Orthogonal array design for the optimization of hollow fiber protected liquid-phase microextraction of salicylates from environmental waters

A new fluorescent probe for the detection of F⁻ (TBA⁺ and Na⁺ salts) has been developed, which is based on a desilylation triggered chromogenic reaction in water. This probe exhibits excellent F⁻ ion selectivity as well as significant color changes visible to the naked eye at the concentration of 1.5 mg L⁻¹, the WHO recommended level of F⁻ ions in drinking water. This new carbohydrate modified probe can be used directly in aqueous medium without using organic co-solvents. Furthermore, the probe presents high sensitivity and selectivity for the imaging of F⁻ ions in HepG2 cells.     

Kinetic aspects of hollow fiber liquid-phase microextraction and electromembrane extraction

In this paper, extraction kinetics was investigated experimentally and theoretically in hollow fiber liquid-phase microextraction (HF-LPME) and electromembrane extraction (EME) with the basic drugs droperidol, haloperidol, nortriptyline, clomipramine, and clemastine as model analytes. In HF-LPME, the analytes were extracted by passive diffusion from an alkaline sample, through a (organic) supported liquid membrane (SLM) and into an acidic acceptor solution. In EME, the analytes were extracted by electrokinetic migration from an acidic sample, through the SLM, and into an acidic acceptor solution by application of an electrical potential across the SLM. In both HF-LPME and EME, the sample (donor solution) was found to be rapidly depleted for analyte. In HF-LPME, the mass transfer across the SLM was slow, and this was found to be the rate limiting step of HF-LPME. This finding is in contrast to earlier discussions in the literature suggesting that mass transfer across the boundary layer at the donor–SLM interface is the rate limiting step of HF-LPME. In EME, mass transfer across the SLM was much more rapid due to electrokinetic migration. Nevertheless, mass transfer across the SLM was rate limiting even in EME. Theoretical models were developed to describe the kinetics in HF-LPME, in agreement with the experimental findings. In HF-LPME, the extraction efficiency was found to be maintained even if pH in the donor solution was lowered from 10 to 7–8, which was below the pK_a-value for several of the analytes. Similarly, in EME, the extraction efficiency was found to be maintained even if pH in the donor solution increased from 4 to 11, which was above the pK_a-value for several of the analytes. The two latter experiments suggested that both techniques may be used to effectively extract analytes from samples in a broader pH range as compared to the pH range recommended in the literature.     

Orthogonal array design for the optimization of ionic liquid-based dispersive liquid-liquid microextraction of benzophenone-type UV filters

In the present study, dispersive liquid-liquid microextraction (DLLME) using an ionic liquid (IL) as the extractant was successfully developed to extract four benzophenone-type UV filters from the different water matrices. Orthogonal array experimental design (OAD), based on five factors and four levels (L(16)(4(5))), was employed to optimize IL-dispersive liquid-liquid microextraction procedure. The five factors included pH of sample solution, the volume of IL and methanol addition, extraction time and the amount of salt added. The optimal extraction condition was as follows. Sample solution was at a pH of 2.63 in the presence of 60 mg/mL sodium chloride; 30 μL IL and 15 μL methanol were used as extractant and disperser solvent, respectively; extraction was achieved by vortexing for 4 min. Using high-performance liquid chromatography-UV analysis, the limits of detection of the target analytes ranged between 1.9 and 6.4 ng/mL. The linear ranges were between 10 or 20 ng/mL and 1000 ng/mL. This procedure afforded a convenient, fast and cost-saving operation with high extraction efficiency for the model analytes. Spiked waters from two rivers and one lake were examined by the developed method. For the swimming pool water, the standard addition method was employed to determine the actual concentrations of the UV filters.     

Determination of residual monomers in latex by headspace hollow fiber protected liquid-phase microextraction combined with high-performance liquid chromatography

