Luca Rivoira

QuEChERS sample preparation for the determination of pesticides and other organic residues in environmental matrices: a critical review

Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) is an extraction and clean-up technique originally developed for recovering pesticide residues from fruits and vegetables. Since its introduction, and until December 2013, about 700 papers have been published using the QuEChERS technique, according to a literature overview carried out using SciFinder, Elsevier SciVerse, and Google search engines. Most of these papers were dedicated to pesticide multiresidue analysis in food matrices, and this topic has been thoroughly reviewed over recent years. The QuEChERS approach is now rapidly developing beyond its original field of application to analytes other than pesticides, and matrices other than food, such as biological fluids and non-edible plants, including Chinese medicinal plants. Recently, the QuEChERS concept has spread to environmental applications by analyzing not only pesticides but also other compounds of environmental concern in soil, sediments, and water. To the best of our knowledge, QuEChERS environmental applications have not been reviewed so far; therefore, in this contribution, after a general discussion on the evolution and changes of the original QuEChERS method, a critical survey of the literature regarding environmental applications of conventional and modified QuEChERS methodology is provided. The overall recoveries obtained with QuEChERS and other extraction approaches (e.g., accelerated solvent extraction, ultrasonic solvent extraction, liquid/solid extraction, and soxhlet extraction) were compared, providing evidence for QuEChERS higher recoveries for various classes of compounds, such as biopesticides, chloroalkanes, phenols, and perfluoroalkyl substances. The role of physicochemical properties of soil (i.e., clay and organic carbon content, as well as cation exchange capacity) and target analytes (i.e., log KOW, water solubility, and vapor pressure) were also evaluated in order to interpret recovery and matrix effect data.

Simple SPE-HPLC determination of some common drugs and herbicides of environmental concern by pulsed amperometry.

In this work the electrochemical behavior of substances of environmental concern [bentazone, atrazine, carbamazepine, phenytoin and its metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin, HPPH] on a glassy carbon working electrode (Ag/AgCl reference electrode) was studied with the aim to develop a HPLC method coupled with amperometric detection. Constant potential (DC), pulsed amperometric detection modes were studied. For the pulsed mode, several waveforms were set and investigated. Detection conditions were optimized as a function of eluent pH. In order to reduce the limits of detection and to analyze natural water samples, a SPE protocol was optimized to be coupled to the developed procedure. For this aim, five sorbents of different physico-chemical characteristics were tested optimizing a recovery procedure for each of the cartridge evaluated. At the optimized SPE conditions, recoveries were included in the range (R=90.2-100.5% for all the analytes, with excellent reproducibility (<%, n=3). The method detection limits obtained by pulsed amperometry after the SPE protocol (preconcentration factor 100) were 113 ng L(-1) (0.47 nmol L(-1)), 67 ng L(-1) (0.25 nmol L(-1)), 234 ng L(-1) (1.1 nmol L(-1)), for bentazone, HPPH and carbamazepine, respectively. Robustness of the method was assessed for each analyte at a concentration level corresponding to about three times the limit of detection, through the evaluation of intra-day (n=13) and inter-day tests (4 days, n=52). Finally the method was successfully applied for the analysis of a river sample (Po River, Turin, Italy).

Fast low-pressure microwave assisted extraction and gas chromatographic determination of polychlorinated biphenyls in soil samples

A new technology equipment for low-pressure microwave assisted extraction (usually employed for organic chemistry reactions), recently launched in the market, is used for the first time in environmental analysis for the extraction of commercial technical Aroclor mixtures from soil. Certified reference materials of Aroclor 1260, Aroclor 1254 and Aroclor 1242 in transformer oils were used to contaminate the soil samples and to optimize the extraction method as well as the subsequent gas chromatographic electron capture detection (GC-ECD) analytical method. The study was performed optimizing the extraction, the purification and the gas chromatographic separation conditions to enhance the resolution of difficult pairs of congeners (C28/31 and C141/179). After optimization, the recovery yields were included within the range 79-84%. The detection limits, evaluated for two different commercial polychlorinated biphenyl (PCB) mixtures (Aroclor 1260 and Aroclor 1242) were 0.056 ± 0.001 mg/kg and 0.290 ± 0.006 mg/kg, respectively. The method, validated with certified soil samples, was used to analyze a soil sample after an event of failure of a pole-mounted transformer which caused the dumping of PCB contaminated oil in soil. Moreover, the method provides simple sample handling, fast extraction with reduced amount of sample and solvents than usually required, and simple purification step involving the use of solvent (cyclohexane) volumes as low as 5 mL. Reliability and reproducibility of extraction conditions are ensured by direct and continuous monitoring of temperature and pressure conditions.

