Mercury determination in edible oils – A combination of Reversed-Phase Dispersive Liquid-Liquid Microextraction and CVG-ICP-MS

doi:10.21203/rs.3.rs-4978400/v1

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Mercury determination in edible oils – A combination of Reversed-Phase Dispersive Liquid-Liquid Microextraction and CVG-ICP-MS

https://doi.org/10.21203/rs.3.rs-4978400/v1

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A method for Hg determination in edible oils based on reversed-phase dispersive liquid-liquid microextraction and cold vapor generation coupled to inductively coupled plasma mass spectrometry was developed. Operational parameters were 5 g of edible oil, 0.5 mL of n-propanol and 0.5 mL of 6 mol L^-1HCl used as dispersant and extractant solvents, respectively, heating (10 min at 80 °C), stirring (60 s), and centrifugation (5 min). No statistical difference (t-test, 95%) was observed for the accuracy assessment using a certified reference material. Moreover, recovery experiments were performed by addition of 0.5, 1.0, and 1.5 µg g^-1 of Hg, and recoveries were close to 100%. A low limit of quantification (0.35 ng g^-1) and relative standard deviation (7%) were obtained. Finally, the proposed method presented advantages, such as high throughput, easy-to-use instrumentation for sample preparation, high pre-concentration factor, low consumption of reagents, and low waste generation.

Edible oil samples

RP-DLLME

Hg determination

CVG-ICP-MS

Sample preparation

Mercury intake is harmful, and it can cause serious damage to humans and animals. The toxicity of Hg is high even when present at low concentrations (e.g., ppb level) (Ferreira et al., 2015; Leermakers et al., 2005; Mahaffey, 2005). In this sense, some health problems can be highlighted, mainly related to toxicological, neurological, and renal diseases (El Youssfi et al., 2023; Mahaffey, 2005; Park & Zheng, 2012; Zhu et al., 2011). Moreover, Hg can be bioaccumulated along the food chain (Mahaffey, 2005).

Edible oils are important products for human nutrition and are used in the culinary preparation of many kinds of foods. Sunflower, fish, peanut, soybean, corn, and canola oils among others, have been used for this purpose (Bockisch, 2015; Knochen & Morales, 2015). However, these oils are not completely free from toxic elements, such as Hg, that can be absorbed from soil, water, or air pollution (Llorent-Martínez et al., 2011; Shah & Soylak, 2022). In this sense, Codex Alimentarius limits the maximum concentration of total Hg in food at 100 ng g^− 1 (Wu, 2014). On the other hand, the World Health Organization (WHO) recommends 4 ng g^− 1, as the maximum level of Hg, but it can change according to the age group (adults or children) (WHO, 2018). Considering the wide use of edible oils for culinary preparations and the low recommended maximum level of Hg, its determination requires a suitable analytical technique after a sample preparation method (Shah & Soylak, 2022; Wu, 2014).

In this sense, some techniques have been employed for Hg determination, such as atomic fluorescence spectrometry (AFS) (Ferreira et al., 2015), graphite furnace atomic absorption spectrometry (GF-AAS) (Manjusha et al., 2019; Standardization, 1994; Zhuravlev et al., 2015), electrothermal atomization coupled to laser-excited atomic fluorescence spectrometry (ETA-LEAFS) (Pagano et al., 1994), and electrothermal vaporization system coupled to inductively coupled plasma mass spectrometry (ETV-ICP-MS) (Silva et al., 2023). Nevertheless, cold vapor generation (CVG) coupled to flame atomic absorption spectrometry (CVG-FAAS)(Duarte et al., 2009; Perring & Andrey, 2001), microwave-induced plasma optical emission spectrometry (CVG-MIP-OES) (Bitencourt et al., 2023; Borowska & Jankowski, 2020), inductively coupled plasma optical emission spectrometry (CVG-ICP-OES)(Grotti et al., 2006; Lech, 2014), or inductively coupled plasma mass spectrometry (CVG-ICP-MS) (Llorent-Martínez et al., 2011; Passariello et al., 1996; Picoloto et al., 2012) are the techniques more frequently used. Among these techniques, CVG-ICP-MS has been employed for subsequent Hg determination in several kinds of samples due to its high throughput, suitable sensitivity as well as low limits of quantification (LOQs) (Druzian et al., 2022; El Hosry et al., 2023; Llorent-Martínez et al., 2011; Passariello et al., 1996; Picoloto et al., 2012).

However, a sample preparation method is generally required to obtain Hg in a suitable solution (El Hosry et al., 2023; Mdluli et al., 2022). In this sense, due to the complexity of oily matrices, the sample preparation step for subsequent Hg determination is not an easy analytical task (Souza et al., 2022; Mdluli et al., 2022). Some strategies used for oily samples and subsequent Hg determination are dry ashing (Oliveira et al., 2009; Guardia, 1991) and acid digestion in closed or opened vessels (by using conventional or microwave heating systems) (Bettinelli et al., 1995; Druzian et al., 2022; López & Mónaco, 2004; Saleh et al., 1988; Sant’Ana et al., 2007; Sanz-Segundo et al., 1999; Schmidt et al., 2013). However, these methods present some drawbacks, such as the use of large amounts of concentrated reagents, which can cause problems related to contamination, as well as analyte losses due to the open systems use (Caroli, 2007; Ferreira et al., 2015).

