An Inductively Coupled Plasma Optical Emission Spectrometric Method for the Determination of Toxic and Nutrient Metals in Spices after Pressure-Assisted Digestion
Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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Authors to whom correspondence should be addressed.
Appl. Sci. 2022, 12(2), 534; https://doi.org/10.3390/app12020534
Submission received: 10 December 2021
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Revised: 29 December 2021
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Accepted: 4 January 2022
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Published: 6 January 2022
(This article belongs to the Special Issue Advanced Analytic Techniques in Food Chemistry)
Abstract
:The aim of this study was to develop a simple and rapid inductively coupled plasma optical emission spectrometric (ICP-OES) method for the determination of 17 metals (Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Tl and Zn) in packaged spices. For this purpose, the spice samples (200 mg) in the form of powder were submitted to pressure-assisted wet-acid digestion with a mixture of 6 mL concentrated HNO3 and 1 mL H2O2. The proposed method was validated in terms of linearity, trueness, precision, limits of detection (LODs) and limits of quantification (LOQs). Good method trueness, precision and linearity were observed for the examined elements. The LODs of the examined analytes ranged between 0.08 and 5.95 mg kg−1. The present method was employed for the analysis of twenty-two packaged commercially available spices including asteroid anise, clove, cardamon, cinnamon, curry, coriander, turmeric, cumin, white pepper, black pepper, nutmeg, allspice, red pepper, paprika, ginger, green pepper and pink pepper from the Greek market that are widely consumed. A wide variety of metal of different concentration ranges were determined in the samples.
1. Introduction
Culinary spices are widely consumed in plenty of cuisines worldwide, as they are associated with the cultural heritage of nations. They are defined/described by the Codex Alimentarius Commission (1995) as dried components or dried plants used to impart flavor, aroma and some of them to add color to foods [1]. The aroma is attributed to the volatile oil constituents present in spices, while the taste that spices impart is due to the oleoresins [2]. Specifically, edible parts of a plant, such as the seeds, bark, buds, roots, berries, and even the stigma of a flower, are obtained and dried to produce a particular spice. Spices can be found in both whole and powder form. Moreover, some dried plants can be blended, resulting in spice mixtures [3,4].
Besides their culinary use, spices have benefits in human health. Therefore they play an important role in the pharmacological and industrial fields, including the cosmetic and personal care industry [2,5]. Spices contain various compounds like terpenes and terpene derivatives that are important aroma compounds that are known to attract beneficial and repel harmful organisms. Physiological effects of spices have been also reported and now spices are believed to affect various health problems including inflammatory disorders, cardiovascular diseases and cancer. Thus, the use of spices has been currently extended beyond taste and flavor purposes [6].
Undoubtedly, spices as dried edible parts of a plant are rich in metals over a wide range of concentrations. Metals can exhibit either positive or negative impact in human health [7]. Metals like iron, copper and zinc are essential metals since they play an important role in biological systems [8]. Among the essential metals, some of them are micronutrients (e.g., Cr, Mn, Fe, Co, Zn, V etc.) and they are needed in very small quantities, while others are macronutrients (e.g., Ca, Mg etc.) and they are needed in higher amounts. On the other hand, metals like lead and cadmium have toxic roles in biochemical reactions on human body [7]. Metals have a tendency to bioaccumulate in biological organisms. Thus, the consumption of spices with increased concentration of toxic metals could potentially cause an accumulation of these contaminants in human organs [8]. Since spices are world widely consumed in daily diet and in pharmaceutical/cosmetic industry, the assessment of their elemental composition is of high importance for understanding their effect in human health [7].
Different analytical techniques can be employed for the determination of metals. Atomic spectrometric methods based on flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS) and plasma-based techniques such as inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) are typical examples of instrumental techniques that are used for the determination of elemental composition [9]. Among these techniques, ICP-OES is a well-established instrument for the trace analysis, since it offers high sensitivity, extended linear working range and the ability to perform rapid multi-element analysis [10]. Prior to ICP-OES analysis, a sample preparation step is typically required to make the sample compatible with the instrument. Different approaches for sample preparation of foodstuffs (e.g., dry ashing, ultrasound-assisted extraction and wet digestion) can be employed [11,12]. In the former approach, losses by volatilization and/or retention problems may occur, which can be overcome using wet digestion. Wet digestion is typically performed by the addition of oxidizing agents (e.g., nitric acid, sulfuric acid etc.), followed by heating. Wet digestion offers many benefits including handling simplicity, flexibility in terms of sample weight, digestion conditions and rapidity [13].
In this work, an ICP-OES method was employed for the determination of 17 metals (Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Tl and Zn) in packaged spices. For this purpose, the samples were subjected to autoclave assisted wet-acid digestion in the form of powder with a mixture of nitric acid and hydrogen peroxide. In total, twenty-two packaged spices including asteroid anise, clove, cardamon, cinnamon, curry, coriander, turmeric, cumin, white pepper, black pepper, nutmeg, allspice, red pepper, paprika, ginger, green pepper and pink pepper were analyzed, and a wide concentration range was determined in these samples.
