Selective extraction of Cu+ and Cu2+ ions from mushroom and lichen samples prior to analysis by micro-volume UV-Vis spectrophotometry: Application of a novel poly (SMIm)-Tris-Fe3O4 nanocomposite

In this study, a novel poly (SMIm)-Tris-Fe₃O₄ nanocomposite was prepared for selective extraction of Cu⁺ and Cu²⁺ ions by ultrasound assisted-cloud point extraction (UA-CPE). The nanocomposite was characterized by analysis of ATR-FT-IR, ¹H NMR and XRD. After optimization of the extraction conditions, the copper ions were independently detected against sample blank at 347 nm by micro-volume UV–vis spectrophotometer. Under the optimal conditions, good linear relationship was obtained in the ranges of 0.3−150 and 10−350 μg L⁻¹ for each ion at pH 7.0 and pH 5.0, respectively, with a better regression coefficient than 0.992. The method detection limits, accuracy and precision were 0.095 and 3.03 μg L⁻¹, 91.5−96.0 % and 93.0−98.5 %, and 2.5–4.5 and 3.8–7.1 % (n:5, 25 and 100 μg L⁻¹) for Cu⁺ and Cu²⁺ ions, respectively. A preconcentration of 70-fold was obtained from 35-mL of sample. After validation, the method was successfully applied to determination of total Cu levels in lichen and mushroom samples after pre-reduction at pH 7.0, and the recoveries in the range of 90−96 % were obtained by two calibration approaches after spiking with 10 μg L⁻¹. The results were also statistically compared with those obtained by FAAS analysis to ensure accuracy and precision.     

Application of deep eutectic solvent as a disperser in reversed-phase dispersive liquid-liquid microextraction for the extraction of Cd(II) and Zn(II) ions from oil samples

A new, sensitive, and safe pretreatment method for the analysis of Cd(II) and Zn(II) ions in oil samples prior to flame atomic absorption spectrometry was developed. For the first time, a deep eutectic solvent is used as a disperser in reversed-phase dispersive liquid-liquid microextraction procedure. For this purpose, a deep eutectic solvent with low viscosity and miscible with both aqueous and organic phases is prepared by mixing glycolic acid and mandelic acid at a molar ratio of 2:1. The variables involved in this process were studied to provide high enrichment factors. Under optimized conditions, the linear ranges of calibration curves for Cd(II) and Zn(II) ions were obtained 0.30−20 and 0.50−30 μg L⁻¹, respectively. The obtained detection limits and enrichment factors were 0.12 and 0.18 μg L⁻¹; and 32.7 and 32.2 for Cd(II) and Zn(II), respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 2.7 to 4.1 % (n = 6, C = 1 μg L⁻¹ of each cation). Finally, the proposed method was successfully applied for the determination of Cd(II) and Zn(II) concentrations in various oil samples.     

Salting-out homogeneous liquid-liquid microextraction for the spectrophotometric determination of iodate in food grade salt

A simple and rapid method has been reported for the determination of iodate in food grade salt samples where iodate has been used for the oxidation of phenylhydrazine to phenyldiazonium ion which then couples with 2-naphthol or with 8-hydroxyquinoline to produce orange red azo dye. The dye was extracted with microliter volume of 2-propanol, when the phase separation occurred by addition of ammonium sulphate, a process called salting out homogeneous liquid liquid microextraction (SH-LLME), and analysed spectrophotometrically. Relative efficiencies of both the coupling reagents were compared for iodate determination, when both coupling agents, 8-hydroxyquinoline and 2-naphthol, produced relatively comparable results. The method has been optimized for the reaction time, and type of extracting solvent and salt for phase separation. A linear calibration curve was obtained for 0.08−10 mg L⁻¹ of iodate with correlation coefficient of 0.998 and limit of detection of 16 μg L⁻¹. Food grade salt samples have been analyzed with adequate recovery in spiking experiments, being, 86.2–114.6 (RSD, 6.6–12.6 %) and 90.8–111.3 (RSD, 7.1–12.6 %) using 2-naphthol and 8-hydroxyquinoline as a coupler, respectively. The SH-LLME avoids pH adjustment of the final test sample before extraction, and Cu(II) and Fe(III) up to 1 and 6 mg L⁻¹, respectively, can be tolerated. Enrichment factors with the two reagents in that order were 21 and 20, respectively.     

