Andres D. Campiglia

Determination of Polycyclic Aromatic Hydrocarbons in Drinking Water Samples by Solid-Phase Nanoextraction and High-Performance Liquid Chromatography

A novel alternative is presented for the extraction and preconcentration of polycyclic aromatic hydrocarbons (PAH) from water samples. The new approachwhich we have named solid-phase nanoextraction (SPNE)takes advantage of the strong affinity that exists between PAH and gold nanoparticles. Carefully optimization of experimental parameters has led to a high-performance liquid chromatography method with excellent analytical figures of merit. Its most striking feature correlates to the small volume of water sample (500 microL) for complete PAH analyses. The limits of detection ranged from 0.9 (anthracene) to 58 ng.L (-1) (fluorene). The relative standard deviations at medium calibration concentrations vary from 3.2 (acenaphthene) to 9.1% (naphthalene). The analytical recoveries from tap water samples of the six regulated PAH varied from 83.3 +/- 2.4 (benzo[ k]fluoranthene) to 95.7 +/- 4.1% (benzo[ g,h,i]perylene). The entire extraction procedure consumes less than 100 microL of organic solvents per sample, which makes it environmentally friendly. The small volume of extracting solution makes SPNE a relatively inexpensive extraction approach.

A simple method for methylmercury, inorganic mercury and ethylmercury determination in plasma samples by high performance liquid chromatography–cold-vapor-inductively coupled plasma mass spectrometry

A simple and sensitive method with a fast sample preparation procedure is proposed for the determination of mercury species in plasma/serum. The method combines online high-performance liquid chromatography separation, Hg cold-vapor formation and inductively coupled plasma mass spectrometry detection. Prior to analysis, plasma (250 μL) was accurately pipetted into 15 mL conical tubes. Then, an extractant solution containing mercaptoethanol, L-cysteine and HCl was added to the samples following sonication for 10 min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 8 min on a C8 reverse phase column with a mobile phase containing 3% v/v methanol + 97% v/v (0.5% v/v 2-mercaptoethanol + 0.05% v/v formic acid). The method detection limits were found to be 12 ng L(-1), 5 ng L(-1) and 4 ng L(-1) for inorganic mercury, ethylmercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from NIST. Additional validation was provided by the analysis of a secondary reference serum sample from the INSQ-Canada. Finally, the method was successfully applied for the speciation of mercury in plasma samples collected from volunteers exposed to methylmercury through fish consumption. For the first time to our knowledge, levels of different species of Hg in plasma samples from riverside populations exposed to MeHg were determined.

Solid-phase nano-extraction and laser-excited time-resolved Shpol’skii spectroscopy for the analysis of polycyclic aromatic hydrocarbons in drinking water samples

A unique method for screening polycyclic aromatic hydrocarbons in drinking water samples is reported. Water samples (500 microl) are mixed and centrifuged with 950 microl of a commercial solution of 20 nm gold nanoparticles for pollutants extraction. The precipitate is treated with 2 microl of 1-pentanethiol and 48 microl of n-octane, and the supernatant is then analyzed via laser-excited time-resolved Shpolskii spectroscopy. Fifteen priority pollutants are directly determined at liquid helium temperature (4.2 K) with the aid of a cryogenic fiber-optic probe. Unambiguous pollutant determination is carried out via spectral and lifetime analysis. Limits of detection are at the parts-per-trillion level. Analytical recoveries are similar to those obtained via high-performance liquid chromatography. The simplicity of the experimental procedure, use of microliters of organic solvent, short analysis time, selectivity, and excellent analytical figures of merit demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.

A fast method for bisphenol A and six analogues (S, F, Z, P, AF, AP) determination in urine samples based on dispersive liquid-liquid microextraction and liquid chromatography-tandem mass spectrometry.

