key: cord-0004282-00n9xho8 authors: Tursynbolat, Satar; Bakytkarim, Yrysgul; Huang, Jianzhi; Wang, Lishi title: Highly sensitive simultaneous electrochemical determination of myricetin and rutin via solid phase extraction on a ternary Pt@r-GO@MWCNTs nanocomposite date: 2019-03-22 journal: J Pharm Anal DOI: 10.1016/j.jpha.2019.03.009 sha: 064fc5c0af69e9be13dee69a113ca743d05fd807 doc_id: 4282 cord_uid: 00n9xho8 The simultaneous electrochemical determination of myricetin and rutin remains a challenge due to their indistinguishable potentials. To solve this problem, we constructed a ternary platinum nanoparticle, reduced graphene oxide, multi-walled carbon nanotubes (Pt@r-GO@MWCNTs) nanocomposite via a facile one-pot synthetic method. Under the optimized conditions, the ternary Pt@r-GO@MWCNTs nanocomposite exhibited good electrocatalytic activity toward myricetin and rutin via solid phase extraction and excellent performance for the simultaneous determination of myricetin and rutin. The oxidation peak current of myricetin was proportional to its concentrations in the range of 0.05–50 μM with a detection limit of 0.01 μM (S/N = 3). The linear range for rutin was 0.05–50 μM with a detection limit of 0.005 μM (S/N = 3). The ternary nanocomposite sensor also exhibited good reproducibility and stability, and was successfully used for the simultaneous determination of myricetin and rutin in real orange juice samples with recoveries ranging between 100.57% and 108.46%. Flavonoids have received significant attention due to their effects on human health. In particular, myricetin and rutin are two important flavonoids naturally present in plants including berries, tea, fruits, vegetables, and medicinal herbs [1] . According to previous reports, myricetin exhibits anti-oxidant, anti-cancer, and cytoprotective properties [2] . Rutin has a wide range of physiological functions, such as anti-inflammatory, anti-bacterial, antiaging, and anti-oxidation abilities [3] . Because of the above listed pharmacological effects, health foods, drinks, and medicinal herbs usually contain myricetin and rutin. Therefore, it is important to develop a method to determine the contents of myricetin and rutin in food and medicine. To date, some analytical methods have been developed to simultaneously detect myricetin and rutin, including capillary electrophoresis [4, 5] , chemiluminescence [6] , high performance liquid chromatography (HPLC) [7] , and spectrophotometry [8] . These methods can sensitively detect myricetin and rutin, but they have many drawbacks including the need for expensive equipment and time-consuming experimental processes, which constrain their practical application [9e18] . Compared to previously developed methods, voltammetry provides a fast response, uses simple equipment, and is highly sensitive to the determination of myricetin or rutin [19e28] . Although many electrochemical sensors have been reported for single determinations of myricetin or rutin [29e35], their simultaneous determination has seldom been reported due to their analogous chemical structures and electrochemical characteristics, resulting in an indistinguishable potential [36, 37] . Therefore, it is imperative to develop an electrochemical sensor that can realize the simultaneous determination of myricetin and rutin. Multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (r-GO) are promising conductor materials with high surface area, stable physical and chemical properties, high mechanical strength, and good absorption properties [38e47]. In addition, they are easily combined with other nanomaterials due to their constituent hydroxyl (eOH), carboxyl (eCOOH), and carbonyl (eC]O) functional groups [48e51]. The noble metal Pt is widely used in the field of catalysis and fuel cells [52] . Pt nanoparticles have been loaded into carbon nanotubes to form novel composite materials that show good performances as electrochemical sensors [53e55] . In this study, we synthesized a novel ternary nanocomposite consisting of Pt NPs, MWCNTs and r-GO for the simultaneous determination of myricetin and rutin. The ternary nanocomposite was fabricated by a facile one-pot synthesis method and showed strong ability to adsorb myricetin and rutin during solid-phase