2. Materials and Methods
2.1. Chemicals and Reagents
Nitric acid (HNO3) 65% and hydrogen peroxide (H2O2) 30% were supplied by Merck (Darmstadt, Germany) and they were of analytical grade. Throughout the study, high purity double distilled water was used. A multi-element stock standard solution containing all the target analytes (i.e., Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Tl and Zn) at a concentration of 1000 mg L−1 in 0.5 mol L−1 HNO3 was supplied by Merck (Darmstadt, Germany). From this solution, working standard solutions were daily prepared through appropriate serial dilutions of the stock solution in 0.5 mol L−1 HNO3.
2.2. Instrumentation
A Perkin-Elmer Optima 3100XL axial viewing ICP-OES instrument was used for the analysis of spices. The ICP-OES instrument was equipped with a cyclonic spray chamber and a GemTip cross-flow nebulizer. A peristaltic pump was used for the introduction of the digested sample into the ICP-OES system at a flow rate of 2.5 mL min−1 through Tygon-type PVC peristaltic pump tubes. The power output of the ICP-OES system and the radiofrequency generator were 1300 W and 40 MHz, respectively. The nebulizer argon gas flow rate was 0.85 L min−1, the auxiliary argon gas flow rate was 0.6 L min−1 and the plasma argon gas flow rate was 15 L min−1.
Sample digestions were carried out in a six-position aluminum block (Berghof, BTR, 941, Eningen, Germany) and the samples were placed in Teflon® (DuPont, Wilmington, DE, USA) vessels of a total volume of approximately 25 mL. The Teflon® vessels and all glassware were soaked in diluted HNO3 for at least 24 h and they rinsed with double distilled water. With this procedure, negligible blank values were obtained.
2.3. Sample Collection
In this study, twenty-two spices samples were analyzed, and their content of toxic and essential metals was determined. All samples were obtained from local market in Thessaloniki, Greece. The following samples were included in this study: asteroid anise (Illicium verum), clove (Syzygium aromaticum) (two samples), cardamon (Elettaria cardamomum), cinnamon (Cinnamomum verum), coriander (Coriandrum sativum), turmeric (Curcuma longa) (two samples), cumin (Cuminum cyminum), white pepper (Piper nigrum), black pepper (Piper nigrum) (two samples), nutmeg (Myristica fragrans), allspice (Pimenta dioica), chilli (Capsicum frutescens) (two samples), paprika (Capsicum annuum) (two samples), ginger (Zingiber officinale), green pepper (Capsicum annuum), pink pepper (Schinus molle) and curry (commercial powder mixture of spices). All samples were in powder form, apart from asteroid anise, pink pepper and coriander samples that were crushed in a mortar to form a fine powder. The samples are often used in Mediterranean cuisine, and they belong to the most common brands found in the Greek market.
2.4. Sample Preparation
For the wet digestion of the spices, an aliquot of 200 mg of the sample was weighted in a Teflon vessel. Subsequently, an amount of 6 mL of concentrated HNO3 and 1 mL of H2O2 was added in the vessel and the vessels were placed in a six-position aluminum block. To ensure complete dissolution of the spice samples, the mixture was heated for 90 min at 120 °C. After this time span, the aluminum block was left to cool down and it was opened when it came to room temperature. Then, the digested sample was transferred in a 25 mL volumetric flask and the volume of the sample was made up to the mark with double distilled water, followed by analysis by ICP-OES. For analytes with concentration above the upper limit of the herein studied linear range, appropriate dilution was done using high purity distilled water.
3. Results and Discussion
3.1. Selection of the Monitored Emission LInes
Two different emission lines were recorded for each analyte. These emission lines were 338.289 nm and 328.068 nm (Ag), 237.313 nm and 308.215 nm (Al), 208.957 nm and 249.772 nm (B), 233.527 nm and 230.425 nm (Ba), 190.171 nm and 223.061 nm (Bi), 396.847 nm and 317.933 nm (Ca), 214.440 nm and 226.502 nm (Cd), 228.616 nm and 238.892 nm (Co), 283.563 nm and 357.869 nm (Cr), 224.700 nm and 324.752 nm (Cu), 239.562 nm and 238.204 nm (Fe), 279.077 nm and 280.271 nm (Mg), 259.372 nm and 257.610 nm (Mn), 221.648 and 232.003 nm (Ni), 220.353 nm and 217.000 nm (Pb), 190.801 nm and 276.787 nm (Tl), 202.548 nm and 213.857 nm (Zn). The selection of the monitored emission lines was based on their sensitivity (in terms of the slope of the respective calibration curve for each analyte), their linearity and the absence of potential interferences. As such, the following emission lines were finally chosen: 328.068 nm (Ag), 308.215 nm (Al), 249.772 nm (B), 230.425 nm (Ba), 223.061 nm (Bi), 317.933 nm (Ca), 226.502 nm (Cd), 238.892 nm (Co), 357.869 nm (Cr), 324.752 nm (Cu), 238.204 nm (Fe), 280.271 nm (Mg), 257.610 nm (Mn), 232.003 nm (Ni), 217.000 nm (Pb), 276.787 nm (Tl), and 213.857 nm (Zn).
