Two operational modes for Lab-In-Syringe automation of direct-immersion single-drop microextraction have been developed and critically compared using lead in drinking water as the model analyte. Dithizone was used in the presence of masking additives as a sensitive chromogenic complexing reagent. The analytical procedure was carried out inside the void of an automatic syringe pump. Normal pump orientation was used to study extraction in a floating drop of a toluene-hexanol mixture. Placing the syringe upside-down allowed the use of a denser-than-water drop of chloroform for the extraction. A magnetic stirring bar was placed inside the syringe for homogenous mixing of the aqueous phase and enabled in-drop stirring in the second configuration while resulting in enhanced extraction efficiency. The use of a syringe as the extraction chamber allowed drop confinement and support by gravitational differences in the syringe inlet. Keeping the stirring rates low, problems related to solvent dispersion such as droplet collection were avoided. With a drop volume of 60 µL, limits of detection of 75 nmol L-1 and 23 nmol L-1 were achieved for the floating drop extraction and the in-drop stirring approaches, respectively. Both methods were characterized by repeatability with RSD typically below 5%, quantitative analyte recoveries, and analyte selectivity achieved by interference masking. Operational differences were critically compared. The proposed methods permitted the routine determination of lead in drinking water to be achieved in less than 6 min.

• Klíčová slova
• Automation, Direct-immersion single-drop microextraction, Drinking water, In-drop stirring microextraction, Lab-In-Syringe, Lead, dithizone assay,
• MeSH
• automatizace * MeSH
• injekční stříkačky * MeSH
• magnetické jevy MeSH
• mikroextrakce kapalné fáze * přístrojové vybavení   MeSH
• olovo analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• olovo MeSH

Lab-In-Syringe direct immersion single drop microextraction is proposed as an automated sample pretreatment methodology and coupled online to HPLC with fluorescence detection for the determination of fluoroquinolones in environmental waters. For the first time, a drop of a natural deep eutectic solvent (NADES), synthesized from hexanoic acid and thymol, has been used as an extractant in automated single-drop microextraction. The extraction procedure was carried out within the 5 mL void of an automatic syringe pump. A 9-position head valve served the aspiration of all required solutions, air, waste disposal, and hyphenation with the HPLC instrument. Sample mixing during extraction was done by a magnetic stirring bar placed inside the syringe. Only 60 μL of NADES were required omitting toxic classical solvents and improving the greenness of the proposed methodology. By direct injection, linear working ranges between 0.1 and 5 μg L-1 were achieved for all fluoroquinolones. The limit of quantification values and enrichment factors ranged from 20 ng L-1 to 30 ng L-1 and 35 to 45, respectively. Accuracies obtained from the analysis of spiked surface water and wastewater treatment plant effluent analysis at two concentration levels (0.5 and 4 μg L-1) ranged from 84.6% to 119.7%, with RSD values typically <3%.

• Klíčová slova
• Automation of sample preparation, Directly immersed single drop microextraction, Fluoroquinolone antibiotics, Lab-in-syringe, Natural deep eutectic solvent, Online coupling to HPLC,
• MeSH
• automatizace MeSH
• fluorochinolony * MeSH
• hluboce eutektická rozpouštědla MeSH
• injekční stříkačky MeSH
• limita detekce MeSH
• mikroextrakce kapalné fáze * metody   MeSH
• ponoření MeSH
• rozpouštědla chemie   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fluorochinolony * MeSH
• hluboce eutektická rozpouštědla MeSH
• rozpouštědla MeSH