Geographical origin discriminatory analysis of onions: Chemometrics methods applied to ICP-OES and ICP-MS analysis.

Geographical origin is an important determinant of agricultural product quality and safety. Herein, inductively coupled plasma (ICP) analysis was applied to determine the inorganic elemental content of onions and identify their geographical origin (Korean or Chinese). Chemometric, including principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal partial least square discriminant analysis (OPLS-DA) were applied to the ICP results. OPLS-DA distinguished each group, and 17 elements with variable importance in projection (VIP) values of ≥ 1 were selected. The receiver operating characteristic (ROC) curve had an area under the curve (AUC) of 1, indicating excellent discriminatory power. Differences in elemental content between groups were visually observed in a heatmap, and the country of origin was determined with 100% accuracy using canonical discriminant analysis (CDA). This method accurately distinguishes between Korean and Chinese onions and is expected to be beneficial for identifying agricultural products.

Target and non-target analytical method for potential hazardous substances in livestock and pet hair using liquid- and gas chromatography quadrupole time-of-flight mass spectrometry.

Extraction using acetonitrile and water and quadrupole time-of-flight mass spectrometry (LC and GC-QTOF/MS) techniques were used to screen for potential hazardous substances in livestock and pet hair. In addition, LC-MS/MS and GC-MS/MS techniques were used for verification of the analytical method and quantitative analysis of pesticides, veterinary drugs, mycotoxins and antioxidants in hair. Optimized sample preparation involves extracting 0.05 g of sample with 0.6 mL of ACN and 0.4 mL of distilled water. In addition, the two layers were separated by adding 0.1 g of NaCl. Then, both the ACN and water layers were analyzed by LC-TOF/MS, and the ACN layer was analyzed by GC-TOF/MS. Most of the matrix effects of livestock and pet hair were less than 50%, but some matrices and components showed high results, so matrix matching correction was applied for more precise quantification. Method validation was performed for 394 constituents (293 pesticides, 93 veterinary drugs, 6 mycotoxins and 2 preservatives) in dog, cat, cow and pig hair and chicken and duck feathers. All components showed good linearity (r2 ≥0.98) in the developed assay. The quantification limit of all compounds was set at 0.02 mg/kg, which is the lowest level that satisfies the recovery rate standard. The recovery experiment was repeated 8 times at 3 concentrations. Most of the components were extracted with the ACN layer, and the recovery rate was 63.35-119.98%. In order to confirm the efficiency of extracting harmful substances from actual samples, 30 hairs of livestock and pets were screened.

Multi-residue analytical method for detecting pesticides, veterinary drugs, and mycotoxins in feed using liquid- and gas chromatography coupled with mass spectrometry.

Modified QuEChERS and triple quadrupole mass spectrometry (LC and GC-MS/MS) technology were used to sequentially analyze pesticides, veterinary drugs, and mycotoxins in feed. In order to analyze the harmful substances that may remain or occur in the feed, we performed optimization experiments for sample preparation and LC-MS/MS and GC-MS/MS conditions. Optimized sample preparation involves extracting 5 g of sample with 15 mL of 0.25 M EDTA and 10 mL of acetonitrile. And some extracts were diluted 10-fold with 100 mM ammonium formate aqueous solution and analyzed by LC-MS/MS, and some extracts were purified through 25 mg PSA and analyzed by GC-MS/MS by adding an analyte protectant. We confirmed the matrix effect of feed ingredients and compound feeds, and added a dilution process after extraction to increase on-site efficiency. Matrix-matched calibration was applied for quantification. Method validation was performed for 197 pesticides, 56 components for veterinary drugs, and 5 components for toxins. All the components showed good linearity (r2 ≥ 0.98) in the developed analytical method. For most compounds, the limit of quantitation was 0.05 mg/kg. The recovery rate experiment was repeated three times at three concentrations including LOQ in feed ingredient, compound feed for livestock, and compound feed for pets. The recovery rate was 70.09-119.76% and relative standard deviations were ≤ 18.91%. And the accuracy and precision were further verified through cross-validation between laboratories. The developed analytical method was used to monitor 414 domestically distributed and imported feeds.

Upgrading analytical methodology through comparative study for screening of 267 pesticides/metabolites in five representative matrices using UPLC-MS/MS.