On the other hand, previous studies have demonstrated the use of extraction methods as an alternative for oily samples since they employ moderate conditions (El Hosry et al., 2023; Mdluli et al., 2022; Salehpour et al., 2024). In this sense, extraction induced by emulsion breaking was used for subsequent Hg determination in oily samples by CVG-FAAS (Vicentino et al., 2015) and recently, reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) was proposed for subsequent determination of Cd, Cr, Mn, Ni, and Pb in edible oil samples (Ferreira et al., 2023; Kalschne et al., 2020; Lopez-Garcia et al., 2014; Ozzeybek et al., 2020). In the RP-DLLME method, the analytes are extracted from an oil matrix and transferred to the aqueous phase by using a suitable extraction solution, which is composed of a mixture of solvents (as dispersant and extractant), such as alcohol and diluted acid solution, respectively (Kalschne et al., 2020; Lopez-Garcia et al., 2014). This method presents many advantages such as the use of diluted extraction solutions, a low volume of reagents required, relatively high sample mass, and a high pre-concentration factor, allowing analyte determination at low concentrations (Hashemi et al., 2010; Lourenço et al., 2019; Mdluli et al., 2022).

Considering the mentioned advantages, we propose, for the first time, the RP-DLLME method for Hg determination by CVG-ICP-MS in edible oils from different origins. The total volume of dispersant and extractant solvents, extractant solvent concentration, sample mass, and stirring time were evaluated. A CRM of mineral oil, the comparison with values obtained by reference method (MAWD), and analyte recovery experiments (in three levels) were performed for accuracy evaluation of the proposed method. All the determinations were performed by CVG-ICP-MS. Finally, the RP-DLLME validation was performed according to the Eurachem recommendations (Eurachem, 1998).

2.1 Instrumentation

A water bath (CE-160/22, Cienlab, Brazil) with capacity and temperature control of 8 L and 80 ± 2°C, respectively, and a centrifuge (Q-222T208, Quimis, Brazil) with a maximum speed of 3450 rpm were used. All samples were weighed by using an analytical balance of 220 g with 0.0001 g of resolution (AW220, Shimadzu, Japan,). Automatic micropipettes (Eppendorf®, Germany) were used to transfer solutions. Polypropylene (PP) tubes of 15 mL (Sarstedt, Germany) were used for the RP-DLLME method. To transfer the aqueous phase into PP tubes a microsyringe of 1.0 mL (Hamilton, United States) was used.

A microwave-assisted wet digestion in a pressurized digestion cavity system (PDC, Multiwave 7000, Anton Paar, Austria), equipped with 18 quartz vessels, was used to digest all samples used in this study to obtain reference values. This microwave oven is composed of a cavity (1 L), pressurized with argon (up to 40 bar, purity of 99.5%, Air Liquide, Brazil). The maximum pressure, power, and temperature were 190 bar, 1700 W, and 300°C, respectively.

Mercury determination was performed using an inductively coupled plasma mass spectrometer (Elan DRC II model, Perkin Elmer-SCIEX, Canada) coupled to a homemade cold vapor generation system (Picoloto et al., 2012). Argon (purity of 99.998%, Air Liquide, Brazil) was used for auxiliary gas, nebulization, and plasma generation in the ICP-MS equipment. Instrumental parameters used for Hg determination by CVG-ICP-MS are presented in Table 1.

Table 1

Instrumental parameters for subsequent Hg determination by CVG-ICP-MS.
Parameter	CVG-ICP-MS
RF power (W)	1300
Plasma gas flow rate (L min^− 1)	15
Nebulizer (L min^− 1)	1.00–1.05*
Auxiliary gas flow rate (L min^− 1)	1.2
Spray chamber	-
Nebulizer	-
Isotopes (m/z)	²⁰²Hg
*The nebulizer gas flow rate was optimized daily based on the signal intensity of ¹¹⁵In⁺, oxides (¹¹⁶CeO⁺/¹⁴⁰Ce⁺), and double charge (⁶⁹Ba⁺⁺/¹³⁸Ba⁺).

2.2. Standards, samples, and reagents

Standards solutions (0.05 to 5.0 µg L^− 1) for Hg determination by CVG-ICP-MS were prepared by using an aqueous standard solution (1000 mg L^− 1 Hg, Merck IV, Germany) in HNO₃ 5% (v/v). In addition, for Hg determination, a solution of NaBH₄ (0.05% m/v, Merck, Germany) in 0.1% m/v NaOH (Vetec, Brazil) was used, and the solid reagents were dissolved in ultra-purified water.

Certified reference material of oil containing Hg (100 ± 0.6 µg g^− 1, OMHG100, SpecSol, Brazil) was used for accuracy evaluation and also for the parameter optimization of the proposed RP-DLLME method. Eight samples of edible oils were purchased in a local market (Brazil, Rio Grande do Sul state, Santa Maria). The oil samples were identified as "A" and "B" (fish oils), "C" and "D" (soybean oil), “E” (sunflower oil), “F” (peanut oil), “G” (corn oil), and "H" (canola oil). For the experimental parameter evaluation of the RP-DLLME method the sample "E" was arbitrarily selected.

