Rafael Lucena

Potential of nanoparticles in sample preparation

The paper presents a general overview of the use of nanoparticles to perform sample preparation. In this way the main uses of nanoparticles to carry out solid phase extraction, solid phase microextraction, liquid-liquid extraction and filtration techniques are described for a wide range of nanoparticles including carbon nanoparticles, metallic, silica and molecular imprinted polymer nanoparticles.

One-step in-syringe ionic liquid-based dispersive liquid–liquid microextraction

Dispersive liquid-liquid microextraction (DLLME) has been proved to be a powerful tool for the rapid sample treatment of liquid samples providing at the same time high enrichment factors and extraction recoveries. A new, simple and easy to handle one step in-syringe set-up for DLLME is presented and critically discussed in this paper. The novel approach avoids the centrifugation step, typically off-line and time consuming, opening-up a new horizon on DLLME automation. The suitability of the proposal is evaluated by means of the determination of non-steroidal anti-inflammatory drugs in urine by liquid chromatography/ultraviolet detection. In the presented approach an ionic liquid is used as extractant. The target drugs can be determined in urine within the concentration range 0.02-10 microg mL(-1), allowing their determination at therapeutic and toxic levels. Limits of detection were in the range from 8.3 ng mL(-1) (indomethacin) to 32 ng mL(-1) (ketoprofen). The repeatability of the proposed method expressed as RSD (n=5) varied between 2.5% (for ketoprofen) and 8.6% (for indomethacin).

Ionic liquid-based single-drop microextraction/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene and xylene isomers in waters

The direct coupling between ionic liquid-based single-drop microextraction and gas chromatography/mass spectrometry is proposed for the rapid and simple determination of benzene, toluene, ethylbenzene and xylenes isomers (BTEX) in water samples. The extraction procedure exploits not only the high affinity of the selected ionic liquid (1-methyl-3-octyl-imidazolium hexaflourophosphate) to these aromatic compounds but also its special properties like viscosity, low vapour pressure and immiscibility with water. All the variables involved in the extraction process have been studied in depth. The developed method allows the determination of these single-ring compounds in water under the reference concentration level fixed by the international legislation. In this case, limits of detection were in the range 20 ng L(-1) (obtained for benzene) and 91 ng L(-1) (for o-xylene). The repeatability of the proposed method, expressed as RSD (n=5), varied between 3.0% (o-xylene) and 5.2% (toluene).

Ionic liquid coated magnetic nanoparticles for the gas chromatography/mass spectrometric determination of polycyclic aromatic hydrocarbons in waters

In this paper, ionic liquid coated magnetic nanoparticles (IL-MNPs) have been prepared by covalent immobilization. The as-synthesized MNPs have been successfully used as sorbent for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples, the analytes being finally determined by gas chromatography/mass spectrometry. The influence of several experimental variables (including the ionic strength, amount of MNPs, sample volume, agitation time and desorption solvent) has been considered in depth in the optimization process. The developed method, which has been analytically characterized under its optimal operation conditions, allows the detection of the analytes in the samples with method detection limits in the range from 0.04μgL(-1) (fluoranthene) to 1.11μgL(-1) (indeno(1,2,3-cd)pyrene). The repeatability of the method, expressed as relative standard deviation (RSD, n=7), varies between 4.0% (benzo[b]fluoranthene) and 8.9% (acenaphthene), while the enrichment factors are in the range from 49 (naphthalene) to 158 (fluoranthene). The proposed procedure has been applied for the determination of thirteen PAHs in water samples (tap, river, well and reservoir ones) with recoveries in the range from 75 to 102%.

Ionic liquid-based dynamic liquid-phase microextraction : Application to the determination of anti-inflammatory drugs in urine samples

Dynamic liquid-phase microextraction (dLPME) using an ionic liquid as acceptor phase is proposed for the determination of six non-steroidal anti-inflammatory drugs (NSAIDs) in human urine samples for the first time. The extraction is carried out in a simple and automatic flow configuration. The chemical affinity between the extractant (1-butyl-3-methylimidazolium hexafluorophosphate) and the analytes permits a selective isolation of the drugs from the sample matrix allowing also their preconcentration. The whole analytical method has been optimized taking into account all the chemical, physical and hydrodynamic variables. The proposed method is a valuable alternative for the analysis of these drugs in urine within the concentration range 0.1-10 microg mL(-1), allowing their determination at therapeutic and toxic levels. Limits of detection were in the range from 38 ng mL(-1) (indomethacin) to 70 ng mL(-1) (naproxen). The repeatability of the proposed method expressed as RSD (n=5) varied between 2.1% (flurbiprofen) and 3.8% (tolmetin).