A comparative study was conducted to replace the traditional screening method (MFDS#83) with the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) EN method for the determination of 267 pesticides/metabolites/plant activators/growth regulators in five representative crop matrices (mandarin, pepper, potato, rice, and soybean). In the traditional method, samples were extracted with acetonitrile and salt, and purified with a solid-phase extraction cartridge. In the QuEChERS method, the sample extraction was carried out using acetonitrile and a mixture of salts, and purification was performed using dispersive solid phase extraction. The limit of quantification (LOQ) for the MFDS#83 method was 0.0004 mg/kg, whereas for the QuEChERS EN method, the LOQ varied from 0.002 to 0.006 mg/kg for all analytes in various matrices. A six-point matrix-matched calibration curve was prepared for all analytes in five matrices for both methods. Both the MFDS#83 and QuEChERS EN methods provided excellent linearity, with the coefficients of determination (R2) ≥ 0.99 for most of the compounds. In both cases, the method was validated in terms of recovery and repeatability after the fortification of two different concentrations with three replicates for each of the concentrations. The QuEChERS EN method provided better recovery than the MFDS#83 method for all matrices except mandarin.

Distribution and ecological risk of pharmaceuticals in surface water of the Yeongsan river, Republic of Korea.

This study examined the distribution of pharmaceuticals in Yeongsan River and at point sources (PSs) in the associated water system, and performed a risk assessment based on our findings. The samples included effluents collected from three sewage treatment plants (PS1, PS2, and PS3) and two industrial complexes (PS4 and PS5) as well as surface water collected from seven mainstreams and 11 tributaries of the river. The target pharmaceuticals were acetylsalicylic acid, carbamazepine, clarithromycin, naproxen, sulfamethazine, sulfamethoxazole, sulfathiazole, and trimethoprim, which were detected by liquid chromatography-tandem mass spectrometry. All pharmaceuticals except acetylsalicylic acid and sulfathiazole were found in PS1, PS2, and PS3 samples, whereas acetylsalicylic acid, carbamazepine, sulfamethazine, and sulfamethoxazole were found in PS4, most of the pharmaceuticals were not present in PS5. The rank order of pharmaceutical concentration in surface water was carbamazepine (97.2%, 0.2067 µg/L) > sulfamethoxazole (88.9%, 0.1132 µg/L) > naproxen (51.4%, 0.0516 µg/L) > clarithromycin (43.1%, 0.0427 µg/L). The distribution of pharmaceuticals in the Yeongsan River at PSs and non-PSs differed, and higher concentrations of human pharmaceuticals were detected in upstream and midstream areas whereas higher concentrations of animal pharmaceuticals were found downstream. Hazard quotients (HQs) evaluated at each sites based on mean concentration and 95% upper confidence limits (95% UCLs) were all less than one, indicating a low risk of toxicity. The findings of this study are expected to be useful for risk assessment of aquatic ecosystems.

Simultaneous quantification of methiocarb and its metabolites, methiocarb sulfoxide and methiocarb sulfone, in five food products of animal origin using tandem mass spectrometry.

A simultaneous analytical method was developed for the determination of methiocarb and its metabolites, methiocarb sulfoxide and methiocarb sulfone, in five livestock products (chicken, pork, beef, table egg, and milk) using liquid chromatography-tandem mass spectrometry. Due to the rapid degradation of methiocarb and its metabolites, a quick sample preparation method was developed using acetonitrile and salts followed by purification via dispersive- solid phase extraction (d-SPE). Seven-point calibration curves were constructed separately in each matrix, and good linearity was observed in each matrix-matched calibration curve with a coefficient of determination (R2) ≥ 0.991. The limits of detection and quantification were 0.0016 and 0.005mg/kg, respectively, for all tested analytes in various matrices. The method was validated in triplicate at three fortification levels (equivalent to 1, 2, and 10 times the limit of quantification) with a recovery rate ranging between 76.4-118.0% and a relative standard deviation≤10.0%. The developed method was successfully applied to market samples, and no residues of methiocarb and/or its metabolites were observed in the tested samples. In sum, this method can be applied for the routine analysis of methiocarb and its metabolites in foods of animal origins.

Simultaneous detection of sulfoxaflor and its metabolites, X11719474 and X11721061, in lettuce using a modified QuEChERS extraction method and liquid chromatography-tandem mass spectrometry.

