magnetic ionic liquid-based dispersive liquid–liquid microextraction for the determination of...

Accepted Manuscript

Title: Magnetic ionic liquid-based dispersive liquid-liquidmicroextraction for the determination of triazine herbicides invegetable oils by liquid chromatography

Author: Yuanpeng Wang Ying Sun Bo Xu Xinpei Li Rui JinHanqi Zhang Daqian Song

PII: S0021-9673(14)01749-XDOI: http://dx.doi.org/doi:10.1016/j.chroma.2014.11.009Reference: CHROMA 355995

To appear in: Journal of Chromatography A

Received date: 28-6-2014Revised date: 4-11-2014Accepted date: 5-11-2014

Please cite this article as: Y. Wang, Y. Sun, B. Xu, X. Li, R. Jin, H. Zhang, D.Song, Magnetic ionic liquid-based dispersive liquid-liquid microextraction for thedetermination of triazine herbicides in vegetable oils by liquid chromatography, Journalof Chromatography A (2014), http://dx.doi.org/10.1016/j.chroma.2014.11.009

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http://dx.doi.org/doi:10.1016/j.chroma.2014.11.009

http://dx.doi.org/10.1016/j.chroma.2014.11.009

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• DLLME was used for preconcentration of triazine herbicides from1

vegetable oils.2

• Magnetic ionic liquid was select as a novel microextraction solvent of 3

DLLME.4

• Magnetic separation of the ionic liquid met the requirement of rapid 5

analysis. 6

• The performances were acceptable in comparison to existing methods.7

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Magnetic ionic liquid-based dispersive liquid-liquid microextraction9

for the determination of triazine herbicides in vegetable oils by liquid 10

chromatography11

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Yuanpeng Wang, Ying Sun, Bo Xu, Xinpei Li, Rui Jin, Hanqi Zhang, 14

Daqian Song*15

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17

18

College of Chemistry, Jilin University, Qianjin Street 2699, 19

Changchun 130012, 20

PR China21

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*Corresponding author: Daqian Song24

Tel.: +86-431-8516839925

Fax: +86-431-8516839926

E-mail address: [email protected]

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Abstract30

Magnetic ionic liquid-based dispersive liquid-liquid microextraction31

(MIL-based DLLME) was developed for extracting triazine herbicides 32

from vegetable oils. The MIL, 1-hexyl-3-methylimidazolium 33

tetrachloroferrate ([C6mim] [FeCl4]), was used as the microextraction 34

solvent. The magnetic separation time was shortened by simply mixing 35

carbonyl iron powder with the MIL in the sample after DLLME. The 36

effects of several important experimental parameters, including the 37

amount of MIL, the time of ultrasonic extraction, the type and the 38

volume of cleanup solvent were investigated. The MIL-based DLLME 39

coupled with liquid chromatography gave the limits of detection of 40

1.31-1.49 ng mL-1 and limits of quantification of 4.33-4.91 ng mL-1 for 41

triazine herbicides. When the present method was applied to the analysis 42

of vegetable oil samples, the obtained recoveries were in the range of 43

81.8 -114.2% and the relative standard deviations were lower than 7.7%.44

Compared with existing methods, the performances achieved by the 45

present method were acceptable.46

47

48

Keywords: Magnetic ionic liquids; Dispersive liquid-liquid 49

microextraction; Vegetable oil; Triazine herbicides 50

1. Introduction51

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Triazine herbicides are a class of pre- and post-emergent broadleaf 52

herbicides with similar chemical structure that inhibit the growth of 53

weeds through disruption of photosynthesis pathways [1]. These 54

herbicides, such as atrazine, cyanazine, and desmetryn, are used widely 55

for maize, sorghum, citrus orchards, and grapes [2]. Because of the 56

prolonged and widespread use, the residues of the herbicides have been 57

found in a lot of agriculture products [3, 4]. The study has indicated that 58

some triazine herbicides are suspected to cause cancers, birth defects, and 59

interruption of hormone functions [5]. Consequently, there is a growing 60

need to monitor triazine herbicides in agriculture products. 61

62

Vegetable oils which are mainly composed of triglycerides, are63

commonly extracted from plant seeds, i.e., the oilseeds, such as the 64

seeds of soybean, maize, and sunflower. Pesticide residues in these seeds 65

may be transfered to vegetable oils during the oil extraction process.66

Maximum residue limits (MRLs) in the range of 0.05-0.1 mg kg-1 for the 67

residues of some triazine herbicides in oilseeds are established by the68

European Union (Commission Directive 2008/149/EC), while the 69

MRLs for triazine herbicide residues in vegetable oils have not been 70

established. Therefore, a sensitive and accurate method for determination 71

of triazine herbicides in vegetable oils is particularly important to 72

guarantee public health and safety. To the best of our knowledge, the 73

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available literatures on determination of triazine herbicides in vegetable 74

