Gradient Elution Of Methanol Research Articles

Determination of stearic acid and 12-hydroxyoctadecanoic acid in PEG-60 hydrogenated castor oil by HPLC-ELSD after alkaline hydrolysis

AbstractA rapid and simple method for the determination of stearic acid and 12-hydroxystearic acid in PEG-60 hydrogenated castor oil by high performance liquid chromatography with evaporative light scattering detection was established. The oil sample was first pretreated by alkaline hydrolysis. The analysis was performed on a Zhongpu Develop XD-C18 column (250 mm × 4.6 mm, 5 µm) with gradient elution of methanol and 1% acetic acid aqueous solution at a flow rate of 1.2 mL·min−1 and a column temperature of 40 °C. The drift tube temperature of the evaporative light scattering detection system was set at 40 °C, and the pressure of carrier gas (N2) was 337 kPa. The regression equation revealed a good linear relation (r = 0.9993–0.9995) during the test ranges (119.1–1190.7 μg·mL−1 for 12-hydroxystearic acid, 10.7–107.4 μg·mL−1 for stearic acid). The detection limits of 12-hydroxystearic acid and stearic acid were 1.1 and 2.5 μg·mL−1, the limits of quantitation were 3.2 and 7.4 μg·mL−1, respectively. And the mean recoveries were 101.5 and 101.0%, the corresponding relative standard deviations (RSDs) were 2.1 and 2.8%, respectively. The RSDs corresponding to repeatability (n = 6) were both less than 1.7% in terms of precision. As to the stability, the test results remained stable after 8 h at room temperature (RSDs were both less than 2.6%). The developed method showed high sensitivity, recovery, repeatability and stability, which indicated that the method could be applied as a quality evaluation method for the determination of stearic acid and 12-hydroxyoctadecanoic acid in PEG-60 hydrogenated castor oil.

An ultrahigh-performance liquid chromatography-tandem mass spectrometry method for quantification of methotrexate and 7-hydroxy-methotrexate and application for therapeutic drug monitoring in patients with central nervous system lymphoma.

A method using ultrahigh-performance liquid chromatography-tandem mass spectrometry was developed, validated, and applied to simultaneously determine plasma methotrexate (MTX) and 7-hydroxy-methotrexate (7-OH-MTX) in 117 patients with central nervous system (CNS) lymphoma. The ion transitions utilized were m/z 455.2 > 308.2 for MTX and m/z 471.2 > 324.1 for 7-OH-MTX. Samples were prepared through protein precipitation using methanol. Chromatographic separation was achieved within 3.0 min on a CMS9030 column (Ruixi, 2.1 × 50 mm, 3 μm) through a gradient elution of methanol and a 10% ammonium acetate solution at a flow rate of 0.4 mL/min. The method demonstrated linearity in the concentration range of 0.05-10 μM for MTX and 0.25-50 μM for 7-OH-MTX. The intra- and inter-day inaccuracy ranged from -7.38% to 7.83%, and the imprecision was less than 6.00% for both analytes. The recovery and matrix effect normalized by the internal standard (MTX-D3 ) remained consistent. Both analytes remained stable under nine different storage conditions. In patients with CNS lymphoma, MTX levels at 12 h and 7-OH-MTX levels at 12, 36, and 60 h after dosing in individuals with impaired renal function were significantly higher compared with those with normal renal function. 7-OH-MTX could potentially serve as a superior indicator for nephrotoxicity compared with MTX.

A UHPLC-MS/MS method for the simultaneous determination of vancomycin, norvancomycin, meropenem, and moxalactam in human plasma and its clinical application.