In this study, a novel method combining dispersive liquid-liquid microextraction (DLLME) and fast liquid chromatography coupled to mass spectrometry (LC-MS/MS) was developed and validated for the extraction and determination of bisphenol A (BPA) and six bisphenol analogues, namely bisphenol S (BPS), bisphenol F (BPF), bisphenol P (BPP), bisphenol Z (BPZ), bisphenol AP (BPAP) and bisphenol AF (BPAF) in human urine samples. Type and volume of extraction and disperser solvents, pH sample, ionic strength, and agitation were evaluated. The matrix-matched calibration curves of all analytes were linear with correlation coefficients higher than 0.99 in the range level of 0.5-20.0ngmL(-1). The relative standard deviation (RSD), precision, at three concentrations (1.0, 8.0 and 15.0ngmL(-1)) was lower than 15% with accuracy ranging from 90 to 112%. The biomonitoring capability of the new method was confirmed with the analysis of 50 human urine samples randomly collected from Brazilians. BPA was detected in 92% of the analyzed samples at concentrations ranging

Classification of geographic origin of rice by data mining and inductively coupled plasma mass spectrometry

We used data mining with ICP-MS to evaluate origin of rice.An accuracy above 93% was obtained with SVM and RF algorithms.Our method can be used for authentication purposes of other food. Rice is one of the most consumed cereals in the world and the main food product in the diet of the Brazilian population. Brazil itself is among the ten largest producers of rice, and most of the harvest comes from the South and Midwest regions. This paper presents a data mining study of samples of rice obtained from producers in Goias (Midwest region) and Rio Grande do Sul (South region), and builds classification models capable of predicting the geographical origin of a rice sample based on its chemical components. We use three popular classification techniques, support vector machines, random forests and neural networks, along with the F-score formula which measures the relative importance of the input variables. We achieved very good performances for the SVM, RF and MLP models with 93.66%, 93.83% and 90% prediction accuracy, respectively, on the 10-fold cross validation. The F-score shows that Cd(cadmium), Rb(rubidium), Mg(magnesium) and K(potassium) are the four most relevant components for prediction.

Direct quantification of monohydroxy-polycyclic aromatic hydrocarbons in synthetic urine samples via solid-phase extraction–room-temperature fluorescence excitation–emission matrix spectroscopy

A screening method for six biomarkers from polycyclic aromatic hydrocarbons (PAH) exposure in urine samples is presented. Solid-phase extraction is carried out on commercial C18 cartridges via an optimized procedure that minimizes metabolite loss. PAH metabolites are directly determined in the eluting solvent (3 mL of methanol) without the need of previous solvent evaporation. Spectral overlapping is resolved with the combination of unfolded partial least squares and residual bilinearization. Excellent analytical figures of merit were obtained for all the studied metabolites. Analytical recoveries varied between 87.9% (9-hydroxyphenanthrene) and 99.4% (3-hydroxybenzo[a]pyrene). For 10 mL of urine sample, the limits of detection varied between 0.01 ng.mL(-1) (3-hydroxybenzo[a]pyerene and 1-hydroxybenzopyrene) and 0.3 ng.mL(-1) (2-hydroxynaphthalene). Because the chemometric algorithm is capable of handling more than six metabolites at once, the application of this approach to a larger number of metabolites is feasible.

Using gold nanoparticles to improve the recovery and the limits of detection for the analysis of monohydroxy-polycyclic aromatic hydrocarbons in urine samples

