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Degradation of the Selected Pesticides by Gas Discharge Plasma
Zaw Win Min,Su-Myeong Hong(홍수명),Chul-Kyoon Mok(목철균),Geon-Jae Im(임건재) 한국농약과학회 2012 농약과학회지 Vol.16 No.1
As increasing the use of pesticides both in number and amount to boost crop production, consumer concerns over food quality and safety with respect to residual pesticides are also continuously increasing. However, there is still lacking of information that can effectively help to remove residual pesticides in foods. In recent years, contaminant removal by gas (or) glow discharge plasma (GDP) attracts great interests on environmental scientists because of its high removal efficiency and environmental compatibility. It was shown to be effective for the removal of some organophosphorus pesticides, phenols, benzoic acid, dyes, and nitrobenzene on solid substrate or in aqueous solution. This work mainly focuses on the removal of wide range of residual pesticides from fresh fruits and vegetables. As for preliminary study, the experiments were carried out to investigate whether GDP can be used as an effective tool for degrading target pesticides or not. With this objective, 60 selected pesticides drop wised onto glass slides were exposed to two types of GDP, dielectric barrier discharge plasma (DBDP) and low pressure discharge plasma (LPDP), for 5 min. Then, they were washed with 2 mL MeCN which were collected and used for determination of remaining concentration of pesticides using LC-MS/MS. Among selected pesticides, degradation of 18 pesticides (endosulfan-total was counted as one pesticide) by GDP could not be examined because control treatments, which were left in ambient environment, of those pesticides recovered less than 70% or even did not recover. However, majority of tested pesticides (42) were degraded by both types of GDP with satisfactory recovery (>80%) of control sample. Pesticides degradation ranged from 66.88% to 100% were achieved by both types of plasma except clothianidin which degradation in LPDP was 26.9%. The results clearly indicate that both types of gas discharge plasma are promising tools for degrading wide range of pesticides on glass substrate.
Min, Zaw Win,Hong, Su-Myeong,Yang, In-Cheol,Kwon, Hye-Young,Kim, Taek-Kyum,Kim, Doo-Ho The Korean Society for Applied Biological Chemistr 2012 Applied Biological Chemistry (Appl Biol Chem) Vol.55 No.6
An efficient and modified Quick Easy Cheap Effective Rugged and Safe (QuEChERS) method combined with liquid chromatography-electrospray ionization with tandem mass spectrometric detection were evaluated for the analysis of residues of 72 pesticides in brown rice including acidic sulfonylurea herbicides. For extraction of pesticides and clean-up of the extract, 1% formic acid in acetonitrile and dispersive solid phase extraction were used, respectively. Two fortified spikes at 50 and $200{\mu}g\;L^{-1}$ levels were performed for recovery test. Mean recoveries of majority of pesticides at two spike levels ranged from 90 to 110% with standard error (Coefficient of Variation) less than 10%. The limits of detection and quantification ranged from 0.24 to $19.92{\mu}g\;L^{-1}$ and 0.79 to $65.74{\mu}g\;L^{-1}$, respectively. Good linearity of calibration curves were achieved with $R^2$ > 0.9943 within the observed concentration range (from 20 to $400{\mu}g\;L^{-1}$). The modified method also provided satisfactory results for sulfonylurea herbicides, which could not be determined properly with previously reported methods. This method was applied to determine residues of target pesticides in real samples. A total of 22 pesticides in 31 out of 40 tested samples were observed. The highest concentration was observed for tricyclazole at 1.17 mg $L^{-1}$. This pesticide found in two brown rice samples exceeded its MRL regulated for rice in Republic of Korea. Except this pesticide, concentrations of all observed pesticides were lower than their MRLs. The results reveal that the method is applicable for routine analysis of residues of target pesticides in brown rice.