Nitric (purity ≥ 65% (Merck, Germany) and hydrochloric acids (purity ≥ 37% (Merck, Germany) were previously distilled in a quartz sub-boiling system (model DuoPur, Milestone, Italy) and used for preparing the extractant solvents and calibration solutions. The n-propanol 99.5%, Vetec, Brazil) was used as dispersant solvent. Moreover, to prepare all reagents and standard solutions, ultra-purified water (resistivity of 18.2 MΩ cm, Water Purification System, Millipore, United States) was employed.

2.3. MAWD (Reference method)

To obtain reference results and compare the values obtained by the RP-DLLME method, all edible oil samples were digested by MAWD, using conditions based on a previous study for food samples (Paar, 2023). For this, about 0.25 g of edible oil A, B, C, D, E, F, G, and H samples were weighed and added to the vessels. After, concentrated HNO₃ (6 mL) was added to the vessels, which were positioned in the rotor that was placed into the microwave cavity, previously filled with 150 mL of the diluted HNO₃ solution. Subsequently, the PDC system was pressurized up to 40 bar with argon and the microwave program was applied, as follows: first step: ramp of 20 min up to 250°C (hold of 10 min) and second step: cooling for 30 min up to 50°C. After, the system pressure was released and the digests were transferred to a volumetric flask and diluted with water (up to 25 mL). Mercury determination was performed by CVG-ICP-MS. After the digestion of edible oil samples, all vessels were cleaned with concentrated HNO₃ (6 mL), and the microwave program was applied, as follows: first step: ramp of 10 min up to 250°C (hold of 20 min) and second step: cooling for 20 min up to 50°C (Paar, 2023).

2.4. RP-DLLME (Proposed method): parameters evaluation and method validation

For the proposed method, a sample mass (1, 2.5, 5, 7.5 or 10 g) was weighed directly into PP tubes and heated in a water bath (10 min at 80°C). Subsequently, a mixture of dispersant and extractant solvents (total volume of 0.5, 1.0 or 1.5 mL) was introduced to the PP tube and it was stirred for 15, 30 or 60 s. After, the separation of the two phases (organic and aqueous) was performed by centrifugation of the tubes for 5 min, at 3500 rpm. Finally, using a micro-syringe, the aqueous solution was collected and transferred to a new PP tube and diluted with water (10 mL) for Hg determination by CVG-ICP-MS. The experiments by the RP-DLLME method were carried out in quintuplicate.

For the development of the RP-DLLME method, the total volume of the extraction solution 0.5, 1.0 or 1.5 mL by using dispersant (0.25, 0.50 or 0.75 mL) and extractant (0.25, 0.50 or 0.75 mL) solvents, the concentration of extractant solvent (2 and 4 mol L^− 1 HNO₃ or 2, 4, 6, and 8 mol L^− 1 HCl), sample mass (1, 2.5, 5, 7.5 or 10 g), and stirring time (15, 30 or 60 s) were evaluated. The temperature, heating time, dispersant solvent type, and centrifugation time were kept at 80°C, 10 min, n-propanol, and 5 min, respectively. It is important to highlight that, for the experiments of the RP-DLLME method, sample “E” was used and 1.0 µg g^− 1 of mineral oil CRM containing Hg was added directly to the sample. After optimization, the RP-DLLME method was performed for Hg extraction and subsequent determination by CVG-ICP-MS in fish, soybean, sunflower, peanut, corn, and canola oils.

For the RP-DLLME method validation, the Eurachem recommendations were used (Eurachem, 1998). Linearity, accuracy, precision, LOD, and LOQ were evaluated for the method validation. For these, the sample “E” was used. The correlation coefficient (R²) of analytical curves was used for linearity evaluation (R² of 0.9991 was the minimum acceptable value). The accuracy was studied using a CRM of mineral oil (100 ± 0.6 µg g^− 1, OMHG100, SpecSol, Brazil), by comparison with reference values (digestion by MAWD method), and by recovery experiments in three concentration levels of Hg (0.5, 1.0, and 1.5 µg g^− 1). The repeatability was obtained by the analysis on the same day in quintuplicate, and was estimated as relative standard deviations (RSDs). The intermediate precision was calculated based on RSDs obtained by the analysis on four days in quintuplicate. The limits of detection (LOD) and quantification (LOQ) were calculated considering the mean of the blank values (߂) and the standard deviation (SD) of the 10 blank readings (LOD = ߂ + 3.SD and LOQ = ߂ + 10.SD). For these calculations, the final volume and sample mass were: MAWD: 25 mL and 0.25 g and RP-DLLME: 10 mL and 5 g. To prepare the blanks, the same procedure and reagents as described in section 2.4 were used.