We developed an ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to determine four antibacterial drugs in human plasma for clinical usage. Samples were prepared using protein precipitation with methanol. Chromatographic separation was accomplished in 4.5min on a BEH C18 column (2.1 × 50 mm, 1.7μm) using a gradient elution of methanol and water (containing 7.71 g/L concentrated ammonium acetate, adjusted to pH6.5 with acetic acid) at a flow rate of 0.4 mL/min. Positive electrospray was used for ionization. The method was linear in the concentration range 1-100 μg/mL for vancomycin, norvoncomycin, and meropenem; and 0.5-50 μg/mL for R-isomer of moxalactam and S-isomer of moxalactam. For all analytes, the intra- and inter-day accuracies and precisions were -8.47%-10.13% and less than 12%, respectively. The internal standard normalized recoveries and matrix effect were 62.72%-105.78% and 96.67%-114.20%, respectively. All analytes were stable at six storage conditions, with variations of less than 15.0%. The method was applied in three patients with central nervous system infection. The validated method might be useful for routine therapeutic drug monitoring and pharmacokinetic study.

Development and application of a liquid chromatography coupled to mass spectrometry method for the simultaneous determination of 23 antineoplastic drugs at trace levels

The goal of this study was to develop a method for the simultaneous quantification of 23 commonly used antineoplastic drugs in a hospital pharmacy, using ultra-high pressure liquid chromatography separation coupled to tandem mass spectrometry detection (UHPLC-MS/MS). The following drugs were investigated: 5-fluorouracil, cytarabine, ganciclovir, gemcitabine, dacarbazine, methotrexate, pemetrexed, busulfan, topotecan, rentitrexed, ifosfamide, cyclophosphamide, etoposide, irinotecan, doxorubicin/epirubicin, vincristine, docetaxel, paclitaxel, daunorubicin, idarubicin, vinblastine, oxaliplatin and carboplatin. The chromatographic separation was performed on a phenyl-hexyl column (2.1 ×100 mm, 1.7 µm) with a gradient elution of methanol and water containing 10 mM ammonium formate adjusted to pH 4.9. All compounds were analyzed in less than 13 min and detected with a triple quadrupole mass spectrometer operating in MRM mode. Limits of detection (LODs) and limits of quantification (LOQs) were comprised between 0.01 and 5 ng.mL−1, and between 0.5 and 5 ng.mL−1, respectively. Accuracies ranged between 117% and 83% at the LOQ, intermediate and upper LOQ concentrations, with relative standard deviations (RSD) inferior to 8%, for all the antineoplastic drugs. Finally, the UHPLC-MS/MS method was successfully applied to the analysis of surface samples to evaluate the chemical contamination by these highly toxic compounds in a chemotherapy preparation unit in a hospital pharmacy with the purpose of monitoring the exposure of health care professionals.

Main components in different varieties of Xihuangcao by UPLC-Q-TOF-MS and UPLC-DAD

This study established an ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry(UPLC-Q-TOF-MS) method to analyze the main components in different varieties of Xihuangcao and established a UPLC-DAD method to simultaneously determine the five active components(caffeic acid, rosmarinic acid, schaftoside, isoschaftoside, and oridonin).The chromatographic separation was performed on a Waters ACQUITY UPLC BEH C_(18) column(2.1 mm×100 mm, 1.7 μm) with a gradient elution of methanol(B)-water containing 0.1% formic acid(A) at a flow rate of 0.3 mL·min~(-1).The column temperature was 30 ℃.The Q-TOF-MS discriminant analysis was performed under positive electrospray ion mode and the split ratio was 1∶1. Quantitative analysis was carried out by UPLC-DAD.The determination wavelength was set at 245 nm.Thirty-two main components of Xihuangcao were separated and identified by UPLC-Q-TOF-MS, where 19 were identified in Rabdosia serra, nine in R.nervosa, 10 in R.lophanthoides, 15 in R.lophanthoides var.graciliflora, 10 in R.lophanthoides var.gerardianus, and seven in R.stracheyi.The UPLC-DVD method was developed for simultaneously determining five active components in different varieties of Xihuangcao.The standard curves for five compounds showed good linearity with correlation coefficients higher than 0.999 0.The precision, repeatability, and stability were good.The average recoveries(n=6) were between 97.01% and 102.7% with RSD<3.0%.The results of UPLC-Q-TOF-MS analysis provided a scientific basis for the use of R.stracheyi as a medicinal material of Xihuangcao and the equivalent use of R.lophanthoides var.gerardianus with R.lophanthoides var.graciliflora to some extent.The UPLC-DAD method for simultaneously determining five active components is simple, rapid, and accurate.This study can provide the basis for the quality control of different varieties of Xihuangcao.

