Solid-Phase Microextraction and Determination of Tin Species
in Beverages and Food Samples by Using Poly (
ε-Caprolactone-b-4-Vinyl
Benzyl-g-Dimethyl Amino Ethyl Methacrylate) Polymer in Syringe
System: a Multivariate Study
Rizwan Ali Zounr1,2&Mustafa Tuzen1,3&Baki Hazer4&Muhammad Yar Khuhawar2
Received: 26 December 2017 / Accepted: 15 March 2018 / Published online: 29 March 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract
A new solid-phase microextraction (SPμE) procedure has been developed for separation and preconcentration of Sn ions by using graphite furnace atomic absorption spectrometry (GFAAS). This technique is based on the complexation of Sn(IV) ions with 1-(2-pyridylazo)-2-naphthol (PAN). The poly (ε-caprolactone-b-4-vinyl benzyl-g-dimethyl amino ethyl methacrylate) polymer (PCL vacr) was used as an adsorbent, and it was loaded in micropipette tip of syringe system. Sn(IV) ions were adsorbed on polymer at pH 6. Different experimental conditions were optimized such as pH, amount of complexing agent, and amount of adsorbent. The detection limit (LOD), limit of quantification, preconcentration factor (PF), and relative standard deviation (RSD) were found as 4.5 ng L−1, 13.5 ng L−1, 100, and 3.3%, respectively. Certified reference materials were used to confirm the accuracy of the investigated procedure, and the procedure was successfully practiced for determination of entire concentration of tin within beverages and different food samples.
Keywords Tin species . SPμE . PCL vacr . Syringe system . Food samples . GFAAS
Introduction
Two main species of tin have been found in environmental samples, i.e., Sn(II) and Sn(IV). Whereas Sn(II) is familiar with its extra toxicity as compared to Sn(IV) (Pawlik-Skowrońska et al.1997). Tin is commonly used in canned beverage and food industries as an anticorrosive protective coating. While, consumed tin for beverage samples packaging
can dissolve into beverage samples depending upon amount of the beverage consumed, pH, acidity, existence of oxidizing agents, degree of adsorption, time, temperature, and solubility. Following the elimination of tin coating, delamination, and leaching of alloys within the stuffs will cause an enrichment of heavy metals within foodstuffs. This is mainly correct for acidic foodstuffs, such as fruit juices as well as canned tomato sauce (Adams and Happiness2010; Somer and Unal2011).
Different analytical techniques such as liquid chromatogra-phy (Yang et al.1995), flame atomic absorption spectrometry (FAAS) (Gholivand et al.2008), UV–Vis spectrophotometry (Huang et al.1997), and spectroflourimetry (Manzoori et al. 2006) were used for determination of tin. Though, majority of these revealed procedures are difficult and prolonged. Therefore, a latest as well as easy separation method is neces-sary for inorganic tin species. In order to find out the ultra-trace amount of inorganic tin species in food and beverage samples, separation and preconcentration steps are essential earlier to the analysis. The usual procedures for the speciation and determination of inorganic tin have been found in the literature including solvent extraction (Saleh et al.2001) and solid-phase extraction (Leepipatpiboon 1995; Lemos et al. * Mustafa Tuzen
mustafa.tuzen@gop.edu.tr
1
Faculty of Science and Arts, Chemistry Department, Gaziosmanpasa University, Tokat, Turkey
2
Institute of Advanced Research Studies in Chemical Sciences, University of Sindh, Jamshoro, Pakistan
3
Research Institute, Center for Environment and Water, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
4 Faculty of Science and Arts, Chemistry Department and Faculty of
Engineering, Departments of Metallurgical and Materials Engineering, Nano Technology Engineering,
2008; Zaporozhets et al.2001). Solid-phase extraction (SPE) procedures having elevated preconcentration factors have be-come famous, and these procedures have also been applied for preconcentration of tin and tin compounds in water samples (Bermejo-Barrera et al.1998; Puri et al.2004).
The properties of polymers are strongly dependent on their architectures (Yildiz et al.2012; Zhang and Müller2010). The increasing diversity in polymer architectures offers novel poly-mer materials with unprecedented properties and functions. Amphiphilic copolymers contain both hydrophobic and hydro-philic character (Hazer2010). Synthesis of antibacterial amphi-philic elastomer based on polystyrene-block-polyisoprene-block-polystyrene via thiol-ene addition. In this work, a new brush-type pH-sensitive amphiphilic copolymer PCL vacr was used in the adsorption studies. This pH-sensitive polymer is soluble in aqueous medium with pH < 12, but insoluble in basic solutions in pH 12.5. Both brush topology and pH-sensitive properties are highly efficient in the adsorption studies.