3.1 Total volume of extraction solution evaluation

As shown in previous studies, the total volume of dispersant and extractant solvents (extraction solution) can influence the analyte extraction (Kalschne et al., 2020; Kalschne et al., 2020; Lourenço et al., 2019). In this sense, the total volume of the extraction solution was evaluated as 0.50, 1.0, and 1.5 mL. For these evaluations, the volume of n-propanol (0.25, 0.50, and 0.75 mL) and 2 mol L^− 1 HCl (0.25, 0.50, and 0.75 mL), as dispersant and extractant solvents respectively, were evaluated. The procedure used is described in Section 2.4. The recoveries obtained for Hg using the evaluated extraction solution are shown in Fig. 1.

According to the results presented in Fig. 1, with the use of 0.50 mL of extraction solution (0.25 mL of n-propanol + 0.25 mL of 2 mol L^− 1 HCl), recoveries lower than 60% for Hg were obtained. Moreover, no significant improvement was observed by using 1.0 or 1.5 mL of extraction solution (0.50 or 0.75 mL of n-propanol + 0.50 or 0.75 mL of 2 mol L^− 1 HCl), and the recoveries obtained for Hg were of 77 and 78%, respectively. These results demonstrated that the volume of dispersant and extractant solvents influences the extraction efficiency of Hg, as already observed in a previous study for other analytes (Kalschne et al., 2020; Kalschne et al., 2020). Considering the results obtained for Hg and the use of a lower amount of reagents, the total volume of 1.0 mL was selected for subsequent experiments and it is in agreement with studies previously reported for similar samples (Kalschne et al., 2020; Kalschne et al., 2020; Lourenço, Eyng et al., 2019).

3.2 Extractant solvent concentration evaluation

As reported in previous studies involving the RP-DLLME method, diluted HNO₃ solutions have been used for analyte extraction (e.g., Cd, Fe, Mn, Ni, Pb, Zn, and among others) from oily samples (Kalschne et al., 2020; Kalschne et al., 2020; Lopez-Garcia et al., 2014; Lourenço et al., 2019; Ozzeybek et al., 2020). In this sense, experiments were carried out using 2 and 4 mol L^− 1 HNO₃, as extractant solvent. However, Hg recoveries obtained for both concentrations were lower than 15%. To improve Hg recoveries, following previous studies, diluted HCl solutions (2, 4, 6, and 8 mol L^− 1 HCl) were evaluated (Uddin et al., 2013; Vicentino et al., 2015). Experiments were performed using n-propanol as dispersant solvent, 5 g of sample "E" and 1.0 mL of a mixture of the dispersant (0.5 mL) and the extractant (0.5 mL) solvents. The recoveries obtained for Hg are shown in Fig. 2.

As shown in Fig. 2, by using 2 or 4 mol L^-1 HCl solutions, Hg recoveries were lower than 80%. However, when 6 or 8 mol L^-1 HCl were used, recoveries higher than 94% were obtained for Hg, and the RSDs were around 5%. These results showed that the use of high HCl concentrations is required to guarantee the total Hg extraction from the edible oil. Probably, the use of HCl can poor the Hg organic compounds stability, which can decompose the organic structure and leave Hg free, as previously reported (Liang et al., 1996; Uddin et al., 2013). Thus, since 6 or 8 mol L^-1 HCl solutions provided recoveries higher than 95% for Hg, to use a lower volume of reagents, the 6 mol L^-1 HCl solution was selected.

3.3 Sample mass and stirring time evaluation

The use of high sample mass is one of the several advantages of the RP-DLLME method (Kalschne et al., 2020; Kalschne et al., 2020; Lourenço et al., 2019). This advantage provides lower LODs and LOQs, improving the analyte detectability at trace levels. In this way, the use of 1, 2.5, 5, 7.5, and 10 g of edible oil was evaluated. For 1 or 2.5 g of sample mass, the recoveries were 75 and 86% for Hg, respectively. The low agreement obtained can be explained by the formation of a stable emulsion between water (aqueous phase) and oil. Moreover, a low volume of aqueous phase was collected in comparison with, when 5 g of sample mass was used. By using 5 g of sample, Hg recoveries were close to 95%. In addition, when 7.5 or 10 g of sample were used, the recoveries for Hg were lower than 90%. In this sense, for the subsequent experiments, 5 g was selected as the maximum sample mass.

Finally, stirring times of 15, 30, and 60 s were evaluated and 60 s showed the highest recovery (95%) for Hg in comparison with 15 and 30 s, in which the recoveries were 78% and 85%, respectively (data no showed). Thus, the stirring time was kept at 60 s for further experiments.

3.4 Validation of the RP-DLLME method

For the validation of the RP-DLLME method, optimized conditions, such as 5 g of edible oil sample, 0.5 mL of n-propanol (dispersant solvent), 0.5 mL of 6 mol L^− 1 HCl (extractant solvent), 60 s of stirring time were applied.

Mercury determination by CVG-ICP-MS was performed using an external calibration curve prepared in 5% HNO₃ (v/v) containing 0.05 to 5.0 µg L^− 1 for Hg. The correlation coefficient (R²) of the calibration curve was higher than 0.9995, indicating a linear response.