Quantification and identification of bile acids in saliva by liquid chromatography-mass spectrometry: Possible non-invasive diagnostics of Barrett's esophagus?

Bile acids are a group of steroid compounds essential for lipid digestion. However, when bile acids are refluxed into the stomach and the esophagus, during the so called duodenogastroesophageal reflux, they can have a detrimental effect on the esophageal epithelium and cause pathological changes of esophageal tissue, e.g., Barrett’s esophagus (BE). The levels of bile acids in saliva could therefore serve as possible biomarkers for the diagnostics of BE. In this work, we focused on optimization of sample collection and preparation by solid-phase extraction and subsequent quantification of 11 bile acids (unconjugated, glycine-conjugated) in saliva from healthy volunteers and BE patients by ultra-high-performance liquid chromatography coupled to triple-quadrupole tandem mass spectrometry. Moreover, high resolution MS (Orbitrap-MS) was utilized for identification of new bile acids in saliva. Methods for saliva collection including simple spitting and the Salivette® saliva collection system were compared; the latter was found to be unsuitable due to excessive retention of bile acids in the cotton swab. Methanol with 0.1% formic acid were selected for protein precipitation and bile acid extraction prior to SPE. Separation was performed in gradient elution of methanol and 0.1% formic acid in less than 10 min. Saliva from BE patients contained higher levels of almost all bile acids, and the tested groups could be distinguished by principal component analysis. In untargeted analysis by high resolution MS, taurine-conjugated bile acids and glycine-conjugated dihydroxy-bile acid sulfate were identified in saliva from healthy volunteers. We propose that analysis of salivary bile acids including taurine conjugates could be applicable in diagnostics of BE, following a larger clinical study.

Green Multiplex Chromatographic Determination of Nine Penicillin Antibiotics Residues in Industrial Air Dust and Wastewater Environmental Samples.

Determination of penicillin residues in different industrial effluents including wastewater and air samples is important to prevent exposure to residual amounts of penicillin and the development of antibiotic resistance. A green high performance liquid chromatography (HPLC) method coupled with diode array detection has been developed and validated for multiplex determination of nine penicillin antibiotics in the industrial air dust and wastewater environmental samples of penicillin facility in addition to the monitoring of facility surface cleaning. Separation was performed on C18 column with gradient elution of methanol and phosphate buffer (pH 4) at a flow rate of 1.5 mL min-1 and ultra violet (UV) detection at 220nm. Low limits of detection were achieved (0.1-0.3 μg mL-1) indicating good sensitivity of the proposed. The method was applied for ensuring the efficiency of cleaning validation after worst-case selection. Recovery studies of the studied penicillins from fortified stainless steel and polycarbonate surfaces and swabs were between 91.91 and 100.22% with relative standard deviation 0.11-1.79%. The presence of any of the studied penicillins in wastewater samples from penicillin plant drainage was checked. Also, total air dust concentration (mg m-3) and % of penicillin active material residues in air dust were calculated from the area of the exposed group in suspension, tablet and vial production lines. The proposed method can be recommended for routine analysis of air and wastewater environmental samples for the detection of penicillin antibiotics at low levels as well as monitoring of facility surface cleaning with high accuracy and precision.

