A method was developed to simultaneously detect six resorcylic acid lactones in feed by GC–MS. Samples were extracted with methanol followed by a two step liquid–liquid extraction and an HLB SPE clean-up. The samples were derivatized with BSTFA + TMCS (99/1; v/v) and determined by GC–MS. For all analytes, the ranges of recoveries were 81.2–98.2%, with RSDs of 3.2–15.2%, and the LODs were 0.2–0.6 μg kg−1.
相似文献A new technique, namely dynamic headspace liquid-phase microextraction, has been developed for the extraction of 1,4-dioxane in cosmetic and hygiene samples followed by gas chromatography–flame ionization detection. In this method, the sample is mixed with acetone as a diluent solvent. Then, a few microliters of n-octanol are added into a home-made extraction vessel placed in the headspace of the sample. By heating, the target analyte is transferred to the headspace of the sample and then extracted into n-octanol. Under the optimized conditions, the method showed a good linearity in the range of 3.24–1000 μg kg−1 with a coefficient of determination 0.998. Figures of merit such as enrichment factor of 375, extraction recovery of 94 %, limits of detection and quantification 0.97 and 3.24 μg kg−1, respectively, and relative standard deviation 4.7 % (n = 6, C = 30 μg kg−1) of the proposed method were satisfactory for determination of the target analyte. Finally, the method was successfully applied in determination of 1,4-dioxane in various cosmetic and hygiene samples including shampoo, toothpaste, lotion, washing liquid, and dishwashing liquid.
相似文献A new method was performed using on-line coupling of nonchiral reversed-phase liquid chromatography (RP-LC) to circular dichroism (CD) spectroscopy for simultaneous determination of artemisinin and arteannuin B in crude plant extracts of Artemisia annua. Analysis was carried out on an LC–CD system equipped with an Agilent TC-C18 column (4.6 mm I.D. × 200 mm L, 5 μm) using gradient of acetonitrile. The method was validated to be practicable and reliable at alterable wavelength in the ranges of 220–420 nm as desired. LOD and LOQ of artemisinin and arteannuin B were 0.08, 0.26 and 0.31, 1.02 μg mL−1, respectively. It was more sensitive than conventional LC–UV and comparatively cheaper than LC–MS in analysis of TCM.
相似文献A reversed-phase liquid chromatography (RP-LC) method was validated for the determination of rupatadine in pharmaceutical dosage forms. The LC method was carried out on a Gemini C18 column (150 mm × 4.6 mm I.D.), maintained at 30 °C. The mobile phase consisted of ammonium acetate buffer (pH 3.0; 0.01 M) with 0.05% of 1-heptanesulfonic acid–acetonitrile (71.5:28.5, v/v), run at a flow rate of 1.0 mL min−1 and using photodiode array (PDA) detection at 242 nm. The chromatographic separation was obtained with retention time of 5.15 min, and was linear in the range of 0.5–400 μg mL−1 (r 2 = 0.9999). The specificity and stability-indicating capability of the method was proven through the degradation studies and showing also, that there was no interference of the excipients. The accuracy was 100.39% with bias lower than 0.58%. The limits of detection and quantitation were 0.01 and 0.5 μg mL−1, respectively. Moreover, method validation demonstrated acceptable results for precision, sensitivity and robustness. The proposed method was applied for the analysis of pharmaceutical dosage forms assuring the therapeutic efficacy.
相似文献A quick, easy, cheap, rugged, effective, and safe (QuEChERS)-based method has been validated for the extraction of 42 pesticides and herbicides including organophosphorus pesticides (OPPs), carbamate pesticides (CBs), herbicides (HBs), organochlorine pesticides (OCPs), and synthetic pyrethroid pesticides (PYRs) from chicken eggs. The QuEChERS-based extraction procedure was followed by cleanup steps using C18 and primary secondary amine sorbents. The supernatant was analyzed by ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) and gas chromatography–mass spectrometry (GC–MS). The OPPs, CBs, and HBs were quantified by UHPLC–MS/MS, while the OCPs and PYRs were detected by GC–MS. The limits of quantification ranged from 0.01 to 8.5 μg kg−1, and the analyte recoveries were in the range of 64.9–123.2 %. Furthermore, the repeatabilities (intra-day and inter-day) were good, and linear matrix-matched calibration curves were obtained. Acetochlor was identified in concentrations ranging from 0.27 to 0.44 μg kg−1 in four samples from 80 chicken eggs. The method was successfully demonstrated for the fast and reliable analysis of pesticides and herbicides in chicken egg samples.
