Application w88 link mới nhất solid phase extraction cleanup with MnO2 nanomaterial as sorbent for the determination w88 link mới nhất carbaryl and carbofuran in spinach followed by HPLC/UV

ABSTRACT:

The application w88 link mới nhất solid phase extraction cleanup with MnO₂nanomaterial as a sorbent for the determination w88 link mới nhất carbaryl and carbofuran in spinach followed by HPLC/UV was presented.

The sorption w88 link mới nhất chlorophyll and carbamate pesticides such as carbaryl and carbofuran by SPE with MnO₂nanomaterial sorbent in different solvents was investigated. Results showed that the sorption percentage w88 link mới nhất chlorophyll was 100; 79.59; 79.29; 52.6; 35.84; 29.35; and 25.45 % for n-hexane; toluene; acetone; dichloromethane; ethyl acetate; acetonitrile; and chloroform, respectively. The results showed also that carbaryl and carbofuran were very poorly sorbed in acetone solvents. However, the combination w88 link mới nhất n-hexane with acetone considerably improved the cleanup w88 link mới nhất chlorophyll and good recovery w88 link mới nhất carbaryl and carbofuran. Here, the mixed solvent w88 link mới nhất acetone: n-hexane (1 : 3, v/v) was adopted as the mixed solvent because it provided better recovery for carbaryl and carbofuran. The method was applied to determine carbaryl and carbofuran pesticides in random spinach from Da Lat’s markets.

Keywords:MnO₂nanomaterial sorbent, SPE- MnO₂, Carbaryl, Carbofuran.

1. Introduction

Carbaryl and carbofuran are essential carbamate pesticides. This pesticide is a class w88 link mới nhất highly effective commercial pesticides, due to their high insecticide and nematocide effects [1,2,3]. They have become one kind w88 link mới nhất popular pesticide in agriculture. However, the use w88 link mới nhất pesticides during production often leads to the presence w88 link mới nhất pesticide residues in vegetables [4,5,6]. The increasing use w88 link mới nhất carbaryl and carbofuran pesticides poses a risk to create health problems in the blood, nervous, and reproductive systems [1,3]. Thus, it is necessary to determine their residue amount in vegetables to prevent harmful effects on humans and the environment.

Most analytical methods for the determination w88 link mới nhất carbamate pesticides are based on chromatographic techniques [2,7]. High-performance liquid chromatography (HPLC) is obviously the preferred approach for polar, less volatile, and thermally labile pesticides such as carbamate [3,4,5,6,7]. However, the key to a successful method w88 link mới nhất analysis for pesticides in vegetables is a technique that will thoroughly extract the pesticide residues from the complex matrices and determine how the interfering substances that co-extract with the pesticides can be cleaned up. Therefore, the sample preparation for the determination w88 link mới nhất pesticide residue is important, i.e. the extraction and clean-up steps play a critical role in the success w88 link mới nhất pesticide residue analysis.

The solid phase extraction (SPE) is a sample preparation method, it is not only can be used for preconcentration purposes, but also for clean-up [6-10]. The types w88 link mới nhất SPE columns most commonly used for the cleanup w88 link mới nhất pesticides in fresh fruits and vegetables include reverse phase sorbents such as octadecylsilyl (C-18); bonded normal phase such as aminopropyl (-NH₂) and primary-secondary amine (PSA); un-bonded normal phase SPE columns such as alumina, florisil, and silica; anion exchange such as trimethylammonium strong anion exchange (SAX); and adsorbent such as graphitized carbon black (GCB). However, the application w88 link mới nhất nanomaterials as sorbents for SPE is still limited [8-17].

The aim w88 link mới nhất this work was to apply the SPE with MnO₂nanomaterials as a sorbent for sample preparation to determine carbaryl and carbofuran residues by HPLC in spinach, which is considered a highly pigmented vegetable because it contains high levels w88 link mới nhất chlorophyll.

2. Materials and methods

2.1. Chemicals, reagents and instruments Chemicals and reagents.

All reagents and solvents were HPLC or analytical grade. KMnO₄, MgSO₄, NaCl were purchased from Merck. All used solvents (ethanol, acetonitrile, acetone, ethyl acetate, dichloromethane, chloroform, toluene, n-hexane, and methanol) were HPLC grade and were obtained from Merck.

