Acetic Acid In Acetonitrile Research Articles

Simultaneous Determination of 27 Pesticides in Ginseng by UPLC/MS/MS and Modified QuEChERS Procedure

A novel, simple, and rapid method for the quantification of 27 commonly used pesticides in ginseng incorporating a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure was developed and validated. The pesticides were extracted with 1% acetic acid in acetonitrile and extracts purified by use of the mixed sorbents primary-secondary amine, C18, and graphitized carbon black. Quantitative analysis of all pesticides was performed by ultra-performance LC/MS/MS in the positive ionization mode in a single run due to the fast polarity switching capability of the mass spectrometer. Two precursor-product ion transitions were monitored for each compound in the multiple reaction monitoring mode. Quantification was carried out using matrix-matched standards for calibration. Recoveries of the proposed method from the spiked samples were achieved in the range 62.8-108.5%, and RSD ranged from 1.5 to 11.8%.

Quantitative analysis of the five marker compounds in Mori Cortex Radicis and its anti-inflammatory effects

Mori Cortex Radicis (MCR, Moraceae), which is root bark of Morus alba L., is used traditionally in the treatment of jaundice, hematemesis, edema, and pollakisuria in Korea. In this study, the anti-inflammatory effects of MCR extract and the five components, neochlorogenic acid (1), chlorogenic acid (2), cryptochlorogenic acid (3), caffeic acid (4), and p-coumaric acid (5) were investigated using RAW 264.7 cells. The simultaneous analysis of the compounds 1 – 5 in MCR extract was performed using high-performance liquid chromatography coupled with photodiode array detector. All analytes were separated on a Gemini C18 column and the column oven temperature was set at 40 ° C with the detection wavelength was set at 320nm. The mobile phase was a gradient comprising 1.0% (v/v) aqueous acetic acid (A) and 1.0% (v/v) acetic acid in acetonitrile (B). The flow rate was 1.0 mL/min and the injection volume was 10 mL. We determined the effects of MCR extract and the compounds 1-5 on the production of nitric oxide (NO), prostaglandin E2 (PGE2), and mRNA expression of cyclooxygenase-2 (COX-2) in RAW 264.7 cells. The HPLC method showed good linearity with a correlation coefficient (r2) ≥0.9999 over the concentration range 0.31 – 20.00 mg/mL. The limit of detection and the quantification of the compounds 1-5 were 12.23 – 61.46 ng/mL and 40.76 – 204.87 ng/mL, respectively. The concentration of the compounds 1-5 was 0.16 – 1.40 mg/g. MCR extract suppressed the production of NO and PGE2 in RAW 264.7 cells in a dose-dependent manner. None of the five components of MCR extract had any influence on the production of NO. However, compounds 4 and 5 were inhibited the production of PGE2 and mRNA expression of COX-2 in RAW 264.7 cells. Our results suggest that MCR extract may offer potential as a therapeutic agent for the treatment of inflammation. The method we have established will help to improve the quality control of MCR extracts.

A validated specific stability-indicating RP-HPLC assay method for the determination of loteprednol etabonate in eye drops.

A new stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of loteprednol etabonate in bulk drugs and in ophthalmic suspensions in the presence of degradation products generated from forced degradation studies. The system consisted of Agilent Technologies Zorbax Eclipse XDB-Phenyl 5 µm 4.6 × 250 mm, and detection was performed at 244 nm. The mobile phase consisted of water-acetonitrile-acetic acid (34.5:65.0:0.5, v/v/v) run at a flow rate of 1 mL/min and maintained at room temperature. The calibration curve was linear from 30 to 70 µg/mL with r > 0.999. Accuracy (mean recovery 100.78%) and precision were found to be satisfactory. Stress conditions including acid and alkali hydrolysis, water stress, oxidation, photolysis and heat were applied. The degradation products did not interfere with the detection of loteprednol etabonate, thus the method can be considered as a stability-indicating method. The proposed method can be used for quality control assay of loteprednol etabonate in bulk drug and in ophthalmic suspensions and for stability studies as a result of the ability of the method to separate loteprednol etabonate from its degradation products and excipients.