Determination of phthalate diesters and monoesters in human milk and infant formula by fat extraction, size-exclusion chromatography clean-up and gas chromatography-mass spectrometry detection

Graphical abstract Figure. No Caption available. HighlightsA method for the analysis of phthalate diesters and monoesters in milk is proposed.Phthalate monoesters and diesters were analysed in breastmilk and infant formulas.Target analytes were found to be present in all the investigated samples.Phthalate contamination was higher in infant formula than in breast milk.Daily intake of phthalates was lower than MADI established by EU‐CSTEE and EU‐SCF. ABSTRACT A sensitive and reliable analytical method was developed for the simultaneous determination of five phthalate diesters and corresponding monoesters in human milk samples and infant formulas. The method involved a liquid–liquid extraction with a CH2Cl2/CH3OH/NaCl 30% 2/1/0.5 (v/v/v) mixture, the clean‐up of the extract by size‐exclusion chromatography (swelling and elution solvent: cyclohexane/ethyl acetate 9/1 v/v), the derivatization of monoesters by trimethylsilyl‐diazomethane and instrumental analysis by gas chromatography coupled with mass spectrometry. Recovery was in the range of 83–115% and precision was found between 9% and 21%. For phthalate diesters, method detection limits (MDLs) ranged from hundreds of ng/kg to 4.2 &mgr;g/kg on a fresh weight milk (f.w.) basis, depending on blank contribution evaluated in matrix. Lower MDLs (0.03‐0.8 &mgr;g/kg f.w.) were achieved for corresponding monoesters. The proposed method was applied to the determination of target compounds in nine human milk samples and four infant formulas, confirming their presence in all samples. However, a generally higher contamination was assessed in artificial milk than in breast milk samples.

3D amperometry in the liquid chromatographic determination of trace pharmaceutical and herbicide emerging compounds

ABSTRACT In this work, we innovatively applied the 3D amperometry detection, coupled to liquid chromatography, for the determination of a mixture of chromatographically unresolved compounds (two herbicides—monuron and bentazon, one drug—propranolol and the main metabolite of an antiepileptic drug—5-(4ʹ-hydroxyphenyl)-5-phenylhydantoin). Exploiting the post-chromatographic current integration, a scanning waveform was successfully applied to explore a wide range of potentials (0.0–1.3 V) to find the peculiar oxidative potential value for each compound. This approach allowed us to obtain 3D chromatograms (elution time vs potential vs current) in which coeluted species could be clearly distinguished. Quantitation was easily obtained by extraction of 2D chromatograms (elution time vs integrated current), from the 3D ones, at the optimised waveform time ranges (800–1,000 msec and 1,500–1,700 msec, corresponding to 0.6–0.8 V and 1.0–1.2, respectively). Validation of the proposed 3D amperometry method was performed in terms of linearity, limits of detection and quantitation and repeatability. Matrix effect was studied by statistical treatment on a wastewater effluent. By coupling an on-line solid phase extraction step prior to separation and detection by 3D amperometry, detection limits were significantly reduced (57 ng/L for bentazon, with recovery yields of 82.9 ± 10.9%). It is worth mentioning that this value fully satisfies the requirements of the 98/83/CE directive for the determination of bentazon in groundwater.

Simultaneous determination of five common additives in insulating mineral oils by high-performance liquid chromatography with ultraviolet and coulometric detection

Dielectric mineral oils are used to impregnate power transformers and large electrical apparatus, acting as both liquid insulation and heat dissipation media. Antioxidants and passivators are frequently added to mineral oils to enhance oxidation stability and reduce the electrostatic charging tendency, respectively. Since existing standard test methods only allow analysis of individual additives, new approaches are needed for the detection of mixtures. For the first time we investigate and discuss the performance of analytical methods, which require or do not require extraction as sample pretreatment, for the simultaneous reversed-phase high-performance liquid chromatography determination of passivators (benzotriazole, Irgamet(®) 39) and antioxidants (N-phenyl-1-naphtylamine, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol), chosen for their presence in marketed oils. Quick easy, cheap, effective, rugged and safe and solid phase extractions were evaluated as sample pretreatments. Direct sample-injection was also studied. Ultraviolet spectrophotometry and direct-current coulometry detection were explored. As less prone to additive concentrations variability, the direct-injection high-performance liquid chromatography with ultraviolet and coulometric detection method was validated through comparison with Standard Method IEC 60666 and through an ASTM interlaboratory proficiency test. Obtained detection limits are (mg kg(-1) ): benzotriazole (2.8), Irgamet(®) 39 (13.8), N-phenyl-1-naphtylamine (11.9), 2,6-di-tert-butylphenol (13.1), 2,6-di-tert-butyl-p-cresol (10.2). Simultaneous determination of selected additives was possible both in unused and used oils, with good precision and accuracy.