•A two-dimensional column switching system involving SFC and RPLC-MS is developed.•The system works at SFC-MS or SFC-LC-MS mode through switching two six-port valves.•Vitamin D in oily supplements ...can be determined simply and fast using this system.•SFC-LC-MS can get more accurate result with better precision even if using ES method.
A two-dimensional system composed of supercritical fluid chromatography (SFC) and reverse phase liquid chromatography (RPLC) coupled a tandem mass spectrometry (MS) was developed for the quantitative analysis of vitamin D in daily oily supplements. Two six-port switching valves are configured, allowing four different valve positions. When the valve positions were fixed at Position A, this system worked at SFC-MS mode. When the valve positions switched between Position B and C, this system worked at a SFC-LC-MS switching mode. Vitamin D3 in two kinds of oily drops, Baby Ddrops and Vitamin AD drops, was determined at both SFC-MS and SFC-LC-MS switching modes by using the same system. The linearity, repeatability and recovery were investigated using the internal and external standard methods for the two modes. The results obtained from the internal standard method are better than those of the external standard method at either mode. The coefficient of determination (r2) for the internal standard method is more than 0.999, with a linear range of 20–1000 μg/L. Both Baby Ddrops and Vitamin AD drops were analyzed with good repeatability (<3.21%) and recovery (94.1%–116.1%) using internal standard method. When calculated by the external standard method, as compared to SFC-MS mode, SFC-LC-MS switching mode has better linearity (r2>0.999), repeatability (Baby Ddrops: 4.45%, Vitamin AD drops: 1.12%) and recovery (86.3%–107.1%). The results indicate that the two-dimensional SFC-MS/SFC-LC-MS system is useful for determination of vitamin D in oily drops. If it works at SFC-MS mode, the internal standard is required. When SFC-LC-MS switching mode is used, external standard method can also obtain the accurate results with good precision.
► Fully automated microextraction by MEPS coupled with large volume injection GC–MS. ► High sensitive analysis of polycyclic aromatic hydrocarbons in environmental water. ► A better sensitivity with ...MEPS compared with conventional SPE and GC–MS analysis. ► MEPS minimizes the volume of organic solvent for the elution and sample volumes. ► MEPS–GC–MS could be used for screening and monitoring PAHs in environmental waters.
A fully automated microextraction by packed sorbents (MEPS) coupled with large volume injection gas chromatography–mass spectrometry (GC–MS) has been developed for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Naphthalene (Nap), pyrene (Pyr), anthracene, acenaphthylene, phenanthrene, fluoranthene (Flr), fluorene and acenaphthene were the PAHs studied. The performance of the microextraction-GC–MS protocol was compared with solid phase extraction (SPE) and GC–MS analysis. Under optimized experimental conditions, the methods were linear for all analytes in the following ranges: 0.05–2.0μgL−1 (MEPS) and 0.25–10.0μgL−1 (SPE). The correlation coefficients (R2) were in the range 0.9965–0.9997 (MEPS) and 0.9978–0.9998 (SPE) for all the analytes. Limits of detection (LODs) for 2mL samples (MEPS) ranged from 0.8ngL−1 to 8.2ngL−1. LODs for 50mL samples (SPE) were between 4.8ngL−1 and 35.9ngL−1. The two methods were successfully applied to the determination of the 8 PAHs in environmental waters, with recoveries in the range of 70–117% (MEPS) and 72–134% (SPE) for a real spiked sample. The two sample preparation processes showed good repeatabilities with intra-day relative standard deviations below 14.0% (MEPS) and 14.6% (SPE). Nap, Flr and Pyr were found in a river water sample.
Keto-enol tautomers of curcumin were confirmed by reversed-phase liquid chromatography（RPLC）/ hybrid quadrupole ion trap/time-of-flight mass spectrometry（QIT/TOFMS）.Tautomers gave different MS/MS ...spectra in negative mode.Different mass spectra were also obtained by hydrogen/deuterium exchange LC/MS/MS in positive mode.Our results suggest that enol form is the major form in the solution（water/acetonitrile）.
A GC/MS method with monolithic material sorptive extraction (MMSE) pretreatment was developed to determine contents of the enantiomers of jasmonic acid and methyl jasmonate in flowers. To optimize ...MMSE extraction, several MMSE parameters were investigated, including extraction temperature, extraction time, and extraction solvent. Under the optimal conditions, extraction efficiency was good. Using the selected-ion monitoring mode, the limit of detection (LOD, S/N = 3) for methyl jasmonates was 0.257 ng/mL. The limit of quantitation (LOQ, S/N = 10) was 0.856 ng/mL. The linearity range was 1–100 ng/mL. The average recovery of methyl jasmonate at lower concentration was 116.8% (2 ng/mL). The relative standard deviation of methyl jasmonate contents determined within the linear range of detection was less than or equal to 15% of the mean determined level. The proposed method is rapid, sensitive, and competently applied to the determination of jasmonic acid and methyl jasmonate enantiomers in flowers.
•A novel online HPLC-DAD–MSn-DNA-PAL-FLD method was first established.•Using palmatine as the DNA fluorescence probe.•Screen compounds with DNA-binding activity fast and conveniently.•25 Compounds ...were identified and 18 were first found from Lophatherum gracile Brongn.•Evaluate the DNA-binding ability of 12 compounds in L. gracile Brongn.
