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.     

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.     

Preconcentration and determination of nickel (II) and copper (II) ions,in vegetable oils by [TBP] [PO4] IL-based dispersive liquid–liquid microextraction technique,and flame atomic absorption spectrophotometry

The present research is a novel enrichment method based on ionic liquid dispersive liquid-liquid micro-extraction that was combined with flame atomic absorption spectroscopy to determine the concentration of Cu²⁺ and Ni²⁺ ions in vegetable oil samples at trace levels. The ionic liquid [TBP] [PO₄] and chloroform were used as the extraction and dispersive solvent respectively. Canola oil containing oil-soluble standard of Cu²⁺ or Ni²⁺ ions as the model compound was used. Under optimum conditions the linear ranges were 1–100 and 1−200 μg/kg for Cu²⁺ and Ni²⁺ respectively with correlation coefficient (R²) of 0.99. The relative standard deviation (RSD, n = 5) for Cu²⁺ and Ni²⁺ at a concentration of 20 μg/kg was 2.2 % and 3.2 % respectively. The LOD (3 s) and LOQ (10 s) were 0.35 ppb and 1.2 ppb; and 0.77 ppb and 2.57 ppb for Cu²⁺ and Ni²⁺ 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.     

Zirconium nanoparticles based ligandless dispersive solid phase extraction for the determination of antimony in bergamot and mint tea samples by slotted quartz tube-flame atomic absorption spectrophotometry

A sensitive and effective analytical method was developed to preconcentrate antimony from the bergamot and mint tea samples for its determination at trace levels by slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS) system. The developed method was based on vortex assisted ligandless dispersive solid phase extraction (VA-LDSPE) using zirconium nanoparticles (Zr-NPs) as sorbent material for the adsorption of the target analyte. All variables involved in the DSPE method (pH value, nanoparticle amount, mixing and eluent type/volume) were optimized to boost the absorbance signal of antimony. Using the optimal parameters, the method provided satisfactory detection and quantification limits of 8.0 and 26.8 μg L⁻¹, respectively. A 180 folds enrichment factor was achieved by the developed method when compared with the detection power of the FAAS. Linear range of the proposed method was found to be 30–250 μg L⁻¹, with a coefficient of determination value of 0.9992. The established Zr-NPs-VA-LDSPE-SQT-FAAS method was successfully implemented to bergamot tea samples in order to check accuracy and applicability. The obtained recovery values ranged between 93–102%, and this demonstrated that the complex matrices tested did not affect the accuracy of quantifying antimony.     

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.     

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.     

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.     

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.     

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.     

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.     

Acute Toxicity and Risk Assessment of Florfenicol for Nile Tilapia Larvae

The aim of this study was to determine the median lethal concentration (LC_50−96h), effective concentration (EC_50−96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6 mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1 L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mg L⁻¹ plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC_50−96h of FF for Nile tilapia larvae was 349.94 mg L⁻¹. The EC_50−96h of FF was 500 mg L⁻¹ for weight reduction and was 1040 mg L⁻¹ for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96 h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.

     

Reference measurements of mercury species in seafood using isotope dilution inductively coupled plasma mass spectrometry

Species-specific isotope dilution inductively coupled plasma mass spectrometry (SS ID ICP-MS) and high-performance liquid chromatography (HPLC) were used to obtain accurate and SI traceable results for methyl mercury in seafood samples such as clam, oyster and fish homogenate. The mass fractions of (62.3 ± 2.3) μg kg⁻¹, (5.44 ± 0.36) μg kg⁻¹ and (531 ± 19) μg kg⁻¹ were obtained for MeHg (as Hg) in IAEA-461, IAEA-470 and IAEA-476, respectively. Direct isotope dilution mass spectrometry was performed for total mercury content then the content of inorganic mercury in selected samples was obtained by calculation. It was found that the content of inorganic Hg in IAEA-461, IAEA-470, and IAEA-476 was as: 328 μg kg⁻¹, 16 μg kg⁻¹, and 62 μg kg⁻¹, respectively. Mathematical modelling of analytical procedure and evaluation of all parameters influencing final results were adequate for validation of measurement procedure, establishing traceability and estimating expanded uncertainty. Developed procedures were successfully applied in the characterization process of fish homogenate candidate reference material and in the calculation of assigned values in the frame of IAEA-476 inter-laboratory comparison study. Compatibility between obtained results and those derived from the certification campaign, organized by International Atomic Energy Agency on the same sample matrix (<2.6 % difference) further validated performed ID ICP-MS protocols.     