3.2. Figures of Merit
The linearity of the proposed method was evaluated by constructing calibration curves for each element. Thus, the peak area of each selected emission line was plotted against the concentration of a series of standard solutions ranging between 0.1 mg L−1 and 10.0 mg L−1, which were prepared in matrix-matched diluent containing 20% v/v concentrated HNO3 and 2% v/v H2O2 in order to mimic the acidic/oxidative conditions after the digestion procedure. Subsequently, least square linear regression analysis was employed and the slope, intercept and coefficient of determination of the calibration curves for each toxic and nutrient metal was calculated. For the calculation of the limits of detection (LODs) and the limits of quantification (LOQs) for the examined analytes, ten blank solutions containing 20% v/v concentrated HNO3 and 2% v/v H2O2 were prepared and analyzed. The LOD value of each analyte was considered to be the concentration that was equal to three times the standard deviation of the responses of the blank solutions versus the slope of the calibration curve. Similarly, the LOQ value of each analyte was considered to be the concentration that was equal to ten times the standard deviation of the responses of the blank solutions versus the slope of the calibration curve. Table 1 summarizes the results of the linearity, as well as the LOD and the LOQ values for the examined analytes. As it can be observed, good linearity was obtained for all analytes, while the LOD values were 0.08–5.95 mg kg−1 and the LOQ values were 0.27–19.83 mg kg−1.
For the evaluation of the trueness and the precision of the proposed method, two different spice samples (i.e., clove and chili) were spiked with different amounts of metals (i.e., 100 mg kg−1, 250 mg kg−1 and 500 mg kg−1, since no certified reference material containing the 17 analytes was available. Spiked samples were prepared by adding appropriate amount of multi-element standard solution containing at the digestion vessel containing the sample and the digestion mixture. The spiked samples were subjected to the experimental procedure described in Section 2.4. The trueness was evaluated in terms of relative recovery (RR%) by comparing the experimentally found concentration of each metal with the added concentration, while the precision of the proposed method was evaluated in terms of relative standard deviation (RSD) of three different complete preparations of the spiked samples [14]. Table 2 summarizes the results for method trueness and precision. Moreover, the herein method was employed for the analysis of the standard reference material 1573 (tomato leaves) and the trueness ranged between 96.2–102.4% for the analytes contained in this sample (i.e., Cr, Cu, Fe, Mn and Zn).
As it can be observed, the RR% values for each metal ranged between 82.0% and 117.5%. Thus, the proposed method exhibits sufficient trueness. The RSD values for the repeated measurements ranged between 0.1% and 9.5%, indicating that the proposed method exhibits good precision.
3.3. Real Samples Analysis and Discussion
The results of the analysis of the twenty-two spices samples are summarized in Table 3. Each spice was analyzed in duplicate, and the average value of each metal concentration is given. Among the examined analytes, Ag, Bi, Cd, Co, Pb and Tl were not detected in all samples. Ca and Mg were the major metal constituents of the spices, and their concentrations were in the range of 931–10,921 mg kg−1 and 468–3847 mg kg−1, respectively. The concentration of Al ranged between 34.1 mg kg−1 and 566.0 mg kg−1, the concentration of B ranged between not detected and 40.0 mg kg−1, the concentration of Ba ranged between 4.38 mg kg−1 and 100.7 mg kg−1, the concentration of Cr ranged between not detected and 4.93 mg kg−1, the concentration of Cu ranged between not detected and 19.9 mg kg−1, the concentration of Fe ranged between 31.2 mg kg−1 and 736.3 mg kg−1, the concentration of Mn ranged between 6.51 mg kg−1 and 501.0 mg kg−1, the concentration of Ni ranged between not detected and 14.7 mg kg−1 and the concentration of Zn ranged between 5.3 mg kg−1 and 63.8 mg kg−1. It must be highlighted that toxic metals that are regulated by the European Union were not detected in the herein analyzed samples [15].
Figure 1 shows the average metal content for the determined metals in the spice samples.
The results of this study regarding the elemental composition of the spices were compared with the findings of other studies, as shown in Table 4. As it can be observed, the elemental composition for all analytes was in agreement with the concentration ranges reported in the literature.
4. Conclusions
In this work, an ICP-OES method was employed for the determination of toxic and nutrient metals in spices after pressure assisted digestion. The proposed method exhibited good performance characteristics in terms of linearity, trueness, precision, while it exhibited satisfactory LOD and LOQ values for the examined analytes. The concentration of Ca ranged between 931 mg kg−1 and 10,921 mg kg−1, while the concentration of Mg ranged between 468 mg kg−1 and 3847 mg kg−1. Ag, Bi, Cd, Co, Pb and Tl were not detected in the samples. Al, B, Ba, B, Cr, Cu, Fe, Mn, Ni and Zn were also determined among the examined samples and their concentration levels were: 34.1–566.0 mg kg−1 for Al, up to 40.0 mg kg−1 for B, 4.38–100.7 mg kg−1 for Ba, up to 4.93 mg kg−1 for Cr, up to 19.9 mg kg−1 for Cu, 31.2–736.3 mg kg−1 for Fe, 6.51–501.0 mg kg−1 for Mn, up to 14.7 mg kg−1 for Ni and 5.3–63.8 mg kg−1 for Zn.