The accuracy evaluation was performed by analyzing a CRM of mineral oil (OMHG100), by comparison with the results obtained after the reference method (MAWD), and by recovery experiments in three levels of concentration for Hg (0.5, 1.0, and 1.5 µg g^-1). No statistical differences were observed (t-test, 95%) comparing the results obtained by RP-DLLME and certified values and by comparing the results obtained by the RP-DLLME and MAWD methods, as shown in Table 2, (Hg determination by CVG-ICP-MS for both methods). The RSDs values were lower than 5%. For recovery experiments in three levels of Hg concentration, recoveries ranging from 95 to 100% and low RSD values lower than 5% were obtained.

The repeatability and intermediate precision were suitable for the RP-DLLME method since the RSD values were lower than 7%. Moreover, the LOD and LOQ values obtained for Hg by RP-DLLME were 0.10 and 0.35 ng g^− 1, respectively. In contrast, for the MAWD method, the LOD and LOQ values were 8 and 26 ng g^− 1, respectively. It is important to mention that the LOQ obtained by CVG-ICP-MS after RP-DLLME is lower than the maximum limit of Hg recommended by Codex Alimentarius (100 ng g^− 1) and WHO (4 ng g^− 1).

3.5 Mercury determination in edible oils by CVG-ICP-MS

The RP-DLLME method was applied for fish, soybean, sunflower, peanut, corn, and canola oils identified as A and B, C and D, E, F, G, and H, respectively. Moreover, for comparison of results, all the samples used in this study were also digested by MAWD. Results for Hg by CVG-ICP-MS after the RP-DLLME and MAWD methods are shown in Table 2.

Table 2

Results for Hg determination by CVG-ICP-MS in edible oils after RP-DLLME and MAWD (results in ng g^− 1, mean ± standard deviation, n = 5).
Samples		Hg concentration, ng g^− 1
	RP-DLLME	MAWD
A, fish oil		81.2 ± 4.5	79.9 ± 3.1
B, fish oil		92.2 ± 3.6	94.0 ± 4.8
C, soybean oil		108 ± 4	109 ± 5
D, soybean oil		20.9 ± 0.7	< 26
E, sunflower oil		< 0.35	< 26
F, peanut oil		< 0.35	< 26
G, corn oil		17.5 ± 0.5	< 26
H, canola oil		< 0.35	< 26

As shown in Table 2, for samples E, F, and H the results obtained for Hg were lower than the LOQs for the RP-DLLME and the MAWD methods. Moreover, the concentration of Hg in samples D and G was lower than the LOQ for the MAWD method (reference method). On the other hand, only by using the proposed RP-DLLME method, it was possible to determine Hg in samples D and G, showing the high detectability of the proposed method. Mercury concentrations in samples A, B, and C could be determined by CVG-ICP-MS after RP-DLLME and MAWD, and no statistical difference (t-test, 95%) was observed between the results obtained by both methods.

Mercury concentration was higher than the maximum limit according to the World Health Organization (4 ng g^− 1) for samples A, B, C, D, and G. It is important to highlight that the LOD and LOQ obtained for the RP-DLLME method are significantly lower than the maximum level of Hg allowed by Codex Alimentarius and WHO (Wu, 2014). Furthermore, the LOD and LOQ obtained by the RP-DLLME method were around 75 times lower than those obtained by the MAWD method. In this way, the proposed method can be a suitable alternative method for routine analysis to meet these legislations.

The RP-DLLME method was considered an alternative sample preparation method for edible oils and subsequent Hg determination by CVG-ICP-MS. The optimized conditions of the proposed method were: 0.5 mL of n-propanol (dispersant solvent), 0.5 mL of 6 mol L^− 1 HCl (extractant solvent), 5 g of edible oil sample, and 60 s of stirring time. Accuracy was assessed by using a CRM of mineral oil, by comparison with results obtained after the MAWD method, and also assessed by using recovery experiments in three levels of concentration, and no statistical differences were observed after all accuracy evaluations (all determinations by CVG-ICP-MS) and the RSD were lower than 7%. The RP-DLLME method was a simple and fast approach for sample preparation since it involves fewer steps and allows relatively easy operation with simple instrumentation. In this sense, some advantages of the proposed method can be mentioned, such as the use of diluted extraction solutions, high pre-concentration factor, moderate temperatures, low consumption of reagents, and low waste generation. Finally, it is important to highlight that this is the first approach of the RP-DLLME method for Hg determination by CVG-ICP-MS in edible oils.

Acknowledgements

This approach was financed by Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (Brazil), National Institute of Science & Technology in Bioanalytics, Conselho Nacional de Desenvolvimento Científico e Tecnológico, and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil) - Finance Code 001.

CRediT author statement

Cristian R. Andriolli: Methodology, Investigation, and Writing - Original Draft. Alessandra S. Henn: Formal analysis, Conceptualization, Writing - Original Draft, and Writing - Review & Editing. Eder L. M. Flores: Resources, and Writing - Review & Editing. Erico M. M. Flores: Resources, Writing - Review & Editing, and Visualization. Rochele S. Picoloto: Project Administration, Conceptualization, Resources, Writing - Review & Editing, and Supervision.

