A cost effective,sensitive, and environmentally friendly sample preparation method for determination of polycyclic aromatic hydrocarbons in solid samples

A simple, cost effective, and yet sensitive sample preparation technique was investigated for determining Polycyclic Aromatic Hydrocarbons (PAHs) in solid samples. The method comprises ultrasonic extraction, Stir Bar Sorptive Extraction (SBSE), and thermal desorption–gas chromatography–mass spectrometry to increase analytical capacity in laboratories. This method required no clean-up, satisfied PAHs recovery, and significantly advances cost performance over conventional extraction methods, such as Soxhlet and Microwave Assisted Extraction (MAE). This study evaluated three operational parameters for ultrasonic extraction: solvent composition, extraction time, and sample load. A standard material, SRM 1649 a (urban dust), was used as the solid sample matrix, and 12 priority PAHs on the US Environmental Protection Agency (US EPA) list were analyzed. Combination of non-polar and polar solvents ameliorated extraction efficiency. Acetone/hexane mixtures of 2:3 and 1:1 (v/v) gave the most satisfactory results: recoveries ranged from 63.3% to 122%. Single composition solvents (methanol, hexane, and dichloromethane) showed fewer recoveries. Comparing 20 min with 60 min sonication, longer sonication diminished extraction efficiencies in general. Furthermore, sample load became a critical factor in certain solvent systems, particularly MeOH. MAE was also compared to the ultrasonic extraction, and results determined that the 20-min ultrasonic extraction using acetone/hexane (2:3, v/v) was as potent as MAE. The SBSE method using 20 mL of 30% alcohol-fortified solution rendered a limit of detection ranging from 1.7 to 32 ng L⁻¹ and a limit of quantitation ranging from 5.8 to 110 ng L⁻¹ for the 16 US EPA PAHs.     

On-line renewable solid-phase extraction hyphenated to liquid chromatography for the determination of UV filters using bead injection and multisyringe-lab-on-valve approach

For the first time, an automatic sample pre-treatment/detection method is proposed for the multiclass determination of UV filters (namely, benzophenone-3, ethylhexylmetoxycinnamate, butylmethoxydibenzoylmethane and homosalate) in environmental samples. The new methodology comprises in-line solid-phase extraction (SPE) of the target analytes by exploiting the bead injection (BI) concept in a mesofluidic lab-on-valve (LOV) format, with subsequent determination by liquid chromatography (LC). The proposed microanalytical system, using a multisyringe burette as propulsion unit, automatically performed the overall SPE steps, including the renewal of the sorbent in each analytical cycle to prevent sample cross-contamination and the post-extraction adjustment of the eluate composition to prevent chromatographic band broadening effects. In order to expedite the LC separation, a C₁₈ monolithic column was applied and an accelerated isocratic elution was carried out by using a cationic surfactant as mobile phase additive. The LOV-BI-LC method was proven reliable for handling and analysis of complex matrices, e.g., spiked swimming pool water and seawater, with limits of detection ranging between 0.45 and 3.2 μg L⁻¹ for 9 mL sample volume. Linear calibration was attained up to 160 μg L⁻¹ for homosalate and up to 35 μg L⁻¹ for the other target analytes, with good reproducibility (RSD < 13%, for 5 different SPE columns). The hyphenated scheme is able to process a given sample simultaneously and within the same time frame than the chromatographic separation/determination of the formerly pre-treated sample, providing concentration values every 9 min. Hence, the sample throughput was enhanced up to 33 times when compared with previously reported off-line SPE methods. A drastic reduction in reagent consumption and effluent production was also attained, contributing to the development of an environment-friendly analyzer.     

Potentialities of polyurethane foams for trace level analysis of triazinic metabolites in water matrices by stir bar sorptive extraction

Polyurethane (PU) foams were applied for stir bar sorptive extraction of five triazinic metabolites (desethyl-2-hydroxyatrazine, desisopropylatrazine, desethylatrazine, 2-hydroxyatrazine and desethylterbuthylazine) in water matrices, followed by liquid desorption and high performance liquid chromatography with diode array detection (SBSE(PU)-LD/HPLC-DAD). The optimum conditions for SBSE(PU)-LD were 5 h of extraction (1000 rpm) and 5% (v/v) of methanol for the analysis of desethyl-2-hydroxyatrazine and 2-hydroxyatrazine, 15% (w/v) of sodium chloride for the remaining compounds and acetonitrile as back-extraction solvent (5 mL) under ultrasonic treatment (60 min). The methodology provided recoveries up to 26.3%, remarkable precision (RSD < 2.4%), excellent linear dynamic ranges between 5.0 and 122.1 μg/L (r² > 0.9993) and convenient detection limits (0.4-1.3 μg/L). The proposed method was applied in the analysis of triazinic metabolites in tap, river and ground waters, with remarkable performance and negligible matrix effects. The comparison of the recoveries obtained by PU and commercial stir bars was also performed, where the yields achieved with the former were up to ten times higher proving that PU is appropriate for analysis at trace level of this type of polar compounds in water matrices.     