extraction. Because of this excellent property, the proposed nanocomposite sensor exhibits a distinguishable potential, high response, wide linear detection range, and low detection limit for both myricetin and rutin. In addition, this sensor exhibits good reproducibility, reversibility, and stability and was successfully used in the quantitative determination of myricetin and rutin in real orange juice samples, yielding satisfactory results. Rutin (98%, analytical grade) and chloroplatinic acid (H 2 PtCl 6 ) were purchased from J&K Chemical Corporation (Beijing, China). Myricetin (97%, analytical grade) was obtained from Tokyo Chemical Industry (TCI) Co., Ltd. The MWCNTs (95%, analytical grade) were purchased from Aladdin Chemical Reagent Co., Ltd. (Shanghai, China). All other chemicals were of analytical grade. Britton-Robinson (BR) buffer was prepared by mixing acetic acid, phosphoric acid, and boric acid. Various pH values of the 0.04 M BR buffer were obtained by adding 0.2 M NaOH and HCl. Stock solutions of 1.0 mmol/dm 3 myricetin and 1.0 mmol/dm 3 rutin were obtained by dissolution in 50 mL of ethanol and subsequent dilution with doubly distilled water to 100 mL. All aqueous solutions were prepared with doubly distilled water. A novel one-pot method was used to synthesize the ternary Pt@r-GO@MWCNTs nanocomposites at room conditions (room temperature is 25 C) (Scheme 1). First, 30 mg of monolayer graphene oxide and 30 mg of MWCNTs were placed in 30 mL of double distilled water and mixed for 30 min under ultrasonication. Subsequently, under stirring conditions, 500 mL of a 60 mM H 2 PtCl 6 solution was added to the above solution. Simultaneously, 10 mL of a 0.05 g/mL NaBH 4 solution was added and the reaction mixture was stirred vigorously for 30 min. The product was washed three times with a mixed solution of ethanol and water at a ratio of 1:1. Finally, 8 mL of an ethanol and water mixture at a ratio of 1:3 was added to the product, yielding the ternary Pt@r-GO@MWCNTs nanocomposite. First, a glassy carbon electrode (GCE, 3 mm in diameter) was polished with 0.3 and 0.05 mm alumina powders, then rinsed ultrasonically with absolute alcohol and distilled water, and dried under a nitrogen stream. Subsequently, 5 mL of a homogeneous suspension of Pt@r-GO@MWCNTs was dropped onto the electrode surface and dried at room temperature (room temperature is 25 C) to obtain the Pt@r-GO@MWCNTs nanocomposite sensor. Electrochemical cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pules voltammetry (DPV) measurements were performed using a CHI 660B electrochemical workstation (Chenhua Co. Ltd. Shanghai, China). A threeelectrode system consisting of a bare or modified GCE (3 mm in diameter) working electrode, platinum wire counter electrode, and saturated calomel reference electrode (SCE) was used. DPV scans from À0.1e0.8 V with an amplitude of 0.05 V, pulse width of 0.05 s, pulse period of 0.5 s, and increment of 0.004 V were performed. For CV, scan rate was 50 mV/s and sample interval was 0.001 V. EIS was obtained in a 5.0 mmol/dm 3 6 ] solution containing 0.1 M KCl under an open circuit potential at a frequency range from 0.1 Hz to 100 kHz and 5 mV amplitude. The surface morphology was characterized via field emission scanning electron microscopy (FE-SEM; Zeiss Ultra 55, Germany) and energy dispersive X-ray spectroscopy (EDS). Fig. 1 shows the SEM images at low and high magnifications of the ternary Pt@r-GO@MWCNTs nanocomposites. The MWCNTs and r-GO were clearly observed, and the Pt NPs were uniformly and densely distributed in the MWCNTs and r-GO. The Pt@r-GO@MWCNTs composite was also analyzed by EDS (Fig. 2) , showing that the main components were C, O and Pt at approximately 85.27, 12.5, and 2.23 wt%, respectively (Si was also observed because the Pt@r-GO@MWCNTs nanocomposite was dropped onto the silicon wafer for SEM sample preparation). The above results indicate the successful fabrication of the Pt@r-GO@MWCNTs nanocomposite. After modification with the Pt@r-GO@MWCNTs nanocomposite (curve b), the redox peak currents increased and a larger background current was observed due to the Pt@r-GO@MWCNTs nanocomposite dramatically increasing the electrode surface area and exhibiting good electrical conductivity [41, 42] . Fig. 3B shows the EIS plots of the bare GCE and Pt@r-GO@MWCNTs/GCE. The bare GCE (curve a) exhibited a small resistance, but when the Pt@r-GO@MWCNTs nanocomposite GCE was used (curve b), it displayed a significantly smaller resistance. Therefore, the CV and EIS diagrams further demonstrate the successful preparation of the Pt@r-GO@MWCNTs/GCE sensor. The CVs of bare GCE and Pt@r-GO@MWCNTs/GCE in 50 mM myricetin and 50 mM rutin solutions are shown in Fig. 4A . Unlike the bare GCE, two pairs of redox peaks of myricetin and rutin were clearly observed when the Pt@r-GO@MWCNTs/GCE was used along with a larger background current. Thus, the Pt@r-GO@MWCNTs nanocomposite showed a good electrocatalytic effect for detection of both myricetin and rutin. In addition, the DPV results shown in Fig. 4B for the bare GCE (I pa ¼ 4.617 mA, E pa ¼ 0.276 V for myricetin, and I pa ¼ 1.316 mA, E pa ¼ 0.432 V for rutin) provided very small current signals. Moreover, the potential differences were insufficient to realize the simultaneous determination of myricetin I pa ¼ 44.45 mA, E pa ¼ 0.320 V for myricetin, and I pa ¼ 51.71 mA, E pa ¼ 0.496 V for rutin), the oxidation peak current signals increased by a factors of 11 and 50 for myricetin and rutin, respectively, over that of the bare GCE. In addition, the potential differences became large enough for the simultaneous detection of myricetin and rutin. Therefore, the Pt@r-GO@MWCNTs/GCE sensor was successful used for the simultaneous determination of myricetin and rutin. The effects of scan rate were investigated by CVs in a pH 3.0 BR buffer solution containing 50 mM myricetin and rutin. As shown in The effect of pH was investigated by DPVs in BR buffer solution containing 50 mM myricetin and rutin at different pH values (Fig. 6A) . As the pH increased (Fig. 6B) , oxidation peak currents of both myricetin and rutin increased until pH 3 and then decreased at higher pH values. Therefore, the optimum pH was determined to be 3. In Fig. 6C , as the pH increased, both oxidation peak potentials of myricetin and rutin negatively shifted with a good linear relationship between the oxidation peak potentials and pH. The linear equation for myricetin was E pa (V) ¼ À0.0702 pH þ 0.5398 (R 2 ¼ 0.9918) and for rutin E pa (V) ¼ À0.0632 pH þ 0.6997 (R 2 ¼ 0.9904). The slopes of the respective equations were 70.2 and 63.2 mV/pH, suggesting that both myricetin and rutin oxidation followed the Nernst equation requiring identical number of protons and electrons. Combined with previous reports [36, 37] , the myricetin and rutin oxidation mechanism involved the same number electron and proton transfer processes (Scheme 2). The pre-concentration time and potential were studied in the pH 3 BR buffer solution containing 50 mM myricetin and rutin. In concentration potential on the oxidation peak currents of myricetin and rutin using the optimized pre-concentration time. In Fig. 7B , the oxidation peak current increased until À0.3 V, after which the oxidation peak currents gradually decreased. Therefore, the optimal pre-concentration potential for determination of myricetin and rutin was À0.3 V. The simultaneous quantitative determination of myricetin and rutin at the Pt@r-GO@MWCNTs/GCE was investigated via DPVs. From Fig. 8E , with an increase in concentration of myricetin and rutin, the corresponding oxidation peaks current gradually increased in intensity. Fig. 8F shows that the concentration of myricetin and oxidation peak current exhibited two linear detection ranges of 0.05e10 and 10e50 mM with linear equations of I p (mA) ¼ 2.0561C (mM) þ 1.6368 (R 2 ¼ 0.9958) and I p (mA) ¼ 0.5643C (mM) þ 17.2910 (R 2 ¼ 0.9731), respectively. From Fig. 8G , the concentration of rutin and oxidation peak current showed two linear detection ranges of 0.05e10 and 10e50 mM with equations of I p (mA) ¼ 2.4047C (mM) þ 3.5326 (R 2 ¼ 0.9944) and I p (mA) ¼ 0.6247C (mM) þ 21.6050 (R 2 ¼ 0.9906), respectively. The detection limits of myricetin and rutin were 10 and 5 nM (S/N ¼ 3), respectively. These results indicated that the Pt@r-GO@MWCNTs nanocomposite modified electrode showed higher sensitivity and selectivity for both myricetin and rutin. Moreover, compared to other reported determinations of myricetin