The contamination of tin in the beverages and food samples owing to the use of metallic containers lined with tin is of great concern for human health. The development of analytical pro-cedure for the trace analysis in the real samples of beverage and food is of paramount interest. Therefore, the aim of our study was to develop a green, easy, fast, and sensitive SPμE procedure for preconcentration and determination of ultra-trace quantity of Sn species in beverages and food samples by employing a micropipette tip of the syringe system packed with PCL vacr as an adsorbent. Different experimental param-eters effecting the separation, preconcentration, and determi-nation of analyte ions were studied and optimized. The SPμE was carried out for quantification of Sn species in beverage samples and total tin in canned food samples.
Experimental
Instrumentations
A Perkin Elmer atomic absorption spectrophotometer model Analyst 700 (Norwalk, CT, USA) employing electrothermal atomizer as well as deuterium background corrector was used for purpose of tin. Ultra-pure argon gas with flow rate of 250 mL min−1 was utilized for entire measurements. A tin hollow cathode lamp was used as radiation source at a wave-length of 224.6 nm with 0.7-nm slit width. The pyrolysis as well as atomization was optimized at 1500 and 2500 °C tem-peratures, correspondingly. The 20-μL sample solution was used to perform all determinations. While 10-μL solution of palladium and magnesium nitrate was applied as matrix mod-ifier. The pH was optimized by using pH meter (model Sartorius pp-15). Microwave digestion of solid samples was carried out by employing a (Milestone Ethos D model, Sorisole-Bg, Italy) microwave system.
Chemicals and Reagents
The complete work was carried out by using deionized water (Bedford, MA, USA) 18.2 MΩ cm−1). The stock solution
(1000 mg L−1) of tin was obtained by dissolving the proper quantity of SnCl4(St. Louis, MO, USA). Potassium
perman-ganate (KMnO4) was purchased from Sigma-Aldrich. The
complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN) was purchased from Sigma-Aldrich (St. Louis, MO, USA), and then 0.1% (w/v) solution was prepared and used as a chelating reagent. The synthesis and characterization of PCL vacr poly-mer was carried out by the procedure described in the cited reference (Şanal et al.2015). Whereas the structural formula of this polymer have been shown in (Fig. 1). The pH was adjusted by using (0.1 mol L−1) acetate and phosphate-buffered solutions.
Sample Collection and Pretreatment
Various beverage and food samples were collected from a local market of Tokat city, Turkey. The collected samples were brought to the research laboratory, where these samples were stored at 4 °C until sample preparation. Food samples were digested with microwave system according to our reported analytical procedures (Naeemullah et al. 2015). Beverages samples were collected from local market of Tokat, Turkey. The samples were acidified with HCl and filtered by means of filter paper (0.45-μm membrane thickness) (Zounr et al. 2017), and an optimized method was applied to samples.
Design of Syringe System
The micropipette tip of syringe system was rinsed by means of deionized water followed by dried out at room temperature. The micropipette tip was loaded with 3.5 mg of synthesized polymer which was used as an adsorbent. Then, a very small
Fig. 1 Structural formula of poly (ε-caprolactone-b-4-vinyl benzyl-g-dimethyl amino ethyl methacrylate) brush-type graft copolymer
piece of cotton was placed at the end of micropipette tip. Followed by loading the adsorbent and cotton, the micropi-pette tip was firmly associated to syringe system. While 1.0-mL HCl (1.0 mol L−1) was used to wash out the probable contaminations from syringe system. Then, deionized water was used for cleaning until it became neutral. Before using the syringe system, the buffer solution of required pH was used to condition the system. Following each elution, 5.0 mL of de-ionized water were used to wash the polymer inside the tip.
Analytical Procedure
Standard solutions containing 1μg L−1 Sn(IV) and Sn(II) were prepared, and 200-μL pH 6 acetate buffer, 200 μL of complexing reagent (PAN 0.1%w/v), was added to this solu-tion and left for 5 min for the complexasolu-tion between metal and PAN complex. Then, each sample solution was allowed to pass through micropipette tip of syringe (containing polymer) by gradually pulling and pushing of syringe plunger by means of hand. The total adsorption of Sn(IV) complex on adsorbent was carried out by 4.0 pulling and pushing cycles with hand gradually within the time of 30–60 s. Finally, the metal com-plex which was retained on PCL vacr was eluted with 250μL of HCl (1.0 mol L−1) in a small flask and was carried out by three pulling or pushing cycles with hand gradually. The ana-lyte ions were then analyzed by graphite furnace atomic ab-sorption spectrometry (GFAAS).