Author Contributions
Conceptualization, N.M. and G.A.Z.; methodology, N.M., E.I. and G.A.Z.; validation, N.M. and E.I.; investigation, N.M., E.I. and G.A.Z.; resources, G.A.Z.; writing—original draft preparation, N.M. and E.I.; writing—review and editing, N.M. and G.A.Z.; supervision, G.A.Z. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Bua, D.G.; Annuario, G.; Albergamo, A.; Cicero, N.; Dugo, G. Heavy metals in aromatic spices by inductively coupled plasma-mass spectrometry. Food Addit. Contam. Part B Surveill. 2016, 9, 210–216. [Google Scholar] [CrossRef]
- Parthasarathy, V.A.; Chempakam, B.; Zachariah, T.J. Chemistry of Spices CABI 2008; Wallingford: Oxfordshire, UK, 2008; ISBN 9781845934057. [Google Scholar]
- Tapsell, L.C.; Hemphill, I.; Cobiac, L.; Sullivan, D.R.; Fenech, M.; Patch, C.S.; Roodenrys, S.; Keogh, J.B.; Clifton, P.M.; Williams, P.G.; et al. Health benefits of herbs and spices: The past, the present, the future. Med. J. Aust. 2006, 185, S1–S24. [Google Scholar] [CrossRef] [PubMed] [Green Version]
- Tokalıoğlu, Ş.; Çiçek, B.; İnanç, N.; Zararsız, G.; Öztürk, A. Multivariate statistical analysis of data and ICP-MS determination of heavy metals in different brands of spices consumed in Kayseri, Turkey. Food Anal. Methods 2018, 11, 2407–2418. [Google Scholar] [CrossRef]
- Kumaravel, S.; Alagusundaram, K. Determination of mineral content in Indian spices by ICP-OES. Orient. J. Chem. 2014, 30, 631–636. [Google Scholar] [CrossRef] [Green Version]
- Bhagya, H.P.; Raveendra, Y.C.; Lalithya, K.A. Mulibenificial uses of spices: A brief review. Acta Sci. Nutr. Health 2017, 1, 3–6. [Google Scholar]
- Karadaş, C.; Kara, D. Chemometric approach to evaluate trace metal concentrations in some spices and herbs. Food Chem. 2012, 130, 196–202. [Google Scholar] [CrossRef]
- Aberie, Z.Z.; Sallilh, F.Z.; Medfu Tarekegn, M. Investigation of heavy metals in selected local spices consumed in Ethiopia. Cogent Food Agric. 2021, 7, 1917091. [Google Scholar] [CrossRef]
- Smichowski, P.; Londonio, A. The role of analytical techniques in the determination of metals and metalloids in dietary supplements: A review. Microchem. J. 2018, 136, 113–120. [Google Scholar] [CrossRef]
- Das, D.; Dutta, M.; Cervera, M.L.; de la Guardia, M. Recent advances in on-line solid-phase pre-concentration for inductively-coupled plasma techniques for determination of mineral elements. TrAC Trends Anal. Chem. 2012, 33, 35–45. [Google Scholar] [CrossRef]
- Gamela, R.R.; Costa, V.C.; Pereira-Filho, E.R. Multivariate Optimization of Ultrasound-Assisted Extraction Procedure for the Determination of Ca, Fe, K, Mg, Mn, P, and Zn in Pepper Samples by ICP OES. Food Anal. Methods 2020, 13, 69–77. [Google Scholar] [CrossRef]
- Shim, J.; Cho, Y.; Lee, K.; An, H.; Lee, C. Multivariate analysis of metals contents in spices commonly consumed in republic of Korea. Food Addit. Contam. Part B Surveill. 2021, 14, 184–192. [Google Scholar] [CrossRef]
- Momen, A.A.; Zachariadis, G.A.; Anthemidis, A.N.; Stratis, J.A. Investigation of four digestion procedures for multi-element determination of toxic and nutrient elements in legumes by inductively coupled plasma-optical emission spectrometry. Anal. Chim. Acta 2006, 565, 81–88. [Google Scholar] [CrossRef]
- Kalogiouri, N.P.; Tsalbouris, A.; Kabir, A.; Furton, K.G.; Samanidou, V.F. Synthesis and application of molecularly imprinted polymers using sol–gel matrix imprinting technology for the efficient solid-phase extraction of BPA from water. Microchem. J. 2020, 157, 104965. [Google Scholar] [CrossRef]
- European Commission Regulation (EC) No 1881/2006 setting maximum levels for certain contaminants in foodstuffs. Off. J. Eur. Union 2006, 364, 5–24.
- Gupta, K.K.; Bhattacharjee, S.; Kar, S.; Chakrabarty, S.; Thakur, P.; Bhattacharyya, G.; Srivastava, S.C. Mineral compositions of eight common spices. Commun. Soil Sci. Plant Anal. 2003, 34, 681–693. [Google Scholar] [CrossRef]
- Khan, N.; Choi, J.Y.; Nho, E.Y.; Jamila, N.; Habte, G.; Hong, J.H.; Hwang, I.M.; Kim, K.S. Determination of minor and trace elements in aromatic spices by micro-wave assisted digestion and inductively coupled plasma-mass spectrometry. Food Chem. 2014, 158, 200–206. [Google Scholar] [CrossRef]
- Shim, J.; Cho, T.; Leem, D.; Cho, Y.; Lee, C. Heavy metals in spices commonly consumed in Republic of Korea. Food Addit. Contam. Part B Surveill. 2019, 12, 52–58. [Google Scholar] [CrossRef]
- Soylak, M.; Tuzen, M.; Narin, I.; Sari, H. Comparison of microwave, dry and wet digestion procedures for the determination of trace metal contents in spice samples produced in Turkey. J. Food Drug Anal. 2004, 12, 254–258. [Google Scholar] [CrossRef]
- Khan, N.; Choi, J.Y.; Nho, E.Y.; Habte, G.; Jamila, N.; Hong, J.H.; Ryu, K.Y.; Park, K.S.; Kim PhD, K.S. Determination of Macronutrients in Spices by Inductively Coupled Plasma-Optical Emission Spectrometry. Anal. Lett. 2014, 47, 2394–2405. [Google Scholar] [CrossRef]
- Potortì, A.G.; Bua, G.D.; Lo Turco, V.; Ben Tekaya, A.; Beltifa, A.; Ben Mansour, H.; Dugo, G.; Di Bella, G. Major, minor and trace element concentrations in spices and aromatic herbs from Sicily (Italy) and Mahdia (Tunisia) by ICP-MS and multivariate analysis. Food Chem. 2020, 313, 126094. [Google Scholar] [CrossRef] [PubMed]
Figure 1.