Determination of 13 Phenolic Compounds in Rice Wine by High-Performance Liquid Chromatography

Rice wines are widely consumed by the general public in Asian countries, while comprehensive studies focused on the individual phenolic compounds in rice wines are limited. A rapid method for simultaneous determination of 13 phenolic compounds in rice wines by high-performance liquid chromatography (HPLC) was developed and validated, and the phenolic compounds in commercial rice wine samples (Chinese rice wine, Japanese sake, and Korean makgeolli) were determined in this paper. The identified compounds contained gallic acid (GA), protocatechuic acid (PRCA), vanillic acid (VA), syringic acid (SRA), caffeic acid (CA), ferulic acid (FA), p-coumaric acid (pCA), sinapic acid (SA), chlorogenic acid (CHA), (+)-catechin (CAT), (−)-epicatechin (EPI), quercetin (QUE), and rutin (RUT). Phenolics were separated with a C18 reversed-phase column at 38 °C by gradient elution using 3 % acetic acid aqueous solution (solvent A) and acetonitrile (solvent B) (0 min, 5 % B; 5 min, 8 % B; 10 min, 15 % B; 20 min, 25 % B; and 25 min, 5 % B) as the mobile phase at 280 nm with flow rate of 1.0 mL min−1. With direct injection of rice wine samples, the chromatograms of all analytes were observed within 20 min, all calibration curves were linear (R 2 > 0.995) within the range, limits of detection (LOD) ranged from 0.02 to 0.06 μg mL−1, and good recoveries (88.07–106.80 %) and precision (relative standard deviation (RSD) < 5.36 % ) were obtained for all compounds. This method was applied to quantify phenolic compounds in commercial rice wine samples (Chinese rice wine, Japanese sake, and Korean makgeolli), and good separation peaks were observed and catechin was the predominant phenolic in the samples. The average values of total phenolic contents of the three groups of rice wine were significantly different (p < 0.01). In conclusion, this procedure can be used to determine the phenolic compounds in various types of rice wines, as well as to characterize and differentiate rice wine samples.

Multi-residue screening of 100 multi-class veterinary drugs in milk powder by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

In this study, a simple and rapid multi-residue screening method for the quantification and confirmation of 100 multi-class veterinary drugs in milk powder by the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method combined with liquid chromatography coupled to quadrupole time-of-flight mass spectrometry was developed. The veterinary drugs investigated belonged to several families such as macrolides, sulfonamides, quinolones, tetracyclines, nitroimidazoles, benzimidazoles, β-agonists, hormones, and tranquilizers. The samples were extracted using a modified QuEChERS procedure: (i) dissolved in a solution of Na2EDTA–McIlvaine buffer (0.1 M, pH 4), (ii) extracted with 5% acetic acid in acetonitrile, and (iii) purified using a C18 sorbent. The linearity, sensitivity, accuracy, repeatability, and reproducibility of the method were fully validated. The average recoveries for the majority of analytes (92.9%) ranged from 70 to 120% at four concentration levels, while the repeatability and reproducibility ranged from 1.1 to 20.1%. A coefficient of correlation (γ2) of 0.995 or above was obtained for all the compounds. The range of the limit of quantification for these compounds in the milk powder was from 0.1 to 25 μg kg−1. More than 93.0% of the analytes were detected when present at 10 μg kg−1 or less in the milk powder samples. For the screening method, the data of the precursor and product ions of the target analytes were simultaneously acquired under the All Ions MS/MS mode in a single run. A homemade library including the elemental composition, retention time, and full-scan product ions was utilized for the confirmation and identification of the target compounds. The applicability of the screening method was verified by applying to real milk powder samples, and certain veterinary drugs were detected in some cases.

Determination of nine phthalate ester metabolites in human urine using ultra high performance liquid chromatography-tandem triple quadrupole mass spectrometry