A high-throughput biochemical detection method based on the combination of high-performance liquid chromatography (HPLC), multiple-stage mass spectrometry (MSn) and DNA-binding activity assay was developed and validated for the simultaneous screening and identification of DNA-binding compounds in complex samples. Palmatine was used as a sensitive, nontoxic and environmentally friendly DNA fluorescence probe. HPLC fingerprints, ultraviolet absorption spectra, MSn fragments of components, and DNA-binding activity profiles could be simultaneously recorded during real-time analysis. Using the proposed method, 25 compounds were identified from Lophatherum gracile Brongn extracts, of which 18 were novel compounds first identified in these extracts. Nineteen compounds showed DNA-binding activity, most of which were flavone glycosides, with distinct dose-effect and structure–activity relationships. The method was validated and was proven to have a good linearity in the range of concentrations used in the study. The limit of detection was 0.2020nmol. Our study indicated that the proposed method was sensitive, accurate, precise and reliable to be used for simultaneous screening and identification of DNA-binding compounds in complex samples.
hloramphenicol is an antibiotic and one of the potential contaminants in honey.Solid-phase extraction is the key pretreatment procedure for analysis of chloramphenicol in honey.In this work,an ...on-line pretreatment liquid chromatography-tandem mass spectrometer system for sensitive,reliable and higher throughput analysis was developed.With the methylcellulose-immobilized reversed-phase column,sugars in a honey sample were efficiently removed in 1 min.As a result,the limit of quantitation of chloramphenicol was 20 pg/mL（0.2 μg/kg honey）.
An automated online gel permeation chromatography–gas chromatograph mass spectrometer (GPC–GC/MS) was developed for the rapid determination of residual pesticides in agricultural products. Pesticides ...were extracted from homogenized food samples with acetonitrile and decontaminated via the matrix solid-phase dispersion (MSPD) technique, using a primary secondary amine as sorbent prior to GPC–GC/MS analysis. A slightly modified preparation method and automated GPC step proved useful in minimizing matrix interference. To evaluate the performance of the system, 97 target pesticides were spiked at a concentration of 0.1
mg/kg into a range of food types, including potato, cabbage, carrot, apple, orange, cucumber, and rice. A low flow rate of 0.1
mL/min in GPC resulted in a 40-fold reduction in solvent consumption compared with conventional GPC column applications. The combination of MSPD technique and GPC–GC/MS for the analysis of the 97 pesticides can be accomplished within 90
min. Most pesticides were recovered in the range of 70–120%, with relative standard deviation generally less than 10%. The results demonstrate that the method can be successfully applied with acceptable recoveries to a broad range of target pesticides within a diverse range of food types.
A solid-phase extraction (SPE) method using triacontyl bonded silica (C30) as sorbent was developed for the determination of 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons ...(PAHs) in airborne particulate matters quantitatively by gas chromatography-mass spectrometry (GC-MS). Optimization experiments were conducted using spiked standard aqueous solution of PAHs and real airborne particulates samples aiming to obtain highest SPE recoveries and extraction efficiency. Factors were studied in SPE procedures including the concentration of organic modifier, flow rate of sample loading and elution solvents. The ultrasonication time and solvents were also investigated. Recoveries were in the range of 68-107% for standard PAHs aqueous solution and 61-116% for real spiked sample. Limits of detection (LODs) and limits of quantification (LOQs) with standard solution were in the range of 0.0070-0.21 microgL(-1) and 0.022-0.67 microgL(-1), respectively. The optimized method was successfully applied to the determination of 16 PAHs in real airborne particulate matters.
A quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample pretreatment method coupled with LC–MS was developed for the determination of 11 pesticides in tobacco. Sample pretreatment ...parameters and instrumental parameters of LC–MS were investigated, and the optimal conditions were selected. Under the optimized conditions, the 11 pesticides were detected simultaneously with a good linear relationship (r2 = 0.9993–0.9999) and high precisions (less than 5% of the RSD of peak areas). The LODs were in the range of 0.1–5.0 μg/L. Compared with SPE clean‐up, QuEChERS greatly simplified the sample pretreatment with simple solvent extraction system. After QuEChERS pretreatment, no serious matrix effects were observed. Used for the analysis of real samples, metalaxyl was found in cigarette and tobacco samples at 63.47 and 132.27 ng/g, respectively. The recoveries for 11 pesticides were in the range of 70.03–118.69%, and RSDs were less than 10%. The proposed method is simple, low cost, and has good reproducibility.
An on-line pretreatment liquid chromatography–tandem mass spectrometry (LC-MS/MS) system was developed for the analysis of chloramphenicol (CAP) in royal jelly. A novel methylcellulose-immobilized ...restricted access media column with a higher-pressure capability of 60 MPa (MC-ODS HP) was developed for the effective removal of proteins and other compounds in the sample matrix. CAP in a sample solution was extracted in 2 min by the column-switching LC-MS/MS system. The system provides a minimum sample pretreatment along with highly sensitive and reproducible analysis. As a result, the limit of quantitation of CAP was 10 pg/mL (= 0.1 μg/kg royal jelly) and the linear dynamic range was between 10 and 10000 pg/mL (correlation coefficient greater than 0.999). The proposed method meets the requirements of regulations in EU (0.3 μg/kg). The inter-day precision and accuracy of CAP at 100 pg/mL over 3 days were 4.5 and 95.4%, respectively. Compared with the conventional method with a pressure of below 25 MPa, the peak separation in the MRM chromatogram was improved by using smaller particles (1.6 μm) for the analytical ODS column. The LC-MS/MS system with an MC-ODS HP expanded the applicability of the automated pretreatment.
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