Average metal content for (a) Ca and Mg, (b) Al, Fe and Mn, (c) B, Ba and Zn and (d) Cu, Cr and Ni in the spice samples.
Figure 1.
Average metal content for (a) Ca and Mg, (b) Al, Fe and Mn, (c) B, Ba and Zn and (d) Cu, Cr and Ni in the spice samples.
Table 1.
Linearity, LODs and LOQs for the examined analytes.
| Element | Emission Line (nm) | Calibration Curve | R2 | LOD (mg kg−1) | LOQ (mg kg−1) | Upper Limit of Calibration Curve (mg kg−1) |
|---|---|---|---|---|---|---|
| Ag | 328.068 | y = 202.7x − 401.36 | 0.9999 | 0.18 | 0.61 | 1000 |
| Al | 308.215 | y = 46.26x − 89.904 | 0.9999 | 2.34 | 7.81 | 1000 |
| B | 249.772 | y = 31.24x − 192.07 | 0.9999 | 2.95 | 9.85 | 1000 |
| Ba | 230.425 | y = 11.80x + 8.3761 | 0.9999 | 0.63 | 2.09 | 1000 |
| Bi | 223.061 | y = 1.40x − 15.393 | 0.9999 | 3.41 | 11.38 | 1000 |
| Ca | 317.933 | y = 34.88x + 678.32 | 0.9989 | 4.51 | 15.02 | 1000 |
| Cd | 226.502 | y = 6.61x + 11.911 | 0.9999 | 1.57 | 5.24 | 1000 |
| Co | 238.892 | y = 10.84x − 32.128 | 0.9999 | 0.67 | 2.22 | 1000 |
| Cr | 357.869 | y = 380.5x − 2575.6 | 0.9999 | 0.43 | 1.45 | 1000 |
| Cu | 324.752 | y = 600.0x − 1284.5 | 0.9999 | 0.15 | 0.52 | 1000 |
| Fe | 238.204 | y = 18.81x + 46.632 | 0.9999 | 2.92 | 9.75 | 1000 |
| Mg | 280.271 | y = 516.3x + 3009.4 | 0.9999 | 0.08 | 0.27 | 1000 |
| Mn | 257.610 | y = 233.7x + 1176 | 0.9999 | 0.09 | 0.29 | 1000 |
| Ni | 232.003 | y=2.76x − 13.599 | 0.9999 | 0.85 | 2.85 | 1000 |
| Pb | 217.000 | y = 0.43x − 4.0975 | 0.9999 | 5.95 | 19.83 | 1000 |
| Tl | 276.787 | y = 2.08x − 20.183 | 0.9998 | 4.98 | 16.60 | 1000 |
| Zn | 213.857 | y = 6.86x + 23.944 | 0.9999 | 1.55 | 5.18 | 1000 |
Table 2.
Trueness and precision study for the examined analytes (mean value ± standard deviation).
