High performance liquid chromatography determination of chlorophenols in water samples after preconcentration by continuous flow liquid membrane extraction on-line coupled with a precolumn

Molecularly imprinted solid phase extraction in a syringe filter for determination of triazine herbicides in Radix Paeoniae Alba by ultra-fast liquid chromatography

A novel, cost-effective and simple solid phase extraction (SPE) method, by using a syringe connected with a nylon membrane filter as the adsorbent container, was developed for the extraction of triazine herbicides from Radix Paeoniae Alba (RPA) samples. The selective molecularly imprinted polymers (MIPs) synthesized with the template of atrazine were employed as the adsorbents for the enrichment and purification of analytes. The extraction parameters, including the volume and type of loading solvent, the type of washing solvent and eluting solvent, were investigated. Under the optimized conditions, the final extracts were analyzed by ultra-fast liquid chromatography (UFLC). Recoveries of the developed method range from 92.4% to 107.3% with intra- and inter-day relative standard deviations (RSDs) lower than 8.2%. The calibration curve is linear in the concentration range of 0.005-2.4 µg g(-1) for desmetryn, atrazine and terbumeton, and 0.005-1.5 µg g(-1) for dimethametryn and dipropetryn, with the correlation coefficient (R(2)) higher than 0.9995. The limits of detection (LODs) of five triazine herbicides are in the range of 0.09-0.39 ng g(-1), which are lower than the maximum residue levels (MRLs) established by various official organizations. Analytical results of three real Radix Paeoniae Alba samples indicate that the proposed method is cost-effective and easy-to-use than other routine pretreatment methods.

Photocatalytic Degradation of Phenol Using a Nanocatalyst: The Mechanism and Kinetics

The study of photocatalytic degradation of phenol was exploited with nano-ZnO as immobilized photocatalysts in a laboratory scale photocatalytic reactor. The photocatalytic degradation mechanism and kinetics of phenol in water were studied using the solid-phase microextraction (SPME) technique. Based on optimized headspace SPME conditions, phenol in water was first extracted by the fibre, which was subsequently inserted into an aqueous system with immobilized photocatalysts (nano-ZnO) exposed to an irradiation source (i.e., ultraviolet A (UVA) lamps). After different irradiation times (5–80 min), four main intermediates of photocatalytic degradation generated on the fibre were determined by GC-MS.

Experimental and statistical validation of SPME-GC-MS analysis of phenol and chlorophenols in raw and treated water

A procedure based on solid-phase microextraction (SPME) and gas chromatography coupled with mass spectrometry (GC-MS) was developed and validated in order to analyse 10 phenols in water samples. The optimised conditions were obtained using polyacrylate fibre (PA), 20ml of sample volume, 10% NaCl, pH 4.0 and direct extraction at 35 degrees C and 1000rpm, for 40min. The linear range and quantification limits for these compounds by SPME-GC-MS were defined. An evaluation of the main uncertainty sources of this method is included, which allows expanded uncertainties in the 9.4-35% range for the majority of the compounds. The main source of uncertainty is associated with matrix effects. The validated method is suitable for monitoring the production and distribution of potable water and was used, in field trials, for the analysis of samples from main intakes of water (surface or underground) and from water supply system of a large area (Lisbon and neighbour municipalities).

Direct determination of chlorophenols in environmental water samples by hollow fiber supported ionic liquid membrane extraction coupled with high-performance liquid chromatography

The 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) ionic liquid was immobilized in the pores of a polypropylene hollow fiber for hollow fiber-protected liquid-phase microextraction. Analytes including 4-chlorophenol (4-CP), 3-chorophenol (3-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were extracted into this ionic liquid membrane, and back extracted into 10microL sodium hydroxide acceptor solution in the lumen of the hollow fiber. Then, the acceptor solution was withdrawn into the high-performance liquid chromatography (HPLC) microsyringe connected to the hollow fiber, and directly injected into the HPLC system for analysis. Some parameters that might affect the extraction efficiency were optimized, and low detection limits (0.5microgL(-1) for 4-CP, 3-CP, DCP and 1.0microgL(-1) for TCP) were obtained. Good repeatability was achieved because of the stability of the hollow fiber-supported ionic liquid membrane. The proposed procedure was applied for direct determination of the four chlorophenols in some real water samples including groundwater, river water, wastewater and tap water. All of the four chlorophenols in these water samples were under the limits of determination, and the recoveries were in the range of 70.0-95.7% at 5microgL(-1) spiked level.

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L(-1), respectively. The experimental results indicated that there was good linearity (R2>0.9993) over the range of 0.08 approximately 100 ng mL(-1) and good reproducibility with the relative standard deviations over the range of 0.7 approximately 1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5 approximately 109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.