or rutin, our Pt@r-GO@MWCNTs/GCE can realize the simultaneous determination of myricetin and rutin with lower detection limits and the wider linear ranges (Table 1) [16,36,37,56e59] . The electrode modified with the Pt@r-GO@MWCNTs nanocomposite showed improved detection sensitivity due to the pre-concentration ability and solid-phase extraction. We also explored the effects of potentially interfering inorganic ions and organic molecules. When 1000-fold excesses of NaNO 3 , NH 4 F, MnSO 4 , CaCl 2 , and Zn(AC) 2 , and 100-fold excesses of citric acid, tartaric acid, cystine, glucose, ascorbic acid, and oxalic acid were added, as showen in Table 2 , no significant signal changes were observed for oxidation peaks currents of myricetin and rutin, indicating that the assay was not disturbed. These results indicate that the modified electrode exhibited good selectivity for the determination of myricetin and rutin. Furthermore, three modified electrodes were stored under refrigerated conditions (4 C) and used regularly for myricetin and rutin analysis at 10-day intervals. After 30 days of storage, the sensor response remained quite stable (the reduction of the sensor output signal was ˂5%), demonstrating the excellent stability of Pt@r-GO@MWCNTs/GCE. The reversibility of the Pt@r-GO@MWCNTs/GCE electrode was investigated by DPVs. We modified an electrode that was stored under refrigerated conditions and subsequently used for myricetin and rutin analysis at 8 h intervals for two days. The standard deviation of the oxidation peak currents of the myricetin and rutin was (3.54 ± 0.41) %, indicating good reversibility. The actual analytical application of the prepared Pt@r-GO@MWCNTs/GCE sensor for the simultaneous determination of myricetin and rutin in real orange juice was achieved by standard addition. Three parallel experiments were performed for all measurements. As shown in Table 3 , the real orange juice sample recovery rate ranged between 100.57% and 108.46%, and the RSD value was ˂6%. These results indicated that the prepared sensor can be successfully applied for the actual simultaneous determination of myricetin and rutin in real orange juice samples. In summary, we successfully manufactured a novel electrochemical sensor based on a ternary Pt@r-GO@MWCNTs nanocomposite. The nanocomposite sensor exhibited improved detection sensitivity due to the superior pre-concentration ability of the nanocomposite for myricetin and rutin. Under the optimized conditions, the oxidation peak currents of myricetin were proportional to its concentration with linearity ranging from 0.05 to 50 mM and a detection limit of 0.01 mM (S/N ¼ 3). For rutin the linear range was from 0.05 to 50 mM with a detection limit of 0.005 mM (S/ N ¼ 3). The sensor also exhibited good reproducibility and stability, and was successfully used for the simultaneous determination of myricetin and rutin in real orange juice samples providing satisfactory results. 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be used in sensors development Direct-methanol fuel cell based on functionalized graphene oxide with mono-metallic and bi-metallic nanoparticles: electrochemical performances of nanomaterials for methanol oxidation Decorating carbon nanotubes with metal or semiconductor nanoparticles Glucose biosensor based on mesoporous Pt nanotubes Functionalized graphene quantum dots with bi-metallic nanoparticles composite: sensor application for simultaneous determination of ascorbic acid, dopamine, uric acid and tryptophan Facile preparation of molecularly imprinted polypyrrole-graphene-multiwalled carbon nanotubes composite film modified electrode for rutin sensing Application of a Cuchitosan/multiwalled carbon nanotube film-modified electrode for the sensitive determination of rutin Electrochemical characterization of in situ functionalized gold organosulfur self-assembled monolayer with conducting polymer and carbon nanotubes for determination of rutin Fabrication of nickel coated graphene oxide composite electrode for sensitive determination of rutin This work was financially supported by the National Natural Science Foundation of China (Grant No. 21874047, 21475046, 21427809). The authors declare that there are no conflicts of interest.