A simple and efficient method based on hollow fiber protected headspace liquid-phase in conjunction with high performance liquid chromatography has been introduced for extraction and determination of three residual monomers (2-ethylhexyl acrylate (EHA), vinyl acetate (VA), glycidyl methacrylate (GM)) in polymer latex. Using this methodology, the analytes of interest extracted from a sample are led into organic solvent located inside the porous hollow fiber membrane. Initially, several experimental parameters were controlled and optimized and the optimum conditions were reached with 8 cm neatly cut hollow fibers containing heptanol, which were exposed to the headspace of a 12 mL sample solution containing 20% (w/v) NaCl thermostated at 110 °C and stirred at 800 rpm for 20 min. Finally, 20 μL of the extraction solution was withdrawn into a syringe and injected into HPLC for analysis. The calibration curves were linear (r² ≥ 0.994) over the concentration range of 0.05-10 mg L⁻¹ for VA and 0.02-10 mg L⁻¹ for other analytes. The relative standard deviation (RSD%) for three-replicate extractions and measurements was below 8.6%. The limits of detection of this method for quantitative determination of the analytes were found within the range of 0.005 to 0.011 mg kg⁻¹ with the enrichment factors within the 5-164 range. The method was successfully applied for determination of residual monomers in polymer latex.     

Hollow‐fiber liquid‐phase microextraction combined with capillary HPLC for the selective determination of six sulfonylurea herbicides in environmental waters

A three‐phase hollow‐fiber liquid‐phase microextraction combined with a capillary LC method using diode array detection was proposed for the determination of six sulfonylurea herbicides, triasulfuron, metsulfuron‐methyl, chlorsulfuron, flazasulfuron, chlorimuron‐ethyl, and primisulfuron‐methyl, in environmental water samples. Different factors that can affect the extraction process such as extraction solvent, acidity of the donor phase, composition and pH of the acceptor phase, salt addition, stirring speed, and extraction time were optimized. Under the optimum conditions, detection and quantitation limits between 0.1 – 1.7 and 0.3 – 5.7 μg/L, respectively, and enrichment factors ranging from 71 to 548 were obtained. The calibration curves were linear within the range of 0.3 – 40 μg/L. Intra‐ and interday RSDs were <6.3 and 8.4%, respectively. The relative recoveries of the spiked ground and river water samples were in the range of 69.4 – 119.2 and 77.4 – 111.7%, respectively. The results of the study revealed that the developed methodology involves an efficient sample pretreatment allowing the preconcentration of analytes, combined with the use of a miniaturized separation technique, suitable for the accurate determination of sulfonylurea herbicides in water.     

中空纤维膜液相微萃取-高效液相色谱联用技术测定尿液中痕量己烯雌酚

采用中空纤维液相微萃取与高效液相色谱联用技术测定了尿液样品中的痕量己烯雌酚;考察了样品相酸度、中间相种类、接收相浓度、搅拌速度、萃取时间等对液-液-液三相微萃取效率的影响,进而确定了最佳萃取条件.结果表明,当样品相pH为2.5,中间相为甲苯,接收相为3μL 0.25mol/L氢氧化钠溶液,搅拌速度为800r/min,萃取时间为50min时,萃取效率最佳.在最佳萃取条件下,样品的回收率为76.4%,相对标准偏差为3.8%.     

Hollow fibre liquid-phase microextraction of parabens from environmental waters

Parabens (alkyl-p-hydroxybenzoates) are antimicrobial preservatives widely used in cosmetics, toiletries, pharmaceuticals, and food. Nowadays, they are considered emerging pollutants and their determination is becoming increasingly important since they are continuously released into the environment. In this work, a hollow fibre liquid-phase microextraction method has been developed for the extraction of parabens from environmental waters. The parameters affecting the extraction of parabens (organic solvent used as liquid membrane; pH of both sample and acceptor solution; salting-out effect; extraction time and stirring speed) were carefully optimized in order to reach high recoveries for all tested analytes. Under optimum conditions, parabens were extracted from river, reservoir and sea water samples with recoveries ranging from 16.7 to 68.6% depending upon the analyte and the sample analyzed, leading to detection limits lower than 0.2?ng?mL^?1 using a simple HPLC-UV instrument.     

A new high-speed hollow fiber based liquid phase microextraction method using volatile organic solvent for determination of aromatic amines in environmental water samples prior to high-performance liquid chromatography

