Meiping Ma

Analysis of phenolic pollutants in human samples by high performance capillary electrophoresis based on pretreatment of ultrasound-assisted emulsification microextraction and solidification of floating organic droplet.

A novel, simple and rapid method, termed ultrasound-assisted emulsification microextraction and solidification of floating organic droplet (UAEM-SFO) coupled to high performance capillary electrophoresis (HPCE), was developed for preconcentration and analysis of five phenolic compounds (PCs) in human urine and blood samples. The proposed method is based on microextraction of target analytes in less-toxic organic solvent under assistance of ultrasound. A micro-droplet of less-toxic organic solvent floating on the surface of liquid samples in a sealed vial can be dispersed into sample solutions under the ultrasound frequency, solidified under ice bath, collected with a medicine spatula, molten at ambient temperature, and finally subjected to HPCE analysis. The parameters of UAEM-SFO procedure including type and volume of extraction solvent, extraction temperature, time of ultrasound-assisted extraction and centrifugation, sample pH, and ionic strength were optimized. The influence parameters on HPCE resolution such as pH, concentration of running buffer, applied voltage and injection time were also investigated. This method requires only 40 μL of 2-dodecanol extraction solvent and 8 min of pretreatment time. The enrichment factors of analytes were in the range of 114-172 and extraction recoveries (69-86%) were obtained. Good linearity was achieved for five analytes in the range of 0.05-100 μg L⁻¹ and the correlation coefficients ranged from 0.9934 to 0.9999. The limits of detection were 0.01 μg L⁻¹ for triclosan (TCS) and biophenol A (BPA), and 0.02 μg L⁻¹ for pentachlorophenol (PCP), 2,4-dichlorophenol (2,4-DCP) and 4-nonylphenol (4-NP) in urine samples, and 0.02 μg L⁻¹ for TCS and BPA, 0.04 μg L⁻¹ for PCP, 2,4-DCP and 4-NP in blood samples. The developed UAEM-SFO-HPCE method has a great potential in routine residual analysis of trace PCs in biological samples.

Optimization of a phase separation based magnetic-stirring salt-induced liquid–liquid microextraction method for determination of fluoroquinolones in food

Herein, we developed a novel integrated apparatus to perform phase separation based on magnetic-stirring, salt-induced, liquid-liquid microextraction for determination of five fluoroquinolones in animal-based foods by HPLC analysis. The novel integrated apparatus consisted of three simple HDPE (high density polyethylene) parts that were used to separate the solvent from the aqueous solution prior to retrieving the extractant. The extraction parameters were optimized using the response surface method based on central composite design: 791 μL of acetone solvent, 2.5 g of Na2SO4, pH 1.7, 3.0 min of stir time, and 5.5 min centrifugation. The limits of detection were 0.07-0.53 μg kg(-1) and recoveries were 91.6-105.0% for the five fluoroquinolones from milk, eggs and honey. This method is easily constructed from inexpensive materials, extraction efficiency is high, and the approach is compatible with HPLC analysis. Thus, it has excellent prospects for sample pre-treatment and analysis of fluoroquinolones in animal-based foods.

Modification to degradation of hexazinone in forest soils amended with sewage sludge

Influences of one sewage sludge on degradation of hexazinone and formation of its major metabolites were investigated in four forest soils (A, B, C and D), collected in Zhejiang Province, China. In non-amended forest soils, the degradation half-life of hexazinone was 21.4, 30.4, 19.4 and 32.8 days in forest soil A, B, C and D, respectively. Degradation could start in soil A and C without lag period because the two soils had been contaminated by this herbicide for a long time, possibly leading to completion of acclimation period of hexazinone-degrading bacteria. In forest soils amended with sewage sludge, the degradation rate constant increased by 17.3% in soil A, 48.2% in soil B, 8.1% in soil C and 51.6% in soil D, respectively. The higher degradation rates (soil A and C) in non-amended soils accord with the lower rate increase in sewage sludge-amended soils. Under non-sterile conditions, biological mechanism accounted for 51.8-62.4% of hexazinone degradation in four soils. Under sterile conditions, the four soils had the similar chemical degradation capacity for hexazinone. In non-amended soil B, only one metabolite (B) was detected, while two metabolites (B and C) were found in sewage sludge-amended soil B. Similarly situated in agricultural soils, N-demethylation at 6-position of triazine ring, hydroxylation at the 4-positon of cyclohexyl group, and removal of the dimethylamino group with formation of a carbonyl group at 6-position of triazine ring appear to be the principal mechanism involved in hexazinone degradation in sewage sludge-amended forest soils. These data will improve understanding of the actual pollution risk as a result of forest soil fertilization with sewage sludge.