A novel application of immobilization on membranes for the separation and spectrofluorimetric quantification of amiloride and furosemide in pharmaceutical samples

A new, simple and highly sensitive method for spectrofluorimetric determination of amiloride (AMI) and furosemide (FUR) in pharmaceuticals is presented. The proposed method is based on the separation of AMI from FUR by solid-phase extraction using a nylon membrane, followed by spectrofluorimetric determination of both drugs, on the solid surface and the filtered aqueous solution, respectively. AMI shows low native fluorescence, but its separation-preconcentration by immobilization (solid-phase extraction) on nylon membrane surface provides a considerable enhancement in fluorescence intensity. The fluorescence determination is carried out at λ_ex = 237, λ_em = 415 nm for FUR; and λ_ex = 365, λ_em = 406 nm for AMI. The calibration graphs are linear in the range 3.20 × 10⁻⁴ to 0.8 μg mL⁻¹and 1.33 × 10⁻³ to 4.0 μg mL⁻¹, for AMI and FUR, respectively, with a detection limit of 9.62 × 10⁻⁵ and 4.01 × 10⁻⁴ μg mL⁻¹ (S/N = 3). The commonly found excipients in commercial pharmaceutical formulations do not interfere. The developed method is successfully applied to the determination of both drugs in pharmaceutical formulations.     

High-throughput salting-out assisted liquid/liquid extraction with acetonitrile for the simultaneous determination of simvastatin and simvastatin acid in human plasma with liquid chromatography

Simvastatin (SS) is an effective cholesterol-lowering medicine, and is hydrolyzed to simvastatin acid (SSA) after oral administration. Due to SS and SSA inter-conversion and its pH and temperature dependence, SS and SSA quantitation is analytically challenging. Here we report a high-throughput salting-out assisted liquid/liquid extraction (SALLE) method with acetonitrile and mass spectrometry compatible salts for simultaneous LC-MS/MS analysis of SS and SSA. The sample preparation of a 96-well plate using SALLE was completed within 20 min, and the SALLE extract was diluted and injected into an LC-MS/MS system with a cycle time of 2.0 min/sample. The seamless interface of SALLE and LC-MS eliminated drying down step and thus potential sample exposure to room or higher temperature. The stability of SS and SSA in various concentration ratios in plasma was evaluated at room and low (4 °C) temperature and the low temperature (4 °C) was found necessary to maintain sample integrity. The short sample preparation time along with controlled temperature (2-4 °C) and acidity (pH 4.5) throughout sample preparation minimized the conversion of SS → SSA to ≤0.10% and the conversion of SSA → SS to 0.00% The method was validated with a lower limit of quantitation (LLOQ) of 0.094 ng mL⁻¹ for both SS and SSA and a sample volume of 100 μL. The method was used for a bioequivalence study with 4048 samples. Incurred sample reproducibility (ISR) analysis of 362 samples from the study exceeded ISR requirement with 99% re-analysis results within 100 ± 20% of the original analysis results.     

Synthesis and application of multi-walled carbon nanotubes-molecularly imprinted sol-gel composite material for on-line solid-phase extraction and high-performance liquid chromatography determination of trace Sudan IV

A novel composite material of multi-walled carbon nanotubes (MWNTs)-Sudan IV molecularly imprinted polymers (MIPs) was prepared by surface molecular imprinting technique in combination with sol-gel technology. The MWNTs-MIPs were evaluated by scanning electron micrograph (SEM), Fourier transform infrared spectroscopy (FT-IR), and adsorption experiments. The results showed that the MWNTs-MIPs exhibited good selective recognition to Sudan IV. The maximum saturated binding capacity (Q_max) is 63.2 μmol g⁻¹. Applied as sorbent, the MWNTs-MIPs were used for the determination of trace Sudan IV in chilli powder by on-line solid-phase extraction-high-performance liquid chromatography (SPE-HPLC). The results showed that an enrichment factor of 741 was achieved with a loading flow rate of 1.0 mL min⁻¹ for sampling 50 mL. The MWNTs-MIPs provided a fast and convenience determination platform for Sudan IV in real samples.     

Application of sugaring-out extraction for the determination of sulfonamides in honey by high-performance liquid chromatography with fluorescence detection

A simple sugaring-out assisted liquid-liquid extraction method combined with high-performance liquid-chromatography with fluorescence detection (HPLC-FL) was developed for the extraction and determination of sulfonamides in honey. Sample preparation consisted of acid hydrolysis to release sugar-bound sulfonamides. After derivatization with fluorescamine, the derivatives were partitioned into the organic layer under the honey (sugar)/water/acetonitrile system. The clear organic extract obtained by centrifugation could be injected into the HPLC system either directly or after dilution. Linearity was obtained with the coefficient of determination (R(2)) higher than 0.998 from 2 to 200 ng/mL. Under the optimal conditions, recoveries were determined for honey fortified at three levels (5, 20, and 100 ng/g) were 80.9-99.6% with coefficients of variation of 0.3-4.4%. Limits of detection for the sulfonamides studied were found to range from 0.6 to 0.9 ng/g.     