Bettinelli, M., Spezia, S., Baroni, U., & Bizzarri, G. (1995). Determination of trace elements in fuel oils by inductively coupled plasma mass spectrometry after acid mineralization of the sample in a microwave oven. Journal of Analytical Atomic Spectrometry, 10(8), 555-560. https://doi.org/10.1039/JA9951000555.
Bitencourt, G. R., Duarte, F. A., Dressler, V. L., Bolzan, R. C., Flores, E. M. M., & Mello, P. A. (2023). On a single method for determining As and Hg in dietary supplements by CVG-MIP OES: optimization of the multimode sample introduction system. Journal of Analytical Atomic Spectrometry, 38(11), 2342-2352. https://doi.org/10.1039/D3JA00261F.
Bockisch, M. (2015). Fats and oils handbook (Nahrungsfette und Öle): Elsevier.
Borowska, M., & Jankowski, K. (2020). Sensitive determination of bioaccessible mercury in complex matrix samples by combined photochemical vapor generation and solid phase microextraction coupled with microwave induced plasma optical emission spectrometry. Talanta, 219, 121162. https://doi.org/10.1016/j.talanta.2020.121162
Caroli, S. (2007). The determination of chemical elements in food: applications for atomic and mass spectrometry: John Wiley & Sons.
Druzian, G. T., Nascimento, M. S., Picoloto, R. S., Mesko, M. F., Flores, E. M. M., & Mello, P. A. (2022). Ultra-trace Hg determination in crude oils by CV-ICP-MS: overcoming the limitations of sample preparation to determine sub-ppb levels. Journal of Analytical Atomic Spectrometry, 37(9), 1799-1805. https://doi.org/10.1039/D2JA00169A.
Duarte, F. A., Bizzi, C. A., Antes, F. G., Dressler, V. L., & Flores, E. M. M. (2009). Organic, inorganic and total mercury determination in fish by chemical vapor generation with collection on a gold gauze and electrothermal atomic absorption spectrometry. Spectrochimica Acta Part B: Atomic Spectroscopy, 64(6), 513-519. https://doi.org/10.1016/j.sab.2009.05.010.
El Hosry, L., Sok, N., Richa, R., Al Mashtoub, L., Cayot, P., & Bou-Maroun, E. (2023). Sample preparation and analytical techniques in the determination of trace elements in food: A review. Foods, 12(4), 895. https:// 10.3390/foods12040895.
El Youssfi, M., Sifou, A., Ben Aakame, R., Mahnine, N., Arsalane, S., Halim, M., Laghzizil, A., & Zinedine, A. (2023). Trace elements in foodstuffs from the Mediterranean basin—occurrence, risk assessment, regulations, and prevention strategies: a review. Biological Trace Element Research, 201(5), 2597-2626. https:// 10.1007/s12011-022-03334-z.
Eurachem, G. (1998). The fitness for purpose of analytical methods. A laboratory guide to method validation and related topics.
Ferreira, S. L., Lemos, V. A., Silva, L. O., Queiroz, A. F., Souza, A. S., Silva, E. G., Santos, W. N., & Virgens, C. F. (2015). Analytical strategies of sample preparation for the determination of mercury in food matrices—A review. Microchemical Journal, 121, 227-236. https://doi.org/10.1016/j.microc.2015.02.012.
Ferreira, V. J., Lemos, V. A., & Teixeira, L. S. G. (2023). Dynamic reversed-phase liquid-liquid microextraction for the determination of Cd, Cr, Mn, and Ni in vegetable oils by energy dispersive X-ray fluorescence spectrometry. Journal of Food Composition and Analysis, 117, 105098. https://doi.org/10.1016/j.jfca.2022.105098.
Grotti, M., Lagomarsino, C., & Magi, E. (2006). Simultaneous determination of arsenic, selenium and mercury in foodstuffs by chemical vapour generation inductively coupled plasma optical emission spectroscopy. Annali di Chimica: Journal of Analytical, Environmental and Cultural Heritage Chemistry, 96(11‐12), 751-764. https://doi.org/10.1002/adic.200690077.
Hashemi, P., Raeisi, F., Ghiasvand, A. R., & Rahimi, A. (2010). Reversed-phase dispersive liquid–liquid microextraction with central composite design optimization for preconcentration and HPLC determination of oleuropein. Talanta, 80(5), 1926-1931. https://doi.org/10.1016/j.talanta.2009.10.051.
Kalschne, D. L., Canan, C., Barin, J. S., Picoloto, R. S., Leite, O. D., & Flores, E. L. M. (2020). Reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) as a green sample preparation method for multielement determination in fish oil by ICP-OES. Food Analytical Methods, 13, 230-237. https://doi.org/10.1007/s12161-019-01606-4.
Kalschne, D. L., Canan, C., Beato, M. O., Leite, O. D., & Flores, E. L. M. (2020). A new and feasible analytical method using reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for further determination of Nickel in hydrogenated vegetable fat. Talanta, 208, 120409. https://doi.org/10.1016/j.talanta.2019.120409.
Knochen, M., & Morales, G. (2015). Edible fats and oils. Handbook of Mineral Elements in Food, 573-586.