A rapid method for simultaneous determination of nitrate,nitrite and thiocyanate in milk by CZE-UV using quaternary ammonium chitosan as electroosmotic flow inverter

This paper proposes a rapid method for the simultaneous determination of nitrate, nitrite and thiocyanate in different milk samples (cow, goat and soy) using capillary zone electrophoresis. The separations were conducted in a fused silica capillary dynamically coated with quaternary ammonium chitosan, with a total length of 48.5 cm (40 cm effective x 75 μm internal diameter) and direct detection in the UV region at 210 nm. The background electrolyte (BGE) was composed of 30 mmol L⁻¹ of aminocaproic acid and 24 mmol L¹ of perchloric acid (pH 3.85).A typical anodic electroosmotic flow of -31 × 10^-9 m² V⁻¹ s⁻¹ was observed at the pH of the separations. Bromate was used as the internal standard. The samples were injected by hydrodynamic pressure (50 mbar, 40 s) and the separation voltage was −30 kV. The proposed method was validated and presented good linearity (R²> 0.99) in the linear range of 0.1–4.0 mg L⁻¹. The ranges of the limit of detection (LOD) and limit of quantification (LOQ) were 0.03-0.04 and 0.05–0.07 mg L⁻¹, respectively. The intra-day and inter-day precision values were better than 4.2 and 8.7 %, respectively. Recovery values ranged from 85 to 104% for the different samples of milk. The proposed method was applied in 12 commercial samples with run times of less than 2 min. The good analytical performance indicates that the method proposed is a promising alternative for the determination of nitrate, thiocyanate and nitrite in milk samples.     

Exposure to nickel through commercial premade baby foods: Is there any risk?

A study was performed to evaluate the risk regarding the presence of nickel in commercial premade baby foods: 26 ready meals, 31 fruits, 8 deserts and 20 paps. The analytical methodology used for the determination of nickel was dry ashing followed by graphite furnace atomic absorption spectrometry. Method detection limit (12.5 μg kg⁻¹) was obtained through a matrix matched calibration curve, using a nickel free commercial ready meal (meat).The results showed that 78 (91.8 %) samples contained nickel, with values up to 225.7 μg kg⁻¹. The group with the highest average concentration was the fruits (50.1 μg kg⁻¹) followed by the ready meals (40.2 μg kg⁻¹). Samples from organic farming presented higher detection frequency and average concentration (54.7 μg kg⁻¹) than the others. Using the average results, the tolerable daily intake proposed by EFSA (2.8 μg kg⁻¹ b.w.) was surpassed for the 2 year old age group, with daily ingestions up to 3.1 μg kg⁻¹ b.w.. This results highlight the risk promoted by the nickel present in commercial premade baby food.     

Single quadrupole inductively coupled plasma-mass spectrometry for the measurement of fluorine in tea infusions and its health risk assessment

Single quadrupole inductively coupled plasma-mass spectrometry (ICP-QMS) method was developed to measure the total F concentration (fluoride and covalently bonded F) in tea infusion and its associated health risks was assessed. The detection was based on the measurement of BaF⁺ generated by F and Ba in ICP. Polyatomic interference from ¹³⁸Ba- hydroxide and ¹⁵⁷Gd⁺ at the target m/z 157 were overcome by combining of aerosol dilution technique and mathematical correction. The limit of detection was 0.032 µg L⁻¹. After 5 min of leaching, the mean F concentration in 100 tea infusion ranged from 0.24 to 7.25 mg L⁻¹ (brick tea > black tea > white tea > oolong tea > green tea). 95th percentile of the chronic daily intake (0.003–0.024 mg/kg/day) and the target hazard quotient (0.089–0.398) indicate that F exposure from tea consumption in adults is within the safe level.     

