title: Ion-pair cloud-point extraction: a new method for the determination of water-soluble vitamins in plasma and urine.
abstract: A novel, simple, and effective ion-pair cloud-point extraction coupled with a gradient high-performance liquid chromatography method was developed for determination of thiamine (vitamin B1 ), niacinamide (vitamin B3 ), pyridoxine (vitamin B6 ), and riboflavin (vitamin B2 ) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion-pair formation approach between these ionizable analytes and 1-heptanesulfonic acid sodium salt as an ion-pairing agent. Influential variables on the ion-pair cloud-point extraction efficiency, such as the ion-pairing agent concentration, ionic strength, pH, volume of Triton X-100, extraction temperature, and incubation time have been fully evaluated and optimized. Water-soluble vitamins were successfully extracted by 1-heptanesulfonic acid sodium salt (0.2% w/v) as ion-pairing agent with Triton X-100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r(2) > 0.9916) and precision in the concentration ranges of 1-50 μg/mL for thiamine and niacinamide, 5-100 μg/mL for pyridoxine, and 0.5-20 μg/mL for riboflavin. The recoveries were in the range of 78.0-88.0% with relative standard deviations ranging from 6.2 to 8.2%.
authors.affiliation: Razi Herbal Medicines Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran.
authors.forename: Rouhollah
authors.initials: R
authors.lastname: Heydari
authors.forename: Najmeh S
authors.initials: NS
authors.lastname: Elyasi
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017830:Octoxynol / Q000737:chemistry; D009994:Osmolar Concentration; D012995:Solubility; D013696:Temperature; D013997:Time Factors; D014815:Vitamins / Q000097:blood* / Q000652:urine*; D014867:Water / Q000737:chemistry*
chemical_list: D014815:Vitamins; D014867:Water; D017830:Octoxynol
keywords: Cloud-point extraction; Ion-pairing agents; Plasma; Urine; Water-soluble vitamins