oils are very limited [6, 7].75

Extraction and cleanup are the most challenging parts for 76

determination of pesticide residues in food stuffs, especially in vegetable 77

oils with inherent complex fatty matrices [8]. Additionally, the low 78

concentrations of pesticide residues in oil samples also make the direct79

determining of them difficult by chromatographic methods, such as liquid 80

chromatography (LC) or gas chromatography (GC) [9]. Therefore, there 81

is a need to employ exhaustive sample preparation technique for the 82

extraction and preconcentration of the residues from oil samples before 83

determination. Various sample preparation techniques, such as 84

liquid-liquid extraction (LLE) [6-8, 10-11] and low-temperature fat 85

precipitation (LTFP) [12, 13], have been widely applied to the extraction 86

and preconcentration of target analytes from fatty samples. However, 87

traditional LLE need time-consuming operating procedure and large 88

amount of organic solvents, and LTFP usually takes a long time to 89

precipitate fats in samples. Other preparation techniques, including 90

solid-phase extraction (SPE) [8, 10, 13], matrix solid-phase dispersion 91

(MSPD) [7, 9], and dispersive solid-phase extraction (dSPE) [11] were 92

commonly coupled with the above-mentioned techniques and applied for 93

the clean-up. In recent years, research efforts on sample preparation 94

techniques have been directed towards simplifying the extraction 95

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procedure, saving operating time and reducing the consumption of 96

organic solvents.97

Since dispersive liquid-liquid microextraction (DLLME) was proposed 98

by Assadi and coworkers [14], this method has attracted much attention 99

owning to its significant advantages including small solvent usage of 100

microliter volumes, rapidity and high enrichment factor. DLLME is a 101

promising alternative to the classic LLE and has been widely appliedto102

the extraction of target analytes in water-soluble samples [15-17], while 103

there are only a couple of reports about the application of DLLME in the 104

sample preparation of fat-soluble vegetable oils [18, 19]. 105

Ionic liquids (ILs) are a class of organic salts with low melting 106

points [20]. The unique properties of ILs, including negligible vapor 107

pressure, good chemical and thermal stability, excellent solubility for both 108

organic and inorganic compounds, and environmental friendliness [21, 109

22], make them promising extraction solvents used in separation [16, 17, 110

23]. The combinations of different organic cations with various organic or 111

inorganic anions leads to a large amount of ILs with numerous possible 112

applications, and ILs with special properties can also be designed through 113

proper chemical modifications [24]. 114

Nowadays, developments and applications of magnetizable ILs 115

become a new field and a hotspot of research in sample preparation 116

techniques [25-28]. Generally, ILs were bonded or immobilized on the 117

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surface of magnetic supports to form solid materials and used as magnetic 118

adsorbents in magnetic solid-phase extraction [25-27], while only few 119

publications reported on the metal-containing ILs, which incorporated the 120

metal in the ILs to introduce magnetic property [28]. Recently, a novel 121

class of magnetic ionic liquids (MILs) with single-component was 122

discovered, of which the magnetic property is no longer introduced as123

external magnetic supports, but provided by complex ions of metals [26, 124

29-30]. The first example of MILs is 1-butyl-3-methylimidazolium 125

tetrachloroferrate ([C4mim] [FeCl4]). Although the compound has been 126

known for some time [31], its magnetic behavior was not described until 127

2004 [32]. These MILs are basically based on the anions containing128

high-spin d5 iron (Ⅲ), which were in the forms of tetrachloro- or 129

tetrabromoferrate (III), with varieties of counter cations. Because of their 130

high single-ion magnetic moments, MILs show a good response to an 131

external magnetic field [28], and are very interesting to be employed as 132

novel extraction solvents to take the place of routine nonmagnetic ILs of133

DLLME. The MILs can be uniformly dispersed in sample solutions134

through ultrasound irradiation and can be isolated from the solutions by 135

means of an external magnetic field. However, to our knowledge, there is 136

only one report about the application of MILs on separation of target 137

analytes, in which the MIL was used for solvent extraction of phenolic 138

compounds from aqueous solution [33]. Because MILs contain polar 139

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functional groups, such as protonated primary amines and esters, as well 140

