Ion‐pair‐based hollow‐fiber liquid‐phase microextraction combined with high‐performance liquid chromatography for the simultaneous determination of urinary benzene, toluene, and styrene metabolites

Abstract

In the current study, a novel technique for extraction and determination of trans,trans-muconic acid, hippuric acid, and mandelic acid was developed by means of ion-pair-based hollow fiber liquid-phase microextraction in the three-phase mode. Important factors affecting the extraction efficiency of the method were investigated and optimized. These metabolites were extracted from 10 mL of the source phase into a supported liquid membrane containing 1-octanol and 10% w/v of Aliquat 336 as the ionic carrier followed by high-performance liquid chromatography analysis. The organic phase immobilized in the pores of a hollow fiber was back-extracted into 24 μL of a solution containing 3.0 mol/L sodium chloride placed inside the lumen of the fiber. A very high preconcentration of 212- to 440-fold, limit of detection of 0.1-7 μg/L, and relative recovery of 87-95% were obtained under the optimized conditions of this method. The relative standard deviation values for within-day and between-day precisions were calculated at 2.9-8.5 and 4.3-11.2%, respectively. The method was successfully applied to urine samples from volunteers at different work environments. The results demonstrated that the method can be used as a sensitive and effective technique for the determination of the metabolites in urine.

Benzene, toluene, ethylbenzene, and xylene: Current analytical techniques and approaches for biological monitoring

“…Because of the inherent limitations of LLE and conventional SPE columns, and to provide maximum recovery of analytes, efficient removal of interferents, minimum or no consumption of solvents, automation, miniaturization, online coupling with analytical instruments, low-cost operation, and ease of use, METs [142] DVB/CAR/PDMS -divinylbenzene/carboxen/polydimethylsiloxane; ND -not determined; RT -room temperature such as LPME [91,93], LLLME [81], DLLME [106], PDLLME [96], SPME [111], and MEPS [82][83][84]95,99] have been developed for determination of BTEX metabolites. The LLLME and LPME methods are equilibrium extraction procedures and thus highest recovery can be achieved by the acceptor phase after equilibrium is obtained [81,91,93]. Similarly, in SPME, analytes partition between a fiber coating and the matrix until an equilibrium is achieved [111].…”

“…Similarly, in SPME, analytes partition between a fiber coating and the matrix until an equilibrium is achieved [111]. In LLLME, LPME, and SPME, the equilibrium constant and the equilibration time are influenced by pH, temperature, salt concentration and stirring [81,91,93,149,150]. As can be seen from Table 2, in addition to relatively low recoveries, the extraction times in LLLME [81], HF-LPME [93], IP-HF-LPME [91], PDLLME [96], HS-SPME [111], and DI-SPME [111] are about 60, 120, 60, ~30, 40, and 60 min, respectively.…”

“…Most of these analytical methods use liquid-liquid extraction (LLE) [14,87,88,109,110,113] or conventional solid phase extraction (SPE) [86,92,103,105,106,112] for sample preparation. However, microextraction techniques (METs) such as hollow-fiber liquid-phase microextraction (LPME) [91,93], single drop liquid-liquid-liquid microextraction (LLLME) [81], partitioned dispersive liquid-liquid microextraction (PDLLME) [96], solid phase microextraction (SPME) [111] and microextraction by packed sorbet (MEPS) [82][83][84]99] are also used in recent years. In addition, the "dilute-and-shoot" approach without need for a sample preparation step is used [97,98,100,102].…”

“…In recent years, a number of METs have been developed for the determination of BTEX metabolites, including LLLME [81], HF-LPME [91,93], SPME [111], PDLLME [96] and MEPS [82][83][84]95,99].…”

“…This technique is performed in the following steps: 1) the HF membranes are manually cut to provide 8.8 cm equal pieces with an internal volume of 24 μL; 2) to remove any contamination, the pieces are washed with acetone for 5 min in an ultrasonic bath and then dried in air; 3) the receiver phase loads into a 25 μL Hamilton syringe and then the syringe's needle is inserted into the lumen of the HF; 4) to fill the pores, the HF is immersed in 10% (w/v) of Aliquat-336 solution as an ionpair reagent for 15 s and then rinsed with distilled water for 10 s to remove excessive organic solvent; 5) while one end of the HF is closed using an aluminum foil, the acceptor phase is injected into the other end of the HF and then it bent to an U-shape configuration; 6) to extract the analytes, the U-shape HF is immersed in a 12 mL sample vial containing 10 mL of the aqueous sample. The extraction efficiency increased with increasing the stirring up to 800 rpm; 7) after 60 min, the end of the HF is cut and the acceptor phase which now contains the analytes is withdrawn into the syringe and injected into HPLC for analysis [91].…”