A new and fast hollow fiber based liquid phase microextraction (HF-LPME) method using volatile organic solvents coupled with high-performance liquid chromatography (HPLC) was developed for determination of aromatic amines in the environmental water samples. Analytes including 3-nitroaniline, 3-chloroaniline and 4-bromoaniline were extracted from 6 mL basic aqueous sample solution (donor phase, NaOH 1 mol L⁻¹) into the thin film of organic solvent that surrounded and impregnated the pores of the polypropylene hollow fiber wall (toluene, 20 μL), then back-extracted into the 6 μL acidified aqueous solution (acceptor phase, HCl 0.5 mol L⁻¹) in the lumen of the two-end sealed hollow fiber. After the extraction, 5 μL of the acceptor phase was withdrawn into the syringe and injected directly into the HPLC system for the analysis. The parameters influencing the extraction efficiency including the kind of organic solvent and its volume, composition of donor and acceptor phases and the volume ratio between them, extraction time, stirring rate, salt addition and the effect of the analyte complexation with 18-crown-6 ether were investigated and optimized. Under the optimal conditions (donor phase: 6 mL of 1 mol L⁻¹ NaOH with 10% NaCl; organic phase: 20 μL of toluene; acceptor phase: 6 μL of 0.5 mol L⁻¹ HCl and 600 m mol L⁻¹ 18-crown-6 ether; pre-extraction and back-extraction times: 75 s and 10 min, respectively; stirring rate: 800 rpm), the obtained EFs were between 259 and 674, dynamic linear ranges were 0.1-1000 μg L⁻¹ (R > 0.9991), and also the limits of detection were in the range of 0.01-0.1 μg L⁻¹. The proposed procedure worked very well for real environmental water samples with microgram per liter level of the analytes, and good relative recoveries (91-102%) were obtained for the spiked sample solutions.     

Orthogonal array designs for the optimization of liquid-liquid-liquid microextraction of nonsteroidal anti-inflammatory drugs combined with high-performance liquid chromatography-ultraviolet detection

Orthogonal array designs (OADs) were applied for the first time to optimize liquid-liquid-liquid microextraction (LLLME) conditions for the analysis of three nonsteroidal anti-inflammatory drug residues (2-(4-chlorophenoxy)-2-methylpropionic acid, ketoprofen, and naproxen) in wastewater samples. Six relevant factors were investigated: type of organic solvent, composition of donor phase and acceptor phase, stirring speed, extraction time and salt concentration. In the first stage, mixed-level orthogonal array design, an OA16 (4(1) x 2(12)) matrix was employed to study the effect of six factors, by which the effect of each factor was estimated using individual contributions as response functions. Based on the results of the first stage, 1-octanol was chosen as organic solvent for extraction. The other five factors were selected for further optimization using an OA16 (4(5)) matrix and a 4 x 4 table to locate more exact levels for each variable. The relative standard deviations for the reproducibility of optimized LLLME varied from 6.2 to 7.1%. The coefficients of determination for calibration curves were higher than 0.9950. The method detection limits for drugs spiked in ultrapure water were in the range of 0.03-0.3 ng/mL. The final optimized conditions were applied to the analysis of drug residues in three wastewater samples in Singapore.     

Environmental and bioanalytical applications of hollow fiber membrane liquid-phase microextraction: a review

In hollow fiber membrane liquid-phase microextraction (LPME), target analytes are extracted from aqueous samples and into a supported liquid membrane (SLM) sustained in the pores in the wall of a small porous hollow fiber, and further into an acceptor phase present inside the lumen of the hollow fiber. The acceptor phase can be organic, providing a two-phase extraction system compatible with capillary gas chromatography, or the acceptor phase can be aqueous resulting in a three-phase system compatible with high-performance liquid chromatography or capillary electrophoresis. Due to high enrichment, efficient sample clean-up, and the low consumption of organic solvent, substantial interest has been devoted to LPME in recent years. This paper reviews important applications of LPME with special focus on bioanalytical and environmental chemistry, and also covers a new possible direction for LPME namely electromembrane extraction, where analytes are extracted through the SLM and into the acceptor phase by the application of electrical potentials.     

A novel approach to automation of dynamic hollow fiber liquid-phase microextraction

An automated dynamic two-phase hollow fiber microextraction apparatus combined with high-performance liquid chromatography was developed for extraction and determination of chlorophenoxy acid (CPA) herbicides from environmental samples. The extraction device, called TT-extractor, consists of a polypropylene hollow fiber mounted inside a stainless steel tube by means of two tee-connectors in flow system. An organic solvent, which fills the lumen and the pores of the hydrophobic fiber, is pumped through the fiber repeatedly and the sample is pumped along the outer side of the fiber. The factors affecting the dynamic hollow fiber liquid-phase microextraction (DHF-LPME) of target analytes were investigated and the optimal extraction conditions were established. To test the applicability of the designed instrument, CPAs were extracted from environmental aqueous samples. The limits of detection (LODs) as low as 0.5 μg/L, linear dynamic range in the range of 1-100 μg/L and the relative standard deviations of <7% were obtained. The developed method can provide perconcentration factors as large as 230. A hollow fiber membrane can be used at least 20 times with neither loss in the efficiency nor carryover of the analytes between runs. The system is cheap and convenient and requires minimal manual handling.     