as the hydrophilic tetrachloroferrate (III) anions, most MILs are miscible 141

with water or other polar solvents after vigorous shaking, which restrict 142

their applications of separation and concentration of analytes dissolved in 143

water. In contrast, they are immiscible with hydrophobic solvents such as 144

carbon tetrachloride and n-hexane [26]. Herein, MILs are promising 145

microextraction solvents of DLLME for vegetable oils.146

147

In this study, 1-hexyl-3-methylimidazolium tetrachloroferrate 148

([C6mim] [FeCl4]) was selected as the microextraction solvent of the149

MIL-based DLLME for extracting triazine herbicides from vegetable oils,150

including two soybean oils, three maize oils and two sunflower seed oils. 151

In addition, carbonyl iron powder (CIP) was added to shorten magnetic 152

separation time after DLLME, which can be magnetically attracted by the 153

MIL to form a combination of CIP and MIL (CIP-MIL). Several 154

important experimental parameters, such as the amount of MIL, the time 155

of ultrasound extraction, the type and the volume of cleanup solvent, were 156

optimized. Under the optimized conditions, the present method was 157

successfully applied to the analysis of real vegetable oil samples158

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2. Experimental160

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2.1. Chemicals and reagents162

Chromatographic grade acetonitrile was purchased from Fisher 163

Scientific Company (UK). [C6mim] [FeCl4] (> 99%) was purchased from 164

Chengjie Chemical Co. LTD (Shanghai, China). CIP with average particle 165

size less than 4.30 μm (Purity > 97.8%) was purchased from Jilin Jien 166

Nickel Industry (Panshi, China). Padding materials of primary secondary 167

amine (PSA, 50 μm), C18 (50 μm) and graphitized carbon black (GCB) 168

were purchased from Bonna-Agela Technologies. All other reagents were 169

of analytical grade and purchased from Beijing Chemical Factory 170

(Beijing, China). 171

Deionized water was obtained with a Milli-Q water purification 172

system (Millipore, New York, USA).173

Standards of cyanazine, desmetryn, secbumeton, terbutryn, 174

dimethametryn and dipropetryn were obtained from National Institute for 175

the Control of Pharmaceutical and Biological Products (Beijing, China). 176

The chemical structures of these herbicides are shown in Fig. 1. Stock 177

solutions were prepared by dissolving each substance in chromatographic 178

grade acetonitrile at a concentration of 400 μg mL-1 and stored at 4 ℃ in 179

darkness. Mixed working solutions at desirable concentrations were 180

prepared by mixing the stock solutions followed by diluting with 181

chromatographic grade acetonitrile.182

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2.2. Instruments184

LC analyses) were performed using a LC-20ADXR liquid 185

chromatograph (Shimadzu, Japan) with two pumps (LC-20AD), an 186

autosampler (SIL-20A), a column oven (CTO-20A) and a UV-vis detector 187

(SPD-20A). Chromatographic separation of the analytes were carried out 188

using a shim-pack VP-ODS column (150 mm × 4.6 mm, 4.6 μm particle 189

size). Relevant data acquisition and processing were accomplished with 190

Shimadzu LC solution software.191

192

The KQ-100 ultrasonic cleaner was purchased from Kunshan 193

Ultrasonic Instrument Co., Ltd. (Kunshan, China). The frequency and 194

output power of the ultrasonic cleaner are 40 kHz and 100 W, 195

respectively. 196

197

2.3. Samples198

The vegetable oil samples were purchased from local supermarkets. 199

Seven vegetable oil samples, including 2 soybean oil (sample 1, 2), 3 200

maize oils (sample 3-5) and 2 sunflower seed oil (sample 6, 7) were 201

analyzed. The samples used for recovery and precision studies were 202

previously analyzed. The experimental results showed that there wasno 203

peak at the retention positions of the analytes in the chromatograms 204

obtained with the sample extracts. The target pesticides in the samples 205

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were undetectable. Spiked samples containing triazine herbicides were 206

prepared by spiking the mixed working standard solutions into samples. 207

After being well mixed, the samples were equilibrated for 1 h in the dark 208

at room temperature. All the experiments were carried out with sample 1 209

except for those mentioned in Section 3.2.4 in which all samples 210

(sample1-7) were used.211

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2.4. Extraction procedure213