Quantification of KRAS inhibitor sotorasib in mouse plasma and tissue homogenates using liquid chromatography-tandem mass spectrometry

Sotorasib is a KRAS inhibitor with promising anticancer activity in phase I clinical studies. This compound is currently under further clinical evaluation as monotherapy and combination therapy against solid tumors. In this study, a liquid chromatography-tandem mass spectrometric method to quantify sotorasib in mouse plasma and eight tissue-related matrices (brain, liver, spleen, kidney, small intestine, small intestine content, lung, and testis homogenates) was developed and validated. Protein precipitation using acetonitrile was utilized in 96-well format to extract sotorasib and erlotinib (internal standard) from mouse plasma and tissue homogenates. Separation of the analytes was performed on an Acquity UPLC® BEH C18 column by gradient elution of methanol and 0.1% formic acid in water at a flow rate of 0.6 ml/min. Sotorasib was detected by a triple quadrupole mass spectrometer with positive electrospray ionization in selected reaction monitoring mode. A linear calibration range of 2–2,000 ng/ml of sotorasib was achieved during the validation. Accuracy values were in the range of 90.7–111.4%, and precision values (intra- and interday) were between 1.7% and 9.2% for all tested levels in all investigated matrices. The method was successfully applied to investigate the plasma pharmacokinetics and tissue accumulation of sotorasib in female wild-type mice.

Gradient HPLC-DAD method for quantification of novel oral anticoagulant “Edoxaban” in plasma: Its selective determination in presence of sixteen co-administered drugs

As an anticoagulant, Edoxaban (EDX) is a high risk drug that may cause a life-threatening bleeding. Also, it is prescribed as a chronic therapy for atrial fibrillation and venous thromboembolism patients. They are special population that needs appropriate care and optimum dosing of EDX. Hence, its monitoring in the patient plasma is fundamental, especially in emergency and special circumstances. However, such patient mostly receives many drugs of different pharmacological classes, side by side with EDX. This study represents the first attempt to quantify EDX in plasma without interference of the plasma matrix or concomitant medications. An accurate RP-HPLC-DAD method was developed for this purpose. It succeeded to monitor EDX level, selectively, without interference of plasma matrix or 16 of its frequently co-administered drugs. All drugs were extracted from plasma samples by protein precipitation followed by evaporation and concentration. EDX was well resolved from the co-administered drugs on C8 column using linear gradient elution of methanol and phosphate buffer (pH 4), at a flow rate of 1 mL/min. EDX appeared at retention time 9.6 min and was quantified at its λmax (290 nm). It exhibited a linear response over the concentration range of 0.15–2.2 μg/mL plasma which covers the reported therapeutic concentration. The suggested method fulfilled the US FDA guidelines for bioanalytical method validation. The developed method is fully discussed in comparison with the reported techniques. An in vivo study was performed to ensure applicability of the method on real plasma samples without interference from plasma matrix, co-administered drugs or the expected metabolites. It presented a unique selectivity of the method that guarantees accurate laboratory monitoring of EDX in plasma in almost all combined treatments including such novel oral anticoagulant drug.

Study on the contents of aristololactams in piper wallichii and their renal cytotoxicities

In the study, three aristololactams were isolated from Piper wallichii and determined simultaneously by a HPLC method using a C 18 column with a gradient elution of methanol and water. The content ranges of the target compounds in twelve batches of Piper wallichii were 0.100-0.110 mg/g dry weight (cepharanone B), 0.198-0.208 mg/g dry weight (aristolactam AII), and 0.047-0.059 mg/g dry weight (aristololactam AIIIa), respectively. Their anti-proliferative effects in HK-2 cells were determined by MTT assay and cells membrane damage were assessed by LDH release assay. Results indicated that the test compounds showed a time- and dose-dependent cytotoxicity in HK-2 cells, and the values of IC 50 were cepharanone B > aristolactam AII > aristololactam AIIIa.

HPLC–MS/MS analysis of degradation products of neosalvarsan in a 76-year-old injection preparation

High-performance liquid chromatography hyphenated with tandem mass spectrometry (LC–MS/MS) was used to analyze a 76-year-old injection preparation of neosalvarsan. The sample constituents were separated on the reverse phase C18 by the optimized gradient elution of methanol and water. Using electrospray ionization in the negative mode (ESI−), the complete disintegration of neosalvarsan was proved. The structures of two degradation products of neosalvarsan, which are 2-(hydroxymethylamino)-4-arsenosophenol and As-(3-amino-4-hydroxyphenyl)arsonous acid were identified by MS2, and the ESI− fragmentation mechanism was proposed.