In-solution derivatization and detection of glyoxal and methylglyoxal in alcoholic beverages and fermented foods by headspace solid-phase microextraction and gas chromatography–mass spectrometry

A simple and sensitive method for the simultaneous determination of glyoxal and methylglyoxal in alcoholic beverages and fermented foods was developed. This method involved simultaneous derivatization in solution with 2,2,2-trifluoroethyl hydrazine (TFEH) and headspace solid phase microextraction, followed by detection via gas chromatography-mass spectrometry (GC–MS). The method established herein can be summarized as follows. The sample was adjusted to pH 6.0 in a headspace vial, saturated with sodium chloride, and allowed to react with TFEH at 85 °C for 20 min. The formed derivatives were vaporized and adsorbed on divinylbenzene/carboxy/polydimethylsiloxane fibers. The TFEH derivatives were subsequently desorbed and analyzed by GC–MS, where the spectrum showed a single sharp peak. Under the established conditions, the quantification limits of glyoxal and methylglyoxal were 3.6 and 2.1 μg kg⁻¹, respectively, and the relative standard deviations were under 8% at concentrations of 20, 100 and 2000 μg kg⁻¹. All samples were detectable at typical glyoxal (62–4116 μg kg⁻¹) and methylglyoxal (11–2342 μg kg⁻¹) concentrations in beverages and foods.     

An efficient,rapid and microwave-accelerated dispersive liquid–liquid microextraction method for extraction and pre-concentration of some organophosphorus pesticide residues from aqueous samples

In this paper, microwave-accelerated dispersive liquid–liquid microextraction has been developed for the extraction/preconcentration of some organophosphorus pesticides from aqueous samples prior to their analysis by gas chromatography–flame ionization detection. In this method, temperature of a high volume of aqueous sample is elevated by a microwave oven and then a mixture of extraction and disperser solvents is rapidly injected into the aqueous phase. After cooling to room temperature, the phase separation is accelerated by centrifuging. The main experimental factors affecting performance of the method including type and volume of the extraction and disperser solvents, temperature, pH, and salt addition were investigated and optimized. Under the optimum extraction conditions, the method resulted in low limits of detection and quantification within the ranges of 0.65–1.3 and 2.2–4.5 μg L⁻¹, respectively. Relative standard deviations were in the range of 2–7% (C = 40 or 100 μg L⁻¹) for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method was successfully applied to analysis of the target analytes in surface water and well water and fruit juice samples; diazinon was determined at μg L⁻¹ level in apple juice.     

Spectrophotometric method for determination of aluminium content in water and beverage samples employing flow-batch sequential injection system

A sensitive, precise and reliable flow-batch method for the determination of aluminium (Al) was developed using a sequential injection-monosegmented flow system incorporating a mixing chamber unit. Eriochrome cyanine R (ECR) was used as a chromogenic reagent in the presence of N,N-dodecyltrimethylammonium bromide (DTAB). The Al-ECR complex at pH 6 gave a maximum absorption at 584 nm. In-line single standard calibration and a standard addition procedure were developed employing the monosegmented flow technique. Under the optimum conditions, a linear calibration graph in the range of 0.0075–0.625 mg L⁻¹ Al was obtained with limits of detection and quantitation of 0.0020 and 0.0070 mg L⁻¹, respectively. Relative standard deviations were 0.8 and 1.3% for 0.010 and 0.025 mg L⁻¹ Al (n = 11), respectively. A sample throughput of 24 h⁻¹ using an in-line standard calibration approach and 6 h⁻¹ using four standard addition levels was achieved. The developed system was successfully applied to water samples and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 85 and 104% were obtained.     

Simultaneous enrichment/determination of six sulfonamides in animal husbandry products and environmental waters by pressure-assisted electrokinetic injection coupled with capillary zone electrophoresis

Pressure-assisted electrokinetic injection (PAEKI) as the online method was developed for the simultaneous enrichment of six sulfonamides (SAs), including sulfamethazine (SMZ), sulfamerazine (SMR), sulfamonomethoxine (SMM), sulfadizine (SDZ), sulfamethoxazole (SMX) and sulfacetamide (SFA) in different animal husbandry products and environmental waters samples, followed by capillary zone electrophoresis (CZE) determination. Various parameters affecting the separation performance of CZE and the enrichment efficiency of PAEKI were optimized in detail. Under optimal conditions, the six SAs were completely separated within 8.5 min, and the enrichment factors for SMZ, SMR, SMM, SDZ, SMX and SFA were 39, 47, 53, 50, 54 and 62 folds, respectively, compared with the direct CZE. The limits of detection (LOD) ranged from 0.0018–0.0163 μg/mL, 0.0083–0.0638 μg/mL and 0.0052–0.0478 μg/mL in milk, pork and egg samples, respectively, as well as limits of quantification (LOQ) within 0.0061–0.0503 μg/mL, 0.0253–0.1826 μg/mL and 0.0164–0.1475 μg/mL, respectively. Tap water, lake water and seawater were also examined for investigation of applicability of the proposed method. Satisfactory recoveries in the range of 89–113 % were obtained with the three spiked food samples, and the relative standard deviations were from 1.6 to 7.3%. Simple and effective online enrichment method provides a promising perspective for CZE measurements of SAs in complex matrices with high accuracy, sensitivity and rapidity.     