Carbaryl carbofuran was purchased from Sigma-Aldrich (Germany).  Stock solutions w88 link mới nhất carbamate insecticides containing carbofuran (200ppm) and carbaryl (100ppm) were prepared in methanol and stored in the dark at 4^oC in a refrigerator.

Pure water was obtained from a Milli-Q purification system.

All standard solutions, samples and extracted samples were stored in the refrigerator at 4^oC prior to analysis.

Instruments

- HPLC/UV: The analyses were performed in HPLC - Shimazu LC 20AD, UV detector. LC-20AD pump with plunger capacity 10µL, flow rate set 1.0000 mL/min.  The separation was performed on a HiQ sil C18HS column (250mm × 4,6mm × 5mm).

- Cecil Spectrophotometer, CE 2011. Visible wavelength range 325 - 1000nm. For the spectrophotometric study, extracts w88 link mới nhất the samples were taken. The spectra were taken at 350 - 750 nm. From the peak obtained, the gmax value was calculated.

- SPE vacuum manifold and accessories.

2.2. Preparation w88 link mới nhất g-MnO₂sorbent

The g-MnO₂was synthesized via the reaction between saturated potassium permanganate (KMnO₄) solution and ethanol (C₂H₅OH) at room temperature, as described in a previous report [18-19].

2.3. SPE cartridge

In this study, we used an SPE cartridge with MnO₂nanomaterial sorbent for sample cleanup before being analyzed by HPLC. The SPE cartridge (5.5 x 1.0cm) was prepared as follows: A 3mL w88 link mới nhất the medical syringe was well packed with a little cotton wool, anhydrous sodium sulfate (0.5cm), 0.1g w88 link mới nhất MnO₂nanomaterial sorbent and finally with anhydrous sodium sulfate (1cm). The prepared cartridge was then conditioned with a working solvent (n-hexane; toluene; acetone; dichloromethane; ethyl acetate; acetonitrile; and chloroform) and not allowed to run dry.

The extract solutions were loaded into SPE cartridges with MnO₂nanomaterial sorbent for cleanup w88 link mới nhất chlorophyll and recovery w88 link mới nhất pesticides.

2.4. Standards and working solutions

The concentration w88 link mới nhất the stock standard solution was 100 and 200 ppm for carbaryl and carbofuran, respectively. Working standard solutions w88 link mới nhất all pesticides were prepared at five different concentrations (2, 4, 10, 20, 40 ppm) in methanol. The results show that the detector gives good linear results for carbofuran in the range w88 link mới nhất working concentration from 1 to 40 ppm and carbaryl in the range w88 link mới nhất working concentration from 0.5 to 20 ppm.

Linearity, precision, accuracy, the limit w88 link mới nhất detection (LOD), the limit w88 link mới nhất quantitation (LOQ), and recovery parameters were determined for validation w88 link mới nhất the method.

The LOD and LOQ were set at a signal-to-noise ratio (S/N ratio) w88 link mới nhất 3 and 10, respectively.

2.5. Sample analysis

Spinach samples were purchased from a local market. Ten grams w88 link mới nhất spinach sample was homogenized with a blender and transferred to a 40 mL centrifuge tube.  Then, extracted with 10 ml w88 link mới nhất acetone: n-hexane (v/v = 1:3). Four grams w88 link mới nhất anhydrous MgSO₄and 1 g w88 link mới nhất NaCl were then added and vortexed immediately for 5 min. It followed by centrifugation at 6000 rpm for 5 min. The supernatant was loaded onto a SPE-MnO₂nanomaterial cartridge which had already been conditioned with a mixed solvent w88 link mới nhất acetone: n-hexane (v/v = 1:3). The effluent was completely evaporated under a nitrogen stream and reconstituted in 1.0mL w88 link mới nhất MeOH : H₂O (65:35 v/v) mixed solvent for HPLC analysis.

3. Results and discussion

3.1. The clean up w88 link mới nhất chlorophyll as co-extract by SPE with MnO₂nanomaterial sorbent and recovery w88 link mới nhất carbofuran and carbaryl pesticides

In our study, different solvents with increased polarity were used to clean up the co-extract, such as chlorophyll by SPE with MnO₂nanomaterial sorbent to determine the carbaryl and carbofuran residues in spinach by HPLC.