Min, Zaw Win,Jeon, Young-Hwan,Kim, Jang-Eok The Korean Society for Applied Biological Chemistr 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.4
Degradation of thiophosphate fungicide, tolclofos-methyl in the aquatic environment is mainly biotic, whereas both hydrolytic and photolytic breakdowns are slow and of minor importance. Thus, hydrolysis of tolclofos-methyl during $Ca(OH)_2$ treatments, degradation of fungicide tolclofos-methyl by zerovalent iron, and effect of ferric salts during zerovalent iron treatment were investigated. Unannealed zerovalent iron was used as zerovalent iron source. Tolclofos-methyl was found to undergo hydrolysis only at pH level as high as 12 in aqueous solutions, and its degradation in the soil appeared to be achieved only by biotic degradation. Ferric sulfate and ferric chloride were the most effective for degrading tolclofos-methyl by unannealed zerovalent iron in aqueous solution. Order of effectiveness of salts is $FeCl_3$ > $Fe_2(SO_4)_3$ > $FeSO_4$ > $Al_2(SO_4)_3$; only ferric chloride salts were effective for enhancing tolclofos-methyl degradation in the soil slurry. Degradation rate of tolclofos-methyl in the soil slurry was observed up to 25 and 37% by adding 1 and 3% $FeCl_3$ respectively. It was 2-3 orders of magnitude higher than the degradation by unannealed zerovalent iron alone. Enhanced effect of ferric chloride on tolclofos-methyl degradation by unannealed zerovalent iron was retarded when 5% salts was added into soil slurry. Addition of $FeCl_3$ into soil, in the absence of unannealed zerovalent iron, was found to degrade tolclofos-methyl to some extent.
Min, Zaw Win,Kim, Tae-Hwa,Shin, Jae-Ho,Lee, Sang-Man,Kim, Jang-Eok The Korean Society for Applied Biological Chemistr 2009 Applied Biological Chemistry (Appl Biol Chem) Vol.52 No.6
In this work, the degradation of fungicide tolclofos-methyl (TM) by zerovalent metals (ZVMs) was first investigated prior to investigation of the effect of ferric salts during zerovalent iron treatment to better understand the feasibility of abiotic degradation mediated by ZVMs. Unannealed zerovalent iron (uZVI), annealed zerovalent iron (aZVI) and zerovalent zinc (ZVZn) were used as ZVMs sources. uZVI was found to be the most effective catalyst for degrading TM in aqueous solution. The TM degradation rate depends not only on the amount and sizes of uZVI used but also on the initial concentration of fungicide itself. By testing various kinds of salt, it was found that ferric sulfate and ferric chloride showed better results for degrading TM by uZVI in aqueous solution. The order of effectiveness of salts is $FeCl_3$>$Fe_2(SO_4)_3$>$FeSO_4$>$Al_2(SO_4)_3$.
Zaw Win Min,Ju Young Lee,Kyung-Ae Son,Geon-Jae Im,Su-Myeong Hong 한국응용생명화학회 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.5
Association of official agricultural chemists official method was adapted and used to develop analytical method for determination of 76 pesticides residues in persimmon, grape, and pear by concurrent use of liquid chromatography-tandem mass spectrometry. Despite few exceptions in particular matrix, two fortified spiking (100 and 400 ppb) in three matrices gave satisfactory results in terms of accuracy, repeatability, precision, and linearity. Method detection limits (MDLs)were determined using five low spiking and eight replicate samples. MDLs were calculated by multiplying the standard deviation with student t-value 2.998 for n-1 (7) degree of freedom at 99% confident level. limit of quantification were obtained by multiplying standard deviation with 10. Experimental results indicate grape was the most problematic matrix among tested fruits and persimmon the least. Etoxazole is the most problematic pesticide and not applicable in this method. Developed method was successfully applied for the determination of residual pesticides in blindincurred samples.