2.4.1. DLLME214

1 mL of vegetable oil sample was diluted with 7 mL of n-hexane in 215

10 mL centrifuge tube and mixed for 2 min. Subsequently, 90 μL of 216

[C6mim] [FeCl4] was added into the tube and ultrasonicated for 7 min to 217

extract the analytes from samples. Then 400 mg of CIP was added, and 218

the mixture was vigorously shaken for 30 s to form the CIP-MIL. Then, 219

the CIP-MIL was subsequently collected with a strong magnet placed out 220

the wall of the tube, and the supernatant was decanted. The CIP-MIL was 221

washed with 500 μL of n-hexane for three times. Then, 1.5 mL of 222

deionized water was added into the tube to dissolve the MIL, and then 1.5 223

mL of ethyl acetate was added to extract the target analytes. The resulting 224

mixture was shaken for 4 min, then the upper layer of ethyl acetate was 225

sucked into a glass tube and evaporated under a gentle nitrogen stream at 226

40℃. Finally, the residuewas redissolved in 100 μL of acetonitrile and 227

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filtered through a 0.22 μm nylon membrane, followed by LC analysis. 228

Illustration of the whole extraction procedure is shown in Fig. 2.229

2.4.2. QuEChERS230

The quick, easy, cheap, effective, robust and safe (QuEChERS) 231

procedure was performed according to a previousliterature [34]. 1 mL of 232

vegetable oil sample and 2.5 mL of water were added into 10 mL 233

centrifuge tube. Then, 3.5 mL of acetonitrile was added, along with 1.4 g 234

of anhydrous magnesium sulphate and 0.35 g of sodium chloride. The 235

tube was vigorously shaken for 1 min. The mixture was centrifuged (4000 236

rpm) for 1 min. The tube was horizontally stored in freezer at -20 ℃ for 2 237

h. Then, the supernatant was transferred into a PTFE centrifuge tube 238

containing 450 mg of anhydrous magnesium sulphate, 150 mg of PSA, 239

150 mg of C18 and 150 mg of GCB. After shaken for 30 s, the mixture 240

was centrifuged (4000 rpm) for 1 min. The supernatant was evaporated to 241

dryness under a gentle nitrogen stream at 40℃. Finally, the residues were 242

redissolved in 100 μL of acetonitrile and filtered through a 0.22 μm nylon 243

membrane, followed by LC analysis.244

245

2.5. LC analysis246

The LC analysis was conducted in gradient mode. The gradient has 247

been optimized in advance. Mobile phases A and B are acetonitrile and 248

water, respectively. The gradient program is as follows: 0-10 min, 249

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80-70% B; 10-18 min, 70-40% B; 18-25 min, 40-35% B; 25-30 min, 250

35-80% B. The flow rate of mobile phase was kept at 1.0 mL min-1. 251

Injection volume of analytical solution was 10 μL. The monitoring 252

wavelength was 220 nm for all the target compounds [35].253

254

3. Results and discussion255

256

3.1. Optimization of MIL-based DLLME conditions257

In order to obtain high extraction efficiency, the effects of several 258

experimental parameters, such as the amount of [C6mim] [FeCl4], the 259

ultrasound extraction time, the type and the volume of cleanup solvent 260

were investigated. All the experiments were performed in triplicate.261

262

3.1.1. Effect of amount of [C6mim] [FeCl4]263

The triazine herbicides were hardly extracted with CIP in the 264

absence of [C6mim] [FeCl4], indicating that the [C6mim] [FeCl4] played a 265

key role in the extraction of target analytes. The effect of the amounts of 266

[C6mim] [FeCl4] ranging from 30 μL to 110 μL were investigated. As can 267

be concluded from Fig. 3, the extraction efficiency increases rapidly 268

when the amount of [C6mim] [FeCl4] increases from 30 μL to 90 μL, 269

indicating the remarkable enrichment ability of [C6mim] [FeCl4]. No 270

obvious change is observed when the amount of [C6mim] [FeCl4] 271

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increases from 90 μL to 110 μL, indicating that excessive MIL without 272

combination to CIP can not be collected by magnetic separation. 273

Therefore, 90 μL was employed as the amount of [C6mim] [FeCl4] in the 274

following experiments.275

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3.1.2. Effect of ultrasound extraction time277