A method was developed to determine trace concentrations of phthalate ester (PAE) metabolites in human urine by using ultra high performance liquid chromatography-triple quadrupole mass spectrometry. Aliquots (2 mL) of human urine samples were purified using strong anion-exchange solid-phase extraction after enzymatic deconjugation by glucuronidase for 2 h. The separation was performed on a Waters ACQUITY UPLC BEH Phenyl column (100 mm×2.1 mm, 1.7 μ m) with gradient elution by 0.1% (v/v) acetic acid in acetonitrile and 0.1% (v/v) acetic acid aqueous solution. The concentrations of nine PAE metabolites were determined under a multiple reaction monitoring mode by negative electrospray ionization. Eight of the determined metabolites showed good linearities in the range of 0.39-200 μ g/L, and the ninth metabolite showed linearity in the range of 1.17-600 μ g/L with correlation coefficients > 0.995. The limits of detection ranged from 0.06 to 0.85 μ g/L, and the limits of quantification ranged from 0.20 to 2.80 μ g/L. The recovery rates at all three spiked levels ranged from 84.1% to 122% with relative standard deviations between 4.5% and 14.3%. The intra-and inter-day precisions were not more than 10.1% and 9.3%, respectively. The matrix effect and stability were found to be favorable for analysis. This method was utilized for the determination of 50 human urine samples. The detection rates of monocyclohexyl phthalate (MCHP) and monobenzyl phthalate (MBZP) were 0 and 44.0%, and the detection rates of the other seven PAE metabolites was 100%. This method has the advantage of convenient operation and good accuracy and stability, and is suitable for the quantitative determination of the nine PAE metabolites in human urine.

Simultaneous determination of ten constituents in herbal formulation Sipjeondaebo-tang using HPLC-PDA

A simple, rapid, and accurate high-performance liquid chromatographic method was applied to the quantitative determination of 10 components, namely, 5-hydroxymethyl-2-furaldehyde, albiflorin, paeoniflorin, liquiritin, ferulic acid, nodakenin, coumarin, cinnamic acid, cinnamaldehyde and glycyrrhizin in the traditional herbal formulation Sipjeondaebo-tang (SJDBT). All components were separated within 40 min using a Gemini C18 column maintained at 40°C. The mobile phase was composed of 1.0% (v/v) aqueous acetic acid and 1.0% (v/v) acetic acid in acetonitrile by gradient elution. The flow rate was 1.0 mL/min and the detector was a photodiode array (PDA) set at 230, 254, 280, 320, and 330 nm. The calibration curves showed good linearity (r2 ≥ 0.9993) in different concentration ranges. The recovery of each component was in the range of 92.3–104.8%, with relative standard deviations (RSDs) less than 2.5%. The RSDs for intra- and inter-day precision were 0.09–2.8% and 0.07–3.2%, respectively. The amounts of the 10 components in SJDBT were in the range of 0.18–5.77 mg/g.

Very fast capillary electrophoresis with electrochemical detection for high-throughput analysis using short, vertically aligned capillaries.

A method for conducting fast and efficient capillary electrophoresis (CE) based on short separation capillaries in vertical alignment was developed. The strategy enables for high-throughput analysis from small sample vials (low microliter to nanoliter range). The system consists of a lab-made miniaturized autosampling unit and an amperometric end-column detection (AD) cell. The device enables a throughput of up to 200 separations per hour. CE-AD separations of a dye model system in capillaries of only 4 to 7.5cm length with inner diameters (ID) of 10 or 15μm were carried out under conditions of very high electric field strengths (up to 3.0kV/cm) with high separation efficiency (half peak widths below 0.2s) in less than 3.5s migration time. A non-aqueous background electrolyte, consisting of 10mM ammonium acetate and 1M acetic acid in acetonitrile, was used. The practical suitability of the system was evaluated by applying it to the determination of dyes in overhead projector pens.

HPLC-PDA Simultaneous Determination and Protective Effect of Anemarrhena asphodeloides Against Acute Renal Failure

We investigated the protective effects against acute renal failure (ARF) of Anemarrhena asphodeloides (AA) and performed simultaneous analysis of three compounds, neomangiferin (1), mangiferin (2), and isomangiferin (3) in AA using a high-performance liquid chromatography-photodiode array. To measure the protective effect of ARF, the levels of reactive oxygen species (ROS) and glutathione depletion were determined using a kit. HPLC analysis was performed using a Gemini Cia column at 40 degrees C. The mobile phase used gradient elution with 1.0% (v/v) aqueous acetic acid (A) and 1.0% (v/v) acetic acid in acetonitrile (B). The flow rate was 1.0 mL/min. In our assay, AA extract inhibits cisplatin-induced production of intracellular ROS. Pre-incubation of AA extracts (10-200 microg/mL) markedly maintained cell viability compared with controls in the noncisplatin-treated cells. Calibration curves of all compounds showed good linearity (r2 > or = 0.9992). Recoveries of the three compounds were 98.9-103.4%. The relative standard deviations of intra- and inter-day precision were 0.07-1.73% and 0.12-1.49%, respectively. The amounts of the three components were 1.22-20.63 mg/g. The AA extract has potential as a therapeutic agent for treatment of ARF. In addition, the established method will help to improve quality control of AA.