Min, Zaw-Win,Lee, Ju-Young,Son, Kyung-Ae,Im, Geon-Jae,Hong, Su-Myeong The Korean Society for Applied Biological Chemistr 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.5
Association of official agricultural chemists official method was adapted and used to develop analytical method for determination of 76 pesticides residues in persimmon, grape, and pear by concurrent use of liquid chromatography-tandem mass spectrometry. Despite few exceptions in particular matrix, two fortified spiking (100 and 400 ppb) in three matrices gave satisfactory results in terms of accuracy, repeatability, precision, and linearity. Method detection limits (MDLs) were determined using five low spiking and eight replicate samples. MDLs were calculated by multiplying the standard deviation with student t-value 2.998 for n-1 (7) degree of freedom at 99% confident level. limit of quantification were obtained by multiplying standard deviation with 10. Experimental results indicate grape was the most problematic matrix among tested fruits and persimmon the least. Etoxazole is the most problematic pesticide and not applicable in this method. Developed method was successfully applied for the determination of residual pesticides in blind-incurred samples.
Zaw Win Min,Su-Myeong Hong,양인철,권혜영,Taek-Kyum Kim,김두호 한국응용생명화학회 2012 Applied Biological Chemistry (Appl Biol Chem) Vol.55 No.6
An efficient and modified Quick Easy Cheap Effective Rugged and Safe (QuEChERS) method combined with liquid chromatography-electrospray ionization with tandem mass spectrometric detection were evaluated for the analysis of residues of 72 pesticides in brown rice including acidic sulfonylurea herbicides. For extraction of pesticides and clean-up of the extract,1% formic acid in acetonitrile and dispersive solid phase extraction were used, respectively. Two fortified spikes at 50 and 200 μg L–1 levels were performed for recovery test. Mean recoveries of majority of pesticides at two spike levels ranged from 90 to 110% with standard error (Coefficient of Variation)less than 10%. The limits of detection and quantification ranged from 0.24 to 19.92 μg L–1 and 0.79 to 65.74 μg L–1, respectively. Good linearity of calibration curves were achieved with R2>0.9943 within the observed concentration range (from 20 to 400μg L–1). The modified method also provided satisfactory results for sulfonylurea herbicides, which could not be determined properly with previously reported methods. This method was applied to determine residues of target pesticides in real samples. A total of 22 pesticides in 31 out of 40 tested samples were observed. The highest concentration was observed for tricyclazole at 1.17 mg L–1. This pesticide found in two brown rice samples exceeded its MRL regulated for rice in Republic of Korea. Except this pesticide, concentrations of all observed pesticides were lower than their MRLs. The results reveal that the method is applicable for routine analysis of residues of target pesticides in brown rice.
( Zaw Win Min ),( Young Hwan Jeon ),( Jang Eok Kim ) 한국응용생명화학회 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.4
Degradation of thiophosphate fungicide, tolclofos-methyl in the aquatic environment is mainly biotic, whereas both hydrolytic and photolytic breakdowns are slow and of minor importance. Thus, hydrolysis of tolclofos-methyl during Ca(OH)2 treatments, degradation of fungicide tolclofos-methyl by zerovalent iron, and effect of ferric salts during zerovalent iron treatment were investigated. Unannealed zerovalent iron was used as zerovalent iron source. Tolclofos-methyl was found to undergo hydrolysis only at pH level as high as 12 in aqueous solutions, and its degradation in the soil appeared to be achieved only by biotic degradation. Ferric sulfate and ferric chloride were the most effective for degrading tolclofos-methyl by unannealed zerovalent iron in aqueous solution. Order of effectiveness of salts is FeCl3>Fe2(SO4)3 >FeSO4 >Al2(SO4)3; only ferric chloride salts were effective for enhancing tolclofos-methyl degradation in the soil slurry. Degradation rate of tolclofos-methyl in the soil slurry was observed up to 25 and 37% by adding 1 and 3% FeCl3 respectively. It was 2-3 orders of magnitude higher than the degradation by unannealed zerovalent iron alone. Enhanced effect of ferric chloride on tolclofos-methyl degradation by unannealed zerovalent iron was retarded when 5% salts was added into soil slurry. Addition of FeCl3 into soil, in the absence of unannealed zerovalent iron, was found to degrade tolclofos-methyl to some extent.