Research ArticleReceived: 28 July 2008, Accepted: 15 August 2008 Published online 27 November 2008 in Wiley Interscience (www.interscience.wiley.com) DOI 10.1002/bmc.1140 Multiresidue analysis of 47 pesticides in cooked wheat flour and polished rice by liquid chromatography with tandem mass spectrometry John Wiley & Sons, Ltd. Sung Jung Lee,a Hyeong Jin Park,a Wooseong Kim,b Jong Sung Jin,c A. M. Abd El-Aty,d,e Jae-Han Shimf* Sung Chul Shina* Multiresidue analysis of 47 pesticides ABSTRACT: Liquid chromatography in conjunction with tandem mass spectrometry was used to directly quantify of 47 pesticide residues from cooked wheat flour and polished rice, which are the most widely consumed cereals in the Republic of Korea. The sample clean-up was carried out according to the method established by the Korea Food and Drug Administration. The mobile phase for liquid chromatograpy separation consisted of water and 5 mM methanolic ammonium formate. Tandem mass spectroscopy experiments were performed in electrospray ionization positive mode and the multiple reaction monitoring mode. The matrix effects estimated for the 47 pesticides had a mean value of 99% and ranged from 45 to 147%. High recoveries (70–140%) and relative standard deviations (£20%) were achieved for most of the pesticides tested. The method used in this study allowed for rapid quantification and identification of low levels of pesticides in cooked wheat flour and polished rice samples. Of the screened pesticide residues, only tricyclazole and fenobucarb were found in polished rice samples. However, no samples contained residues above the MRL established by the Korea Food and Drug Administration. Copyright © 2008 John Wiley & Sons, Ltd. Keywords: tandem mass spectrometry; pesticide residues; validation; multiresidue; bioanalytical application Introduction Pesticides are used at various stages of cultivation to protect agricultural crops against pests and to preserve their quality (Klein and Alder, 2003). Since pesticides are known to cause several human health problems, which range from short-term sickness such as headaches to chronic diseases like cancer and endocrine disruption, pesticide residues in food products must be closely monitored and strictly controlled (Fong et al., 1999; Eddleston et al., 2002; Saieva et al., 2004). In order to ensure the safety of consumable food products and supervise international trade, governmental authorities of each country and international organizations have established maximum residue limits (MRLs) to regulate pesticide concentration in food products (Codex Alimentarius Commission, 2005; European Union On-line, 2005; Korea Food and Drug Administration, 2005). Analytical methods that are used to monitor pesticide levels in food should be capable of measuring pesticide residues at very low levels (Taylor et al., 2002). In addition, these methods should be able to identify and quantity the types of pesticides found in food products (Sannino et al., 2004). Furthermore, these methods should be fast, robust and simple in order to minimize the requirements for training and time spent on sampling and maintaining equipment (Hill, 1997). Multiresidue methods are ideally suited to satisfy these requirements for pesticides, since they are typically simple, robust and rapid. Until recently, the multiresidue methods that have frequently been used were gas chromatography (GC) equipped with an electroncapture detector (ECD), nitrogen–phosphorous detector (NPD) or mass spectrometer (MS) (Sherma, 2001; Pang et al., 2006). For less volatile and thermally unstable residues that are not * Correspondence to: Sung Chul Shin, Department of Chemistry and Research Institute of Life Science, Gyeongsang National University, Jinju, 660-1701, Republic of Korea. Tel: +82-55-75-6022; Fax: +82-55-76-0244; E-mail:
[email protected] Jae-Han Shim, Natural Products Chemistry Lab., Department of Biological Chemistry, College of Agriculture and Life Science, Chonnam National University, 300 Yongbong-dong, Bukgu, Gwangju 500-757, Republic of Korea. Tel: +82-62-530-2135; Fax: +82-62-530-0219; E-mail:
[email protected]† a Department of Chemistry and Research Institute of Life Science, Gyeongsang National University, Jinju, 660-701, Republic of Korea Busan Regional Korea Food and Drug Administration, 123-7 Yong-Dong Dong Nam-Ku Busan, Republic of Korea Korea Basic Science Institute Busan Center, High Technique Components and Materials Team, Gangseo-gu, Busan, 618-230, Republic of Korea Department of Veterinary Pharmacology and Toxicology, College of Veterinary Medicine, Konkuk University, 1 Hwayang-dong, Kwangjin-gu, Seoul 143-701, Republic of Korea Department of Pharmacology, Faculty of Veterinary Medicine, Cairo University, 12211-Giza, Egypt Natural Products Chemistry Laboratory, Institute of Agricultural Science and Technology, College of Agriculture and Life Science, Chonnam National University, 300 Yong-Bong Dong, Buk-Ku, Gwangju 500-757, Republic of Korea Amendment made to corresponding authors’ details after initial online publication on 27 November 2008 Abbreviations used: ECD, electron-capture detector; KFDA, Korea Food and Drug Administration; MRLs, maximum residue limits; MRM, multiple reaction monitoring; NPD, nitrogen–phosphorous detector. Contract/grant sponsor: KFDA, the Republic of Korea; Contract/grant number: 07182-833. b c d e f † 434 Copyright © 2008 John Wiley & Sons, Ltd. Biomed. Chromatogr. 2009; 23: 434–442 It has a number of inherent properties that are advantageous for this application. Ltd (Ansan City. Whereas some studies have been devoted to the development of an LC-MS/MS method to determine some of our targeted pesticide residues in cereal (Granby et al.interscience. thermal instability.Multiresidue analysis of 47 pesticides GC-compatible. CT. liquid chromatography coupled to tandem mass spectroscopy (LC-MS/MS) was found to be far superior to the LC-MS technique for analysis of pesticide residues in a variety of food samples. CA.. Each boiled wheat flour and polished rice (50 g) sample was placed into a 200 mL screw-capped glass bottle.6 mm. Scientific Industries Inc. The mixtures were filtered with filter paper (Whatman no. using a step size of 0. A number of multiresidue methods using LC-MS/MS for residue determination have been reported (Jansson et al. Tokyo Rikakikai Co.). Branson Ultrasonics Corporation. 2005. The chromatographic separation was carried out on an Zorbax XDB-C18 column (Agilent Technologies. Mass Spectrometry MS/MS detection was achieved using a Qtrap 3200 triple quadrupole mass spectrometer (Applied Biosystems. Chromatogr. or a tedious clean-up procedure is required for sampling. 2000. www.. Ltd.com/journal/bmc . Sancho et al. 2006. The funnels were maintained at 4°C for 1 h. a G1313A autosampler and a G1316A oven (Agilent Technologies.. liquid chromatography coupled to a UV and fluorescence detector or mass spectrometer has been used (Picó et al. UK).5 kV and the source temperature was set at 500°C... then 100 mL of acetonitrile was added and the bottles were sealed. Whatman International Ltd. 2004. Republic of Korea). 2000. 