The effect of ultrasound extraction time was investigated by 278

increasing the time from 2 to 15 min. The profiles of extraction time and 279

extraction efficiency for the analytes are shown in Fig. 4. The recoveries 280

of triazine herbicides increase with the increase of extraction time from 2 281

to 5 min, and remain stable with a further increase of extraction time from 282

5 to 10 min. To ensure the complete extraction of analytes, the extraction 283

time was selected as 7 min.284

285

3.1.4. Effect of cleanup solvent type286

The cleanup solvent can significantly affect the extraction of the 287

target analytes and cleanup capability within one step in this experiment. 288

In order to improve the cleanup efficiency and reduce the extraction loss, 289

a selection of cleanup solvent is indispensable. The cleanup solvent 290

should have low solubility in water, high dissolving ability for triazine 291

herbicides and low dissolving ability for interference constituents. Based 292

on these considerations, four kinds of organic solvents, including 293

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petroleum ether, diethyl ether, ethyl acetate and dichloromethane, were 294

considered as the cleanup solvent. The extraction capabilities of the above 295

solvents are compared in Fig. 5. Under the same extraction conditions, 296

ethyl acetate provided the highest extraction efficiency due to its 297

strongest dissolving ability for triazine herbicides, and the clean 298

chromatogram with low baseline level and signal noise was also obtained 299

with ethyl acetate. Therefore, ethyl acetate was used as the cleanup 300

solvent in the following experiments301

302

3.1.5. Effect of the volume of cleanup solvent303

The volume of ethyl acetate ranging from 0.5 mL to 2.5 mL was 304

investigated. As can be seen from Fig. 6, an increase in volume of ethyl 305

acetateranging from 0.5 to 1.5 mL results in an increase in the recoveries306

of triazine herbicides, and no obvious change is observed when the 307

volume of ethyl acetate is larger than 1.5 mL. Therefore, 1.5 mL of ethyl 308

acetate was selected for extraction of triazine herbicides in the following 309

experiments. 310

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3.2. Evaluation of the method312

After the important conditions of extracting these herbicides were313

validated, a new analytical method was developed for quantitative 314

determination of the six triazine herbicides in vegetable oils. In order to 315

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evaluate the performances of the present method, the working curves, 316

linear range, correlation coefficient (r), limit of detection (LOD) and 317

quantification (LOQ), and reproducibility were studied. The spiked 318

samples were analyzed by the present method.319

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3.2.1. Linearity321

The working curves were constructed by plotting the corresponding 322

peak areas measured versus the concentrations of triazine herbicides in a 323

series of spiked samples. As listed in Table 1, the present method exhibits 324

satisfactory linearity in the concentration range of 5.00-1000.00 ng mL-1325

with good correlation coefficients (r) higher than 0.9992.326

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3.2.2. Limit of detection and quantification328

The LODs and LOQs were determined based on the signal-to-noise 329

ratio of 3 and 10, respectively. The results obtained are given in Table 1. 330

The LODs and LOQs are in the range of 1.31-1.49 ng mL-1 and 4.33-4.91 331

ng mL-1, respectively. Because of the interferences of complex fatty 332

matrices in vegetable oils, the LODs obtained by the present method are 333

somewhat higher than that obtained by several previous methods [36, 37], 334

which were applied to the determination of triazine herbicides in aqueous 335

samples.336

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3.2.3. Precision and recovery338

The intra- and inter-day precision of the present method were 339

obtained by analyzing the spiked sample at concentrations of 25.00, 50.00 340

and 100.00 ng mL-1. The intra-day RSDs were obtained by analyzing the 341

sample five times a day, and the inter-day RSDs were obtained by 342

analyzing samples which were independently prepared for consecutive 343

five days. The RSDs obtained are listed in Table 2. The intra- and 344

inter-day RSDs were in the range of 1.9-5.7% and 2.5-7.5%, respectively, 345

indicating the acceptable precision.346

347

3.2.4. Analysis of real vegetable oil samples348

The developed MIL-based DLLME method coupled with LC was 349

applied to the determination of the six triazine herbicides in vegetable oil 350

samples. The real samples were pretreated under the optimized conditions 351

and no herbicides were detectable. Seven kinds of spiked samples at 352

analyte concentrations of 50.00 and 100.00 ng mL-1 were analyzed. The 353

typical chromatograms of the blank and spiked sample are shown in Fig. 354

7, and the analytical results are listed in Table 3. As can be seen, the 355

present method provides good recoveries ranging from 81.8-114.2% and 356

acceptable precision lower than 7.7%.357

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3.2.5. Comparison with QuEChERS359