| Element | Clove_1 | Chilli_1 | |||||
|---|---|---|---|---|---|---|---|
| Added (mg kg−1) | Found (mg kg−1) | RR% | RSD% | Found (mg kg−1) | RR% | RSD% | |
| Ag | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 100.6 ± 0.3 | 100.6 | 0.3 | 104.8 ± 1.47 | 104.8 | 1.4 | |
| 250 | 250.6 ± 1.1 | 100.2 | 0.4 | 249.5 ± 4.62 | 99.8 | 1.9 | |
| 500 | 454.6 ± 7.9 | 90.9 | 1.7 | 490.2 ± 1.96 | 98.0 | 0.4 | |
| Al | 0 | 312.2 ± 3.4 | - | 1.1 | 166.6 ± 2.4 | - | 1.4 |
| 100 | 405.1 ± 9.4 | 92.9 | 2.3 | 258.9 ± 12.1 | 92.3 | 4.7 | |
| 250 | 517.2 ± 2.7 | 82.0 | 0.5 | 448.5 ± 28.8 | 112.8 | 6.5 | |
| 500 | 784.7 ± 2.7 | 94.5 | 0.3 | 665.1 ± 6.1 | 99.7 | 0.9 | |
| B | 0 | 39.4 ± 2.5 | - | 6.2 | 11.0 ± 0.9 | - | 8.2 |
| 100 | 131.9 ± 1.5 | 92.5 | 1.1 | 114.7 ± 0.9 | 103.7 | 0.8 | |
| 250 | 255.2 ± 0.8 | 86.3 | 0.3 | 232.7 ± 6.1 | 88.7 | 2.6 | |
| 500 | 542.6 ± 0.3 | 100.6 | 0.1 | 515.0 ± 2.9 | 100.8 | 0.6 | |
| Ba | 0 | 34.1 ± 1.9 | - | 5.8 | 23.9 ±1.3 | - | 5.4 |
| 100 | 126.8 ± 0.3 | 92.7 | 0.2 | 135.8 ± 1.3 | 111.9 | 1.0 | |
| 250 | 255.1 ± 3.9 | 88.4 | 1.5 | 287.9 ± 25.7 | 105.6 | 8.9 | |
| 500 | 515.9 ± 2.0 | 96.4 | 0.4 | 525.3 ± 0.7 | 100.3 | 0.1 | |
| Bi | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 88.4 ± 5.1 | 88.4 | 5.8 | 104.5 ± 8.53 | 104.5 | 8.2 | |
| 250 | 224.8 ± 3.7 | 89.9 | 1.7 | 233.0 ± 21.4 | 93.2 | 9.2 | |
| 500 | 535.5 ± 6.6 | 107.1 | 1.2 | 533.5 ± 8.70 | 106.7 | 1.6 | |
| Ca | 0 | 2245 ± 20.7 | - | 0.9 | 2449 ± 45.9 | - | 1.9 |
| 250 | 2498.3 ± 74.9 | 101.3 | 3.0 | 2710.5 ± 17.4 | 104.6 | 0.6 | |
| 500 | 2784.0 ± 12.5 | 107.8 | 0.5 | 2930.5 ± 31.7 | 96.3 | 1.1 | |
| Cd | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 98.7 ± 0.5 | 98.7 | 0.5 | 103.0 ± 0.7 | 103.0 | 0.7 | |
| 250 | 250.7 ± 1.6 | 100.3 | 0.6 | 253.0 ± 22.3 | 101.2 | 8.8 | |
| 500 | 491.5 ± 0.6 | 98.3 | 0.1 | 497.0 ± 2.0 | 99.4 | 0.4 | |
| Co | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 106.8 ± 0.7 | 106.8 | 0.7 | 107.5 ± 0.3 | 107.5 | 0.3 | |
| 250 | 263.7 ± 4.2 | 105.5 | 1.6 | 267.3 ± 11.6 | 106.9 | 4.3 | |
| 500 | 515.8 ± 1.7 | 103.2 | 0.3 | 514.7 ± 0.3 | 102.9 | 0.1 | |
| Cr | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 114.9 ± 1.1 | 114.9 | 1.0 | 117.5 ± 4.5 | 117.5 | 3.8 | |
| 250 | 244.8 ± 1.0 | 97.9 | 0.4 | 273.4 ± 7.9 | 109.4 | 2.9 | |
| 500 | 555.7 ± 10.0 | 111.1 | 1.8 | 537.4 ± 11.5 | 107.5 | 2.1 | |
| Cu | 0 | 1.30 ±0.01 | - | 0.8 | 4.71 ±0.21 | - | 4.3 |
| 100 | 92.3 ± 0.8 | 91.0 | 0.9 | 97.5 ± 3.1 | 92.8 | 3.1 | |
| 250 | 236.1 ± 0.4 | 93.9 | 0.2 | 235.4 ± 15.8 | 92.3 | 6.7 | |
| 500 | 528.1 ± 8.7 | 105.4 | 1.7 | 520.0 ± 9.4 | 103.1 | 1.8 | |
| Fe | 0 | 183.8 ± 3.2 | - | 1.7 | 137.4 ± 4.9 | - | 3.6 |
| 100 | 277.8 ± 1.6 | 94.0 | 0.6 | 232.6 ± 4.3 | 95.2 | 1.9 | |
| 250 | 402.8 ± 2.9 | 87.6 | 0.7 | 342.7 ± 15.1 | 82.1 | 4.4 | |
| 500 | 646.2 ± 2.5 | 92.5 | 0.4 | 623.5 ± 1.1 | 97.2 | 0.2 | |
| Mg | 0 | 1230.0 ± 12.8 | - | 1.0 | 1542.0 ± 21.4 | - | 1.4 |
| 250 | 1456.0 ± 7.3 | 90.4 | 0.5 | 1770.5 ± 1.8 | 91.4 | 0.1 | |
| 500 | 1736.5 ± 1.4 | 101.3 | 0.1 | 2060.0 ± 3.7 | 103.6 | 0.2 | |
| Mn | 0 | 159.2 ± 1.4 | - | 0.9 | 75.7 ± 4.9 | - | 6.5 |
| 100 | 241.2 ± 0.5 | 82.0 | 0.2 | 169.1± 2.4 | 93.4 | 1.4 | |
| 250 | 408.7 ± 2.0 | 99.8 | 0.5 | 308.1 ± 6.2 | 93.0 | 2.0 | |
| 500 | 590.9 ± 1.5 | 86.3 | 0.3 | 573.6 ± 1.7 | 99.6 | 0.3 | |
| Ni | 0 | <LOD | - | - | <LOD | - | 8.0 |
| 100 | 82.2 ± 0.35 | 82.2 | 0.4 | 82.6 ± 1.2 | 82.6 | 1.5 | |
| 250 | 223.2 ± 3.3 | 89.3 | 1.5 | 242.8 ± 3.7 | 97.1 | 1.5 | |
| 500 | 522.2 ± 0.52 | 104.4 | 0.1 | 518.2 ± 0.4 | 103.6 | 0.1 | |