We present a novel approach to improve the analytical figures of merit of solid-phase extraction high-performance liquid chromatography (SPE-HPLC) for the analysis of monohydroxy-polycyclic aromatic hydrocarbons in urine samples. The novel alternative substitutes the evaporation step that is currently used in SPE-HPLC methodology with a pre-concentration procedure that extracts metabolites with gold nanoparticles. The analytical potential of the new approach is evaluated with the following six metabolites: 9-hydroxyphenanthrene, 2-hydroxyfluorene, 1-hydroxypyrene, 6-hydroxychrysene, 3-hydroxybenzo[a]pyrene and 4-hydroxybenzo[a]pyrene. We demonstrate that the substitution of the evaporation step with the gold nanoparticles procedure improves the overall recoveries, the relative standard deviations of the average recoveries and the limits of detection of SPE-HPLC analysis. The overall recoveries of the studied metabolites varied from 59.7 +/- 3.6% (2-hydroxyfluorene) to 92.3 +/- 2.5% (6-hydroxychrysene). The relative standard deviations of the average recoveries were lower than 6%. The limits of detection were at the parts-per-trillion levels and varied from approximately 2 pg mL(-1) (6-hydroxychrysene) to approximately 18 pg mL(-1) (2-hydroxyfluorene).

Portable mercury sensor for tap water using surface plasmon resonance of immobilized gold nanorods.

The surface plasmon resonance of surface immobilized gold nanorods (Au NRs) was used to quantify mercury in tap water. Glass substrates were chemically functionalized with (3-mercaptopropyl)trimethoxysilane, which chemically bound the nanorods to produce a portable and sensitive mercury sensor. The analytical capabilities of the sensor were measured using micromolar mercury concentrations. Since the analytical response was dependent upon number of nanorods present, the limit of detection was 2.28×10(-19) M mercury per nanorod. The possibility to using glass substrates with immobilized Au NRs is a significant step towards the analysis of mercury in tap water flows at this low concentration level.

High Levels of Bisphenol A and Bisphenol S in Brazilian Thermal Paper Receipts and Estimation of Daily Exposure

Bisphenol A (BPA) is an endocrine and metabolic disruptor commonly employed as a color developer in thermal papers. Consequently, BPA derived from thermal papers has been considered an important source of exposure for humans, since this chemical may migrate from paper to skin upon contact. Further, due to recent restrictions on BPA use in some countries, it has been replaced by a new analogue, bisphenol S (BPS). The aim of the present study was to determine levels of BPA and BPS in 190 different thermal receipts, randomly collected from different locations in São Paulo State, Brazil, including receipts from supermarkets, general and fast-food restaurants, gas stations, bus and airplane tickets, and credit card and bank accounts. BPA and/or BPS were detected in 98% of samples at concentrations ranging from below the quantification limit to 4.3% (mg/100 mg paper). The obtained values were higher than amounts previously reported in other countries. The estimated daily intake through dermal absorption from handling of thermal receipt papers was estimated on the basis of concentrations and frequencies of handling of papers by humans in both the general population and occupationally exposed individuals. Fifth percentile, median, and 95th percentile daily intakes by the general population were 0.44, 1.42, and 2 μg/d, respectively, whereas the corresponding values for occupationally exposed population are 21.8, 71 and 101 μg/d. The potential adverse consequences of elevated occupational exposure are currently being examined.

Gold nanoparticles deposited capillaries for in-capillary microextraction capillary zone electrophoresis of monohydroxy-polycyclic aromatic hydrocarbons.

This article presents the first application of gold nanoparticles deposited capillaries as pre‐concentration devices for in‐capillary microextraction CZE and their use for the analysis of monohydroxy‐polycyclic aromatic hydrocarbons in synthetic urine samples. The successful separation of 1‐hydroxypyrene, 9‐hydroxyphenanthrene, 3‐hydroxybenzo[a]pyrene (3‐OHbap), 4‐hydroxybenzo[a]pyrene and 5‐hydroxybenzo[a]pyrene under a single set of electrophoretic conditions is demonstrated as well as the feasibility to obtain competitive ultraviolet absorption LOD with commercial instrumentation. Enrichment factors ranging from 87 (9‐OHphe) to 100 (3‐OHbap) made it possible to obtain LOD ranging from 9 ng/mL (9‐OHphe and 3‐OHbap) to 14 ng/mL (4‐hydroxybenzo[a]pyrene).