical dispersive liquid–liquid microextraction technique preceded by protein precipitation. Finally, the DLLME-nano-LC–UV method was validated in a matrix following the main FDA guidelines for bioanalytical methods.

Enantiomeric analysis of drugs in water samples by using liquid–liquid microextraction and nano‐liquid chromatography

“…An essential aspect of the mobile phase composition study is the change of the organic, water, and additive content to enhance specific CSP‐analyte interactions, especially enantioselective ones. In our previous chiral studies, it has been reported that changing the composition of binary mobile ACN/water, MeOH/water [22], and MeOH/ACN [18] had a significant effect on the analytes’ k′ 1 and Rs .…”

“…All nano‐LC analyses were carried out employing a semi‐laboratory‐assembled instrumentation previously reported by our group [18]. The CSP was polysaccharide‐based, where 20% (w/w) AMY–3Cl–5Me) as chiral selector was covalently immobilized on native silica (nominal particle size and pore size, 5 µm and 1000 Å, respectively).…”

“…This material was provided by Enantiosep GmbH (Münster, Germany). Capillary columns were prepared following a procedure based on the slurry packing method [18]. The Supporting Information file reports a detailed description of the nano‐LC system, CSP, and the packing procedure.…”

“…Mianserin E2 108 (3) 92 ( 9) 117 ( 9) 115 ( 12) 93 ( 5) 77 (18) Tolperisone E1 44 ( 17) 46 ( 18) 43 ( 14) 45 ( 12) 39 ( 16) 41 (19) Tolperisone E2 44 ( 17) 45 ( 17) 43 ( 16) 44 ( 14) 38 ( 20) 41 (18) Temazepam E1 90 (3) 92 ( 5) 96 ( 4) 94 ( 6) 95 ( 11) 74 (7) Temazepam E2 93 (1) 91 ( 5) 100 ( 6) 99 ( 10) 96 ( 8) 74 ( 7)…”

Enantioseparation/Recognition based on nano techniques/materials

“…Diverse CSs have been employed to separate enantiomers from various kinds of chemicals. Peptides, proteins, chiral AAs, CDs or their derivatives, polysaccharides (modified amylose and cellulose), glycopeptide antibiotics, chiral surfactants, chiral crown-ethers, and other CS are among the most often used [17,21,[39][40][41][42]. A brief review of the key CSs in nano-LC/CLC is provided below.…”