Determination of ultraviolet filters in environmental water samples by temperature-controlled ionic liquid dispersive liquid-phase microextraction

In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named temperature-controlled ionic liquid dispersive liquid-phase microextraction (TC-IL-DLPME), followed by high performance liquid chromatography (HPLC) was developed for the extraction, preconcentration and determination of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from water samples. An ultra-hydrophobic ionic liquid (IL) 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]), was used as the extraction solvent in TC-IL-DLPME. Temperature served two functions here, the promotion of the dispersal of the IL to the aqueous sample solution to form infinitesimal IL drops and increase the interface between them and the target analytes (at high temperature), and the facilitation of mass transfer between the phases, and achievement of phase separation (at low temperature). Due to the ultra-hydrophobic feature and high density of the extraction solvent, complete phase separation could be effected by centrifugation. Moreover, no disperser solvent was required. Another prominent feature of the procedure was the combination of extraction and centrifugation in a single step, which not only greatly reduced the total analysis time for TC-IL-DLPME but also simplified the sample preparation procedure. Various parameters that affected the extraction efficiency (such as type and volume of extraction solvent, temperature, salt addition, extraction time and pH) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 240–350, and relative standard deviations (n = 5) below 6.3%. The limits of detection were in the range of 0.2–5.0 ng/mL, depending on the analytes. The linearities were between 1 and 500 ng/mL for BP, 5 and 1000 ng/mL for BP-3, 10 and 1000 ng/mL for HMS and 5 and 1000 ng/mL for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in swimming pool and tap water samples and acceptable relative recoveries over the range of 88.0–116.0% were obtained.     

Development of negligible depletion hollow fiber membrane-protected liquid-phase microextraction for simultaneous determination of partitioning coefficients and acid dissociation constants

A new method based on negligible depletion hollow fiber-protected liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC) was developed for the simultaneous determination of partitioning coefficients (K_OW) and acid dissociation constants (pK_a), by using phenol, 4-chlorophenol and 2,4-dichlorophenol as model compounds. A 37-mm length polypropylene hollow fiber membranes (600 μm inner diameter, 200 μm wall-thickness, 0.2 μm pore size, ∼70% porosity) with two-end sealed were filled with 1-octanol by ultrasonic agitation to prepare the extraction device. The extraction device was deployed in sample solutions, prepared by spiking target analytes in 1-octanol saturated aqueous solutions (500 mL), for negligible depletion extraction. After equilibrium was reached (∼5 h), the 1-octanol in the lumen of the hollow fiber membrane was collected for HPLC determination of the target analytes. As the depletion of the analytes in aqueous samples was negligible, the distribution coefficient (D_OW) could be calculated based on the measured equilibrium concentration in 1-octanol (C_O) and the initial concentration (C_W) in the aqueous sample of the target analyte (D_OW = C_O/C_W). The D_OW values measured at various pH values were nonlinearly regressed with pH to obtain the K_OW and pK_a values of a compound. Results showed that the measured values of the K_OW and pK_a of these model compounds agreed well with literature data.     

Hollow fiber liquid-phase microextraction for the determination of trace amounts of rosiglitazone (anti-diabetic drug) in biological fluids using capillary electrophoresis and high performance liquid chromatographic methods

A three-phase hollow fiber liquid-phase microextraction (HF-LPME) coupled either with capillary electrophoresis (CE) or high performance liquid chromatography (HPLC) with UV detection methods was successfully developed for the determination of trace levels of the anti-diabetic drug, rosiglitazone (ROSI) in biological fluids. The analyte was extracted into dihexyl ether that was immobilized in the wall pores of a porous hollow fiber from 10 mL of aqueous sample, pH 9.5 (donor phase), and was back extracted into the acceptor phase that contained 0.1 M HCl located in the lumen of the hollow fiber. Parameters affecting the extraction process such as type of extraction solvent, HCl concentration, donor phase pH, extraction time, stirring speed, and salt addition were studied and optimized. Under the optimized conditions (extraction solvent, dihexyl ether; donor phase pH, 9.5; acceptor phase, 0.1 M HCl; stirring speed, 600 rpm; extraction time, 30 min; without addition of salt), enrichment factor of 280 was obtained. Good linearity and correlation coefficients of the analyte was obtained over the concentration ranges of 1.0–500 and 5.0–500 ng mL⁻¹ for the HPLC (r² = 0.9988) and CE (r² = 0.9967) methods, respectively. The limits of detection (LOD) and limits of quantitation (LOQ) for the HPLC and CE methods were (0.18, 2.83) and (0.56, 5.00) ng mL⁻¹, respectively. The percent relative standard deviation (n = 6) for the extraction and determination of three concentration levels (10, 250, 500 ng mL⁻¹) of ROSI using the HPLC and CE methods were less than 10.9% and 13.2%, respectively. The developed methods are simple, rapid, sensitive and are suitable for the determination of trace amounts of ROSI in biological fluids.     