Development of a solid phase dispersion-pressurized liquid extraction method for the analysis of suspected fragrance allergens in leave-on cosmetics

A new method based on solid phase dispersion-pressurized liquid extraction (PLE) followed by gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of 26 suspected fragrance allergens (all the regulated in the EU Cosmetics Directive amenable by GC, as well as pinene and methyleugenol) in cosmetic samples. The effects of the temperature, extraction time and solvent, and dispersing sorbent, affecting the whole proposed procedure, have been evaluated using a multifactor strategy. The optima conditions after the analysis of main and second order effects entailed the extraction at 120°C for 15 min, using hexane/acetone as solvent, and florisil as dispersing sorbent. The method performance has been studied, showing good linearity (R≥0.996) as well as good precision (RSD≤10%). Detection limits (S/N=3) ranged from 0.000001 to 0.0002% (w/w), values far below the established restrictions as regard labelling in the European Cosmetics Regulation. Reliability was demonstrated through the quantitative recoveries of all the studied compounds. The absence of matrix effects allowed quantification of the compounds by calibration with standard solutions. The analysis of 10 samples (several moisturizing and anti-wrinkle creams and lotions, hand creams, and sunscreen and after-sun creams), covering very different matrices, showed the presence of suspected allergens in all the analyzed samples; in fact, half of the samples contained an elevated number of them. Although the ubiquity of these compounds was demonstrated, labelling was in all cases in consonance with the European Cosmetics Regulation.     

Metal ion mediated molecularly imprinted polymer for selective capturing antibiotics containing beta-diketone structure

A new molecularly imprinted polymer (MIP) targeting to quinolones (Qs) and tetracyclines (TCs) was synthesized using itaconic acid (ITA) and ciprofloxacin (CIP) as a functional monomer and template molecule, respectively. Factors affecting the overall performance of MIP were investigated, and the results showed that Fe(3+) ion play a vital role in the formation of MIP with high molecular imprinting effect. Meanwhile, the chelating ability of monomer, species of template molecule, as well as the molar ratio of monomer and template also contribute to the performance of the obtained MIP. Cyclic voltammetry verified that, with the participation of Fe(3+) ions, a ternary complex of ITA-Fe(3+)-CIP could be formed before polymerization. Compared with conventional MIP prepared from commonly used monomer, methacrylic acid (MAA), the new MIP show significantly enhanced molecular imprinting effect and higher capacity for specific adsorption of target compounds as revealed by static and dynamic binding experiments. The MIP was successfully used as solid-phase extraction (SPE) adsorbent for enriching a broad spectrum of antibiotics containing beta-diketone structure from surface water sample. HPLC detection showed that high recovery rate (78.6-113.6%) was found in these spiked antibiotics, whereas recovery rate for the non structurally related drugs, epinephrine (EP) and dopamine (DOPA), was very low (4.7-7.6%) on the MIP cartridges. The results demonstrate that the MIP prepared by the strategy proposed in this work, could specifically target to a series of structurally related antibiotics containing beta-diketone structure.     

Determination of fungicides in wine by mixed-mode solid phase extraction and liquid chromatography coupled to tandem mass spectrometry

A novel procedure for the determination of nine selected fungicides (metalaxyl-M, azoxystrobin, myclobutanil, flusilazole, penconazole, tebuconazole, propiconazole, diniconazole and difenoconazole) in wine samples is presented. Sample enrichment and purification is simultaneously performed using mixed-mode, anion exchange and reversed-phase, OASIS MAX solid-phase extraction (SPE) cartridges. Analytes were determined by liquid chromatography coupled to tandem mass spectrometry using atmospheric pressure electrospray ionization (LC-ESI-MS/MS). Parameters affecting the chromatographic determination and the extraction-purification processes were thoroughly investigated. Under optimized conditions, 10 mL of wine were firstly diluted 1:1 with ultrapure water and then passed through the mixed-mode SPE cartridge at a flow of ca. 5 mLmin(-1). After a washing step with 5 mL of an aqueous NH(4)OH solution (5%, w:v), analytes were recovered with just 1 mL of methanol and injected in the LC-MS/MS system without any additional purification. The selective extraction process avoided significant changes in the ionization efficiency for red and white wine extracts in comparison with pure standards in methanol. Performance of the method was good in terms of precision (RSDs<11%) and accuracy (absolute recoveries>72%, determined against pure standards in methanol) reporting method LOQs in the range of 0.01-0.79 ngmL(-1) for target compounds, which are far below the EU maxima residue levels (MRLs) for fungicides in vinification grapes and wine. Several commercial wines from different geographic areas in Spain were analyzed. In most samples, metalaxyl-M and azoxystrobin were found at concentrations up to several ngmL(-1).