HPLC–DAD–FLD Determination of Veterinary Pharmaceuticals in Pharmaceutical Industry Wastewater with Precolumn Derivatization Using Fluorescamine

A simple and robust method suitable for routine analysis of pharmaceuticals from different classes in pharmaceutical industry wastewater samples is presented. Seven veterinary pharmaceuticals (antibiotics and anesthetic) were simultaneously isolated from a highly complex wastewater matrix. Target compounds were three sulfonamide antibiotics (sulfaguanidine, sulfadiazine, and sulfamethazine), three fluoroquinolone antibiotics (ciprofloxacin, enrofloxacin, norfloxacin), and one anesthetic, procaine. The investigated compounds were simultaneously pre-concentrated and cleaned up by solid-phase extraction using Strata-X extraction cartridges. The analysis was performed using liquid chromatography (LC) with diode array and fluorescence detectors connected in series to the chromatographic system. LC separation was performed on a C18 modified column (Phenomenex) with a gradient elution of mobile phase (0.1 % acetic acid in water and 0.1 % acetic acid in acetonitrile) in 25 min at 30 °C. Recoveries ranged from 86.9 to 110 % with relative standard deviations below 10.1 %. Method limits of quantification were in the range of 0.005–0.1 μg L−1 depending on the fluorescence intensity after precolumn derivatization by fluorescamine.

Simultaneous determination of multi-class veterinary drug residues in different muscle tissues by modified QuEChERS combined with HPLC-MS/MS

A novel method for the determination of 55 multi-class veterinary drug residues in different muscle tissues (porcine, bovine and ovine animals) by modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) combined with high performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-MS/MS) is described. The veterinary drugs focused on here belong to several families, such as macrolides, quinolones, sulfonamides, benzimidazoles, and β-agonists (unbound). The samples were first extracted with 5% acetic acid in acetonitrile, followed by cleanup with QuEChERS and sequential analysis by HPLC-MS/MS technique. It was found that the majority of analytes (89.1%) can achieve the mean recoveries between 70% and 120% in the examined matrices. The repeatability and reproducibility are lower than 20% for 94.1% and 90.3% of total analytes in these matrices, respectively. 86.7% of the compounds could have γ2 of 0.99 or above. The range of limits of quantification (LOQ) for these compounds in porcine, bovine and ovine is 0.1 to 18.4 μg kg−1, 0.1 to 20.0 μg kg−1, and 0.1 to 18.4 μg kg−1, respectively. Finally, the method was applied to real samples, and ofloxacin was found in one bovine sample at 2.5 μg kg−1. The method is sensitive, accurate, quick and simple, and suitable for the routine analysis of meat products.

Synthesis and structures of dinickel(II) complexes with a binucleating ligand, N,N′-bis[3-(N,N-dimethyl)aminopropyl]-N,N′-dimethyl-1,3-diamino-2-hydroxypropane (HL1), and investigation of carboxylic acid capture assisted by intramolecular hydrogen bonding

New carboxylic-acid-coordinated dinickel(II) complexes with binucleating ligands—HL1, which contains dimethylaminopropyl arms, and its analog HL2, which contains one dimethylaminopropyl arm and one bis(methoxyethyl) arm—both of which contain a 2-hydroxytrimethylene bridge between the two chelating sites, were synthesized. The structures of acetic acid coordinated complexes, [Ni2L1(μ-CH3COO)2(CH3COOH)]BPh4 (1), and [Ni2L2(μ-CH3COO)2(CH3COOH)]BPh4 (6), a propionic acid coordinated complex, [Ni2L1(μ-C2H5COO)2(C2H5COOH)]BPh4 (3), and a benzoic acid coordinated complex, [Ni2L1(μ-PhCOO)2(PhCOOH)]BPh4 (4) were revealed by X-ray crystallography, as well as those of the parent dinickel(II) complexes [Ni2L1(μ-CH3COO)2]BPh4 (2), and [Ni2L2(μ-CH3COO)2]BPh4 (5). In complexes 1, 3, 4, and 6, one carboxylic acid molecule is coordinated to one of the dinuclear nickel(II) ions, forming an intramolecular hydrogen bond with a μ-alkoxo bridge. Spectrophotometric investigation revealed that complex 1 underwent partial dissociation of the acetic acid in acetonitrile to give an equilibrium between 1 and 2, and that 2 reversibly associated with an acetic acid molecule in acetonitrile to form 1. Intramolecular hydrogen bonding plays an important role in the stabilization of carboxylic acid coordination to the dinickel(II) complexes with binucleating ligands.