Oxidation of Sn(II) to Sn(IV) and Determination
of Total Tin
A reported technique was carried out for oxidation of Sn(II) ions to Sn(IV) ions (Ulusoy et al.2012). According to this, KMNO4is a suitable and good oxidizing agent in acidic
me-dium which permits a quick and total oxidation of Sn(II) to Sn(IV) ions at the temperature of 30 °C. Once the oxidation of Sn(II) to Sn(IV) was achieved, then analytical procedure was applied for determination of total tin. The GFAAS was employed for calculation of tin concentration. The Sn(II) con-centration was achieved by difference between Sn(IV) and total Sn concentrations prior as well as following the oxidation.
Factorial Design Test
Plackett–Burman Design
A Plackett–Burman Design (PBD) was done with the help of Minitab (release 13 of Minitab) version 5.1 (Cruz-Vera et al. 2009; Zhou et al.2008). To assess the most favorable aspects for the presented process at two levels, PBD by means of just 16 numbers of experiments was revealed as a replacement of 25= 32 obligatory for complete factorial designs, as given in
Table1which shows the low (−) and high (+) levels, whereas Table 2shows the optimization by the PB matrix. The out-comes can be observed by standardized (P = 95.0%). The Pareto chart of major effects is shown in Fig.2. The experi-mental design application reduced the time for method devel-opments and gave less uncertain conditions of extraction, therefore facilitating interpretation of data.
Central 23+ Star Orthogonal Composite Design
Following by the consecutive screening out variables having no any significant effect on analyte recovery, three left over variables were investigated to give optimum recovery for met-al. Therefore a 23+star orthogonal CCD, through six degrees of freedom and concerning 16 new experiments was done to Table 1 Factors and levels used in the factorial design
Variable Low (−) High (+)
pH 3.0 8.0
Amount of adsorbent (mg) 1.0 6.0
Ligand (μL) 100 500
Aspirating and dispensing cycles of the syringe system for desorption
2.0 6.0
Aspirating and dispensing cycles of the syringe system for adsorption
2.0 10
Table 2 Plackett–Burman design for the significant variable determination (n = 6) Experiments P A L AD AA % R 1 + − − − − 9.23 2 − + − + + 27.1 3 − + − − − 13.4 4 + − + − + 37.3 5 + + − + − 45.1 6 + − + + − 38.7 7 − − − − + 7.56 8 + − − + + 14.8 9 + + + − − 45.4 10 + + − − + 41.0 11 + + + + + 76.3 12 − + + + − 24.4 13 − + + − + 29.1 14 − − + + + 19.7 15 − − + − − 12.3 16 − − − + − 6.42
P pH, A amount of adsorbent, L ligand, AD aspirating and dispensing cycles of syringe system for desorption,AA aspirating and dispensing cycles of syringe system for adsorption
optimize the variables counting P (pH), A (adsorbent), and ligand (L) for Sn(IV) % recovery, as observed in Table3. Throughout the PBD, those variables which observed to be less significant were set at appropriate values, i.e., after PBD the insignificant factors were set at suitable values such as aspirating and dispensing cycles of syringe system for desorp-tion were four and aspirating and dispensing cycles of syringe system for adsorption were seven.
Results and Discussion
Optimization of Experimental Variables
There are five factors which were decided to be observed. The factors as well as their values, low (−) and high (+), are given in Table1. For all experiments, the volume of sample was kept constant as 10 mL. The percentage (%) recovery was chosen to check the effect of change in factor from low level to high level value. The results of design (% recovery) are given in Table2and designed by employing a Pareto chart of standard-ized effect, as shown in Fig.2.
Estimated Effects of Variables
Considering for planned technique, five variables including pH (P), amount of adsorbent (A), concentration of L, aspirat-ing and dispensaspirat-ing cycles of syraspirat-inge system for desorption (AD), and aspirating and dispensing cycles of syringe system for adsorption (AA) were chosen to optimize % recovery of Sn(IV) as experimental results by PBD are given in Table2. The (1–16) resulting values are being the extraction efficiency of Sn(IV) in 10 mL of the working model solution comprising 1μg L−1of standard Sn(IV). From PBD results, the most major effects investigated for pH are amount of ad-sorbent and ligand of Sn(IV) for recovery.