Simultaneous determination of 75 abuse drugs including amphetamines, benzodiazepines, cocaine, opioids, piperazines, zolpidem and metabolites in human hair samples using liquid chromatography–tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric method for the simultaneous determination of 75 abuse drugs and metabolites, including 19 benzodiazepines, 19 amphetamines, two opiates, eight opioids, cocaine, lysergic acid diethylamide, zolpidem, three piperazines and 21 metabolites in human hair samples, was developed and validated. Ten-milligram hair samples were decontaminated, pulverized using a ball mill, extracted with 1 mL of methanol spiked with 28 deuterated internal standards in an ultrasonic bath for 60 min at 50°C, and purified with Q-sep dispersive solid-phase extraction tubes. The purified extracts were evaporated to dryness and the residue was dissolved in 0.1 mL of 10% methanol. The 75 analytes were analyzed on an Acquity HSS T3 column using gradient elution of methanol and 0.1% formic acid and quantified in multiple reaction monitoring mode with positive electrospray ionization. Calibration curves were linear (r ≥ 0.9951) from the lower limit of quantitation (2-200 pg/mg depending on the drug) to 2000 pg/mg. The coefficients of variation and accuracy for intra- and inter-assay analysis at three QC levels were 4.3-12.9% and 89.2-109.1%, respectively. The overall mean recovery ranged from 87.1 to 105.3%. This method was successfully applied to the analysis of 11 forensic hair samples obtained from drug abusers.

Simultaneous determination of four components in Sanhuang tablets by RP-HPLC

Objective To establish a RP-HPLC method for simultaneously determining berberine hydrochloride, baicalin, emodin and chrysophanol in Sanhuang tablets. Methods The analysis was performed on an Thermo Hypersil GOLD aQ column (250 mm×4.6 mm, 5.0 μm) with gradient elution of methanol and 0.1% orthophosphoric acid at the flow rate of 1.0 ml/min. The column temperature was 30 ℃, and the detection wave length was 254 nm. Results The peaks of berberine hydrochloride, baicalin, emodin and chrysophanol were successfully separated from each other. The liner ranges of calibration curves were 0-0.6348 μg (r=0.999 9), 0-1.017 2 μg (r=0.999 9), 0-0.802 4 μg (r=0.999 9), 0-0.967 2 μg (r=0.999 9). The average recoveries (n=9) were 101.03%, 99.81%, 99.35%, 99.54%, respectively. The limits of quantification (LOQs) were 0.036 3, 0.021 0, 0.049 7, 0.079 3 mg/g, respectively. The sample solution was stable within 24 h, the RSD (n=5) were 0.48%, 0.56%, 0.68%, 0.49%, respectively. The robustness was investigated by varying the conditions of column temperature (± 1 ℃) and flow rate (± 0.1 ml/min), with the RSD s 0.57% and 0.42%, 0.44% and 0.65%, 0.74% and 0.29%, 0.46% and 0.56%, respectively. The contents of berberine hydrochloride, baicalin, emodin and chrysophanol in twelve samples were 4.630 3-5.586 6, 14.551 4-18.818 9, 0.171 1-2.798 4, 0.529 9-2.925 4 mg/tablet, respectively. Conclusion The establish method is validated to be suitable for quality control of Sanhuang tablets. Key words: Chromatography, reverse-phase; Sanhuang tablets; Berberine; Baicalin; Emodin; Chrysophanol; Quality control; Assay (TCD)

Simultaneous analysis of vitamin D and K in processed food products via ultra high- performance liquid chromatography (UHPLC)