50 × 4.45 μm) were obtained from Whatman (Whatman International Ltd. 2007. CA. The spectrometer was operated in the positive ion spray mode with the multiple reaction monitoring (MRM) mode.2 were used for instrument control and data acquisition. The mobile phase initially consisted of water (solvent A)–5 mM methanolic ammonium formate. and easy and reliable identification and quantification of pesticide residues at even very low levels (Picó et al. Nitrogen was used as both the nebulizing and drying gas. volatility. Maidstone.. Therefore. PTFE HPLC syringe filters (0. Banbury. USA) for 10 min. For LC-MS/MS measurements the stock solutions were mixed and diluted in methanol to give concentrations ranging between 0. Tokyo..0 μg/mL. However. including high selectivity and sensitivity. Sample Preparation Sample preparations were carried out according to the method of Food Code no. Mass spectra were acquired over a scan range of m/z 50–1000.. 1. it is more reasonable that their hazard to human health be evaluated on the basis of the data obtained after the food products have been cooked. respectively.. analyses in polished rice are rather restricted (Payá et al. Ltd. A flow rate of 0. More recently. USA).2 mL/min. Alder et al.2 and Analyst software version 1. All other chemicals were obtained from Sigma Aldrich Korea (Yongin. UK). The pesticides indentified were compounds with properties that did not match well with GC methods (polarity. 2009. USA) equipped with a Turboionspray interface (ESI). 2005. Ortelli et al. High-performance Liquid Chromatography High-performance liquid chromatography (HPLC) was performed using an 1100 series liquid chromatograph system that was equipped with a G1322A degasser. The data collected using this analytical method could be utilized to regulate the concentration of the residues in food products and estimate the hazard of the residues to human health. Schwedler et al. Japan). Wheat flour and polished rice are the most widely consumed cereals in the Republic of Korea. a 20 mL aliquot of the organic layer was transferred to a 50 mL conical flask. a column temperature of 20°C and an injection volume of 20 μL were used in all experiments. Wheat flour and polished rice were purchased from local markets located in the eight major cities in the Republic of Korea at three different days (May 27. Individual stock solutions were prepared by dissolving neat pesticides in methanol to a final concentration of 500 μg/mL. Residues contained in food products are usually monitored in raw samples that have not been cooked. pH 4 (solvent B): at the start 20% solvent B and after 11 min the percentage of solvent B was linearly increased to 90% in 4 min and then equilibrated for 5 min. Forster. 1. BioAnalst™ version 1. 2004. The chemical structures of the tested pesticides are shown in Fig. USA) twice for 1 min each with 5 min between. and September 24) in 2007.01 and 2. Cavaliere et al. After phase separation. Chen and Chen. etc. Republic of Korea). UK) and stored at 4°C until injection into the LC-MS/MS system. Hernández et al. Palo Alto. 2007). cooking might change or degrade the chemical structure of the residues. A number of pesticides are extensively applied to rice paddy fields during various stages of cultivation in the Republic of Korea.0 μm).. Therefore.. Sannino.8 (unit resolution) for both the first and third quadrupole.6– 0. Hiemstra and de Kok. 2007). 2006). The residues were re-dissolved in 3 mL of methanol and then vigorously shaken in a vortex mixer (G560E. 2003. 2006).4. USA) and treated with an ultrasonic wave in an ultrasonic bath (Bransonic 3510R-DTH. a G1312A pump. All solvents and water were purchased from Duksan Pure Chemical Co. such methods frequently suffer from low selectivity and sensitivity. In the present study we monitored the presence of 47 pesticides in wheat flour and rice matrices that were collected from the Korean market and boiled according to the standard cooking guidelines of the Society of Korean Nutritional Science. Experimental Reagents and Chemicals Pesticides reference standards were purchased from Dr Ehrenstorfer (Augsburg.1 u. 2004. Maidstone. Terre Haute. Maidstone. 