相似文献A simple, specific and sensitive liquid chromatographic method has been developed for the assay of ketorolac in human plasma and urine. The clean-up of plasma and urine samples were carried out by protein precipitation procedure and liquid–liquid extraction, respectively. Separation was performed by a Waters sunfire C18 reversed-phase column maintained at 35 °C. The mobile phase was a mixture of 0.02 M phosphate buffer (pH adjusted to 4.5 for plasma samples and to 3.5 for urine samples) and acetonitrile (70:30, v/v) at a flow rate of 1.0 mL min−1. The UV detector was set at 315 nm. Nevirapine was used as an internal standard in the assay of urine sample. The method was validated over the concentration range of 0.05–8 and 0.1–10 μg mL−1 for ketorolac in human plasma and urine, respectively. The limits of detection were 0.02 and 0.04 μg mL−1 for plasma and urine estimation at a signal-to-noise ratio of 3. The limits of quantification were 0.05 and 0.1 μg mL−1 for plasma and urine, respectively. The extraction recoveries were found to be 99.3 ± 4.2 and 80.3 ± 3.7% for plasma and urine, respectively. The intra-day and inter-day standard deviations were less than 0.5. The method indicated good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. This assay demonstrated to be applicable for clinical pharmacokinetic studies.
相似文献A sensitive and simple LC method for the quantification of ginkgolic acids in mice plasma has been developed. Following acetonitrile deproteinization, samples were separated on a SinoChrom ODS-AP C18 column. The mobile phase was 3% (v/v) acetic acid water solution–methanol (8:92, v/v) at a flow rate of 1.0 mL min−1. Detection was at 310 nm. Calibration curve was linear over the range of 0.25–50 μg mL−1 with intra- and inter-day precisions (RSD%) of less than 9.5%. The extraction recovery ranged from 87.0 to 90.2% (RSD 2.4–6.4%) for ginkgolic acids. The method was successfully applied to the pharmacokinetic study of ginkgolic acids in mice after oral dosing of 1.0 g kg−1.
相似文献Rapid, inexpensive, and efficient sample-preparation by dispersive liquid–liquid microextraction (DLLME) then gas chromatography with flame ionization detection (GC–FID) have been used for extraction and analysis of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) in water samples. In this extraction method, a mixture of 25.0 μL carbon disulfide (extraction solvent) and 1.00 mL acetonitrile (disperser solvent) is rapidly injected, by means of a syringe, into a 5.00-mL water sample in a conical test tube. A cloudy solution is formed by dispersion of fine droplets of carbon disulfide in the sample solution. During subsequent centrifugation (5,000 rpm for 2.0 min) the fine droplets of carbon disulfide settle at the bottom of the tube. The effect of several conditions (type and volume of disperser solvent, type of extraction solvent, extraction time, etc.) on the performance of the sample-preparation step was carefully evaluated. Under the optimum conditions the enrichment factors and extraction recoveries were high, and ranged from 122–311 to 24.5–66.7%, respectively. A good linear range (0.2–100 μg L−1, i.e., three orders of magnitude; r 2 = 0.9991–0.9999) and good limits of detection (0.1–0.2 μg L−1) were obtained for most of the analytes. Relative standard deviations (RSD, %) for analysis of 5.0 μg L−1 BTEX compounds in water were in the range 0.9–6.4% (n = 5). Relative recovery from well and wastewater at spiked levels of 5.0 μg L−1 was 89–101% and 76–98%, respectively. Finally, the method was successfully used for preconcentration and analysis of BTEX compounds in different real water samples.
相似文献Determination of flavonoid markers quercetin, hesperetin, and chrysin, found in north Iranian citrus honey samples, was carried out by solid phase extraction (SPE) and isocratic liquid chromatographic separation using central composite design. Optimum conditions for SPE were achieved using 10 mL methanol/water (13:87, v/v, pH = 7) as the washing solvent and 4 mL methanol for elution. Good clean-up and high recovery >90% were observed for all analytes. The use of water/ACN/THF/AcOH (54:36:5:5, v/v) was found to serve as the optimum mobile phase composition and allowed for the separation of analytes from endogenous compounds present in honey. SPE parameters, such as maximum loading capacity and breakthrough volume, were also determined for each analyte. Limit of detection, linear range, recovery, repeatability of retention times, and peak heights were 3.11 × 10−8–4.44 × 10−8 g g−1, 0.50–50.0 μg mL−1 (R 2 > 0.99), 90.7–96.9%, 3.0–3.6%, and 1.0–2.6%, respectively. Precision of the overall analytical procedure, estimated by five replicate measurements for quercetin, hesperetin and chrysin in citrus honey, as well as the relative standard deviations were 4.3%, 3.8%, and 5.5%, respectively.