Simultaneous quantification and inhibitory effect on LDL oxidation of the traditional Korean medicine, Leejung-tang

BackgroundLeejung-tang (LJT) is a traditional Korean herbal medicine for the treatment of gastrointestinal disorders. In this study, we performed quantification analysis of five marker components, liquiritin (1), ginsenoside Rg1 (2), ginsenoside Rb1 (3), glycyrrhizin (4), and 6-gingerol (5) in LJT using a high performance liquid chromatography-photodiode array (HPLC–PDA). In addition, we investigated the inhibitory effect on low-density lipoprotein (LDL) oxidation by the LJT sample.MethodsCompounds 1–5 were separated within 35 min using a Gemini C18 column. The mobile phase used gradient elution with 1.0% (v/v) aqueous acetic acid (A) and 1.0% (v/v) acetic acid in acetonitrile (B). The flow rate was 1.0 mL/min and the detector was a photodiode array (PDA) set at 203 nm, 254 nm, and 280 nm. The inhibitory effect on LDL oxidation conduct an experiment on thiobarbituric acid reactive substance (TBARS) assay, relative electrophoretic mobility (REM) assay, and electrophoresis of ApoB fragmentation of LJT.ResultsCalibration curves of compounds 1–5 showed good linearity (r2 ≥0.9995) in different concentration ranges. The recoveries of compounds 1–5 were in the range of 98.90–103.39%, with relative standard deviations (RSD) below 3.0%. The RSDs (%) of intra-day and inter-day precision were 0.10–1.08% and 0.29–1.87%, respectively. The inhibitory effect of LJT on Cu2+-induced LDL oxidation was defined by TBARS assay (IC50: 165.7 μg/mL) and REM of oxLDL (decrease of 50% at 127.7 μg/mL). Furthermore LJT reduced the fragmentation of ApoB of oxLDL in a dose-dependent manner.ConclusionsThe established HPLC-PDA method will be helpful to improve quality control of LJT. In addition, LJT is a potential LDL oxidation inhibitor.

방풍통성산의 동시분석 및 항산화 효능 연구

Objectives : We carry out the simultaneous quantification for quality control of four components in Bangpungtongseong-san (BPTSS) sample. In addition, we assessed the antioxidant effects of BPTSS sample. Methods : The used column for separation and analysis of four compounds was Luna C18 column and column oven temperature was maintained at <TEX>$40^{\circ}C$</TEX>. The mobile phase for simultaneous determination consisted of two solvent systems, 1.0% acetic acid in water and 1.0% acetic acid in acetonitrile. High performance liquid chromatography-photodiode array (HPLC-PDA) method for analysis was performed at a flow rate of 1.0 mL/min with PDA detection at 254 and 280 nm. The injection volume was 10 <TEX>${\mu}L$</TEX>. The antioxidant activities of BPTSS were evaluated by measuring free radical scavenging activities on 2,2'-Azinobis-3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) and 1-1-diphenyl-2-picrylhydrazyl (DPPH). The inhibitory effects on low-density lipoprotein (LDL) oxidation were evaluated by the formation of thiobarbituric acid relative substances (TBARS) and relative electrophoretic mobility (REM). Results : Calibration curves were acquired with <TEX>$r^2{\geq}0.9999$</TEX>. The values of limit of detection (LOD) and quantification (LOQ) were 0.06-0.29 <TEX>${\mu}g/mL$</TEX> and 0.20-0.98 <TEX>${\mu}g/mL$</TEX>, respectively. The amounts of geniposide, liquiritin, baicalin, and glycyrrhizin in BPTSS were 5.06, 7.33, 27.56, and 7.81 mg/g, respectively. The BPTSS showed the radical scavenging activity in a dose-dependent manner. The concentration required for 50% reduction (RC50) against ABTS and DPPH radicals were 72.51 <TEX>${\mu}g/mL$</TEX> and 128.49 <TEX>${\mu}g/mL$</TEX>. Furthermore, GMGHT reduced the oxidation properties of LDL induced by CuSO4. Conclusions : The established HPLC-PDA method will be helpful to improve quality control of BPTSS. In addition, BPTSS has potentials as therapeutic agent on anti-atherosclerosis.