It can be observed in experiments 1 that the pH is only variable which was at highest level (+) while other all four variables were at a low level (−) and the % recovery of analyte was found to be 9.23%. In experiment number 9, the three variables including pH, amount of adsorbent, and ligand con-centration were at a high level (+) while aspirating and dis-pensing cycles of syringe system for adsorption and Fig. 2 Pareto chart for the
significance of response of the variables: pH, amount of adsorbent (A), ligand (L), aspirating and dispensing cycles of syringe system for desorption (AD), and aspirating and dispensing cycles of syringe system for adsorption (AA)
Table 3 Central 23+ star
orthogonal composite design (n = 16) for the set of (P), (A), (L), and (R) Run P A L %R 1 P° A° L° 99.2 2 − − − 14.0 3 + − − 25.0 4 − + − 21.0 5 + + − 34.0 6 − − + 12.0 7 + − + 38.0 8 − + + 45.0 9 + + + 87.0 10 −P1 A° L° 7.0 11 +P2 A° L° 65.0 12 P° −A1 L° 12.0 13 P° +A2 L° 84.0 14 P° A° −L1 3.0 15 P° A° +L2 87.0 16 P° A° L° 99.3 P° = 5.5,−P1 = 1.42, +P2= 9.5825, A° = 3 . 5 m g , −A1= 0 . 5 8 2 m g , + A2 = 7.5825 mg, L° = 300 μL, −L1=− 26.6μL, +L2= 626.6μL
desorption were at a low (−) level. In experiments 11, the Sn(IV) recovery was found to be 76.3%, whereas all the var-iables remain at maximum (+) levels. In experiment number 16, the lowest extraction efficiency of analyte was found as 6.42%, whereas all the variables were at low (−) levels except aspirating and dispensing cycles of syringe system for desorp-tion which was at a high level (+). It can be seen in experiment number 5 that the % recovery of analyte was found to be 45.1% while the variables including pH, amount of adsorbent, aspirating, and dispensing cycles of syringe system for de-sorption were at high (+) level while other two variables re-main at low level. The major effects of variable (under inves-tigation) on percentage recovery of Sn(IV) were observed in increasing order of variables, AA < AD < L < A < pH (Fig.2).
Optimization by Central Composite Designs
In the central composite design, it was observed in experiment number 1 and 16 that three variables remain at optimum values for the highest extraction efficiency of analyte were found to be from 99.2 up to 99.3%, respectively. The lowest extraction efficiency (3%) of analyte was observed in experi-ment number 14. A low extraction efficiency (7%) of analyte was observed in experiment number 10. The variable and their levels are given in Table 3. In experiments 9 and 15, the optimum recovery was found to be 87%, while in experiment number 13, the 84% extraction efficiency of analyte was found as shown in Table3. It can be seen in experiment 8 that two variables such as amount of adsorbent and ligand Fig. 3 Three dimension (3D)
surface response for % recovery of Sn(IV) by SPμE. Interaction b/w pH and ligand
Fig. 4 Three dimension (3D) surface response for % recovery of Sn(IV) by SPμE. Interaction b/w pH and amount of the adsorbent
concentration were at the highest (+) level while pH at a low (−) level and the recovery of analyte was found to be 45%. A three-array relation between variables [pH vs L] and [pH vs A] offered important effects on extraction efficiency of Sn(IV) was observed as shown in Figs.3and4.
Interfering Effect of Various Ions
The effect of some coexisting ions was also carried out during this work. Hence, the effect of various interfering ions in actual
samples was checked under optimized parameters. The recovery for analyte ions to be achieved as > 96%. The tolerance limit may be characterized as maximum quantity for interfering ions that creates error less than 5% for an analysis of analyte with the help of GFAAS. The observed outcomes are given in Table4. It was investigated that key matrix ions within food as well as water samples did not show a noticeable interference through preconcentration of Sn(IV) ions. Therefore, it was achieved that common cations as well as anions available in water had no critical effects on measurement of analyte ions.