Concentrations and health risk assessment of total mercury in canned tuna marketed in Southest Brazil

The aim of this research was to determine total mercury (Hg) content in 69 canned tuna of 13 brands marketed in southwest Brazil. All values are reported in μg.g⁻¹ wet weight basis. Potential health risk was estimated on the basis of mercury concentration and average consumption (175 g/per week) of fish in Brazil comparing to PTWI of 1.6 μg.kg⁻¹ (FAO/WHO, 2010). A large variation in the concentration of mercury in different species was observed. Mean mercury concentration was 0.256 ± 0.215 μg.g⁻¹ with a highest value of 1.060 μg.g⁻¹ in a single can. In general average concentration was below the legislation of 1.0 μg.g⁻¹ for predatory species (BRASIL, 2010). Estimate weekly intake (EWI) varied 0.2–1.7 μg.kg⁻¹. For the analyzed brands and Brazilian fish consumption, no human health risk is likely to occur. However one brand was higher than PTWI of 1.6 μg.kg⁻¹ showing no safety for specific risk group. Further studies including specific data on canned tuna consumption in specific populations will be needed as well as the fish type, fish size and fishing location.     

Fluoroquinolones extraction from meat samples based on deep eutectic solvent formation

A simple, highly available and cheap approach for effective pretreatment of meat samples, based on the formation of deep eutectic solvent (DES), was proposed for the first time. The procedure assumed dissolution of a hydrogen bond acceptor of DES (quaternary ammonium salt) in homogenized meat sample, followed by heating with a hydrogen bond donor of DES (medium-chain alcohol). Heating the mixture promoted DES formation and separation of analytes from the meat sample into the DES phase formed. The developed approach was proven to be highly effective for ofloxacin and fleroxacin separation from meat samples (chicken and beef). It was shown, that the developed procedure provided higher extraction efficiency of analytes (extraction recovery 98–100 %) in comparison with conventional extraction in pre-synthesized viscous DES, composed of tetrabutylammonium bromide and heptanol (extraction recovery 33–67 %). The developed approach was coupled with high-performance liquid chromatography with fluorometric detection for the determination of ofloxacin and fleroxacin in real and spiked meat samples. The limits of detection obtained from peaks 3 times the signal-to-noise ratio were 10 μg kg⁻¹ for ofloxacin and 15 μg kg⁻¹ for fleroxacin.     

Development of a new method for determination of aluminum (Al) in Jordanian foods and drinks: Solid phase extraction and adsorption of Al3+-d-mannitol on carbon nanotubes

In this work, a new method was developed for determination of aluminum (Al) in traditional Jordanian foods (Mansaf, Kofta, Tabboola, Hummous, bread), tea, Arabian coffee and water samples. The method involved solid phase extraction (SPE) of Al³⁺ from the digested samples after complexation with d-mannitol using carbon nanotubes (CNT) as the extractive sorbent. Formation of the Al³⁺-d-mannitol complex was confirmed by infrared spectroscopy. Optimization of the SPE method involved sample pH, d-mannitol-to-Al mole ratio, sample loading and elution flow rates, adsorbent mass, eluent concentration and volume. Based on spiked water samples, the characteristics of the method were as follows: the limit of quantification: 23 μg l⁻¹; sensitivity: 0.0036 (mg l⁻¹)⁻¹; %RSD range: 0.4–1.9%; recovery range: 76.0–93.0%. The equilibrium, thermodynamic and kinetic adsorption studies of Al³⁺-d-mannitol on CNT revealed that adsorption was spontaneous, exothermic, preferred, of physical nature; followed second-order rate kinetics; pore diffusion was not the only rate-controlling step; both Langmuir and Freundlich isotherms represented the data satisfactorily.     

