Simultaneous determination of six phthalate esters in bottled milks using ultrasound-assisted dispersive liquid-liquid microextraction coupled with gas chromatography.

A new method was developed for the simultaneous determination of six phthalate esters in bottled milks using ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) followed by gas chromatography-flame ionization detection (GC-FID). 0.8 mL of methanol (dispersant) and 40 µL of CCl(4) (extractant) were injected into 8.0 mL of milk solution and then emulsified the mixture by ultrasound for 2.0 min to form the cloudy solution. Under the optimum condition, the enrichment factors of the analytes ranged from 220 to 270 fold and the recovery ranged from 93.2% to 105.7%. Good linearity was observed for all analytes in a range of 0.8-51 ngg(-1) with the correlation coefficient (r(2)) ≥ 0.9992. The limits of detection (LODs) based on signal to noise of 3 were 0.64-0.79 ngg(-1). The repeatability evaluated as intra-day and inter-day precision (relative standard deviation, RSD) were less than 4.0% (n=5). The presented UA-DLLME-GC-FID method was successfully applied to determine the six phthalate esters in different bottled milk products.

Ultrasound-assisted dispersive liquid-liquid microextraction for determination of fluoroquinolones in pharmaceutical wastewater.

A simple and rapid ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) coupled with liquid chromatography-ultraviolet detection (LC-UV) was developed for the determination of four fluoroquinolones (ofloxacin, norfloxacin, enrofloxacin, and lomefloxacin) in pharmaceutical wastewater samples. Various parameters affecting the extraction efficiency including type and volume of extraction and dispersive solvents, sample pH, and extraction time were investigated. Good linear relationships were obtained for all analytes in a range of 0.01-2.0 µg/ml with LODs ranged from 0.14 to 0.81 µg/l. Average recoveries at three spiking levels were over the range of 82.7-110.9% with RSD less than 5.2% (n=3). Under the optimized conditions the enrichment factors for the four fluoroquinolones were ranged from 32 to 134 folds. The presented method was applied for the determination of four fluoroquinolones in pharmaceutical wastewater samples.

Determination of clenbuterol in porcine tissues using solid-phase extraction combined with ultrasound-assisted dispersive liquid-liquid microextraction and HPLC-UV detection.

A new pretreatment method, solid-phase extraction combined with dispersive liquid-liquid microextration (SPE-DLLME), was proposed in first time for the determination of clenbuterol (CLB) in porcine tissue samples. The tissue samples were firstly extracted by SPE, then its eluents were used as dispersant of the followed DLLME for further purification and enrichment of CLB. Various parameters (such as the type of SPE sorbent, the type and volume of elution solvent, the type and volume of extractant and dispersant, etc.) that affected the efficiency of the two steps were optimized. Good linearity of CLB was ranged from 0.19 µg/kg to 192 µg/kg with correlation coefficient (r²) of 0.9995. The limit of detection (LOD) was 0.07 µg/kg (S/N=3) and the recoveries at three spiked levels were ranged from 87.9% to 103.6% with the relative standard deviation (RSD) less than 3.9% (n=3). Under the optimized conditions, the enrichment factor (EF) for CLB could up to 62 folds. The presented method that combined the advantages of SPE and DLLME, had higher selectivity than SPE method and was successfully applied to the determination of CLB in tissue samples.

Simultaneous determination of four phthalate esters in bottled water using ultrasound-assisted dispersive liquid-liquid microextraction followed by GC-FID detection.

A simple and rapid sample pretreatment procedure based on ultrasound-assisted dispersive liquid-liquid microextraction is proposed for the determination of four phthalate esters (dibutyl phthalate, butyl benzyl phthalate, diisooctyl phthalate, dioctyl phthalate) in bottled water samples using gas chromatography-flame ionization detection. An ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution using less disperser solvent, which markedly increased the extraction efficiency and reduced the equilibrium time. Under optimum conditions, the enrichment factor of the four analytes ranged from 490- to 530-fold and the recovery ranged from 84.8%∼104.7%. A good linear relationship between the peak area and the concentration of analytes was obtained in the range of 6.9∼444 µg L(-1). Intra-assay and inter-assay precision expressed as relative standard deviation (RSD) were in the range of 1.4∼2.0% and 3.0∼3.7%, respectively. This method offers a good alternative for routine analysis due to its simplicity and reliability.

Simultaneous determination of cypermethrin and permethrin in pear juice by ultrasound-assisted dispersive liquid-liquid microextraction combined with gas chromatography.

A new method was developed for simultaneous determination of cypermethrin and permethrin residues in pear juice with ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) and gas chromatography-flame ionization detection (GC-FID). 3.5 mL of methanol (dispersant) and 30 microL of C(2)Cl(4) (extractant) were injected into 5.0 mL of pear juice sample and then emulsified by ultrasound for 2.0 min to forming the cloudy solution. Under the optimum condition, the enrichment factors for cypermethrin and permethrin were 344 and 351 fold respectively. Good linearity was observed in a range of 0.009-1.52 microg g(-1) with the correlation coefficient (r(2))>or=0.9993. The limits of detection (LODs) were 3.1 and 2.2 microg kg(-1) for cypermethrin and permethrin, respectively (S/N=3). The recoveries of the method evaluated at three spiked levels were in the range of 92.1%-107.1%. The repeatability evaluated as intra-day and inter-day precision (RSDs) were less than 4.0% (n=5). The developed method was successfully applied to determine the two pesticide residues in different pear juice samples.

Ultrasound-assisted dispersive liquid-liquid microextraction for the determination of six pyrethroids in river water.

A simple ultrasound-assisted dispersive liquid-liquid microextraction method combined with liquid chromatography was developed for the preconcentration and determination of six pyrethroids in river water samples. The procedure was based on a ternary solvent system to formatting tiny droplets of extractant in sample solution by dissolving appropriate amounts of water-immiscible extractant (tetrachloromethane) in watermiscible dispersive solvent (acetone). Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvent, extraction time, ultrasonic time, and centrifuging time) were evaluated. Under the optimum condition, good linearity was obtained in a range of 0.00059-1.52 mg L(-1) for all analytes with the correlation coefficient (r(2))>0.999. Intra-assay and inter-assay precision evaluated as the relative standard deviation (RSD) were less than 3.4 and 8.9%. The recoveries of six pyrethroids at three spiked levels were in the range of 86.2-109.3% with RSD of less than 8.7%. The enrichment factors for the six pyrethroids were ranged from 767 to 1033 folds.