Separations, Volume 4, Issue 2 (June 2017) – 13 articles

Fabric phase sorptive extraction (FPSE) combines the advanced material properties of sol–gel derived microextraction sorbents and the flexibility and permeability of fabric to create a robust, simple and green sample preparation device. It simultaneously improves the extraction sensitivity and the speed of the extraction by incorporating high volumes of sponge-like, porous sol–gel hybrid inorganic–organic sorbents into permeable fabric substrates that are capable of extracting target analytes directly from both simple and complex aqueous sample matrices. For the first time, this technique was applied to the trace-level determination of selected polycyclic aromatic hydrocarbons (PAHs) in environmental water samples using a non-polar sol–gel C18 coated FPSE media. Several extraction parameters were optimized to improve the extraction efficiency and to achieve a high detection sensitivity. Validation tests of spiked samples showed good linearity for four selected PAHs (R² = 0.9983–0.9997) over a wide range of concentrations (0.010–10 ng/mL). Limits of detection (LODs) and quantification (LOQs) were measured at pg/mL levels; 0.1–1 pg/mL and 0.3–3 pg/mL, respectively. Inter- and intra-day precision tests showed variations of 1.1%–4.1% for four selected PAHs. Average absolute recovery values were in the range of 88.1%–90.5% with relative standard deviations below 5%, surpassing the values predicted by the recovery prediction model. Finally, the developed FPSE-HPLC-FLD protocol was applied to analyze 8 environmental water samples. Out of four selected PAHs, fluoranthene (Flu) and phenanthrene (Phen) were the most frequently detected in four samples, at concentrations of 5.6–7.7 ng/mL and 4.1–11 ng/mL, respectively, followed by anthracene (Anth) and pyrene (Pyr) in two samples. The newly developed FPSE-HPLC-FLD protocol is simple, green, fast and economical, with adequate sensitivity for trace levels of four selected PAHs and seems to be promising for routine monitoring of water quality and safety. Full article

The theory and working principle of fabric phase sorptive extraction (FPSE) is presented. FPSE innovatively integrates the benefits of sol–gel coating technology and the rich surface chemistry of cellulose/polyester/fiberglass fabrics, resulting in a microextraction device with very high sorbent loading in the form of an ultra-thin coating. This porous sorbent coating and the permeable substrate synergistically facilitate fast extraction equilibrium. The flexibility of the FPSE device allows its direct insertion into original, unmodified samples of different origin. Strong chemical bonding between the sol–gel sorbent and the fabric substrate permits the exposure of FPSE devices to any organic solvent for analyte back-extraction/elution. As a representative sorbent, sol–gel poly(ethylene glycol) coating was generated on cellulose substrates. Five (cm²) segments of these coated fabrics were used as the FPSE devices for sample preparation using direct immersion mode. An important class of environmental pollutants—substituted phenols—was used as model compounds to evaluate the extraction performance of FPSE. The high primary contact surface area (PCSA) of the FPSE device and porous structure of the sol–gel coatings resulted in very high sample capacities and incredible extraction sensitivities in a relatively short period of time. Different extraction parameters were evaluated and optimized. The new extraction devices demonstrated part per trillion level detection limits for substitute phenols, a wide range of detection linearity, and good performance reproducibility. Full article

Since the introduction in 2014 of fabric phase sorptive extraction (FPSE) as a sample preparation technique, it has attracted the attention of many scientists working in the field of separation science. This novel sorbent extraction technique has successfully utilized the benefits of sol–gel derived hybrid sorbents and a plethora of fabric substrates, resulting in a highly efficient, sensitive and green sample pretreatment methodology. The proposed procedure is an easy and efficient pathway to extract target analytes from different matrices providing inherent advantages such as high sample loading capacity and short pretreatment time. The present review mainly focuses on the background and sol–gel chemistry for the preparation of new fabric sorbents as well as on the applications of FPSE for extracting target analytes, from the time that it was first introduced. New modes of FPSE including stir FPSE, stir-bar FPSE, dynamic FPSE, and automated on-line FPSE are also highlighted and commented upon in detail. FPSE has been effectively applied for the determination of various organic and inorganic analytes in different types of environmental and biological samples in high throughput analytical, environmental, and toxicological laboratories. Full article