Development and validation of a UPLC‐MS/MS method for the determination of 7‐hydroxymitragynine, a μ‐opioid agonist, in rat plasma and its application to a pharmacokinetic study

A simple, sensitive and specific ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated to determine the concentrations of 7-hydroxymitragynine in rat plasma. Following a single-step liquid-liquid extraction of plasma samples using chloroform, 7-hydroxymitragynine and the internal standard (tryptoline) were separated on an Acquity UPLC(TM) BEH C18 (1.7 µm, 2.1 × 50 mm) column using an isocratic elution at a flow rate of 0.2 mL/min. The mobile phase consisted of 0.1% acetic acid in water and 0.1% acetic acid in acetonitrile (10:90, v/v). The run time was 2.5 min. The analysis was carried out under the multiple reaction-monitoring mode using positive electrospray ionization. Protonated ions [M + H](+) and their respective product ions were monitored at the following transitions: 415 → 190 for 7-hydroxymitragynine and 173 → 144 for the internal standard. The calibration curve was linear over the range of 10-4000 ng/mL (r(2) = 0.999) with a lower limit of quantification of 10 ng/mL. The extraction recoveries ranged from 62.0 to 67.3% at concentrations of 20, 600 and 3200 ng/mL). Intra- and inter-day assay precisions (relative standard deviation) were <15% and the accuracy was within 96.5-104.0%. This validated method was successfully applied to quantify 7-hydroxymitragynine in rat plasma following intravenous administration.

Microwave-assisted derivatisation and LC-MS/MS determination of nitrofuran metabolites in farm-raised prawns (Penaeus monodon)

A new microwave-assisted derivatisation and LC-MS/MS method has been developed for the analysis of nitrofuran metabolites – 3-amino-5-morpholino-methyl-1,3-oxa-zolidinone (AMOZ), 3-amino-2-oxazolidinone (AOZ), 1-aminohydantoin (AHD) and semicarbazide (SEM) – in farm-raised prawns (Penaeus monodon) from the coastal regions of South India. Analysis was carried out by reverse-phase column (Phenomenex Luna C18) with gradient elution using mobile phase A (0.02% acetic acid in water) and mobile phase B (0.02% acetic acid in acetonitrile), at a flow rate of 200 μl min–1 and an injection volume of 20 μl. Microwave-assisted derivatisation was achieved in 6 min with good recovery. The results showed that the samples collected from Andhra Pradesh and Karnataka contained residues of nitrofuran metabolites in the range from 5.0 to 40 ng g–1. This work emphasises the importance of ensuring the safety of seafood and that a new method of derivatisation is applicable for the analysis of nitrofuran metabolites in seafood.

Determinative and confirmatory method for residues of tetracyclines in honey by LC-MS/MS

A limited number of substances are authorised for the treatment of bees. Maximum residue limits (MRLs) are set for tetracyclines in several matrices, but not for honey. Nevertheless, tetracycline antibiotics may be used in order to prevent bacterial diseases and the loss of honey bee populations. In this study, a sensitive multi-residue LC-MS/MS method was developed and optimised for the quantitative and qualitative determination of tetracycline residues in honey. Homogenisation of samples under acidic conditions was performed and solid-phase extraction was carried out. The eluate was evaporated under nitrogen and dissolved in an aqueous methanol solution prior to filtration. A mobile phase composed of acetic acid–water and acetic acid–acetonitrile was used. Separation of tetracycline, oxytetracycline, chlortetracycline and doxytetracycline was achieved by using gradient elution on a C18 chromatography column. The analytical method was validated according to Commission Decision 2002/657/EC by the analysis of spiked samples around the recommended concentration of 20 μg kg−1 by EURL Guidance Paper, December 2007. A matrix effect was observed, so quantification was based on an external matrix calibration curve. Calculated decision limits (CCα) were lower than 10 μg kg–1 for all tetracyclines. Good linearity, repeatability and within-laboratory reproducibility were achieved.