An analytical method has been developed to quantify the residual levels of sulfoxaflor and its metabolites (X11719474 and X11721061) in/on cultivated lettuce grown under greenhouse conditions. Samples were extracted and purified using a quick, easy, cheap, effective, rugged, and safe 'QuEChERS' method (original version) following systematic method optimization and were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Good linearity with coefficient of determination ≥0.9930 was obtained and the limits of detection (LOD) and quantification (LOQ) were in the ranges of 0.003-0.006 and 0.01-0.02 mg/kg, respectively. The recovery rates of both the parent compound and its metabolites (fortified at 10 and 50× the LOQ) estimated from six replicates ranged between 81.9 and 115.5% with a relative standard deviation <12%. The validated method was applied to field-incurred samples (collected over 7 days) sprayed once or twice with a water-dispersible granule formulation. Notably, a substantial reduction in rate was observed after 3 days and the half-life was short, only 1.5 days. The developed method is simple and versatile and can be used for various leafy vegetables.

Simultaneous determination and identity confirmation of thiodicarb and its degradation product methomyl in animal-derived foodstuffs using high-performance liquid chromatography with fluorescence detection and tandem mass spectrometry.

A high-performance liquid chromatography-fluorescence detection method was developed for the simultaneous determination of thiodicarb and its degradation product methomyl in animal-derived food products, including chicken muscle, beef, pork, table eggs, and milk. Thiodicarb is known to degrade during analysis; therefore, a thorough investigation was carried out, revealing that thiodicarb degrades to methomyl immediately after spiking into a matrix of animal-derived food products. Consequently, thiodicarb was determined as the sum of the parent compound and methomyl. Samples were extracted with acetonitrile and sodium salts, and purified using solid-phase extraction (SPE). The limits of detection (LODs) and quantification (LOQs) were 0.0013 and 0.004mg/kg, respectively, for both analytes in various matrices. Seven-point external calibration curves were obtained, and they showed excellent linearity with determination coefficients (R2)≥0.999 for all tested matrices. The method was validated at three fortification levels (LOQ, LOQ×2, and LOQ×10) in triplicate with average recoveries ranging from 84.24 to 112.8% (for methomyl) and relative standard deviations (RSDs)≤6.5% in all matrices. The converted recoveries of thiodicarb in various matrices ranged from 74.80 to 107.80% with RSDs≤4.5%. The identities of both compounds in standard solutions and for recovery were confirmed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The developed method was further validated by accurate reproduction at another laboratory. Finally, the method was applied to market samples collected from different areas (and, in the case of milk, different brands), and none of the samples tested positive for thiodicarb or methomyl. In conclusion, the developed method can be successfully applied for a single-run analysis of thiodicarb and methomyl in livestock products.

A simple extraction method for the detection and quantification of polyoxin D, a nucleoside antibiotic, in butterbur using UPLC-MS/MS.

An effective analytical method was developed for the detection and quantification of polyoxin D in butterbur using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted using acidified deionised water and purified via solid-phase extraction (SPE) using an HLB cartridge. An external matrix-matched standard calibration curve was prepared, which provided an excellent linearity with a coefficient of determination (R2) ⩾0.999. Limits of detection (LOD) and quantification (LOQ) were 0.015 and 0.0.05µg/g, respectively. The developed method was validated in terms of recovery performance using two fortification levels in triplicate. The storage stabilities of the various field samples were also determined. Our method provided consistent recovery (86.26-87.37%) with a relative standard deviation (RSD) of <5%, and was successfully applied to field-treated butterbur grown under greenhouse conditions and collected at various times following commercial fungicide application. As expected, a gradual degradation of polyoxin D was observed, with a half-life (t1/2) of 2.11d being recorded. Finally, we propose that the developed method can be extrapolated to other crops for routine analysis and can be used to determine the pre-harvest intervals (PHIs), thus preventing the development of antibiotic resistance genes in humans and in the environment.

QuEChERS method for the simultaneous quantification of phorate and its metabolites in porcine and chicken muscle and table eggs using ultra-high performance liquid chromatography with tandem mass spectrometry.