DETERMINATION OF TRIHALOMETHANES IN WATERS BY IONIC LIQUID-BASED SINGLE DROP MICROEXTRACTION/GAS CHROMATOGRAPHIC/MASS SPECTROMETRY

A simple, rapid, solventless method for the determination of trihalomethanes (THMs) (chloroform, bromodichloromethane, dibromochloromethane and bromoform) in water samples is presented. The analytes are extracted from the headspace of the aqueous matrix into a 2 microL drop of the ionic liquid 1-octyl-3-methyl-imidazolium hexafluorophosphate working at 30 degrees C for 30 min. The separation and detection of the target compounds is accomplished by gas chromatography/mass spectrometry owing to the use of an interface that efficiently transfers the analytes extracted in the ionic liquid drop to the gas chromatograph while preventing the ionic liquid from entering the column. The detection limits obtained are below the values compelled by the legislation, ranging from 0.5 microg L(-1) for chloroform and bromodichloromethane to 0.9 microg L(-1) for dibromochloromethane. The use of ionic liquid in the extraction procedure avoids the use of organic solvents and leads to relative standard deviations that range from 3.1% to 4.8%.

Determination of phenols in waters by stir membrane liquid-liquid-liquid microextraction coupled to liquid chromatography with ultraviolet detection.

A simple and rapid method for the determination of eleven phenols in water samples is presented. The target analytes are isolated by stir membrane liquid-liquid microextraction working under the three-phase mode. An alkaline aqueous solution is used as extractant phase while octanol is selected as supported liquid membrane solvent. The target analytes are separated and determined by liquid chromatography (LC) with ultraviolet detection (UV). All the variables involved in the extraction process have been studied in depth. Low detection limits (in the range from 82.1 ng/L for phenol to 452 ng/L for 2,4,5-trichlorophenol) were obtained. The repeatability, expressed as relative standard deviation (RSD), varied between 1.3% (for 4-nitrophenol) and 8.0% (for 4-chlorophenol). The enrichment factors were in the range from 168 (for 2,4,5-trichlorophenol) to 395 (for 3-chlorophenol). The proposed procedure was applied for the direct determination of the eleven phenols in some real water samples including river, well and tap waters. The accuracy was evaluated by means of a recovery study, the results being in the range of 87-120%.

Sample treatments based on dispersive (micro)extraction

Sample treatment has evolved in the last few years following basic trends, simplification, automation and miniaturization being the most remarkable ones. Microextraction techniques, including solid phase microextraction (SPME) and liquid phase microextraction (LPME), have emerged in this context showing very competitive features if they are compared with their classic counterparts. Essentially, extraction techniques are surface dependent processes since their kinetics depend directly on the contact surface between the sample and the extractant phase. This aspect, which is important in any extraction procedure, becomes critical when the amount of extractant is reduced to the microscale. In this context, dispersive-based procedures have gained importance as rapid and efficient sample treatment methodologies. This review article deals with the use of dispersion in micro-solid phase extraction (μ-SPE) and LPME. The main techniques as well as their powerful combinations will be described in depth with references to the most relevant applications.

Ionic liquid-based single drop microextraction and room-temperature gas chromatography for on-site ion mobility spectrometric analysis

The combination of ionic liquid-based headspace single drop microextraction (IL-HS-SDME) and room-temperature gas chromatography/ion mobility spectrometry (RTGC-IMS) is presented for the first time using the direct determination of trihalomethanes in waters as model analytical problem. The ionic liquid allows the transference of the analytes from the sample to the analytical system, at the same time that it provides an increase of the sensitivity and selectivity of the determination. An injection unit has been designed to permit the efficient volatilization of the analytes at room temperature and to avoid the entering of IL in the system. The direct combination allows the determination of the halocompounds in a rapid and simple way taking advance of their characteristic IMS spectra. The limits of the detection range between 0.1 ng mL(-1) (bromoform) and 0.9 ng mL(-1) (chloroform), the reproducibility of the system being better than 7.1% (RSD). The proposed coupling opens up a new horizon in IMS-based applications.

Effervescence assisted dispersive liquid-liquid microextraction with extractant removal by magnetic nanoparticles.

In this article, effervescence assisted dispersive liquid-liquid microextraction with extractant removal by magnetic nanoparticles is presented for the first time. The extraction technique makes use of a mixture of 1-octanol and bare Fe3O4 magnetic nanoparticles (MNPs) in acetic acid. This mixture is injected into the sample, which is previously fortified with carbonate, and as a consequence of the effervescence reaction, CO2 bubbles are generated making possible the easy dispersion of the extraction solvent. In addition, the MNPs facilitates the recovery of the 1-octanol after the extraction thanks to the interaction between hydroxyl groups present at the surface of the MNPs and the alcohol functional group of the solvent. The extraction mode has been optimized and characterized using the determination of six herbicides in water samples as model analytical problem. The enrichment factors obtained for the analytes were in the range 21-185. These values permit the determination of the target analytes at the low microgram per liter range with good precision (relative standard deviations lower than 11.7%) using gas chromatography (GC) coupled to mass spectrometry (MS) as analytical technique.