三相中空纤维液相微萃取在羟基苯甲酸类化合物分析中的应用

在优化的三相中空纤维液相微萃取(3p-HFLPME)条件下,研究了6种羟基苯甲酸类化合物(HBAs)的3p-HFLPME行为;揭示了HBAs的富集因子(EF)与其正庚醇/水条件分配系数(log Pn-heptanol/5 mmol/L HCl)、pKa和羟基数目(N)的相关性,初步阐明了聚偏氟乙烯中空纤维对HBAs的电荷转移传递机理以及有机溶剂对HBAs的选择性萃取机理。优化的3p-HFLPME条件: 以MOF 503聚偏氟乙烯中空纤维为有机溶剂支持体,正庚醇为有机相,5 mmol/L HCl体系为给体,80 mmol/L NH3·H2O为接受相,搅拌速度为1200 r/min,萃取35 min。该方法的精密度（以相对标准偏差计）小于3%,检出限为0.09~30.00 μg/L,加标回收率为93.3%~107.1%,HBAs质量浓度为5 mg/L时的富集因子最高达107.6倍。     

Headspace liquid-phase microextraction using ionic liquid as extractant for the preconcentration of dichlorodiphenyltrichloroethane and its metabolites at trace levels in water samples

A novel technique, high temperature headspace liquid-phase microextraction (HS-LPME) with room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]) as extractant, was developed for the analysis of dichlorodiphenyltrichloroethane (p,p′-DDT and o,p′-DDT) and its metabolites including 4,4′-dichlorodiphenyldichloroethylene (p,p′-DDE) and 4,4′-dichlorodiphenyldichloroethane (p,p′-DDD) in water samples by high performance liquid chromatography with ultraviolet detection. The parameters such as salt content, sample pH and temperature, stirring rate, extraction time, microdrop volume, and sample volume, were found to have significant influence on the HS-LPME. The conditions optimized for extraction of target compounds were as follows: 35% NaCl (w/v), neutral pH condition, 70 °C, 800 rpm, 30 min, 10 μL [C₄MIM][PF₆], and 25 mL sample solutions. Under the optimized conditions, the linear range, detection limit (S/N = 3), and precision (R.S.D., n = 6) were 0.3-30 μg L⁻¹, 0.07 μg L⁻¹, and 8.0% for p,p′-DDD, 0.3-30 μg L⁻¹, 0.08 μg L⁻¹, and 7.1% for p,p′-DDT, 0.3-30 μg L⁻¹, 0.08 μg L⁻¹, and 7.2% for o,p′-DDT, and 0.2-30 μg L⁻¹, 0.05 μg L⁻¹, and 6.8% for p,p′-DDE, respectively. Water samples including tap water, well water, snow water, reservoir water, and wastewater were analyzed by the proposed procedure and the recoveries at 5 μg L⁻¹ spiked level were in the range of 86.8-102.6%.     

Determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples using hollow fiber-protected liquid-phase microextraction and high performance liquid chromatography

A new method based on hollow fiber-protected liquid-phase microextraction (LPME) was developed for the simultaneous determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples. In LPME, analytes were extracted into 1-octanol immobilized in the micropores of a poly(vinylidene fluoride) porous hollow fiber membrane, and back extracted into the acceptor (4 M HCl) filled in the lumen of the hollow fiber. After LPME, the analytes trapped in the acceptor were analyzed with high-performance liquid chromatography after neutralization. The effect of extraction factors such as sample pH, acceptor pH, salinity, extraction time, stirring rate, and humic acid were studied. Under the optimized conditions, the limits of detection and relative standard deviations were respectively in the range of 0.5–1.0 μg L⁻¹ and 3.9–4.7% (n = 5). The proposed method was applied to determine atrazine, desethyl atrazine and desisopropyl atrazine in wastewater and groundwater samples. The three analytes were below the limits of detection, but good relative spiked recoveries over 90.1 ± 5.9% at 5 μg L⁻¹ spiked level were obtained.     