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In order to further evaluate the present method, the present method 360

was compared with QuEChERS [35]. The recoveries and RSDs of the six 361

triazine herbicides obtained by QuEChERS at concentrations of 50.00 362

and 100.00 ng mL-1 range from 80.3 to 121.7% and 2.3 to 9.2%, 363

respectively. By comparation, the recoveries and RSDs of the same 364

spiked samples obtained by the present method range from 94.1-110.7% 365

and 1.4 to 7.4%. The LODs of QuEChERS are in the range of 4.32-5.12 366

ng mL-1, which are higher than these of the present method. These results 367

indicates that the precision and the sensitivity of the present method are 368

both better than that of QuEChERS. In addition, the consumption of 369

extraction solvent in the present method is low and the extraction time 370

(7min) is much shorter than that (122 min) of QuEChERS. Moreover, the 371

magnetic separation simplifies the sample preparement process and 372

eliminates the routine centrifugation procedure. 373

3.2.6. Comparison with other reported methods374

The present method was further compared with the reported methods 375

for the determination of target analytes in fatty matrices [6, 7, 10, 11, 18]. 376

The results are shown in Table 4. It can be seen that the consumption of 377

extraction solvent in the present method is lower than that in other 378

methods. Compared with acetonitrile and dichloromethane used in some 379

methods, n-hexane and ethyl acetate used in the present method have 380

lower toxicity. The LODs and RSDs obtained by the present method are 381

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similar to or lower than these obtained by the reported methods. 382

Therefore, it can be concluded that the present method is suitable for383

the determination of triazine herbicides in vegetable oils.384

385

4. Conclusion386

In summary, a rapid, easy and low-solvent-consumption extraction 387

method, MIL-based DLLME was successfully developed and applied for 388

the extraction of triazine herbicides from vegetable oils. It is the first time 389

to use MIL as the microextraction solvent for fat-soluble samples, and 390

magnetic separation was selected to simplify separation procedure. The 391

present method overcame the drawback of MILs being miscible with 392

water and the limitation unsuitable for fat-soluble samples. It could be 393

considered that this method is very promising for the extraction of 394

analytes from complex fat-soluble samples by varying extraction 395

parameters. Since the present method is pretty straightforward and easy to 396

perform. The extraction step could be combined withLC for online 397

determination of the herbicides. [38]398

399

400

Acknowledgments401

This work was supported by National Natural Science Foundation of 402

China (No. 20727003, 21075049, and 21105037), Program for New 403

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Century Excellent Talents in University (No. NECT-10-0443), 404

Special-funded Programme on National Key Scientific Instruments and 405

Equipment Development (No. 2012YQ090194) and Science and 406

Technology Developing Foundation of Jilin Province (No. 20100356 and 407

20110162).408

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[36] D. Nagaraju, S.D. Huang, Determination of triazine herbicides in 547

aqueous samples by dispersive liquid–liquid microextraction with gas 548

chromatography-ion trap mass spectrometry, J. Chromatogr. A 1161 549

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microextraction based on membrane-protected molecularly imprinted 552

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extraction of triazine herbicides using a molecularly imprinted polymer 556

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558

559

560

561

562

563

564

565

566

Figure Captions567

568

Fig. 1. Chemical structures of the triazine herbicides.569

570

Fig. 2. Schematic diagram of the extraction procedure.571

572

Fig. 3. Effect of the amount of [C6mim] [FeCl4] on the recoveries of the 573

triazine herbicides. 574

Ultrasound extraction time, 7 min; cleanup solvent, ethyl acetate; volume 575

of cleanup solvent, 1.5 mL; spiked concentration, 100 ng mL-1.576

577

Fig. 4. Effect of the ultrasound extraction time on the recoveries of the 578


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Amount of [C6mim] [FeCl4], 90 μL; cleanup solvent type, ethyl acetate; 580

the volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng 581

mL-1.582

583

Fig. 5. Effect of cleanup solvent type on the recoveries of the triazine 584

herbicides. 585

The amount of [C6mim] [FeCl4], 90 μL; Ultrasound extraction time, 7 586

min; volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng 587

mL-1.588

589

Fig. 6. Effect of the volume of cleanup solvent on the recoveries of the 590


Amount of [C6mim] [FeCl4], 90 μL; Ultrasound extraction time, 7 min; 592

cleanup solvent, ethyl acetate; spiked concentration, 100 ng mL-1.593

594

Fig. 7. Chromatograms of sample 1 (A) and spiked sample 1 (B). 1, 595

Cyanazine; 2, desmetryn; 3, secbumeton; 4, terbutryn; 5, dimethametryn; 596

6, dipropetryn. Spiked concentration, 100 ng mL-1.597

598

Tables599

600

Table 1. Analytical performances of the present method601

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29

602

Table 2. Inter- and intra-day precisions of the present method (n=5)603

Table 3. Analytical results of real vegetable oil samples604

605

Table 4. Comparison of the present method with other reported methods606

607

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Table 1. Analytical performances of the present method668

