Homogeneous liquid–liquid extraction and micellar electrokinetic chromatography using sweeping effect concentration system for determination of trace amounts of several polycyclic aromatic hydrocarbons

Abstract

A powerful capillary electrophoresis (CE) method, with preconcentration in excess of 100,000-fold, has been developed by using a specific characteristic of perfluoro surfactants. Highly sensitive determination and separation of polycyclic aromatic hydrocarbons (PAH) were achieved by following a combination of two kinds of efficient preconcentration method using perfluoro surfactants. The two preconcentration methods combined were homogeneous liquid-liquid extraction for off-line concentration and a sweeping method as on-line concentration. Five PAH (1,2,3,4-dibenzanthracene, 1,2,5,6-dibenzanthracene, benzo( a)pyrene, benzo( e)pyrene, and pyrene) were investigated, and were completely separated. When the concentration-factor (volume ratio) was 8335-fold, the determination limits were in the range 10(-10) to 10(-9) mol L(-1). The maximum concentration-factor (volume ratio) obtained was 125,000-fold. Addition and recovery experiments were performed for three kinds of natural water (rain water, river water, and spring water).

Effects of organic solvents on sample pretreatment and separation performances in capillary electrophoresis

“…In a recent paper, So and Huie [102] reported the feasibility of employing salting-out solvent extraction for the off-line preconcentration of cationic surfactants (benzalkonium chloride, BAK) in CZE and the improved detection capability was demonstrated for the sensitive determination of BAK in real samples (e.g., eye care products). Using a homogeneous liquid-liquid extraction method (i.e., based on a pH-dependent phase separation phenomenon involving the use of a perfluoro surfactant and a water miscible organic solvent as the sample matrix), Takagai and Igarashi [99] reported the development of a CE method with impressive concentration enhancement factors (exceeding 100 000-fold) by combining homogeneous liquid-liquid extraction with the sweeping effect in MEKC (developed by Quirino and Terabe [103]) for the determination of several polycyclic aromatic hydrocarbons in natural water samples at nanomolar levels. Furthermore, Lee and co-workers [104] reported in a recent paper that dramatic improvement in peak heights (100 000-fold) was obtained by combining anionic-selective exhaustive injection and the "sweeping" method in MEKC for the CE determination of some phenoxy acidic herbicides, in which a low pH buffer was used to suppress the EOF as well as the ionization of the analytes.…”

“…However, for MEKC, the direct injection of these nonpolar organic solvents (containing the preconcentrated analytes) will cause a number of problems, including insolubility in the separation buffer and disruption of analyte-micelle distribution. These particular solvent incompatibility problems, however, can be resolved by employing liquid-liquid extraction systems in which water-miscible organic solvents are used as the extractants [99]. The use of saltingout effect with water-miscible organic solvents, such as acetonitrile and acetone, for the extraction/preconcentration of metal chelates prior to atomic absorption [100] and HPLC [101] analysis is known for many years.…”

Homogeneous Liquid-Liquid Extraction (HoLLE) via Flotation Combined with Gas Chromatography-Flame Ionization Detection as a Very Simple, Rapid and Sensitive Method for the Determination of Fenitrothion in Water Samples

“…The main disadvantage of ternary systems including DLLME [10][11][12][13][14] and HoLLE [15][16][17][18] is that the extraction solvent is generally limited to solvents of density higher than water in order to be sedimented by centrifugation. In addition, the use of high-density solvents as extractants limits wider applicability of DLLME and HoLLE.…”

Powerful Concentration of Rhodium in Plating Wastewater Using Homogeneous Liquid–Liquid Extraction (HoLLE) and Study for Scale-up

“…HoLLE has been widely used to extract target solutes such as indium (In) (Kato, Igarashi, Ishiwatari, Furukawa, & Yamaguchi, 2013), cobalt (Co) (Kato, Igarashi, Saito, Ando, & Asano, 2014), rare earth elements (Saito, Ohno, Igarashi, Kato, & Yamaguchi, 2015), and Pd (Kato, Igarashi, Ohno, Saito, & Ando, 2016), although the target solute is not limited to metals. Additionally, HoLLE can be applied to organic compounds (Takagai & Igarashi, 2002) and biological materials (Sudo & Igarashi, 1996). With respect to trace amounts of metals, nanofiltration (Otero-Fernandez et al, 2017) and solid-phase extraction (Molaei, Bagheri, Asgharinezhad, Ebrahimzadeh, Shamsipur, 2017) have been reported.…”

“…Such homogeneous liquid-liquid extraction was applied to the extraction of metal ions (Mori et al, 2015;Hoogerstraete, Onghena, & Binnemans, 2013;Depuydt, Liu, Glorieux, Dehaen, & Binnemans, 2015). Compared with homogeneous liquid-liquid extraction based on temperature, HoLLE based on pH-dependent phase separation can be used to achieve 100-100,000-fold concentration in several minutes down to micro-volume levels (Takagai & Igarashi, 2002). For this reason, HoLLE based on pH-dependent phase separation was investigated.…”