Photolysis of Low-Brominated Diphenyl Ethers and Their Reactive Oxygen Species-Related Reaction Mechanisms in an Aqueous System.

To date, no report was concerned with participation of reactive oxygen species in waters during photolysis of low-brominated diphenyl ethers (LBDEs). Herein, we found that electron spin resonance (ESR) signals rapidly increased with increasing irradiation time in the solution of LBDEs and 4-oxo-TMP solutions. But this phenomenon did not occur in the presence of NaN3 (1O2 quencher) demonstrating generation of 1O2 in process of LBDEs photolysis. The indirect photolytic contribution rate for BDE-47 and BDE-28 was 18.8% and 17.3% via 1O2, and 4.9% and 6.6% via ·OH, respectively. Both D2O and NaN3 experiments proved that the indirect photolysis of LBDEs was primarily attributable to 1O2. The bimolecular reaction rate constants of 1O2 with BDE-47 and BDE-28 were 3.12 and 3.64 × 106 M-1 s-1, respectively. The rate constants for BDE-47 and BDE-28 (9.01 and 17.52 × 10−3 min-1), added to isopropyl alcohol, were very close to those (9.65 and 18.42 × 10−3 min-1) in water, proving the less indirect photolytic contribution of ·OH in water. This is the first comprehensive investigation examining the indirect photolysis of LBDEs in aqueous solution.

Effects of imidazolium room temperature ionic liquids on the fluorescent properties of norfloxacin

The effects of 12 imidazolium room temperature ionic liquids (RTILs), including [C(n)mim]BF4, [C(n)mim]PF6, and [C(n)mim]Br (n = 4, 6, 8, 10), on the fluorescent properties of norfloxacin were examined. The fluorescence intensity of norfloxacin at 0.1 mg/L in methanol significantly increased with the addition of [C(n)mim]BF4 and [C(n)mim]PF6 into the solvent at 0.1-15.0%. The sensitizing effect may result from the higher viscosity of the RTILs-methanol mixture solvent than that of the methanol itself. However, the quenching effect on fluorescence of norfloxacin was observed in [C(n)mim]Br-methanol solvent. The fluorescence intensities of norfloxacin decreased with an increase in the alkyl chain length of the alkyl substituents of the imidazolium ring of RTILs. The main interaction between the RTILs and norfloxacin is not by hydrogen bonding. The fact, that some RTILs can significantly sensitize fluorescence of norfloxacin, indicates that RTILs could be a group of promising solvents for development of sensitive spectrofluorimetric methods for determination of norfloxacin at ultra-trace levels in environmental samples.

Determination of Phenolics in Water and Arthrospira (Spirulina) platensis by Concentrated Sulfuric Acid and Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction and High Performance Liquid Chromatography

A novel, practical, and environmentally friendly technique, termed concentrated sulfuric acid cleanup and ultrasound-assisted surfactant-enhanced emulsification microextraction (CSAC-UASEM), was combined with HPLC for the preconcentration and determination of five phenolics in water and Arthrospira (Spirulina) platensis samples. The main advantages include that the concentrated sulfuric acid is used to decrease macromolecular interferences prior to microextraction and, unlike dispersive liquid–liquid microextraction procedures, no dispersive organic solvent is required. Chloroform and sodium dodecyl sulfate were used as the extraction solvent and emulsifier, respectively. The algal cell preparation and CSAC-UASEM procedure parameters, including selection of cleanup method, ultrasound power, cell cytocylasis time, type and volume of extraction solvent, extraction temperature, ultrasound-extracted time, and sample pH, were optimized. At the fortification levels of 1.0 and 10.0 µg/L, the enrichment factors of analytes were in the range of 201.38 to 269.24. The percent extraction ranged from 71.57% to 107.42% in environmental Arthrospira-350, -793, and -834 samples, whereas the range was from 74.17% to 106.72% in water samples. The limits of detection (at S/N = 3) were 0.02 to 0.04 µg/L (except for 4-bromobisphenol A of 0.10 µg/L). These values indicate an approximately ten-fold improvement compared with the values reported by other techniques. In summary, the CSAC-UASEM sample preparation technique has great potential in the routine determination of trace phenolics in environmental waters and aquatic biological samples.