Analyte Linear range

(ng mL-1)

Regression equation Correlation

coefficient (r)

LOD

(ng mL-1)

LOQ

(ng mL-1)

Cyanazine 5.00-1000.00 A=194.61c-118.41 0.9996 1.34 4.42

Desmetryn 5.00-1000.00 A=419.31c-515.13 0.9999 1.49 4.91

Secbumeton 5.00-1000.00 A=456.64c+3683.2 0.9994 1.31 4.33

Terbutryn 5.00-1000.00 A=339.25c+910.18 0.9994 1.40 4.61

Dimethametryn 5.00-1000.00 A=325.69c+908.44 0.9995 1.49 4.91

Dipropetryn 5.00-1000.00 A=314.07c+1700.2 0.9992 1.41 4.67

669

670

671

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Table 2. Inter- and intra-day precisions of the present method (n=5)607

Analyte Concentration Intra-day Inter-day

(ng mL-1) Recovery (%) RSD (%) Recovery (%) RSD (%)

Cyanazine 25.00 98.3 4.4 101.7 5.7

50.00 103.8 3.2 101.9 5.3

100.00 105.1 3.5 103.0 4.1

Desmetryn 25.00 93.7 3.4 100.7 7.4

50.00 104.9 5.7 103.1 5.8

100.00 95.2 2.1 96.3 2.5

Secbumeton 25.00 99.1 4.7 102.8 6.3

50.00 102.0 3.3 95.9 5.8

100.00 98.8 4.5 97.8 6.0

Terbutryn 25.00 100.7 2.6 105.2 7.4

50.00 108.1 5.7 101.1 6.7

100.00 96.2 2.5 95.0 2.8

Dimethametryn 25.00 102.2 2.8 109.4 7.5

50.00 103.8 3.3 99.3 7.4

100.00 100.5 2.5 100.3 5.1

Dipropetryn 25.00 96.0 5.5 91.1 6.5

50.00 103.4 1.9 106.5 7.3

100.00 103.6 3.2 101.6 4.6

608

609

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34

674

Table 3. Analytical results of real vegetable oils samples675

676

677

678

Sam

ple

Spik

ed

Cyanazi

ne

Desmetry

n

Secbum

eton

Terbutry

n

Dimetha

metryn

Dipropet

ryn

(ng

mL-1

)

Reco

very

(%)

R

S

D

(

%

)

Reco

very

(%)

R

S

D

(

%

)

Reco

very

(%)

R

S

D

(

%

)

Reco

very

(%)

R

S

D

(

%

)

Reco

very

(%)

R

S

D

(

%

)

Reco

very

(%)

R

S

D

(

%

)

Sam

ple 1

50.0

0

10

5.7

2.

6

98.

2

7.

4

10

2.0

4.

6

11

0.7

6.

4

10

4.5

1.

4

10

3.4

2.

6

100.

00

10

4.5

4.

9

94.

1

1.

7

99.

7

4.

5

95.

8

3.

3

10

0.9

2.

1

10

2.4

3.

7

Sam

ple 2

50.0

0

99.

4

2.

6

10

5.9

5.

7

99.

4

4.

4

10

1.5

4.

5

10

2.6

4.

4

99.

8

5.

9

100.

00

10

0.0

1.

2

95.

9

2.

9

95.

9

6.

4

95.

5

3.

0

99.

5

3.

0

99.

0

4.

2

Sam

ple 3

50.0

0

95.

9

7.

7

99.

6

3.

8

10

4.7

3.

2

10

1.0

3.

4

86.

9

7.

4

81.

8

7.

6

100.

00

10

0.5

1.

4

91.

1

7.

4

98.

1

5.

4

10

1.1

1.

1

10

3.7

4.

5

10

1.6

4.

1

Sam

ple 4

50.0

0

89.

3

5.

5

10

5.3

7.

4

10

6.2

5.

8

10

3.6

6.