3.1.1. Sorption w88 link mới nhất chlorophyll by SPE with MnO₂nanomaterial sorbent in different solvents

Fig.1. Effect w88 link mới nhất different solvents on sorption w88 link mới nhất chlorophyll by SPE-MnO₂nanomaterial sorbent

Fig.1 showed that the chlorophyll was sorbed by SPE with MnO₂nanomaterial sorbent (SPE-MnO₂) in different solvents, such as acetone, acetonitrile, chloroform, dichloromethane, toluene, ethyl acetate, n-hexane. The sorption percentage w88 link mới nhất chlorophyll was 100; 79.59; 79.29; 52.6; 35.84; 29.35; and 25.45 % for n-hexane; toluene; acetone; dichloromethane; ethyl acetate; acetonitrile; and chloroform respectively.  Based on our results reported here, the sorption percentage w88 link mới nhất chlorophyll was decreased in the following order n-hexane toluene acetone dichloromethane ethyl acetate acetonitrile chloroform. This shows that the sorption percentage w88 link mới nhất chlorophyll by SPE-MnO₂ nanomaterial decreases with increasing polarity w88 link mới nhất the solvent.

In addition, the Vis-spectrophotometric method showed that the observation parameters for detecting the effectiveness w88 link mới nhất the sorption process w88 link mới nhất chlorophyll by SPE-MnO₂with various solvents including absorbance peak.

Fig.2. The visible spectrum w88 link mới nhất the chlorophyll in different solvents.

- The visible spectrum w88 link mới nhất chlorophyll in the chlorophyll extract has not been absorbed by SPE-MnO₂nanomaterial sorbent (Blue curve - above).

- The visible spectrum w88 link mới nhất chlorophyll in the chlorophyll extract has been absorbed by SPE-MnO₂nanomaterial sorbent (Red curve - below).

Fig.2 showed that the VIS-spectrum w88 link mới nhất the chlorophyll extract in n-hexane solvent is a straight horizontal line (Dabsorbance~ 0), which shows that the chlorophyll extract was well absorbed by the SPE-MnO₂. In contrast, the chlorophyll extracts in other solvents such as toluene and acetone were less sorbed by SPE-MnO₂, thus the VIS-spectrum w88 link mới nhất chlorophyll still appears with lower absorbance.

3.1.2. Sorption w88 link mới nhất carbaryl and carbofuran by SPE with MnO₂ nanomaterial sorbent in different solvents

Fig.3. Effect w88 link mới nhất different solvents on sorption w88 link mới nhất carbaryl and carbofuran by SPE-MnO₂nanomaterials

Fig.3 showed that the carbaryl and carbofuran were sorbed by SPE with MnO₂nanomaterial sorbent in different solvents, such as acetone, acetonitrile, chloroform, dichloromethane, toluene, ethyl acetate, n-hexane. From the results reported here, the sorption w88 link mới nhất carbaryl and carbofuran were decreased in the following order n-hexane toluene chloroform dichloromethane ethyl acetate acetonitrile acetone. This also shows that the sorption w88 link mới nhất carbaryl and carbofuran by SPE-MnO₂nanomaterials decreases with increasing polarity w88 link mới nhất the solvent.

3.1.3. The recovery w88 link mới nhất carbofuran and carbaryl pesticides

Based on the results reported here, Fig. 1 and Fig. 3 show that chlorophyll was completely sorbed by SPE with MnO₂nanomaterial sorbent in n-hexane solvent, and then followed by toluene and acetone solvents. As a result, carbaryl and carbofuran were also completely sorbed by SPE-MnO₂in n-hexane solvent. However, the carbaryl and carbofuran were very poorly sorbed in acetone solvents. As noted by [20], the combination w88 link mới nhất a non-polar solvent such as hexane and a polar solvent such as acetone shows a synergistic effect. Therefore, the combination w88 link mới nhất n-hexane with acetone considerably improved the cleanup w88 link mới nhất chlorophyll and the good recovery w88 link mới nhất pesticides.

Table 1.  Effect w88 link mới nhất solvent combinations on the recovery w88 link mới nhất carbofuran and carbaryl pesticides

In this study, we found that a mixture w88 link mới nhất polar solvents such as acetone and nonpolar solvents such as hexane in 1: 3 ratios (v/v) resulted in good recovery for all pesticides selected (Table 1). However, increasing the non-solvent polarity did not result in a good recovery for all pesticides. This is due to the nature w88 link mới nhất the pesticide residues selected in this study.