| Pb | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 97.2 ± 2.3 | 97.2 | 2.4 | 87.5 ± 7.7 | 87.5 | 8.8 | |
| 250 | 266.8 ± 5.2 | 106.7 | 2.0 | 285.3 ± 27.1 | 114.1 | 9.5 | |
| 500 | 562.1 ± 0.9 | 112.4 | 0.2 | 563.9 ± 3.9 | 112.8 | 0.7 | |
| Tl | 0 | <LOD | - | - | <LOD | - | - |
| 100 | 87.6 ± 1.6 | 87.6 | 1.8 | 98.8 ± 0.5 | 98.8 | 0.5 | |
| 250 | 228.8 ± 5.5 | 91.5 | 2.4 | 270.2 ± 4.2 | 108.1 | 1.6 | |
| 500 | 550.9 ± 11.2 | 110.2 | 2.0 | 556.6 ± 10.2 | 111.3 | 1.8 | |
| Zn | 0 | 46.0 ± 2.4 | - | 5.1 | 33.9 ± 1.3 | - | 3.8 |
| 100 | 136.5 ± 0.8 | 90.5 | 0.6 | 125.1 ± 0.2 | 91.2 | 0.2 | |
| 250 | 287.2 ± 4.8 | 96.5 | 1.7 | 286.9 ± 7.0 | 101.2 | 2.4 | |
| 500 | 538.8 ± 2.2 | 98.6 | 0.4 | 530.1 ± 1.5 | 99.2 | 0.3 | |
Table 3.
Elemental composition of the examined samples. Each value is the average obtained from duplicate analysis of the examined sample.
Table 3.
Elemental composition of the examined samples. Each value is the average obtained from duplicate analysis of the examined sample.
| Sample | Al | B | Ba | Ca | Cu | Cr | Fe | Mg | Mn | Ni | Zn |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Asteroid anise (Illicium verum) | 142.9 | 40.0 | 51.3 | 931 | 7.98 | <LOD | 82.3 | 468 | 89.9 | <LOD | 61.4 |
| Clove_1 (Syzygium aromaticum) | 312.2 | 39.4 | 34.1 | 2245 | 1.30 | <LOD | 183.8 | 1230 | 159.2 | <LOD | 46.0 |
| Clove_2 (Syzygium aromaticum) | 156.9 | 39.9 | 52.4 | 1145 | <LOD 2 | <LOD | 87.6 | 498 | 88.8 | <LOD | 63.8 |
| Cardamon (Elettaria cardamomum) | 136.1 | 11.4 | 26.1 | 4756 | 7.96 | 4.53 | 119.3 | 3847 | 387.8 | 8.02 | 51.9 |
| Cinnamon (Cinnamomum verum) | 232.4 | <LOQ 1 | 100.7 | 7844 | 7.10 | 3.65 | 178.7 | 908 | 344.9 | <LOQ | 40.0 |
| Curry (Commercial powder) | 256.0 | <LOQ | 4.38 | 3298 | 7.80 | 3.94 | 338.0 | 1793 | 73.0 | <LOQ | 13.8 |
| Coriander (Coriandrum sativum) | 237.3 | 21.2 | 27.2 | 2816 | 10.6 | <LOD | 177.8 | 1666 | 103.3 | <LOD | 42.5 |
| Turmeric_1 (Curcuma longa) | 291.3 | 28.6 | 34.5 | 2520 | 0.98 | <LOD | 213.4 | 1507 | 130.2 | <LOD | 44.2 |
| Turmeric_1 (Curcuma longa) | 80.5 | 22.7 | 9.8 | 2335 | <LOD | 3.02 | 49.1 | 748 | 28.2 | <LOQ | 10.6 |
| Cumin (Cuminum cyminum) | 438.8 | 34.6 | 17.2 | 10921 | 13.1 | 3.50 | 359.3 | 3065 | 28.6 | 8.94 | 37.1 |
| White pepper (Piper nigrum) | 73.5 | <LOQ | 20.6 | 2369 | 15.9 | 1.80 | 93.2 | 842 | 123.7 | <LOQ | 5.3 |
| Black pepper _1 (Piper nigrum) | 350.6 | 23.1 | 59.1 | 4481 | 15.4 | 3.34 | 357.4 | 1991 | 289.5 | 8.97 | 5.9 |
| Black pepper_2 (Piper nigrum) | 67.2 | 22.1 | 12.3 | 2691 | <LOD | 2.60 | 50.1 | 749 | 29.7 | 6.25 | 10.9 |
| Nutmeg (Myristica fragrans) | 68.2 | 10.2 | 14.8 | 1642 | 15.2 | 4.93 | 70.7 | 1709 | 43.9 | 14.7 | 20.5 |
| Allspice (Pimenta dioica) | 34.1 | 23.4 | 11.3 | 9239 | 19.9 | 3.04 | 31.2 | 1256 | 6.51 | 5.82 | 17.8 |
| Chilli_1 (Capsicum frutescens) | 166.6 | 11.0 | 23.9 | 2449 | 4.71 | <LOD | 137.4 | 1542 | 75.7 | <LOD | 33.9 |
| Chilli_2 (Capsicum frutescens) | 88.4 | 12.9 | 8.31 | 2054 | <LOD | 2.60 | 51.6 | 770 | 29.3 | 3.63 | 11.9 |
| Paprika_1 (Capsicum annuum) | 316.4 | 12.6 | 5.17 | 3976 | 14.8 | 3.97 | 450.3 | 2957 | 24.5 | 3.79 | 12.4 |
| Paprika_2 (Capsicum annuum) | 82.3 | 11.7 | 11.2 | 2945 | <LOD | 3.36 | 56.1 | 880 | 33.1 | <LOQ | 13.2 |
| Ginger (Zingiber officinale) | 566.0 | <LOQ | 19.8 | 2863 | 13.9 | 2.37 | 736.3 | 2369 | 501.0 | 7.84 | 26.7 |
| Green pepper (Capsicum annuum) | 57.0 | <LOD | 10.9 | 2452 | <LOD | 2.83 | 46.4 | 671 | 25.7 | <LOQ | 11.2 |
| Pink pepper (Schinus molle) | 248.8 | 23.9 | 31.7 | 2674 | 5.68 | <LOD | 202.7 | 1503 | 119.5 | <LOD | 40.1 |