This study highlights a simplified extraction and method development of Ultra High-Performance Liquid Chromatography for simultaneous determination of vitamin D and K in selected processed food products. Simultaneous analysis of vitamin D and K was achieved via gradient elution of methanol with ultra-pure water (95:5–100:0–95:5), at programmed flow rate of (1.0–0.2–1.0 mL/min) for left pump and constant 1 mL/min for right pump within 25 min on HPLC Dionex Ultimate 3000 Series system using two Dionex Acclaim Polar Advantage II C18 columns at 30 °C and acquisition wavelength of 265 nm. The limits of detection and quantification ranged between 0.05 and 0.12 µg/mL and 0.16–0.41 µg/mL; for both vitamins. The method showed good linearity (R2: 0.996–0.999) and high accuracy (85.35–106.36%) for both vitamin D and K. Recovery above 70% was achieved for vitamin D, whereas lower recovery of 60–70% was obtained for vitamin K. The proposed analytical and extraction procedure was advantageous for sample purification and improved detection of trace vitamin levels from selected cereal and flour products.

Determination of coriatin and corianin in plasma and urine using ultra-performance liquid chromatography-triple quadrupole mass spectrometry

An ultra-performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS) method has been developed for the determination of coriatin and corianin in plasma and urine, which are the biomarkers of poisoning caused by Coriaria sinica Maxim. Plasma and urine samples were extracted and purified using a solid supported liquid/liquid extraction method. Chromatographic separation was performed on a Cortecs C18 column (100 mm×2.1 mm, 1.6 μm) using a gradient elution of methanol and water. Coriatin and corianin were detected using negative electrospray ionization tandem mass spectrometry in multiple reaction monitoring (MRM) mode and quantified via a matrix working standard curve internal standard method; florfenicol was used as the internal standard. The assay was linear in the calibration range of 0.03-5.0 μg/L for coriatin and 0.3-50 μg/L for corianin in plasma, and 0.1-10 μg/L and 1-100 μg/L for coriatin and corianin in urine, respectively. The average recoveries were 86.2%-110% for coriatin and corianin in plasma and urine with relative standard deviations of 5.1%-14.6% (n=6). The limits of detection (S/N=3) for coriatin and corianin were 0.01 μg/L and 0.1 μg/L in plasma, and 0.03 μg/L and 0.3 μg/L in urine, respectively. The method is simple, sensitive and accurate for the determination of coriatin and corianin in plasma and urine for toxicological purposes.

Antibacterial Activity of Bohera (Terminaliabellirica) Extract against Dental Carries Causing Bacteria Streptococcus mutans

Dental caries is very common to people of Bangladesh. The treatment of dental carries is very expensive so alternative lowcost option from plant products are important for the rural people. Bohera (Terminaliabellirica) is known to people for its medicinal values. The antibacterial activity of methanolic extracts of bohera bark and fruits were tested against dental caries causing bacteria Streptococcus mutans. It was found that crude extracts of both bark and fruits of bohera have the antibacterial activity against Streptococcus mutans. The crude extract was purified with sillica gel (230-300mesh)with gradient elution of methanol, ethanol and chloroform. The purified extract of bohera also showed strong antibacterial activity against dental caries causing bacteria Streptococcus mutans. The rural people of Bangladesh may use the barks and fruits of bohera to control the dental caries problem locally.J. Environ. Sci. & Natural Resources, 10(2): 117-120 2017

A high‐performance liquid chromatography–tandem mass spectrometry method for simultaneous determination of imigliptin, its five metabolites and alogliptin in human plasma and urine and its application to a multiple‐dose pharmacokinetic study

Imigliptin is a novel DPP-4 inhibitor, designed to treat type 2 diabetes mellitus (T2DM). A selective and sensitive method was developed using high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) to simultaneously quantify imigliptin, its five metabolites, and alogliptin in human plasma and urine. Solid-phase extraction (SPE) and direct dilution were used to extract imigliptin, its five metabolites, alogliptin from plasma and urine, respectively. The extracts were injected onto a SymmetryShield RP8 column with a gradient elution of methanol and water containing 10 mM ammonium formate (pH = 7). Ionization of all analytes was performed using an electrospray ionization (ESI) source in positive mode and detection was carried out with multiple reaction monitoring (MRM) mode. The results revealed that the method had excellent selectivity and linearity. Inter- and intra-batch precisions of all analytes were less than 15% and the accuracies were within 85%-115% for both plasma and urine. The sensitivity, matrix effect, extraction recovery, linearity, and stabilities were validated for all analytes in human plasma and urine. In conclusion, the validation results showed that this method was robust, specific, and sensitive and it can successfully applied to a pharmacokinetic study of Chinese T2DM subjects after oral dose of imigliptin and alogliptin.