2007). 23: 434–442 Copyright © 2008 John Wiley & Sons.. which were flowed at 60 psi.. The filtrate was then shaken vigorously for 1 min. 5. The filtrates were transferred into separation funnels followed by the addition of 15 g of sodium chloride. the pesticide residues in these food products were analyzed using an LC-MS/MS method. The samples were shaken for 20 min using a benchtop shaker (Glas-Col®. 2007. The capillary voltage was set at 5. Sancho et al. 435 Biomed. The solutions were filtered through FTFE syringe filters (Whatman International Ltd. minimization of sample cleanup steps. July 23..wiley. IN. However. Mertz et al. The resolution was 0.4. 58 established by the Korea Food and Drug Administration (2005). Germany). The solvent was completely dried out by evaporating at 40°C in a rotary evaporator (Eyela NVC2100. Ltd. 23: 434–442 .S.wiley.com/journal/bmc Copyright © 2008 John Wiley & Sons. Chromatogr. 436 www. Lee et al.interscience. 2009. J. Structures of the 47 selected pesticides. Figure 1. Biomed. 23: 434–442 Copyright © 2008 John Wiley & Sons.11 9.35 8.05 5.9 DPc (V) 31 31 31 31 36 31 16 16 41 41 46 51 36 31 36 40 31 31 21 21 31 31 25 25 21 21 25 25 15 15 25 25 31 31 46 46 41 27 27 36 36 25 25 51 61 CEd (V) 19 33 21 33 27 45 13 21 29 83 31 37 23 21 17 40 19 11 25 41 16 39 34 21 21 11 27 21 13 13 20 13 25 41 35 71 25 19 11 19 29 14 25 33 33 Compound Boscalid Dimethomorph Methoxyfenozide Iprovalicarb Fenhexamide Thenylchlor Flufenacet Tiadinil Fluquinconazole Mepanipyrim Tebufenozide Pyraclostrobin Benzoximate Pyrazolynate Trifloxystrobin Oxaziclomefon Pentoxazone Imibenconazole Pyributicarb Pyriproxyfen Flufenoxuron Fenpyroximate Spirodiclofen MW 342 387 368 320 301 323 363 267 375 223 352 387 363 438 408 375 353 410 330 321 488 421 410 Transition 343 → 307 343 → 140 388 → 301 388 → 165 369 → 149 369 → 133 321 → 119 321 → 203 302 → 97 302 → 55 324 → 127 324 → 53 364 → 194 364 → 152 268 → 101 268 → 77 376 → 307 376 → 349 224 → 106 224 → 77 353 → 133 353 → 105 388 → 194 388 → 163 364 → 105 364 → 77 439 → 91 439 → 65 409 → 186 409 → 206 376 → 190 376 → 55 354 → 286 354 → 186 411 → 125 331 → 190 331 → 133 322 → 96 322 → 185 489 → 158 489 → 141 422 → 366 422 → 107 411 → 71 411 → 313 tR (min) 11.3 14.04 9.2.8 14 14.48 7. and 2. which were analyzed in triplicate (n = 3). b Retention time.5 10. a Molecular weight. 2009.5 13. 0. 0.4 11.84 7.0. www.2 11.48 7. LC-MS/MS conditions for the analysis of the 47 selected pesticides Compound MWa 291 249 222 190 252 189 413 165 173 209 223 201 238 225 354 162 193 221 337 247 207 403 225 199 Transition 292 → 211 292 → 132 250 → 132 250 → 113 223 → 126 223 → 90 208 → 116 208 → 89 253 → 126 253 → 73 190 → 163 190 → 136 414 → 183 414 → 215 166 → 109 174 → 117 210 → 111 210 → 168 224 → 109 224 → 81 202 → 145 202 → 127 239 → 72 239 → 182 226 → 107 226 → 164 355 → 88 355 → 108 163 → 88 163 → 106 194 → 95 194 → 137 222 → 165 222 → 150 338 → 264 338 → 112 248 → 129 208 → 95 208 → 152 404 → 372 404 → 344 226 → 169 226 → 121 200 → 107 200 → 82 tRb (min) 3.6 14.9 10.6 DP (V) 71 76 46 36 36 41 21 21 91 91 31 31 11 11 46 46 51 56 21 31 16 16 27 27 31 31 41 41 11 6 51 51 36 36 66 30 30 16 11 41 41 31 31 36 36 CE (V) 27 27 27 43 23 31 23 12 33 57 21 75 17 27 27 73 25 33 35 49 27 55 19 29 29 71 67 101 13 21 23 65 19 31 53 23 35 21 29 29 71 25 71 31 19 Thiamethoxam Clothianidin Acetamiprid Aldicarb Thiacloprid Tricyclazole Cinosulfuron Metolcarb Pyroquilon Propoxur