Inhibitory effects of natural organic matter on methyltriclosan photolysis kinetics

This study evaluated the effects and related mechanisms of natural organic matter (NOM) on the photolysis of methyltriclosan (MTCS), a metabolite of triclosan. Addition of two representative NOM isolates, Pony Lake fulvic acid (PLFA-microbial origin) and Suwannee River fulvic acid (SRFA-terrestrial origin), significantly inhibited the direct photolytic rate of MTCS by ∼70%. The MTCS photolytic rate in the presence of PLFA was greater than for SRFA. NOM not only suppressed photolysis by light-shielding, but also produced ROS to oxidatively degrade MTCS and/or triplet NOM (3NOM*) to sensitize degradation. The dual effects of light-screening and photo-sensitization led to an overall decrease in photolysis of MTCS with a positive concentration-dependence. Upon addition of NOM, EPR documented the occurrence of 1O2 and ˙OH in the photolytic process, and the bimolecular k value for the reaction of 1O2 with MTCS was 1.86 × 106 M−1 s−1. ROS-quenching experiments indicated that the contribution of ˙OH (19.1–29.5%) to indirect photolysis of MTCS was lower than for 1O2 (38.3–58.7%). Experiments with D2O further demonstrated that 1O2 participated in MTCS photodegradation. Moreover, the addition of sorbic acid and O2 gas to the reaction confirmed the participation of 3NOM* as a key reactant in the photochemical transformation of MTCS. This is the first comprehensive analysis of NOM effects on the indirect photolysis of MTCS, which provides new insights for understanding the environmental fate of MTCS in natural environments.

Extraction of triclosan and methyltriclosan in human fluids by in situ ionic liquid morphologic transformation

Herein, we established an ionic liquid (IL)-based liquid-solid transformation microextraction (IL-LTME) combined with HPLC-UV detection for the simultaneous determination of triclosan (TCS) and its methylated product, methyltriclosan (MTCS), in human fluids. The IL-LTME method was based on an in situ metathesis between hydrophilic IL and ion-exchange salt to form a solid hydrophobic IL. According to the above principle, a hydrophilic IL, [C12MIM]Br, was selected as the extractant, and NH4PF6 as ion-exchange salt. The prominent advantages of the newly developed method are: (1) the in-situ reaction between the extractant [C12MIM]Br and ion-exchange salt NH4PF6 changed the IL from hydrophilic to hydrophobic that avoiding the stick of ionic liquid on the tube wall; (2) bubbling with NH3 greatly increased the contact area between IL-extractant and analytes resulting in improved extraction recovery; and (3) solidification of the [C12MIM] PF6 provided a good separation and avoided the use of specialized equipment. A series of main parameters were optimized by single-factor screening and central composite design as follows: 0.9 mL of NaOH, 2.0 min of second ultrasonically time, 10 min of centrifugation time, 21 mg of extractant [C12MIM]PF6, 2.4 min of ultrasonic time, 65 mg of NH4PF6 and 13.8 min of cooling time. Under the optimized conditions, the limits of detection for TCS and MTCS were 0.126-0.161 μg L-1 in plasma samples, and 0.211-0.254 μg L-1 in urine samples, respectively. The extraction recoveries for TCS and MTCS were in the range of 94.1-103.8%. The intra-day and inter-day precisions were 1.00-4.74% and 1.02-5.21%, respectively. In general, the IL-LTME method is environment-friendly, time-saving, economical, high efficient and robust with low detection limits and high recoveries. Thus, the newly developed method has excellent prospects for sample pretreatment and analysis of trace TCS and MTCS in blood and urine samples.