An analytical method to detect phorate and its metabolites, including phorate sulfone, phorate sulfoxide, phoratoxon, phoratoxon sulfone, and phoratoxon sulfoxide, in porcine and chicken muscles and table eggs was developed and validated. Extraction was performed using a quick, easy, cheap, effective, rugged, and safe method and analysis was conducted using ultra-high performance liquid chromatography-tandem mass spectrometry. Matrix-matched calibrations were linear over the tested concentrations, with determination coefficient ≥ 0.995 for all tested analytes in the different matrices. The limits of detection and quantification were 0.001 and 0.004 mg/kg, respectively. The calculated recovery rates at three fortification levels were satisfactory, with values between 74.22 and 119.89% and relative standard deviations < 10%. The method was applied successfully to commercial samples collected from locations throughout the Korean Peninsula, and none of them showed any traces of the tested analytes. Overall, the developed method is simple and versatile, and can be used for monitoring phorate and its metabolites in animal products rich in protein and fat.

Enhancement of antioxidative and antimicrobial activities of immature pear (Pyrus pyrifolia cv. Niitaka) fruits by fermentation with Leuconostoc mesenteroides.

Immature pear (Pyrus pyrifolia cv. Niitaka) fruits were fermented with Leuconostoc mesenteroides and Aspergillus oryzae, which are commonly used as starters for manufacturing fermented foods. Fermented immature pear fruit extracts (FIPF) by L. mesenteroides showed significantly higher radical-scavenging activity using DPPH, ABTS, superoxide anion, and hydroxyl radicals and reducing power capacity than unfermented immature pear fruit extracts. L. mesenteroides-FIPF more effectively inhibited the formation of cholesteryl ester hydroperoxide in copper ion-induced rat blood plasma. In addition, the L. mesenteroides-FIPF strongly inhibited tyrosinase activity and the growth of pathogenic skin bacteria. In contrast, enhanced antioxidative and antibacterial activities were not apparent in A. oryzae-FIPF. The antioxidative and antimicrobial activities of the fermented and unfermented immature pear fruits were correlated with the flavonoid contents. These results indicate that fermentation enhances antioxidative and antimicrobial activities of immature pear fruits.

Dissipation pattern and pre-harvest residue limit of abamectin in perilla leaves.

The pre-harvest residue limit (PHRL) of abamectin (abamectin B1a and B1b) in Perilla frutescens leaves grown under greenhouse conditions were investigated using high-performance liquid chromatography with a fluorescence detector. Samples were extracted with acetonitrile. The extract was purified through a solid phase extraction procedure. Then the purified extract was derivatized with trifluoroacetic anhydride and N-methylimidazole to form a strong stable fluorescent derivative of abamectin. Finally, derivatized abamectins were conveyed to the detector via an Atlantis C18 column, with water and methanol as a mobile phase. Calibration curves were linear over the calibration ranges with coefficients of determinants r (2) ≥ 0.999. The limits of detection and quantification were 0.0033 and 0.01 mg kg(-1) for abamectin B1a and B1b, respectively. Recovery was assessed in a control matrix at two different fortification concentrations, with three replicates for each concentration. Good recoveries were obtained for the target analytes and ranged from 82.11 to 93.03%, with relative standard deviations of less than 8%. The rate of disappearance of total abamectin on perilla leaves for recommended and double the recommended doses was described as first-order kinetics with a half-life of 0.7 days. Using the PHRL curve, we could predict the residue level of total abamectin to be 0.92 mg kg(-1) at 7 days before harvest or 0.26 mg kg(-1) at 4 days before harvest, which would be below the provisional MRL designed by the Korea Food and Drug Administration.

Development of an extraction method for the determination of avermectins in soil using supercritical CO2 modified with ethanol and liquid chromatography-tandem mass spectrometry.

The aim of the present study was to develop a multiresidue analytical method for determination of avermectins (abamectin, ivermectin, moxidectin, and doramectin) in soil samples using supercritical fluid extraction and LC-MS/MS. The optimal extraction conditions for supercritical fluid extraction were 80°C for temperature, 300 kg/cm(2) for pressure, 40 min as an extraction time, and 30% of a modifier ratio. The linearity of the calibration curves was excellent and yielded the correlation coefficients (r(2) = 0.998-0.999, at a range of 1.5-500 ng/g). Soil samples were fortified with known quantities of the analytes at three different concentration levels (5, 10, and 50 ng/g) and the recoveries were in the range of 82.5-96.2% with relative standard deviation values ranging between 2.1 and 7.9%. The limits of detections and limits of quantitations were 1.5 and 5 ng/g, respectively. The developed method was successfully applied to analyze avermectin residues in soil samples collected from 13 sites in the Honam area, Republic of Korea. In sum, a combination of supercritical fluid extraction and LC-MS/MS has been proven to be highly efficient as an environmentally friendly technique for the simultaneous determination of avermectins in soil samples.