Bendiocarb Carbaryl Pirimicarb Ethiofencarb Thiodicarb Methomyl Isoprocarb Methabenzthiazuron Azafenidin Forchlorfenurone Fenobucarb Azoxystrobin Methiocarb Pyrimethanil The ion used for quantification purposes is indicated in bold.76 6. Chromatogr.57 10 10.92 9. The linearity in the response was evaluated by taking five standard solu- tions. The recovery and relative standard deviations (RSDs) were determined within-day by analyzing fortified samples at two spiking 437 Biomed.76 6. Validation and Matrix Effect Calibration curves were constructed using matrix-matched standards (blank extracts fortified with the pesticides).7 11.7 10.49 9.8 12 12.7 6.05 8.Multiresidue analysis of 47 pesticides Table 1.7 11.9 8.4 10.24 5.8 11.wiley. d Collision energy.interscience.9 13 13. 0.8 11. 1.7 11.2 11.26 9.1 14. Ltd.34 9.1.2 11. c Declustering voltage (cone voltage of other manufactures). The integrated peak area of the selected quantification masses (Table 1) was used to construct the curves.8 12.1 13.com/journal/bmc .0 μg/mL.5 14.01. All pesticides were detected in the ESI positive mode. Satisfactory recoveries and RSDs were achieved for most of the pesticides evaluated. which is determined by the peak area of matrix-matched standard/peak area of the solvent standard × 100. 2000. The full-scan mass spectra and the MS/MS spectra were required to obtain two transitions (product ions) for each pesticide. A pesticide mixture was added to an aliquot of the blank extract (in methanol) of each cereal to give a final concentration of 1 mg/kg. and ranged from 45 to 147%. The MRM chromatograms of the detected residues are shown in Fig. Calibration curves were constructed from the leastsquare regression of concentration vs relative peak area of the calibration standards. One plausible way to compensate for the matrix effect would be to use an isotopically labeled standard. Only two pesticide residues.wiley.0 mg/kg concentration level. Ammonium formate was determined to be essential for obtaining good peak separation with minimal peak tailing. however these are often not available (Niessen et al.. The separation was accomplished within 15 min. were found in polished rice samples.. The LODs ranged from 0. The recoveries.1 mg/kg). and LODs based upon Korea Food and Drug Administration (KFDA) (2005) guidelines. tricyclazole was detected in 14 cases and fenobucarb in one case. was evaluated in both matrices. respectively. Lee et al. Method Validation and Linearity of Calibration A validation study was carried out to determine the method linearity. 3.S. The most abundant product ion was selected for quantification and the second most abundant product ion was used for confirmation. Choi et al.. 2006).0 μg/mL were prepared in triplicate. the Republic of Korea. The limits of detection (LODs) were measured in three independently spiked samples. none of the residues were detected above the MRLs established by the Korea Food and Drug Administration (2005) (Table 4). Table 1 shows the MS/MS transitions selected for confirmation and quantification together with the optimized parameters for the 47 selected pesticides. except for metolcarb. The MRM conditions for every pesticide were optimized by injecting the individual standard solutions at a concentration of 10 μg/mL in methanol. The matrix effects were determined for the 47 pesticides investigated in this study at the 1. In contrast. Ltd. the mean value of the matrix effect was determined to be 99% and ranged from 45 to 147%. Only two residues were found in the polished rice samples as shown in Table 4. The mobile phase consisted of water and 5 mM methanolic ammonium formate (pH 4). However. tricyclazole and fenobucarb. 