6

10

1.5

2.

7

10

5.3

6.

7

100.

00

10

2.2

4.

3

88.

2

3.

6

91.

6

5.

5

94.

3

6.

0

10

3.6

4.

6

87.

9

6.

4

Sam

ple 5

50.0

0

11

4.2

3.

4

10

0.6

6.

3

10

2.7

4.

8

94.

9

3.

9

94.

8

4.

2

92.

8

5.

6

100.

00

10

5.7

7.

4

97.

3

3.

6

10

1.8

3.

5

97.

6

1.

7

10

0.9

3.

2

10

5.3

6.

8

Sam

ple 6

50.0

0

11

3.6

4.

4

10

1.5

1.

4

10

9.3

6.

8

91.

6

1.

3

99.

7

7.

7

10

2.5

4.

8

100.

00

10

6.5

4.

5

10

2.6

7.

1

10

2.3

4.

3

97.

5

4.

0

10

4.8

2.

9

93.

6

6.

9

Sam

ple 7

50.0

0

10

6.2

7.

3

97.

5

5.

0

10

0.3

4.

7

96.

7

6.

7

86.

2

4.

7

85.

7

3.

9

100.

00

10

2.7

5.

7

10

0.1

2.

6

92.

9

6.

3

98.

8

3.

7

10

0.3

7.

6

10

1.5

7.

2

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Table 4. Comparison of the present method with other reported methods

Matrix Analytes Extraction (time) Cleanup procedure Detection Recovery

(%)

RSD

(%) LOD LOQ References

Vegetable

oil

Triazine

herbicides

90 μL [C6mim] [FeCl4]

(7 min)

1.5 mL deionized water +

1.5 mL ethyl acetate

LC-UV 81.8 -110.7 1.1-7.7 1.31-1.49

ng mL-1

4.33-4.91

ng mL-1

This work

Olive oil

and olives

Multiclass

pesticides

35 mL acetonitrile

(6 min)

MSPD:

2 g aminopropyl-bonded

silica + 2 g florisil

GC-MS 73.2-129. 3-15 3-80

ng g-1

- 7

Olive oil

and olives

Multiclass

pesticides

35 mL acetonitrile

(6 min)

MSPD:



LC-MS 81-108 5-10 0.2-4

ng g-1

- 7

Edible oil Organoarsenic

compounds

1.25 mL hexane containing

0.05 mL ammonium formate

buffer solution (pH=7)

(4 min)

- LC-MS 89.9-94.7 2.9-9.6 1.0-5.8

ng g-1

- 18

Cooking

oil Ricinine

5 mL ethanol/water

(20:80, v/v)

(6 min)

dSPE:

200 mg anhydrous

sodium sulfate + 30 mg

PSA + 30 mg C18

LC-MS/MS 86.0-98.3 2.6–7.0 - 0.5

ng g-1

11

Olive oil Triazine

herbicides

35 mL acetonitrile

(7 min)

MSPD:



LC/TOF-MS 81-111 2-4 1-5

ng g-1

- 6

Olive oil Organophos-

phorus

5 mL acetonitrile/

dichloromethane (90:10, v/v)

(10 min)

SPE:

500 mg ENVI-Carb

cartridge

GC-FPD 64-104 1-10 - 7-20

ng g-1

10

Table 4

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Figure 1

http://ees.elsevier.com/chroma/download.aspx?id=1417045&guid=482ccc7f-e49f-43ed-b3df-8a03a249b745&scheme=1

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Figure 2

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Figure 3

http://ees.elsevier.com/chroma/download.aspx?id=1417040&guid=78f175b6-3a7e-4ebb-9104-032974cebaca&scheme=1

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Figure 4

http://ees.elsevier.com/chroma/download.aspx?id=1417041&guid=66769696-e6fd-4ddc-838a-599239a3288b&scheme=1

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Figure 5

http://ees.elsevier.com/chroma/download.aspx?id=1417042&guid=fc1bb992-0e38-4c1f-a8cc-0d7182748ec4&scheme=1

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Figure 6

http://ees.elsevier.com/chroma/download.aspx?id=1417043&guid=e8fc330e-4575-4860-b1e2-6d0c1c17ef4f&scheme=1

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Figure 7

http://ees.elsevier.com/chroma/download.aspx?id=1417036&guid=44535954-6e38-4556-80c8-093d6bd2d8a1&scheme=1

magnetic ionic liquid-based dispersive liquid–liquid microextraction for the determination of...

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