La Guardia, M. (1991). Direct determination of copper and iron in edible oils using flow injection flame atomic absorption spectrometry. Journal of Analytical Atomic Spectrometry, 6(7), 581-584. https://doi.org/10.1039/JA9910600581.
Lech, T. (2014). ICP OES and CV AAS in determination of mercury in an unusual fatal case of long-term exposure to elemental mercury in a teenager. Forensic Science International, 237, e1-e5. https://doi.org/10.1016/j.forsciint.2014.02.015.
Leermakers, M., Baeyens, W., Quevauviller, P., & Horvat, M. (2005). Mercury in environmental samples: speciation, artifacts and validation. TrAC Trends in Analytical Chemistry, 24(5), 383-393. https://doi.org/10.1016/j.trac.2004.01.001.
Liang, L., Horvat, M., & Danilchik, P. (1996). A novel analytical method for determination of picogram levels of total mercury in gasoline and other petroleum based products. Science of The Total Environment, 187(1), 57-64. https://doi.org/10.1016/0048-9697(96)05129-7.
Lopez-Garcia, I., Vicente-Martinez, Y., & Hernandez-Cordoba, M. (2014). Determination of cadmium and lead in edible oils by electrothermal atomic absorption spectrometry after reverse dispersive liquid–liquid microextraction. Talanta, 124, 106-110. https://doi.org/10.1016/j.talanta.2014.02.011.
López, L., & Mónaco, S. L. (2004). Geochemical implications of trace elements and sulfur in the saturate, aromatic and resin fractions of crude oil from the Mara and Mara Oeste fields, Venezuela. Fuel, 83(3), 365-374. https://doi.org/10.1016/j.fuel.2003.06.001.
Lourenço, E. C., Eyng, E., Bittencourt, P. R., Duarte, F. A., Picoloto, R. S., & Flores, E. L. M. (2019). A simple, rapid and low cost reversed-phase dispersive liquid-liquid microextraction for the determination of Na, K, Ca and Mg in biodiesel. Talanta, 199, 1-7. https://doi.org/10.1016/j.talanta.2019.02.054.
Mahaffey, K. R. (2005). Mercury exposure: medical and public health issues. Transactions of the American Clinical and Climatological Association, 116, 127.
Manjusha, R., Shekhar, R., & Kumar, S. J. (2019). Ultrasound-assisted extraction of Pb, Cd, Cr, Mn, Fe, Cu, Zn from edible oils with tetramethylammonium hydroxide and EDTA followed by determination using graphite furnace atomic absorption spectrometer. Food chemistry, 294, 384-389. https://doi.org/10.1016/j.foodchem.2019.04.104.
Mdluli, N. S., Nomngongo, P. N., & Mketo, N. (2022). A critical review on application of extraction methods prior to spectrometric determination of trace-metals in oily matrices. Critical Reviews in Analytical Chemistry, 52(1), 1-18. https:// 10.1080/10408347.2020.1781591.
Oliveira, A. P., Villa, R. D., Antunes, K. C. P., Magalhães, A., & Silva, E. C. (2009). Determination of sodium in biodiesel by flame atomic emission spectrometry using dry decomposition for the sample preparation. Fuel, 88(4), 764-766. https://doi.org/10.1016/j.fuel.2008.10.006.
Ozzeybek, G., Sahin, I., Erarpat, S., & Bakirdere, S. (2020). Reverse phase dispersive liquid–liquid microextraction coupled to slotted quartz tube flame atomic absorption spectrometry as a new analytical strategy for trace determination of cadmium in fish and olive oil samples. Journal of Food Composition and Analysis, 90, 103486. https://doi.org/10.1016/j.jfca.2020.103486.
Paar, A. Digestion of food and other organic samples for elemental analysis with ICP.Aplication note, 2023.
Pagano, S. T., Smith, B. W., & Winefordner, J. D. (1994). Determination of mercury in microwave-digested soil by laser-excited atomic fluorescence spectrometry with electrothermal atomization. Talanta, 41(12), 2073-2078. https://doi.org/10.1016/0039-9140(94)00181-2.
Park, J. D., & Zheng, W. (2012). Human exposure and health effects of inorganic and elemental mercury. Journal of preventive medicine and public health, 45(6), 344. https://doi.org/10.3961/jpmph.2012.45.6.344.
Passariello, B., Barbaro, M., Quaresima, S., Casciello, A., & Marabini, A. (1996). Determination of mercury by inductively coupled plasma—mass spectrometry. Microchemical Journal, 54(4), 348-354. https://doi.org/10.1006/mchj.1996.0110.
Perring, L., & Andrey, D. (2001). Optimization and validation of total mercury determination in food products by cold vapor AAS: Comparison of digestion methods and with ICP-MS analysis. Atomic Spectroscopy-Norwalk Connecticut, 22(5), 371-378.
Picoloto, R. S., Wiltsche, H., Knapp, G., Barin, J. S., & Flores, E. M. M. (2012). Mercury determination in soil by CVG-ICP-MS after volatilization using microwave-induced combustion. Analytical methods, 4(3), 630-636. https://doi.org/10.1039/C1AY05410D.