2000).1 and 1 mg/kg concentration levels. Chromatogr. a relatively high RSD (>20%) was observed at a high fortification level in some other pesticides. 2001). the results obtained for most of the pesticides were satisfactory. This phenomenon. For both matrices. indicating high sensitivity. is attributed to the competition between matrix components and analytes for droplet formation in the solution that is sprayed (King et al. 2009. The matrix effect (%). As shown in Table 3. 2.2 to 8. Aldicarb gave a poor protonated molecular ion spectrum. In this study. which were calculated as determination coefficients (r2). 2005). 2003.. RSDs. King et al.interscience. However. The effect is measured as an area ratio of the signal in the matrix-matched standard to that in the solvent standard. whose precursor ion appeared with [M + NH4]+. A total of 16 samples of the two cereals were boiled according to the standard cooking guidelines of the Society of Korean Nutritional Science and analyzed for the presence of 47 pesticide residues.01 to 2. The matrix effects estimated for the 47 pesticides had a mean value of 99%. The retention times were listed in Table 1.1 and 1 mg/kg in quintuplicate (n = 5). forchlorfenuron and imibenconazole (each of these pesticides gave only one product ion). Matrix Effect The ionization of the target analytes may be affected when matrix components co-elute during the electron spray ionization and consequently change the efficiency of ion formation. except for aldicarb. were above 0.995. All linearity values. J. which is called the matrix effect.0 μg/kg. Acknowledgements This work was supported by a grant (07182-833) from KFDA. Most recovery values ranged from 70 to 140%. pyroquilon. recoveries. Biomed. The recoveries and RSDs were determined at 0. levels of 0. Five calibration standards ranging from 0. The MRM signal area of the pesticide-added extract was compared with the signal of the standard in methanol. Taylor.com/journal/bmc Copyright © 2008 John Wiley & Sons. 438 www. The optimized method developed in this study allowed for the rapid quantification and identification of low levels of pesticide residues in cooked wheat flour and polished rice samples. The collision energy was set to produce the maximum sensitivity for the protonated precursor ion [M + H]+. 23: 434–442 . and LODs are listed in Table 2. Four pesticides both in wheat flour and polished rice samples gave recovery values that were below 70% at a low spiking level (0. calibrations were achieved by matrix-matched standards to minimize the matrix effect. RSD (%).. Results and Discussion Optimization of LC-MS/MS conditions The gradient in the LC measurement was optimized to achieve the successful separation of 47 pesticides in both matrices. A considerable ion suppression (<70%) was observed in seven pesticides and five pesticides from wheat flour and polished rice. These ions were filtered in the first quadrupole Q1 and further submitted to collision-induced fragmentation in Q2 such that the correspondent product ions could be monitored in Q3. 2000. The LOD values were calculated by using signal-to-noise ratio (the ratio between the peak intensity and the noise intensity) of Conclusions A total of 47 pesticides were analyzed in cooked samples obtained from wheat flour and polished rice using LC-MS/MS. Method Application to Wheat Flour and Polished Rice Samples Taken from the Korean Market The optimized procedures were applied to wheat flour and polished rice purchased from eight markets located in the Republic of Korea. The effect depends on the nature of both matrices and the analytes (Cech and Enke. no samples contained residues above the MRL. The results