1 LOQ: Limit of quantification. 2 LOD: Limit of detection.
Table 4.
Comparison of the elemental composition of spices found in this study with reported composition of other studies.
Table 4.
Comparison of the elemental composition of spices found in this study with reported composition of other studies.
| Element | This work | [7] | [16] | [17] | [18] | [19] | [20] | [21] | [12] 1 |
|---|---|---|---|---|---|---|---|---|---|
| Ag | <LOD 2 | - | - | - | - | - | - | - | - |
| Al | 34.1–566.0 | - | 40–700 | - | - | - | - | - | - |
| B | <LOD–40.0 | - | - | 3.65–31.7 | - | - | - | - | - |
| Ba | 4.38–100.7 | 2.02–39.22 | - | 0.63–77.34 | - | - | - | - | - |
| Bi | <LOD | - | - | 0.46 × 10−3–14.96 × 10−3 | - | - | - | - | - |
| Ca | 931–10,921 | 2510–9600 | 6560–13,700 | - | - | - | 2282–15,579 | 4300–24,500 | 11,032 |
| Cd | <LOD | <LOD–8.0 × 10−3 | - | 3.56 × 10−3–94.3 × 10−3 | 13 × 10−3–315 × 10−3 | 0.10–0.93 | - | ≤0.0966 | 0.066 |
| Co | <LOD | 0.006–0.522 | <LOD–4.12 | 50.99 × 10−3–432.7 × 10−3 | - | - | - | - | |
| Cr | <LOD–4.93 | 0.44–1.79 | <LOD–3.99 | 0.38–3.33 | - | 0.67–7.15 | - | - | - |
| Cu | <LOD–19.9 | 2.78–11.70 | 2.5–19.03 | 2.35–77.68 | - | 4.1–28.7 | - | ≤100 | 8.55 |
| Fe | 31.2–736.3 | 53–409 | 70–950 | - | - | 88.9–376.3 | 46.12–1002 | ≤592 | 587 |
| Mg | 468–3847 | 400–2590 | 1790–4250 | - | - | - | 492.2–3870 | 640–7160 | - |
| Mn | 6.51–501.0 | 14.2–164.7 | 26.17–79.73 | 18.99–879.8 | - | 11.9–211.3 | - | ≤307 | - |
| Ni | <LOD–14.7 | 0.32–6.50 | <LOD–7.71 | 0.94–3.19 | - | 0.65–8.69 | - | ≥0.165 | 0.486 |
| Pb | <LOD | - | <LOD–5.80 | 121.3 × 10−3–451.1 × 10−3 | 3.9 × 10−3–972 × 10−3 | 0.47–1.89 | - | 0.0631–2.053 | 0.282 |
| Tl | <LOD | - | - | 0.387 × 10−3–28.50 × 10−3 | - | - | - | - | - |
| Zn | 5.3–63.8 | 16.5–45.7 | 6.35–77.5 | 12.64–84.95 | - | 7.84–47.6 | - | ≤100 |
1 Mean values. 2 LOD: Limit of detection.
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Manousi, N.; Isaakidou, E.; Zachariadis, G.A. An Inductively Coupled Plasma Optical Emission Spectrometric Method for the Determination of Toxic and Nutrient Metals in Spices after Pressure-Assisted Digestion. Appl. Sci. 2022, 12, 534. https://doi.org/10.3390/app12020534
AMA Style
Manousi N, Isaakidou E, Zachariadis GA. An Inductively Coupled Plasma Optical Emission Spectrometric Method for the Determination of Toxic and Nutrient Metals in Spices after Pressure-Assisted Digestion. Applied Sciences. 2022; 12(2):534. https://doi.org/10.3390/app12020534
Chicago/Turabian StyleManousi, Natalia, Eleni Isaakidou, and George A. Zachariadis. 2022. "An Inductively Coupled Plasma Optical Emission Spectrometric Method for the Determination of Toxic and Nutrient Metals in Spices after Pressure-Assisted Digestion" Applied Sciences 12, no. 2: 534. https://doi.org/10.3390/app12020534
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