Saleh, M., Murray, R., & Chin, C. (1988). Ashing techniques in the determination of iron and copper in palm oil. Journal of the American Oil Chemists' Society, 65(11), 1767-1770. https://doi.org/10.1007/BF02542378.
Salehpour, N., Nojavan, S., Alahmad, W., & Tabani, H. (2024). Chapter Six - Recent trends in microextraction methodology for food analysis. In S. Ul Islam & C. Mustansar Hussain (Eds.), Green Chemistry in Food Analysis, (pp. 137-190): Elsevier.
Sant’Ana, F. W., Santelli, R. E., Cassella, A. R., & Cassella, R. J. (2007). Optimization of an open-focused microwave oven digestion procedure for determination of metals in diesel oil by inductively coupled plasma optical emission spectrometry. Journal of hazardous materials, 149(1), 67-74. https://doi.org/10.1016/j.jhazmat.2007.03.045.
Sanz-Segundo, C., Hernández-Artiga, M. P., Hidalgo-Hidalgo de Cisneros, J. L., Bellido-Milla, D., & Naranjo-Rodriguez, I. (1999). Determination of wear metals in marine lubricating oils by microwave digestion and atomic absorption spectrometry. Microchimica Acta, 132, 89-94. https://doi.org/10.1007/PL00010078.
Schmidt, L., Bizzi, C. A., Duarte, F. A., Dressler, V. L., & Flores, E. M. M. (2013). Evaluation of drying conditions of fish tissues for inorganic mercury and methylmercury speciation analysis. Microchemical Journal, 108, 53-59. https://doi.org/10.1016/j.microc.2012.12.010.
Shah, N. S., & Soylak, M. (2022). Advanced methodologies for trace elements in edible oil samples: a review. Critical Reviews in Analytical Chemistry, 52(7), 1572-1582. https://doi.org/10.1080/10408347.2021.1895710.
Silva, J. S., Heidrich, G. M., Poletto, B. O., Paniz, J. N. G., Dressler, V. L., & Flores, E. M. M. (2023). Mercury determination in bioresorbable calcium phosphate using a new electrothermal vaporization system coupled to ICP-MS. Journal of Analytical Atomic Spectrometry, 38(5), 1000-1006. https://doi.org/10.1039/D2JA00414C.
Souza, R. M., Toloza, C. A. T., & Aucélio, R. Q. (2022). Fast determination of trace metals in edible oils and fats by inductively coupled plasma mass spectrometry and ultrasonic acidic extraction. Journal of Trace Elements and Minerals, 1, 100003. https://doi.org/10.1016/j.jtemin.2022.100003.
Standardization, I. O. f. (1994). Animal and Vegetable Fats and Oils: Determination of Copper, Iron and Nickel Contents: Graphite Furnace Atomic Absorption Method: International Organization for Standardization.
Uddin, R., Al-Fahad, M. A., Al-Rashwan, A. K., & Al-Qarni, M. A. (2013). A simple extraction procedure for determination of total mercury in crude oil. Environmental monitoring and assessment, 185, 3681-3685. https://doi.org/10.1007/s10661-012-2819-2.
Vicentino, P. d. O., Brum, D. M., & Cassella, R. J. (2015). Development of a method for total Hg determination in oil samples by cold vapor atomic absorption spectrometry after its extraction induced by emulsion breaking. Talanta, 132, 733-738. https://doi.org/10.1016/j.talanta.2014.10.019.
W. H. O. (2018). Safety evaluation of certain contaminants in food: prepared by the eighty-third meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA): World Health Organization.
Wu, Y. (2014). General standard for contaminants and toxins in food and feed. Codex stan, 193-1995.
Zhu, F., Fan, W., Wang, X., Qu, L., & Yao, S. (2011). Health risk assessment of eight heavy metals in nine varieties of edible vegetable oils consumed in China. Food and chemical toxicology, 49(12), 3081-3085. https://doi.org/10.1016/j.fct.2011.09.019.
Zhuravlev, A., Zacharia, A., Gucer, S., Chebotarev, A., Arabadji, M., & Dobrynin, A. (2015). Direct atomic absorption spectrometry determination of arsenic, cadmium, copper, manganese, lead and zinc in vegetable oil and fat samples with graphite filter furnace atomizer. Journal of Food Composition and Analysis, 38, 62-68. https://doi.org/10.1016/j.jfca.2014.10.002.

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Mercury determination in edible oils – A combination of Reversed-Phase Dispersive Liquid-Liquid Microextraction and CVG-ICP-MS

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Abstract

Figures

1. Introduction

2. Experimental

2.1 Instrumentation

2.2. Standards, samples, and reagents

2.3. MAWD (Reference method)

2.4. RP-DLLME (Proposed method): parameters evaluation and method validation

3. Results and Discussion

3.1 Total volume of extraction solution evaluation

3.2 Extractant solvent concentration evaluation

3.3 Sample mass and stirring time evaluation

3.4 Validation of the RP-DLLME method

3.5 Mercury determination in edible oils by CVG-ICP-MS

4. Conclusions

Declarations

References

Additional Declarations

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Version 1