demonstrated that this method had a satisfactory analytical performance in terms of selectivity and sensitivity. Ion suppression by matrix components in the ESI source has been extensively discussed in the literature (Zrostlíková et al. com/journal/bmc .5 1 6.7 2.3 Polished Rice 2.9 1.1 mg/kg 75 (10) 62 (19) 90 (5) 78 (9) 81 (12) 88 (2) 40 (10) 83 (13) 92 (10) 79 (9) 85 (5) 80 (13) 91 (5) 69 (13) 79 (9) 88 (11) 78 (5) 85 (13) 69 (5) 73 (12) 89 (5) 80 (13) 85 (22) 79 (10) 80 (5) 75 (9) 82 (8) 84 (12) 116 (15) 83 (3) 88 (10) 90 (11) 125 (10) 103 (13) 116 (6) 81 (10) 80 (7) 77 (12) 75 (6) 82 (10) 109 (8) 121 (11) 79 (9) 105 (6) 111 (10) 120 (4) 103 (7) LODs (μg/kg) Wheat flour 1.9 2.3 1.wiley.6 2.5 1.interscience.8 2. Chromatogr. 23: 434–442 Copyright © 2008 John Wiley & Sons. 19: 2085–2093.6 1.5 2 1 2.5 2.2 1.8 1. Development of a multiresidue method for analysis of major Fusarium mycotoxins in corn meal using liquid chromatography/tandem mass spectrometry.3 5. Greulich K. Ltd. Chen T and Chen G.2 2.5 2.8 4.0 mg/kg Thiamethoxam Clothianidin Acetamiprid Aldicarb Thiacloprid Tricyclazole Cinosulfuron Metolcarb Pyroquilon Propoxur Bendiocarb Carbaryl Pirimicarb Ethiofencarb Thiodicarb Methomyl Isoprocarb Methabenzthiazuron Azafenidin Forchlorfenuron Fenobucarb Azoxystrobin Methiocarb Pyrimethanil Boscalid Dimethomorph Methoxyfenozide Iprovalicarb Fenhexamide Thenylchlor Flufenacet Tiadinil Fluquinconazole Mepanipyrim Tebufenozide Pyraclostrobin Benzoximate Pyrazolynate Trifloxystrobin Oxaziclomefone Pentoxazone Imibenconazole Pyributicarb Pyriproxyfen Flufenoxuron Fenpyroximate Spirodiclofen 77 (17) 81 (31) 89 (21) 100 (14) 102 (24) 111 (15) 100 (25) 99 (22) 114 (8) 112 (14) 116 (8) 112 (22) 115 (5) 113 (16) 134 (23) 117 (16) 128 (20) 133 (9) 104 (13) 131 (12) 99 (29) 131 (7) 122 (16) 127 (5) 123 (9) 134 (10) 135 (12) 129 (12) 116 (10) 128 (25) 130 (8) 131 (13) 118 (5) 110 (4) 102 (6) 129 (10) 119 (19) 132 (7) 130 (12) 103 (8) 101 (5) 101 (8) 127 (12) 111 (7) 109 (9) 106 (11) 93 (7) 0.7 3.4 3.Multiresidue analysis of 47 pesticides Table 2. Identification and quantitation of pyrethroid pesticide residues in vegetables by solid-phase extraction and liquid 439 Biomed.9 1 0.5 3.4 0.1 mg/kg 46 (6) 42 (17) 90 (7) 51 (8) 82 (7) 97 (4) 47 (14) 71 (5) 107 (9) 75 (2) 94 (7) 74 (12) 111 (2) 71 (13) 107 (2) 96 (9) 92 (8) 114 (5) 70 (7) 92 (2) 93 (7) 114 (2) 95 (6) 110 (4) 115 (12) 118 (8) 103 (10) 109 (5) 127 (2) 112 (9) 118 (7) 124 (3) 140 (11) 133 (2) 120 (11) 125 (4) 94 (11) 127 (10) 117 (9) 92 (10) 113 (6) 114 (5) 116 (13) 120 (13) 115 (3) 127 (13) 103 (19) Polished Rice 1.2 2.4 1. Analytical Chemistry 2000.9 2. Foglia P.4 0.8 3. Rapid Communications in Mass Spectrometry 2005.2 1.7 References Alder L.3 0.4 0.1 2.2 2.8 3.0 mg/kg 95 (10) 91 (8) 84 (15) 95 (2) 89 (5) 100 (13) 92 (2) 92 (11) 100 (6) 90 (22) 101 (12) 105 (10) 95 (7) 104 (10) 102 (5) 100 (18) 90 (11) 100 (15) 84 (9) 85 (17) 100 (2) 91 (9) 101 (11) 86 (2) 85 (15) 83 (5) 99 (9) 95 (7) 100 (8) 92 (22) 103 (10) 95 (9) 100 (18) 86 (22) 108 (15) 89 (7) 101 (13) 87 (11) 91 (12) 99 (11) 91 (5) 96 (9) 90 (12) 94 (1) 100 (22) 102 (5) 96 (10) 0.4 0.8 0.4 4.3 2 1.8 0.4 0.3 0. www.9 8 1.8 1.1 0.5 1. Residue analysis of 500 high priority pesticides: better by GC-MS or LC-MS/MS? Mass Spectrometry Reviews 2006.4 1. Recoveries (%) and LODs (μg/kg) of the tested pesticides in cooked wheat flour and polished rice Recovery % (RSD %) Compound Wheat flour 1.7 2.5 6.9 1.6 1. 2009.8 4.5 1.2 2. Samperi R and Lagana A.4 1.1 2.8 2.8 5.9 0.7 2.5 1 6.6 2.5 0.3 1.3 1.1 2.5 3. Cech NB and Enke CG. Pastorino E.2 0. Cavaliere C.3 0.8 6 0.7 2. 25: 838–865.2 2.6 3 6. 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