HPLC-PDA을 이용한 이진탕 중 6종 성분의 동시분석

Objectives : Yijin-tang has been used in the treatment of gastrointestinal diseases such as irritable bowel syndrome, gastritis, and gastric ulcer. In this study, a high-performance liquid chromatography (HPLC) method was established for simultaneous analysis of six compounds, liquiritin, glycyrrhizin, hesperidin, 6-gingerol, homogentisic acid, and 3,4-dihydroxybenzaldehyde in Yijin-tang, a traditional Korean herbal medicinal preparation. Methods : A Gemini C18 column was used for the separation of six constituents at <TEX>$40^{\circ}C$</TEX>. The mobile phase using gradient elution consist of two solvent systems, 1.0% acetic acid in water (A) and 1.0% acetic acid in acetonitrile (B). The flow-rate was 1.0 mL/min and injection volume was <TEX>$10{\mu}g$</TEX>. The detector was a photodiode array (PDA) detector set at 254 nm and 280 nm. Results : The calibration curves of six compounds showed good linearity in various concentration ranges (<TEX>$R^2{\geq}0.9997$</TEX>). The limits of detection (LOD) and limits of quantification (LOQ) were 0.028-<TEX>$0.192{\mu}g/mL$</TEX> and 0.093-<TEX>$0.540{\mu}g/mL$</TEX>, respectively. The RSD (%) of the intra and inter day validations were 0.03-0.84% and 0.05 -1.00%, respectively. Recovery was 96.14-01.90% and RSD (%) was less than 1.5%. Conclusions : The established simultaneous analysis methods will help management to improve the quality of Yijin-tang.

Determination of Pyrethroids in Environmental Waters Using Magnetic Chitosan Extraction Coupled with High Performance Liquid Chromatography Detection

The magnetic chitosan was prepared by adding chitosan, Fe2+ and Fe3+ into a basic precipitant of NaOH solution. The synthetic magnetic chitosan was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and physical properties. The adsorption characteristics of magnetic chitosan for extracting pyrethroids from water samples were investigated. The analytes were separated by magnetic solid phase extraction and determined by high performance liquid chromatography. The optimum conditions of adsorption experiments were obtained: the amount of sorbent was 80 mg, the extraction time was 20 min, the washing solvent was 50% aqueous methanol, and the eluent was acetonitrile-acetic acid (99: 1, v/v). The obtained linearity of three pyrethroids was in the range of 30–3000 ng L−1. The detection limits of beta-cyfluthrin, cyhalothrin, and cyphenothrin were 7.5, 5.6, and 6.1 ng L−1, respectively. The intra-day and inter-day precisions of three pyrethroids were in the range of 3.6–5.2% and 5.9–8.6%, respectively. In the optimized conditions, three water samples were analyzed, and the recoveries of pyrethroids obtained were 83.2–95.2%.

A simple method for the determination of fluoroquinolone residues in tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) employing LC-MS/MS QToF

The use of antimicrobials in livestock production is a powerful resource applied throughout the world to guarantee high yield and control bacterial diseases in aquaculture. However, residues of these substances in animal products represent a potential risk to consumer health when residue levels are above the established maximum residue limits (MRLs). Fluoroquinolones (FQs) are antimicrobials commonly used worldwide in aquaculture. The aim of this work was to develop and validate a simple analytical method for the simultaneous determination of norfloxacin, danofloxacin, enrofloxacin and ciprofloxacin levels in tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) fillets using liquid chromatography–tandem mass spectrometry (LC-MS/MS) quadrupole time of flight (QToF). The FQs were extracted from the fillets with 1% acetic acid–methanol and 1% acetic acid–acetonitrile solutions using ultrasonic assistance. The clean-up was performed with hexane. Chromatographic separation was conducted in an XTerra RP18 column (2.1 × 150 mm, 5 µm) at 25 °C with a flow of 0.2 mL min−1. The mobile phase consisted of 0.1% aqueous formic acid and acetonitrile, with gradient elution. The validation parameters for all FQs were linearity (>0.99), intra-day precision (CV of 1%–9%), inter-day precision (CV of 3%–17%), decision limit (63–126 ng g−1), detection capability (76 –152 ng g−1) and accuracy (90%–111%). The limit of quantification was lower than the MRL for each FQ, indicating that the method is suitable for the determination of the FQ levels in the fish fillets. The mass analyser of the QToF type was able to confirm the identities of the FQs with an error of the accuracy of the mass (reasons m/z) of less than 10 ppm.