Determination of 3 components in Xinjiang Ziziphora bungeana by HPLC

This study aimed to develop an HPLC method for simultaneous determination of the 3 components in Ziziphora bungeana. The optimum HPLC condition was as follows：ZORBAX SB-C₁₈ column（4.6 mm×250 mm, 5.0 μm）with gradient elution of methanol (A)-0.2% glacial acetic acid (B), detection wavelength 340 nm,column temperature 30 °C, flow rate 1 mL·min⁻¹. There were good linearity between peak areas and injection quantity of caffeic acid, rosmarinic acid, and linarin in the range of 2-40 mg·L⁻¹（r=0.999 9）, 3-60 mg·L⁻¹（r=1）, 7-140 mg·L⁻¹（r=0.999 9）, respectively. The average recoveries were 100.9%（RSD 1.3%）,98.25%（RSD 2.0%）,and 98.73%（RSD 1.5%）, respectively. The HPLC method was stable and accurate, which could be used to detect caffeic acid,rosmarinic acid, and linarin in Ziziphora bungeana.

Simultaneous quantitative determination of 11 sesquiterpene lactones in Jerusalem artichoke (Helianthus tuberosus L.) leaves by ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry.

A method of ultra high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry was developed for the simultaneous quantification of 11 sesquiterpene lactones in 11 Jerusalem artichoke leaf samples harvested in a number of areas at different periods. The optimal chromatographic conditions were achieved on a ZORBAX Eclipse Plus C18 column (3.0 × 150mm, 1.8μm) with linear gradient elution of methanol and water in 8min. Quantitative analysis was carried out under selective ion monitoring mode. All of the sesquiterpene lactones showed good linearity (R2 ≥ 0.9949), repeatability (relative standard deviations < 4.66%), and intra- and interday precisions (relative standard deviations < 4.52%) with an accuracy of 95.24-104.84%. The recoveries measured at three concentration levels varied from 95.07 to 104.87% with relative standard deviations less than 4.9%. The limit of detection and limit of quantitation for this method were 0.89-5.05 and 1.12-44.33ng/mL, respectively. The results showed that the contents of sesquiterpene lactones varied significantly in the Jerusalem artichoke leaf samples from different areas. Among them, the content of sesquiterpene lactones in the sample collected from Dalian, Liaoning province was the highest and the early flowering period was considered to be the optimal harvest time.

Rapid determination of benzo[a]pyrene in foods by ultra performance liquid chromatography-triple quadrupole mass spectrometry with atmospheric pressure chemical ionization

A method for the determination of benzo[a]pyrene in foods was developed by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) based on isotope dilution and molecularly imprinted solid-phase extraction (MIP-SPE). The target analyte in samples was extracted with n-hexane after spiked with benzo[a]pyrene-d12, and purified using MIP-SPE to eliminate most of the coextracts. The separation of benzo[a]pyrene was carried out on an XBridge BEH C18 column with gradient elution of methanol and water. An atmospheric pressure chemical ionization (APCI) interface was used as the ion source and the analysis was performed in the multiple reaction monitoring (MRM) mode. Benzo[a]pyrene levels in the range of 0.07-50 μg/kg were measured accurately by this method, and the limit of quantification (LOQ) was 0.07 μg/kg. The average recoveries were between 86% and 104% with the relative standard deviations within 2.3%-14%. The method was sensitive and accurate, and it has been successfully applied to the measurement of benzo[a]pyrene in food samples.