High performance liquid chromatography (HPLC) coupled with a diode array detector (HPLC-DAD) for the identification and quantification of carotenoids, namely all-trans lutein, zeaxanthin, β-cryptoxanthin, α-carotene, and β-carotene, in biological samples such as human serum and breast milk, has been developed and validated. Good chromatography separation was achieved using a binary mobile phase system on a YMC C₃₀ column (150 × 2.1 mm, 3 µm) at 30 °C. Owing to the smaller column particle size and diameter of the column, the separation was achieved in 18 min, which is significantly reduced from the typical 30–40 min of other methods. The diode array detector (DAD) acquisition was set at a wavelength of 445 nm; 3D spectra ranging from wavelengths of 240–600 nm were also recorded. Peaks were identified by matching their retention time and spectra with those of standards. Quantification was achieved by internal standard calibration using echinenone as the internal standard. Good linearity was obtained for each compound (R² > 0.9999). The method quantification limits (MQLs) for serum and breast milk were 10 ng/mL and 5 ng/mL, in matrix, respectively. A spike recovery study and standard reference material (SRM) from the National Institute of Standards and Technology (NIST) 968e analysis has proven that the method has a high degree of accuracy, precision, and robustness. The stability study showed that the carotenoid standard and sample extracts could be stored in a chilled autosampler at 8 °C up to 48 h without being comprised, which provides guidance on re-test time frames. The freeze/thaw process was found to be detrimental to carotenoids, and should always be avoided. Most importantly, UV standardization of the stock standard is to be performed prior to each assay, and simply taking the values on Certificate of Analysis (CoA) for calculation of the standard concentration is not recommended. Full article

Antipsychotic drugs are a class of psychiatric medication worldwide used to treat psychotic symptoms principally in bipolar disorder, schizophrenia and other psycho-organic disorders. The traditional sample preparation techniques such as liquid-liquid extraction (LLE) or solid phase extraction (SPE), which were widely used, tend to have many drawbacks because they include complicated, time-consuming steps and they require large sample size as well large amounts of organic solvent. Therefore, due to the modern analytical requirements, such as miniaturization, automation and reduction of solvent volume and time, many microextraction procedures have been developed. In this review we aim to present an overview of those techniques which are used prior to liquid chromatography analyses both for forensic toxicology in different biological matrices as well as for therapeutic drug monitoring. Full article

The nutritional assessment of individuals is usually performed using highly subjective data collecting tools such as food frequency questionnaires, dietary recalls and food records. However, people are not always capable of recalling all foods (and ingredients) consumed, and in some cases, the intake of specific foods is intentionally omitted. Even though wine is considered positive for cardiovascular status, and is an essential part of Mediterranean culture, individuals may not always report its consumption accurately due to the existence of social preconceptions about alcoholic beverages. In this study, the presence of free resveratrol has been determined in human plasma from 25 Spanish volunteers using liquid chromatography coupled to mass spectrometry (LC-MS). This phenolic compound proved to be useful as a dietary biomarker for wine intake in a known population, and the results were compared with those obtained by self-reported dietary assessments. However, certain limitations must also be taken into account such as inter-individual variations and the type of wine consumed. The LC-MS method was validated for trans-resveratrol determination in human plasma, with an LOD (limit of detection) of 50 ng·mL⁻¹ and an LOQ (limit of quantification) of 150 ng·mL⁻¹, respectively. Full article

A sensitive high-performance liquid chromatographic (HPLC) method is described for the determination of posaconazole in human plasma/serum. The method is based on a single dilution step by treating the sample with methanol, and followed by the direct injection of the sample into the HPLC system. Posaconazole and internal standard ketoconazole in the methanol extract are subsequently analyzed by using a fluorescence (FL) detector at optimized wavelengths (excitation 245 nm and emission 380 nm). The method achieves a linear detector response for peak height measurements over the concentration range of 0.1–10 µg/mL which adequately covers the therapeutic range for appropriate patient monitoring. The chromatographic time is less than 8 min per injection, an improvement over most published HPLC/FL or HPLC/UV methods. The method’s limit of quantitation, linearity, imprecision, and accuracy met all criteria required by the Guidance for Industry Bioanalytical Method Validation. In comparison to other published methods, the current method would be of interest to analytical and clinical laboratories because it employs simple, rapid, and cost-effective procedures. Full article