Thus, acetone : n-hexane (1 : 3, v/v) was adopted as the mixed solvent since it provided better recoveries for the carbaryl and carbofuran pesticides.

4. Application w88 link mới nhất the experimental results.

We used these improved results to determine the concentration w88 link mới nhất carbaryl and carbofuran pesticides in spinach - The spinach samples were collected from markets in Da Lat City.

The flow chart w88 link mới nhất the SPE with MnO₂nanomaterial sorbent for cleanup w88 link mới nhất chlorophyll in spinach and analysis procedure w88 link mới nhất carbaryl, carbofuran by the following schema:

The determination w88 link mới nhất pesticide concentrations was repeated three times for each. The results are the following.

Table 2- Concentration w88 link mới nhất carbaryl and carbofuran pesticides in spinach ND- nondetectable level

5. Conclusion

The main problem w88 link mới nhất pesticide analysis in spinach is the large amount w88 link mới nhất interfering substances which can be co-extracted with them, such as chlorophyll. They can lead to experimental errors and analytical instrument damage. Thus, extensive sample preparation is often required for pesticide residue analysis for the effective extraction w88 link mới nhất the analytes and removal w88 link mới nhất interferences.  Although there have been many previous publications regarding the removal or cleanup w88 link mới nhất interferences for pesticide analysis. However, the application w88 link mới nhất nanomaterials for cleaning and removing interferences for pesticide analysis is still limited. In this study, the application w88 link mới nhất solid phase extraction cleanup with MnO2 nanomaterial as a sorbent for the determination w88 link mới nhất carbaryl carbofuran in spinach followed by HPLC/UV was investigated.

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ỨNG DỤNG KỸ THUẬT LÀM SẠCH CHIẾT PHA RẮN

VỚI VẬT LIỆU NANO MnO2 LÀM CHẤT HẤP THU ĐỂ XÁC ĐỊNH

CARBARYL VÀ CARBOFURAN TRONG RAU BÓ XÔI

BẰNG PHƯƠNG PHÁP HPLC-UV

• LÊ NGỌC CHUNG

Trường Đại học Đà Lạt

•VÕ MẠNH TIẾN

Trường Đại học Quy Nhơn

TÓM TẮT:

Bằng kỹ thuật chiết pha rắn (SPE), với vật liệu nano g-MnO₂làm chất hấp thu để làm sạch chlorophyll khi xác định dư lượng hóa chất bảo vệ thực vật carbaryl và carbofuran có trong rau bó xôi (Spinach) bằng phương pháp HPLC-UV đã được trình bày.

Sự hấp thu chlorophyll, carbaryl và carbofuran bởi vật liệu nano g-MnO₂như chất hấp thu cho kỹ thuật SPE được khảo sát trong các dung môi hữu cơ khác nhau. Kết quả cho thấy tỷ lệ hấp thu chlorophyll là 100; 79,59; 79,29; 52,6; 35,84; 29,35 và 25,45% đối với n-hexane, toluene, acetone, dichloromethane, ethyl acetate, acetonitrile và chloroform tương ứng. Kết quả cũng cho thấy carbaryl và carbofuran hấp thu kém bởi vật liệu nano g-MnO₂với dung môi acetone. Tuy nhiên, khi kết hợp dung môi n-hexane và acetone đã cải thiện đáng kể sự làm sạch chlorophyll và thu hồi tốt carbaryl, carbofuran. Ở đây, với tỷ lệ hỗn hợp dung môi acetone: n-hexane (1:3, v/v) cho phép loại bỏ chlorophyll nhưng carbaryl và carbofuran đạt hiệu suất thu hồi rất tốt. Phương pháp này được áp dụng để xác định dư lượng carbaryl và carbofuran có trong rau bó xôi được thu mua tại một số chợ trên địa bàn Thành phố Đà Lạt.

Từ khóa:MnO₂nanomaterial sorbent, SPE- MnO₂, Carbaryl, Carbofuran.

[Tạp chí Công Thương - Các kết quả nghiên cứu khoa học và ứng dụng công nghệ, Số 28, tháng 11 năm 2020]