Analysis of imidacloprid and pyrimethanil in shallot (Allium ascalonicum) grown under greenhouse conditions using tandem mass spectrometry: establishment of pre-harvest residue limits.

In this study, the original Quick, Easy, Cheap, Effective, Rugged and Safe method was used for the extraction of imidacloprid and pyrimethanil followed by a rapid clean-up through dispersive solid-phase extraction technique with primary secondary amine sorbent and magnesium sulfate in shallot. Residues were analyzed using LC-tandem mass spectrometry in positive-ion electrospray ionization mode. The limits of detection and quantification were estimated to be 0.006 and 0.02 mg/kg, respectively. The samples were fortified at two different concentration levels (0.2 and 1.0 mg/kg), and the recoveries ranged between 79.7 and 83.9% with relative standard deviation values < 6%. The method was successfully applied for the establishment of the pre-harvest residue limits (PHRL). The rate of disappearance of imidacloprid and pyrimethanil on shallot was described with first-order kinetics (imidacloprid, y(2) = 0.9670; pyrimethanil, y(2) = 0.9841), with half-lives of 2.87 and 2.08 days, respectively. Based on the dissipation patterns of the pesticide residues, the PHRL was recommended at 7.86 mg/kg for 14 days (PHRL14 ) and 1.98 mg/kg for 7 days (PHRL7 ) before harvest for imidacloprid, and 21.64 mg/kg for 7 days (PHRL7 ) and 9.28 mg/kg for 4 days (PHRL4 ) before harvest for pyrimethanil in shallot.

A QuEChERS-based extraction method for the residual analysis of pyraclofos and tebufenpyrad in perilla leaves using gas chromatography: application to dissipation pattern.

The objective of this work was to establish a simple extraction method for the residual analysis of pyraclofos and tebufenpyrad in Perilla leaves. A QuEChERS (quick, easy, cheap, effective, rugged and safe) method was used for extraction using ethyl acetate as an extraction solvent, and cleanup was carried out using dispersive solid-phase extraction technique. The samples were analyzed using gas chromatography with nitrogen phosphorous detector and confirmed by gas chromatography-mass spectrometry. The linearity was excellent (r(2) = 1.0) in matrix-matched calibration for both pesticides. The recoveries at two fortification levels were 80.76-95.38% with relative standard deviation lower than 5%. The limits of detection and limits of quantification were 0.01 and 0.033 mg/kg for both pesticides, respectively. The results revealed that the dissipation pattern of pyraclofos and tebufenpyrad followed first-order kinetics. The pyraclofos and tebufenpyrad residues declined to a level below the maximum residue limits within 14 day between the last application and harvesting. We suggest that pyraclofos and tebufenpyrad could be used efficiently on perilla leaves under the recommended dosage conditions.

Pepper leaf matrix as a promising analyte protectant prior to the analysis of thermolabile terbufos and its metabolites in pepper using GC-FPD.

During gas chromatography (GC), the matrix can deactivate the active site during the transport of the compound from the injector to the detector. This deactivation capacity varies among matrices, as it is dependant on the concentrations of the different constituent compounds of each matrix. During the analysis of terbufos and its metabolites, two of its metabolites were highly thermolabile, and were readily decomposed inside the GC system. As the matrix can mask the active site, we carried out a matrix-matched calibration in an effort to protect the analyte against decomposition. As a component of our analysis, the pepper matrix was the first to be matched; however, it failed to completely protect the metabolites. Subsequently, a variety of different compounds, including 3-ethoxy-1,2-propanediol, gulonolactone, and sorbitol at 10, 1, and 1mg/mL were tested; however, none of these generated the desired effect. We surmised that some of the compounds may have decomposed inside the injection port, so we introduced a carbofrit inlet liner, which is highly inert. But, this step did not improve the protective qualities of the matrices. Finally, pepper leaf matrix was added to the pepper matrix, and we observed a profound protective effect for almost all of the analytes tested. A selective detector (flame photometric detector with phosphorus filter) was used to facilitate a high matrix concentration without interaction with the analyte. After resolving the problem of these two metabolites, terbufos and its five toxic metabolites were analyzed in pepper and pepper leaf samples. The recovery rates for terbufos and its metabolites were 73-114.5% with a relative standard deviation of <12%. This method was successfully applied to field samples, and terbufos sulfone, terbufos sulfoxide, and terbufoxon sulfoxide were found as residues in the suspected pepper and pepper leaf samples.

