An automated in-syringe switchable hydrophilicity solvent-based microextraction.

A fully automated in-syringe switchable hydrophilicity solvent-based microextraction approach was suggested for the first time. Di-(2-ethylhexyl)phosphoric acid was investigated as a novel switchable hydrophilicity solvent. The microextraction procedure implemented into a syringe pump included dissociation of the extractant in alkaline sample solution resulting in homogeneous solution formation followed by in situ organic phase generation by acidification and its separation. The microextraction procedure was applied to the HPLC-UV determination of antimicrobial drugs (sulfamethoxazole and sulfamethazine) in human urine samples as a proof-of-concept example. The calibration graphs were linear over the concentration ranges of 0.06-50 mg L-1 for sulfamethoxazole and 0.13-50 mg L-1 for sulfamethazine. The LODs calculated from the blank tests based on 3σ were 0.02 and 0.04 mg L-1 for sulfamethoxazole and sulfamethazine, respectively. The sample throughput was 12 samples h-1. The possibility of using the proposed procedure for assessing sulfamethoxazole/sulfamethazine acetylation in metabolic processes by individual human phenotypes was shown.

Flow method based on liquid-liquid extraction using deep eutectic solvent for the spectrofluorimetric determination of procainamide in human saliva.

In the current study, liquid-liquid extraction, using deep eutectic solvent (DES) as a "green" extraction solvent, was coupled with a stepwise injection system for the first time. The suggested approach was applied for the development of spectrofluorimetric method for procainamide determination. The method is based on aspiration of saliva sample and DES (choline chloride with glycerol at a 1:2M ratio) solution into the mixing chamber of a flow system, followed by injection of acetonitrile into the mixed DES-sample solution. The extraction process and final phase separation were then promoted by air-bubbling. After phase separation, the DES phase, containing the extracted procainamide, was transported to a spectrofluorimetric detector. The excitation and emission wavelengths were set at 280nm and 347nm, respectively. The calibration plot was linear in the range of 5×10-6 to 5×10-5molL-1. The limit of detection, calculated as 3σ of a blank test (n=10), was found to be 1.5×10-6molL-1. The developed method was successfully applied for the determination of procainamide in human saliva samples, and the analytical results agreed rather well with the results obtained by the reference HPLC-UV method.

Automated sugaring-out liquid-liquid extraction based on flow system coupled with HPLC-UV for the determination of procainamide in urine.

A fully automated sugaring-out assisted liquid-liquid extraction procedure was suggested. The procedure was based on the separation of the acetonitrile phase, containing a target analyte from the homogeneous sample solution after injection of sugaring-out reagent (glucose) into a mixing chamber of the flow system. Air bubbling was used to promote the extraction process and phase separation. After the fast phase separation in the mixing chamber, the acetonitrile phase containing the target analyte was transferred to an HPLC-UV system. Under the optimal conditions, the detector response of procainamide was linear in the concentration range of 6×10-7-4×10-5molL-1. The limit of detection, calculated from a blank test based on 3σ, was 2×10-7molL-1. The proposed method was successfully applied for the determination of procainamide in human urine samples and the analytical results agreed fairly well with the results obtained by reference CE method.

Determination of antipyrine in saliva using the dispersive liquid-liquid microextraction based on a stepwise injection system.

A fully automated stepwise injection spectrophotometric method for determination of antipyrine in saliva (agent for non-invasive assessment of the activity of the drug metabolizing system in hepatocytes) has been developed. The method is based on the antipyrine derivatization by nitrite-ion dispersive liquid-liquid microextraction (DLLME) of formed 4-nitrosoantipyrine with subsequent UV-vis spectrophotometric detection. Under optimal experimental conditions (0.5 М sulfuric acid, 6×10(-3) М sodium nitrite, time 6 min) the absorbance of the colored extract at the 345 nm obeys Beer׳s law in the range of 3-200 µM of antipyrine in saliva. The LOD, calculated from a blank test, based on 3σ, found to be 1 µM. The relative standard deviation for the determination of 50 µM antipyrine was 4.5% (n=10). The proposed method was successfully applied to the determination of antipyrine in saliva and the analytical results agreed fairly well with the results obtained by reference HPLC method.