相似文献A sensitive, simple, and accurate method for determination and pharmacokinetic study of ferulic acid and isoferulic acid in rat plasma was developed using a reversed-phase column liquid chromatographic (RP-LC) method with UV detection. Sample preparations were carried out by protein precipitation with the addition of methanol, followed by evaporation to dryness. The resultant residue was then reconstituted in mobile phase and injected into a Kromasil C18 column (250 × 4.6 mm i.d. with 5 μm particle size). The mobile phase was methanol-1% formic acid (33:67, v/v). The calibration plots were linear over the range 5.780–5780 ng·mL−1 for ferulic acid and 1.740–348.0 ng·mL−1 for isoferulic acid. Mean recoveries were 85.1% and 91.1%, respectively. The relative standard deviations (RSDs) of within-day and between-day precision were not above 15% for both of the analytes. The limits of quantification were 5.780 ng·mL−1 for ferulic acid and 1.740 ng·mL−1 for isoferulic acid. This RP-LC method was used successfully in pharmacokinetic studies of ferulic acid and isoferulic acid in rat plasma after intravenous injection of Guanxinning Lyophilizer.
相似文献A simple and sensitive method was developed for the determination of three nonsteroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, naproxen and fenbufen in human plasma. The method involved in column liquid chromatographic separation and chemilumenescence (CL) detection based on the CL reaction of NSAIDs, potassium permanganate (KMnO4) and sodium sulfite (Na2SO3) in sulfuric acid (H2SO4) medium. The chromatographic separation was carried out using a reversed-phase C18 column, which allowed the selective determination of the three medicines in the complicated samples. The special features of the CL detector provided lower LOD for determination than that of existing chromatographic alternatives. The results indicated that the linear ranges were 0.01–10.0 μg mL−1 for ibuprofen, 0.001–1.0 μg mL−1 for naproxen, and 0.01–10.0 μg mL−1 for fenbufen. The limits of detection were 0.5 ng mL−1 for ibuprofen, 0.05 ng mL−1 for naproxen and 0.5 ng mL−1 for fenbufen (S/N = 3). All average recoveries were in the range of 90.0–102.3%. Finally, the method had been satisfactorily applied for the determination of ibuprofen, naproxen and fenbufen in human plasma samples.
相似文献A sample preparation method for aflatoxin M1 (AFM1) determination in raw milk was optimized following the quick, easy, cheap, effective, rugged and safe (QuEChERS) strategy, as an alternative to the classic immunoaffinity column clean-up (IAC). The method was adapted to address the complexity of the milk matrix, and to be suitable for final determination by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). This approach proved also to be compatible with the simultaneous extraction of pesticide residues and other contaminants (mycotoxins). Regarding AFM1, satisfactory linearity was achieved and appropriate sensitivity was maintained, using matrix-matched calibration to compensate for the heavy ion suppression. The accuracy and precision, which were determined through recovery studies, were 70–95 %, with the relative standard deviation below 15 % in all of the cases. The limit of detection (LOD, 0.002 μg L−1) and limit of quantification (0.007 μg L−1) are compatible with current worldwide regulations (maximum levels of 0.5 and 0.05 μg L−1). The procedure was applied to samples that were naturally contaminated with a range of AFM1 at LOQ–0.187 μg L−1, with comparable results to IAC clean-up, which was employed as a reference method. Therefore, AFM1 determination in raw milk by UHPLC–MS/MS detection through the present QuEChERS extraction constitutes a reliable alternative to IAC clean-up and exhibits advantages related to cost, accessibility of materials and simplicity of operation.
相似文献A rapid and simple analytical method for the determination of ten chlorinated priority substances (hexachloro-1,3-butadiene, pentachlorobenzene, hexachlorobenzene, hexachlorocyclohexane isomers, heptachlor, and heptachlor epoxides) in fish samples using QuEChERS extraction, dual dispersive solid-phase extraction (dSPE) clean-up, and GC analysis was developed. For the extraction, two published extraction/partitioning procedures were evaluated, and the recoveries obtained for the analytes (in range 54–98 % with RSDs ≤15 %) were in favour of the conventional QuEChERS method. The use of the dual dSPE clean-up yields cleaner extracts than in the case of single dSPE, which enables the use of ECD for the detection of the analytes and simplifies the maintenance of the GC system. The method was optimised using homogenates of chub fish that is frequently sampled for monitoring purposes. The linearity of the method was evaluated using matrix-matched calibration curves (in the range 2–50 μg kg−1), and correlation coefficients (r 2) in the range 0.9927–0.9992 and RSDs of the relative response factors (RRF) below the value of 20 % were achieved. LODs ranged from 0.5 to 1.1 μg kg−1, while LOQs ranged from 1.5 to 3.5 μg kg−1. The accuracy of the method was verified by the analysis of the NIST standard reference material SRM 1946 (Lake Superior Fish Tissue), and most of the analytes of interest presented good agreement with the certified values.
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