Simultaneous determination of Fe and Ni in guarana (Paullinia cupana Kunth) by HR-CS GF AAS: Comparison of direct solid analysis and wet acid digestion procedures

Direct solid sampling method was compared with the conventional wet acid digestion method to simultaneously assay iron and nickel in guarana by high-resolution continuum source graphite furnace atomic absorption spectrometry. Measurements were done with the secondary lines of Fe and Ni. Four digestion procedures using mixtures of HNO₃ and H₂O₂ (procedure A), HNO₃ and HCl (procedure B), HNO₃, HCl and H₂O₂ (procedure C) and HNO₃, H₂SO₄ and H₂O₂ (procedure D) were evaluated. All tested procedures provided quantitative recoveries for Ni, whereas a good recovery for Fe was obtained only with procedure D. Procedure D was chosen for the digestion of all guarana samples. The limit of detection for the direct solid sampling method was 1.004 μg g⁻¹ for Fe and 0.022 μg g⁻¹ for Ni, and the precision ranged from 3.5–20.0% and 2.8–8.0% for Fe and Ni, respectively. Method accuracy was evaluated by statistical comparison between analyte concentrations, obtained by measurements in the solid samples by the proposed method and after the digestion of the samples by procedure D. The validation of the analytical results obtained for the solid and the digested sample was performed by Energy Dispersive X-Ray Fluorescence.     

Determination of inorganic arsenic in Argentinean rice by selective HGAAS: Analytical performance for paddy,brown and polished rice

Inorganic As (iAs) species require strict monitoring in foodstuff due to their toxicity. Rice is of particular concern, with recent legislations establishing limits for these species. In this work we develop a method based on selective hydride generation atomic absorption spectrometry (HGAAS) for the determination of iAs in different types of rice (polish, parboiled, brown and paddy rice). The multivariate design of experiments used for optimization showed interactions between different factors involved in hydride generation. Matrix effects were systematically studied, where the flow rate of the carrier gas proved to be a critical parameter for the minimization of matrix interferences. Nevertheless, matrix-matching was found to be necessary for accurate quantification of paddy rice samples. Comparison of the iAs concentrations obtained by HGAAS and HPLC-ICP-MS showed non-significant differences between the methods. Analysis of 86 rice samples from the province of Entre Ríos showed relatively low concentrations of iAs (<282 μg kg⁻¹ for paddy rice and <120 μg kg⁻¹ for polished rice), regardless of total As concentrations (which ranged from 63 μg kg⁻¹ to 932 μg kg⁻¹), suggesting that the rice analyzed tends to accumulate As in its organic forms.     

Aluminium in infant foods: Total content,effect of in vitro digestion on bioaccessible fraction and preliminary exposure assessment

The objective of this study was to determine the total concentration and bioaccessible fraction of aluminium (Al) in 95 different baby food samples and estimate the exposure assessment. Total Al content was determined following oxidative microwave digestion by inductively coupled plasma optical emission spectrometry. An in vitro digestionmethod was optimized to evaluate the bioaccessible fraction. Total concentration and bioaccessibility varied according to the sample composition (saltypurees, fruit purees, infant drinks and petitsuisse). Petit suisse, soy-based drink and salty puree samples presented the highest total Al concentrations of 4170 μg kg⁻¹, 2860 μg kg⁻¹ and 2760 μg kg⁻¹, respectively. Bioaccessiblefraction varied from 0.5%–48% according to their composition.Exposure to Al was estimated and compared with the tolerable weekly intakes currently established. The results showed that the consumption of 3 portions/day of soy-based drink along the week could represent a concern.     