Coccidiostats are synthetic drugs administered to animals, especially to poultry, to cure coccidiosis. In this paper, we present a selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to analyze residues of five synthetic coccidiostats in eggs: clazuril, diclazuril, robenidine, nicarbazin, toltrazuril and its two metabolites. The extraction efficiency was evaluated by testing several solvents, pH, different volumes and time of extraction. The clean-up procedures were optimized using different solid phase extraction cartridges and different eluants. The chromatographic separation was achieved in reversed phase using a gradient of 0.1% formic acid in water and acetonitrile, whereas the MS detection was performed in negative electrospray ionization (ESI) for all the analytes, except for the robenidine. The developed method has been validated according to Commission Decision 2002/657/CE. The validation parameters, as linearity, precision, recovery, specificity, decision limit (CCα), detection capability (CCβ), and robustness have been determined. The proposed method resulted simple, fast, and suitable for screening and confirmation purposes. Full article

A large number of carbon-based nanomaterials has been investigated as sorbents in sample preparation, including fullerenes, carbon nanotubes, nanofibers, nanohorns and graphene, as well as their functionalized forms. Taking into account their properties, carbon-based nanomaterials have found a wide range of applications in different sample preparation techniques. Ionic liquids, as an alternative to environmentally-harmful ordinary organic solvents, have attracted extensive attention and gained popularity in analytical chemistry covering different fields like chromatography, electrochemistry and (micro)extraction. Some of the properties of ionic liquids, including polarity, hydrophobicity and viscosity, can be tuned by the proper selection of the building cations and anions. Their tunable nature allows the synthesis of tailor-made solvents for different applications. This review provides a snapshot of the most important features and applications of different carbon-based nanomaterials functionalized with ionic liquids for sample preparation. Emphasis is placed on the description of the different works that have provided interesting results for the use of graphene and carbon nanotubes, in this analytical field. Full article

The original publication [1] was a short communication paper where a series of experiments were performed using a range of headspace oven temperatures and vial pressures to measure the resulting accuracy and precision of ethanol concentrations using headspace gas chromatography coupled to flame ionization detection (HS-GC-FID) analysis.[...] Full article

The 2015 publication of original research by Boswell and Dorman [1], Uncertainty of Blood Alcohol Concentration (BAC) Results as Related to Instrumental Conditions: Optimization and Robustness of BAC Analysis Headspace Parameters described an evaluation of the effect of modifying headspace parameters on ethanol analysis by gas chromatography with dual flame ionization detection (GC-FID).[...] Full article

Mycotoxins are a very diverse group of natural products produced as secondary metabolites by fungi. Patulin is produced by mold species normally related to vegetable-based products and fruit, mainly apple. Its ingestion may result in agitation, convulsions, edema, intestinal ulceration, inflammation, vomiting, and even immune, neurological or gastrointestinal disorders. For this reason, the European Commission Regulation (EC) 1881/2006 established a maximum content for patulin of 10 ppb in infant fruit juice, 50 ppb for fruit juice for adults and 25 ppb in fruit-derived products. In this work, a rapid and selective method based on magnetic molecularly imprinted stir-bar (MMISB) extraction has been developed for the isolation of patulin, using 2-oxindole as a dummy template. The final extraction protocol consisted of simply pouring in, stirring and pouring out samples and solvents from a beaker with the MMISB acting inside. The magnetic device provided satisfactory recoveries of patulin (60%–70%) in apple samples. The successful MMISB approach has been combined with high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) to determine patulin. Full article

Lactoperoxidase (LP), which is a high-value minor whey protein, has recently drawn extensive attention from research scientists and industry due to its multiplicity of function and potential therapeutic applications. In this study, the separation and optimization of two similar-sized proteins, LP and lactoferrin (LF) were investigated using strong cation exchange column chromatography. A two-step optimization strategy was developed for the separation of LP and LF. Optimization was started with central composite design-based experiments to characterize the influences of different decision variables, namely, flow rate, length of gradient, and final salt concentration in the linear elution gradient step on the yield of LP. This was followed by a more accurate optimization of ion-exchange chromatography (IEC) separation of LP and LF based on an experimentally verified chromatographic model. The optimal operating points were found and the results were compared with validation experiments. Predictions respecting yield confirmed a very good agreement with experimental results with improved product purity. Full article