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.     

Distribution of essential and non-essential elements in rice located in a Protected Natural Reserve “Marjal de Pego-Oliva”

Anthropogenic agronomic practices could negatively affect the agricultural soil which is the main source for inorganic arsenic (i-As) contamination in rice fields due to flooding. The presence of essential elements could be impacted by food industry units operations. The aim of this study was to evaluate the effect of husking and polishing on mineral essential elements and inorganic As species in rice from Protected Natural Reserve “Marjal de Pego-Oliva”. The amount of all studied elements was significantly affected by husking (a decrease of Ca, Na and Pb, 360 to 101 mg kg⁻¹, 202 to 46.9 mg kg^-1 and 17.9 to 5.70 μg kg⁻¹, respectively) and by polishing (a reduction of Na, Mg, P, K, Ca and Cu, 46.9–26.8 mg kg⁻¹, 1600 to 481 mg kg⁻¹, 4050 to 1530 mg kg⁻¹, 2780 to 882 mg kg⁻¹, 101 to 53.7 mg kg⁻¹, and 3600 to 2840, μg kg⁻¹, respectively).The replacement of white rice (WR) to brown rice (BR) could enhance the daily dietary intake of essential elements to reach the dietary reference values and the maximum i-As (40.9 and 44.9 i-As μg kg^-1 for BR and WR, respectively) was below the maximum level recently established by European Food Safety Agency.     

Multi-walled carbon nanotubes/nickel hydroxide composite applied as electrochemical sensor for folic acid (vitamin B9) in food samples

Folic acid (FA) acts as an essential nutrient for body functions. Several countries have already proposed a resolution for flour fortification with iron and FA; thus, of food industry concern. Therefore, a new electroanalytical method based on a composite material of functionalized MWCNTs with nickel hydroxide (f-MWCNT-Ni(OH)₂) is hereby proposed. This composite material was characterized by FT-IR, TGA, SEM and TEM techniques. An inorganic ionic silsesquioxane polymer (Si4Pic⁺Cl⁻) was used to disperse the composite and applied on the modification of a glassy carbon electrode (GCE). Linear response from 0.5–26 μmol L⁻¹ was obtained based on FA electrochemical oxidation through differential pulse voltammetry. The LoD and LoQ values obtained were 0.095 μmol L⁻¹ and 0.3 μmol L⁻¹ of FA, respectively. The GCE/f-MWCNT-Ni(OH)₂-Si4Pic⁺Cl⁻ was applied for the quantification of FA in wheat flour, fortifier, and dietary supplement. Validation was performed through a comparison with molecular absorption spectrometry, showing the accuracy of the newly proposed method.     

Optimization of Solvent Terminated Dispersive Liquid–Liquid Microextraction of Copper Ions in Water and Food Samples Using Artificial Neural Networks Coupled Bees Algorithm

A multivariate method based on solvent terminated dispersive liquid–liquid microextraction was developed for the determination of Cu²⁺ ions in aqueous samples. In the proposed approach, di-2-ethylhexylphosphoric acid, xylene and acetone were used as chelating agent, dispersive and extraction solvents, respectively. The effects of various factors on the extraction efficiency such as extraction and dispersive solvent volumes, salt addition and pH were studied using central composite design (CCD) and artificial neural networks coupled bees algorithm (ANN-BA). Upon comparison of these techniques, ANN-BA model was considered to be better optimization method due to its higher percentage relative recovery (about 5%) as compared to the CCD approach. The linear range and the limits of detection (S/N?=?3) and quantitation (S/N?=?10) were 0.22–140, 0.08 and 0.22 µg L^?1, respectively. Under the optimal conditions, the recoveries for real samples spiked with 0.1 and 0.3 mg L^?1 were in the range of 85–98%.     

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.     

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.