Table 4 The effect of interfering ions on determination of 1.0μg L−1of Sn(IV) ions by the proposed method
Ions Tolerance limit Recovery (%)
Cations Na+, K+, Pb2+, Ba2+, Cu2+, NH4+ 3000 96.3–97.9 Al3+, Cr3+, and Ca2+ 2000 98.1–99.2 Mg2+, Ag+, 1000 95.5–97.7 Mn2+, Cd2+ 200 96.8–98.5 Co2+ 200 97.4 Fe3+ 100 98.9 As3+ 50 97.8 Anions CO32−, PO43−, Cl−, Br−, SO42−, NO2−, F− 5000 97.6–98.3 NO3−, SO32−, I− 1000 96.9–99.0
Table 5 Speciation of Sn(II) and Sn(IV) and total tin in beverage samples (sample volume 25 mL, final volume 0.25 mL,N = 5)
Sample Added (ng mL−1) Found (ng mL−1) Total Sn %Recovery Total Sn
Sn(II) Sn(IV) Sn(II) Sn(IV) Sn(II) Sn(IV)
Mineral water – – BDLa BDL – – – – 2.0 2.0 1.99 ± 0.11b 1.98 ± 0.12 3.97 ± 0.23 99 ± 2 99 ± 4 99 ± 3 5.0 5.0 4.92 ± 0.42 4.95 ± 0.67 9.87 ± 1.89 98 ± 3 99 ± 3 98 ± 3 Ice tea – – 2.02 ± 0.12 2.85 ± 0.16 4.87 ± 0.27 – – – 1.0 1.0 2.93 ± 0.14 3.82 ± 0.26 6.75 ± 0.45 97 ± 2 99 ± 3 98 ± 3 2.0 2.0 4.83 ± 0.27 4.79 ± 0.34 9.62 ± 0.59 96 ± 2 99 ± 4 97 ± 2 Peach juice – – 1.57 ± 0.15 2.28 ± 0.18 3.85 ± 0.33 – – – 1.0 1.0 2.51 ± 0.18 3.15 ± 0.33 5.66 ± 0.53 97 ± 2 96 ± 2 97 ± 3 3.0 3.0 4.42 ± 0.20 5.07 ± 0.41 9.49 ± 0.62 97 ± 3 96 ± 2 97 ± 4 Cherry juice – – 1.35 ± 0.13 1.93 ± 0.17 3.28 ± 0.31 – – – 1.0 1.0 2.28 ± 0.15 2.85 ± 0.22 5.13 ± 0.36 97 ± 3 97 ± 2 97 ± 2 3.0 3.0 4.21 ± 0.23 4.79 ± 0.35 9.0 ± 0.62 97 ± 4 97 ± 3 97 ± 3
Canned mixed juice – – 2.98 ± 0.15 4.43 ± 0.23 7.41 ± 0.35 – – –
3.0 3.0 5.88 ± 0.26 7.40 ± 0.39 13.3 ± 0.65 98 ± 3 99 ± 3 99 ± 4 5.0 5.0 7.77 ± 0.46 9.31 ± 0.55 17.0 ± 1.03 97 ± 2 99 ± 2 98 ± 3 Red wine – – 3.35 ± 0.18 5.32 ± 0.27 8.67 ± 0.43 – – – 3.0 3.0 6.31 ± 0.35 8.21 ± 0.39 14.5 ± 0.63 99 ± 3 98 ± 2 99 ± 3 5.0 5.0 8.12 ± 0.42 10.1 ± 0.63 18.2 ± 1.04 97 ± 2 98 ± 3 97 ± 3 a
BDL blow limit of detection
b
Analytical Performance of the Method
The analytical performance of the developed technique for determination of tin in beverage and food samples by preconcentration as well as separation from various samples was studied and investigated by using external calibration graphs. The LOD, LOQ, and EF for the developed procedure were found to be 4.5 ng L−1, 13.5 ng L−1, and 100, respec-tively. Whereas repeatability and reproducibility of this tech-nique were evaluated in terms of RSD from six calculations of the standard solution containing the analyte of interest, and RSD was calculated as 3.3%. The accuracy of developed pro-cedure was investigated by using SRM1548a, typical diet.