Headspace hollow fiber protected liquid-phase microextraction combined with gas chromatography-mass spectroscopy for speciation and determination of volatile organic compounds of selenium in environmental and biological samples

A simple and novel speciation method for the determination of volatile organic compounds of selenium (dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) has been developed using a headspace hollow fiber protected liquid-phase microextraction (HS-HF-LPME) combined with capillary gas chromatography-mass spectrometry (GC-MS). The organic solvent impregnated in the pores and filled inside the porous hollow fiber membrane was used as an extraction interface in the HS-HF-LPME of the compounds. The effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the HS-HF-LPME were sample volume, extraction time, temperature of sample solution, ionic strength, stirring rate and dwelling time. A Plackett-Burman design was performed for screening in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by a Box-Behnken design (BBD) and the response surface equations were derived. Under optimum conditions, preconcentration factors up to 1250 and 1170 were achieved for DMSe and DMDSe respectively. The detection limit and relative standard deviation (RSD) (n=5, c=50 μg L(-1)) for DMSe were 65 ng L(-1) and 4.8%, respectively. They were also obtained for DMDSe as 57 ng L(-1) and 3.9%, respectively. The developed technique was found to be applicable to spiked environmental and biological samples.     

Application of hollow fiber liquid phase microextraction for the determination of insecticides in water

In the present work, a novel sample pre-treatment technique for the determination of trace concentrations of some insecticide compounds in aqueous samples has been developed and applied to the determination of the selected analytes in environmental water samples. The extraction procedure is based on coupling polypropylene hollow fiber liquid phase microextraction (HF-LPME) with gas chromatography by flame thermionic detection (GC-FTD). For the development of the method, seven organophosphorous insecticides (dichlorvos, mevinphos-cis, ethoprophos, chlorpyrifos methyl, phenthoate, methidathion and carbofenothion) and one carbamate (carbofuran) were considered as target analytes. Several factors that influence the efficiency of HF-LPME were investigated and optimized including agitation, organic solvent, sample volume, exposure time, salt additives and pH. The optimized methodology exhibited good linearity with correlation coefficient = 0.990. The analytical precision for the target analytes ranged from 4.3 to 11.1 for within-day variation and 4.6 to 12.0% for between-day variation. The detection limits for all analytes were found in the range from 0.001 to 0.072 microg/L, well below the limits established by the EC Drinking Water Directive (EEC 80/778). Relative recoveries obtained by the proposed method from drinking and river water samples ranged from 80 to 104% with coefficient of variations ranging from 4.5 to 10.7%. The present methodology is easy, rapid, sensitive and requires small sample volumes to screen environmental water samples for insecticide residues.     

Application of hollow fiber-based liquid-phase microextraction (HF-LPME) for the determination of acidic pharmaceuticals in wastewaters

The presence of pharmaceuticals in the environment is a very important problem that requires analytical solutions. The wide variety of matrices and, usually, the low pharmaceuticals levels in the environmental samples requires high sensitive and selective analytical procedures. Wastewaters are one of the more important sources of environmental pollutants but they are very complex matrices that need clean-up procedures prior the analysis. Hollow fiber-based liquid-phase microextraction (HF-LPME) is a relatively new technique used in analytical chemistry for sample pre-treatment that offers high selectivity and sensitivity compared to most traditional extraction techniques. The low organic solvent consumption derived from the use of HF-LPME is according to the current trends to a “Green Chemistry”, and Analytical Chemistry should follow these environmental good practices. This paper describes an extraction method using a polypropylene membrane supporting dihexyl ether (three-phase hollow fiber-based liquid-phase microextraction (HF-LPME)) for the direct analysis of three pharmaceuticals (salicylic acid (SAC), ibuprofen (IBU) and diclofenac (DIC)) in raw and treated wastewaters followed by a HPLC/MS-MS determination using a highly packed Pursuit^® XRs Ultra 2.8 μm C18 column that allows high resolution using low flow-rates and, simultaneously, short retention times. Detection limits were 20, 100 and 300 ng L⁻¹ for salicylic acid, diclofenac and ibuprofen, respectively.