Determination of spinetoram and its metabolites in amaranth and parsley using QuEChERS-based extraction and liquid chromatography-tandem mass spectrometry.

In this study, a simultaneous method was developed for the determination of spinetoram (XDE-175-J and XDE-175-L) and its demethyl metabolites (N-demethyl-175-J and N-demethyl-175-L) and formyl metabolites (N-formyl-175-J and N-formyl-175-L) in the minor crops; amaranth and parsley. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction. Afterwards, the analytes were quantified and confirmed via liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM). Calibration curves were linear over the calibration ranges for all the analytes tested with r(2)>0.993. Limits of detection and quantitation were 0.01 and 0.03 mg/kg for all the tested analytes in amaranth and parsley, respectively. Recovery values, at spiking levels 0.05 and 0.25 mg/kg, ranged from 71.0% to 115.2% with relative standard deviations <15%, except for N-formyl-175-J in both amaranth and parsley. This method was applied to field-incurred samples and was shown to provide an adequate sensitivity and performance for the simultaneous determination of spinetoram and metabolites. To the best of our knowledge, this is the first time spinetoram and its metabolites were quantified using LC-MS/MS in minor crops.

Simultaneous multiresidue determination of 48 pesticides in Yeongsan and Sumjin River water using GC-NPD and confirmation via GC-MS.

In a continuation of our earlier work, a multiresidual analytical method using 48 frequently used neutral pesticides in a water matrix was developed and validated in this study. The samples were extracted with dichloromethane and the pesticides were analyzed via GC-NPD followed by confirmation with GC-MS. Good linearity was detected over a concentration range of 0.01-1.0 microg/mL with correlation coefficients (r(2) ) in excess of 0.982. The recoveries were measured between 70.7 and 111.4% for the majority of the targeted pesticides with relative standard deviations (RSDs) of less than 20%. The LODs and LOQs were in ranges of 0.1-2 and 0.33-6.6 microg/L, respectively. A total of 66 water samples were collected from different locations in Yeongsan and the Sumjin River, Republic of Korea, and were analyzed in accordance with the developed method. None of the water samples were determined to contain any of the targeted pesticides. The method has been shown to be simpler, faster, and more cost-effective than the method established by the Environmental Protection Agency (EPA).

Development and validation of a multiresidue method for determination of 37 pesticides in soil using GC-NPD.

In this study, a multiresidue analytical method for the detection of 37 pesticides in a soil matrix was developed and validated. The soil sample was fortified with a known quantity of pesticides at two different concentration levels (0.1 and 0.01 µg/g) and the analytes were extracted via a liquid-solid extraction method. The pesticides were separated on an HP5 capillary column and were analyzed with a gas chromatograph coupled to a nitrogen-phosphorous detector (GC-NPD). Method validation was accomplished with good linearity (r(2) = 0.994-0.999) within a considerable range of concentrations. Satisfactory recoveries (70.5-110.4%) were obtained with 32 pesticides at both spiking concentration levels, whereas five pesticides-dimepiperate, buprofezin, prometryn, pirimicarb, and fludioxonil-were recovered at relatively low levels (43.6-61.8%). The applicability of the method was demonstrated by analyzing field samples collected from 24 different sites around Yeongsan and Sumjin rivers in the Republic of Korea. No residues of the selected pesticides were detected in any of the samples. The developed method could be employed as a simple and cost-effective method for the routine detection and analysis of 37 pesticides in soil samples.

Bufferized solvent extraction and HPLC fluorometric detection method for sarafloxacin in pig and chicken muscles.

In this study, a method for the detection of sarafloxacin in pig and chicken muscles was developed using HPLC-FLD as a regulatory residue technique. Good extraction efficiency was achieved using a mixture of 1% orthophosphoric acid-0.2 m MgCl(2) in water and acetonitrile as an extraction solvent, and n-hexane partitioning and centrifugation for cleanup was used in the absence of dehydration. Specificity, linearity, detection and quantification limits, recovery, accuracy and precision were all validated, and all results were sufficient for the SARA regulatory residue method in pig and chicken muscles. The method developed and described herein was not only simple but also reliable, and was applied to market samples to determine their residue contents.