Effect of the number of frying cycles on the composition,concentrations and risk of polycyclic aromatic hydrocarbons (PAHs) in vegetable oils and fried fish

The use of the same batch of oil for deep-frying on several occasions is a common practice. This study sought to determine the effects of repeated frying cycles on the composition, concentrations and risk of polycyclic aromatic hydrocarbons (PAHs) in six types of vegetable oils and the samples of fish fried therein. The PAH concentrations in the oils were measured before use and after each of three successive cycles of frying. Fish was fried at each time of use of the oils and, also, monitored for their PAH content. The PAH content in all samples was determined by gas chromatography-mass spectrometry (GC–MS). The concentrations of Ʃ22 PAHs in the unused oils ranged from 43.3–2107 μg kg⁻¹, while those in the used oil ranged from 40.8–4090 μg kg⁻¹. There were significant changes (p < 0.05) in the concentrations and composition of PAHs with respect to vegetable oil types and number of frying cycles. The cancer risk values for the vegetable oils (10⁻⁴ to 10⁻⁵) after three frying cycles exceeded the acceptable risk value of 10^-6 indicating a probable lifetime carcinogenic risk. However, adverse non-carcinogenic risks through consumption of these oils and fried fish were low.     

Sequential injection for determination of gamma-aminobutyric acid based on its effect on second order light scattering of silver nanoparticles

An automated sequential injection (SI) with second order light scattering (SOS) detection for determination of gamma-aminobutyric acid (GABA) was developed. Quantitation is based on electrostatic interaction between GABA and citrate-capped silver nanoparticles (AgNPs). In acetate buffer at pH 3.8, the positively charged GABA induces the nanoparticles to aggregate. This results in a change of light scattering monitored using a spectrofluorometer. In this work, working standard solutions of GABA were prepared in-line by the SI system pumping appropriate volumes of a stock solution of GABA and acetate buffer into a holding coil. Solution of AgNPs was subsequently drawn into the coil. The reaction zone was then transferred to the spectrofluorometer, set with excitation and detection wavelengths at 300 and 600 nm, respectively. Under optimised condition, the SOS intensity was proportional to the concentration of GABA. As a result, a linear curve was obtained in the range of 100–400 mg L⁻¹ GABA, with a lower limit of detection of 39.6 mg L^‐1. Good precision of analysis was achieved, with 0.6 and 3.3% relative standard deviation (RSD) for external calibration (n = 5) and standard addition (n = 3), respectively. The developed method was successfully applied for quantification of GABA in dietary supplements (2 samples) and samples of instant green tea (2 samples).     

Assessing sialic acid content in food by hydrophilic chromatography-high performance liquid chromatography

We have established a novel hydrophilic chromatography (HILIC)-high performance liquid chromatography (HPLC) method to assess sialic acid content in food products. Single-factor and response surface methodologies (RSM) were used to systematically optimize the hydrolysis conditions of the food samples to extract the maximum amount of sialic acid. Chromatographic conditions were also adjusted. In foods containing sialic acid, we observed a strong linear relationship between sialic acid and peak area, ranging from 5 to 100 μg/mL (R² = 0.9998). The lowest detectable sialic acid concentration (RSN = 3) was 0.2 μg mL⁻¹, and the method detection limit was 0.02mg kg⁻¹. Sample recovery ranged from 95.85% to 99.78%, with an RSD of 1.46% (n = 6). Thus, the described method can be applied to the study of sialic acid content in foods.     

Chloride adduct tandem mass spectrometry for the quantification of thiamphenicol and florfenicol in bovine muscle

LC–MS/MS analytical performance characteristics of chloride adduct ions [M + Cl]⁻ of thiamphenicol (TAP) and florfenicol (FFC) as precursor ions for quantification were studied. The calculations were based on a THF/Water solvent system to which dichloromethane was added as an additive at a composition of 2 % to generate chloride (Cl⁻) ions during electrospray ionization (ESI) of the solutions. The selectivity and signal to noise (S/N) ratio when the [M + Cl]⁻ adduct ions were used as precursor ions were excellent compared to deprotonated [M−H]⁻ ions that are traditionally used to determine the two analytes. The S/N ratios in the total ion chromatogram (TIC) of TAP and FFC were 577 and 3062 respectively, compared to 167 and 452 when [M−H]⁻ were used at the same spike levels of 50 and 100 μg/kg respectively. The limits of detection (LODs) for TAP and FFC were 4.0 and 3.7 μg/kg respectively using [M + Cl]⁻ as opposed to 2.1 and 4.3 μg/kg respectively when [M−H]⁻ were used. [M + Cl]⁻ adduct ions proved to be excellent substitutes for [M−H]⁻ especially where identity and selectivity would be the key drivers of the analytical method before quantification of the two analytes.