The Validation and Application of the Method
Determination of Sn(IV) was carried out in the first step, and the entire amount of tin was observed in the second step earlier to the oxidation of Sn(II) to Sn(IV). At last, the Sn(II) was measured by variation. The proposed procedure was efficient-ly used for the tin speciation in beverage sample in Table5. The validity and accuracy of developed SPμE procedure was achieved by using SRM1548a, typical diet certified reference materials as given in Table6. The certified values were ob-served to be in agreement with investigated results. The tech-nique was also employed for the determination of entire amount of tin in canned food sample, as given in Table 6. Table 6 The concentration of tin
in food samples and certified reference material
Reference material Certified value (μg kg−1) Found value (μg kg−1) Recovery (%)
SRM1548a, typical diet 17.2 ± 2.57a 17.0 ± 1.3 98.8
Samples Concentration (μg g−1) Beef 0.19 ± 0.018 Sheep meat 0.57 ± 0.06 Cheese 0.62 ± 0.04 Canned peas 0.39 ± 0.04 Green tea 0.12 ± 0.01 Canned olives 1.45 ± 0.13 Canned corn 0.77 ± 0.06 Canned beans 0.81 ± 0.05 Tomato paste 0.59 ± 0.02
Canned tuna fish 0.67 ± 0.03
Cheese 0.71 ± 0.05
Butter 0.42 ± 0.03
a
Mean ± SD
Table 7 Comparison of present technique with reported methods
Technique Detection system Samples LOD (μg L−1) RSD (%) PF/EF Reference
CPE FAAS Food 2.86 2.10 100 Ulusoy et al. (2012)
CPE GFAAS Water 0.012 < 4.1 96.2 Yuan et al. (2005)
CPE FAAS Canned beverage 0.33 2.1–6.2 50 Gürkan and Altunay (2015)
Coprecipitation GFAAS Beverage 0.013 5 50 Uluozlu and Tuzen (2015)
SPE GFAAS-HGAAS Water 0.1–0.25 < 6.1 19.7 Tsogas et al. (2009)
MMCPE FAAS Water and environmental samples 8.4–12.6 2.4 100 Gholivand et al. (2008)
CPE FAAS Canned food 2.86 2.5 Ulusoy et al. (2013)
MMCPE UV/Vis spectrometer Canned juice, water, soft drinks 0.16 2.9–3.4 20 Madrakian and Ghazizadeh (2009)
FISPE HGICP-MS Natural water 0.142 1.5 2.5 Fornieles et al. (2013)
SPμE GFAAS Water, fruit juice, and canned food 4.5 ng L−1 3.3 100 Present method
CPE cloud-phase extraction, SPE solid-phase extraction, SPμE solid-phase microextraction, FAAS flame atomic absorption spectrometry, GFAAS graphite furnace atomic absorption spectrometry,HGAAS hydride generation atomic absorption spectrometry, MMCPE micelle-mediated cloud-phase extraction,FISPE flow injection solid-phase extraction, HGICP-MS hydride generation inductively coupled plasma mass spectrometry, LOD limit of detection,RSD relative standard deviation, PF preconcentration factor, EF enrichment factor
The determination of tin within canned foods has frequently been studied, because tin is the major element in the manufacturing of packaging materials to protect these foods (Tuzen and Soylak2007). The maximum permitted levels of tin for beverages and canned foods are 100 and 200μg g−1 (Commission Regulation (EC)2006). Tin levels in present study were found to be lower than permissible limits for bev-erages and food samples.
Conclusions
A green, novel, and innovative SPμE procedure has been devel-oped for the speciation of tin in beverage samples and total tin in food samples. The developed technique is easy, highly sensitive, fast, portable, and eco-friendly. The synthesized polymer, PCL vacr, was employed as an adsorbent in the tip of micropipette syringe system. This adsorbent has a high capacity of adsorption and free of chemical hindrance. The investigated technique was also compared fruitfully with the analytical techniques reported in the literature, as shown in Table7. The developed procedure is superior to the reported analytical methods with respect to the detection limit, RSD, and preconcentration factor. Low detection limit, low RSD values, and high preconcentration factors were observed in the developed method than literature values. The method could be used for the selective determination of tin at trace levels (ng mL−1) and speciation of Sn(II), Sn(IV) and total tin in the real samples. In the future, this technique may be useful for determination of other metals from the complex food matrix.
Funding Information Rizwan Ali Zounris gratefully acknowledge the financial support from TUBITAK, Government of Turkey, through the 2216 fellowship program for the foreign citizens and providing financial support. Dr. Mustafa Tuzen thank the Gaziosmanpasa University and King Fahd University of Petroleum and Minerals, Research Institute, Center for Environment and Water for their supports. He also thank the Turkish Academy of Sciences for the financial support.
Compliance with Ethical Standards
Conflict of Interest R. A. Zounr declares that he has no conflict of interest. Mustafa Tuzen declares that he has no conflict of interest. Baki Hazer declares that he has no conflict of interest. M. Y. Khuhawar de-clares that he has no conflict of interest.
Ethical Approval This research does not have any studies with human subjects or animals performed by any of the authors.
Informed Consent Not applicable.
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