Ultra-fast Liquid Chromatography-tandem Mass Spectrometry Research Articles

Agarwood Essential Oil Displays Sedative-Hypnotic Effects through the GABAergic System.

Although agarwood has been used as a tranquilizer in Asian countries for hundreds of years, the underlying pharmacological basis is still unclear. This study investigated the sedative-hypnotic effect of agarwood essential oil (AEO) using locomotor activity and pentobarbital-induced sleeping assays in mice. Single (1-day) and multiple (7- and 14-days) administrations of 60 mg/kg AEO generated significant sedative effect on inhibiting locomotor activity and hypnotic effect on pentobarbital-induced sleeping in mice. Interestingly, prolonged AEO treatment did not result in obvious desensitization. Concoitant measurement of the levels of brain neurotransmitters using ultrafast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) indicated that AEO had no significant effect on the levels of glutamic acid (Glu) and γ-aminobutyric acid (GABA) in the brain. However, the sedative-hypnotic effects were blocked by the type A GABA (GABAA) receptor antagonists bicuculline and flumazenil. In addition, AEO significantly elevated the expression of GABAA receptor subunits and subtypes in the cerebral cortex. Furthermore, AEO increased chlorine ion (Cl−) influx through GABAA receptors in human neuroblastoma cells. These results together demonstrate that AEO exerts its sedative-hypnotic effects through regulating gene expression of GABAA receptors and potentiating GABAA receptor function.

Pharmacokinetics of the prototype and hydrolyzed carboxylic forms of ginkgolides A, B, and K administered as a ginkgo diterpene lactones meglumine injection in beagle dogs

AbstractGinkgo diterpene lactones meglumine injection (GDLI) is a commercially available product used for neuroprotection. However, the pharmacokinetic properties of the prototypes and hydrolyzed carboxylic forms of the primary components in GDLI, i.e., ginkgolide A (GA), ginkgolide B (GB), and ginkgolide K (GK), have never been fully evaluated in beagle dogs. In this work, a simple, sensitive, and reliable method based on ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) was developed, and the prototypes and total amounts of GA, GB, and GK were determined in beagle dog plasma. The plasma concentrations of the hydrolyzed carboxylic forms were calculated by subtracting the prototype concentrations from the total lactone concentrations. For the first time, the pharmacokinetics of GA, GB, and GK were fully assessed in three forms, i.e., the prototypes, the hydrolyzed carboxylic forms, and the total amounts, after intravenous administration of GDLI in beagle dogs. It was shown that ginkgolides primarily existed in the hydrolyzed form in plasma, and the ratio of hydrolysates to prototype forms of GA and GB decreased gradually to a homeostatic ratio. All of the three forms of the three ginkgolides showed linear exposure of AUC to the dosages. GA, GB, and GK showed a constant half-life approximately 2.7, 3.4, and 1.2 h, respectively, which were consistent for the forms at three dose levels (0.3, 1.0, and 3.0 mg·kg−1) and after a consecutive injection of GDLI for 7 days (1.0 mg·kg−1).

Development of an ultra-fast liquid chromatography-tandem mass spectrometry method for simultaneous determination of seven flavonoids in rat plasma: Application to a comparative pharmacokinetic investigation of Ginkgo biloba extract and single pure ginkgo flavonoids after oral administration.

For deeper pharmacokinetic investigation and further curative application of ginkgo flavonoids, a delicate, efficient and precise UFLC-MS/MS technique for synchronous quantitation of seven flavonoids, apigenin, luteolin, naringenin, quercetin, diosmetin, kaempferol and isorhamnetin in rat plasma has been established. After mixing with the internal standard (IS) linarin, bio-samples were pretreated via ethyl acetate for liquid-liquid extraction, then isolated at 0.2ml/min flow rate on a Venusil MP C18 chromatographic column (100mm×2.1mm, 3μm) by means of gradient elution. 0.1% formic acid-water and methanol system was used as the mobile phase. Mass spectrometric inspection was conducted on a 4000Q UFLC-MS/MS system with turbo ion spray source in patterns of negative ion and multiple reaction-monitoring (MRM). All calibration curves proved favorable linearity (R2≥0.9918) in linear ranges. Intra-day and inter-day precisions didn't exceed 14.0% for all the analytes, and the accuracy was within 6.9%. Extraction recoveries of analytes and IS were less than ±15.0% of nominal concentrations. This method has been under thorough and firm verification for a comparative pharmacokinetic research after gavage between Ginkgo biloba extract and single pure ginkgo flavonoids. The results demonstrated that there're evident pharmacokinetic discrepancies, and possible structural influences were innovatively proposed. Generally, substitution with 3-hydroxylation, a double bond in ring C, ring B methoxylation often confer longer onset period. The existence of ring B catechol group gives rise to faster clearance.

Simultaneous determination of eight bioactive components of Qishen Yiqi dripping pills in rat plasma using UFLC-MS/MS and its application to a pharmacokinetic study.

In this study, a rapid and reliable ultra-fast liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of eight active ingredients, including astragaloside IV, ononin, tanshinol, protocatechualdehyde, protocatechuic acid, salvianolic acid D, rosmarinic acid and ginsenoside Rg1 , in rat plasma. The plasma samples were pretreated by protein precipitation with acetonitrile. Chromatographic separation was performed on a Waters Acquity UPLC® BEH C18 column (1.7 μm particles, 2.1 × 100 mm). The mobile phase consisted of 0.1% aqueous formic acid (A)-acetonitrile with 0.1% formic acid (B) at a flow rate of 0.4 mL/min. Quantification was performed on a triple quadruple tandem mass spectrometry with electrospray ionization by multiple reaction monitoring both in the negative and in the positive ion mode. The lower limit of quantification of tanshinol was 2.0 ng/mL and the others were 5.0 ng/mL. The extraction recoveries, matrix effects, intra- and inter-day precision and accuracy of eight tested components were all within acceptable limits. The validated method was successfully applied to the pharmacokinetic study of the eight active constituents after intragastric administration of three doses (1.0, 3.0, 6.0 g/kg body weight) of Qishen Yiqi Dripping Pills to rats.

Determination of a natural DNMT1 inhibitor, peperomin E, in rat plasma by UFLC-MS/MS and method application in a pharmacokinetic study.

Peperomin E (PepE), a naturally occurring secolignan isolated from Peperomia dindygulensis, has drawn much attention recently owing to its anticancer and DNA methyltransferase 1 (DNMT1) inhibitory activity. Here, a simple and sensitive ultra-fast liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of PepE in rat plasma for the first time. Samples were prepared by simple protein precipitation. Separation was performed on an XBridge™ C18 column using a mobile phase of acetonitrile and 0.1% (v/v) aqueous formic acid. PepE and the internal standard arctigenin were detected in a positive-ion mode using multiple reaction monitoring of the transitions at m/z 413.2 → 261.0 and 373.2 → 137.2, respectively. The calibration curve for PepE was linear over the range of concentrations of 1.46-6000 ng/mL, with a lower limit of quantitation of 1.46 ng/mL. Both intra- and interday precisions were within 11.05%, and the accuracy ranged from -11.5 to 5.51%. The extraction recovery and matrix effect were within acceptable limits. Stability tests showed that PepE remained stable throughout the analytical procedure. The validated method was then used to analyze the pharmacokinetics of PepE administered to rats orally (12.5 and 25 mg/kg) or intravenously (6.25 and 12.5 mg/kg).

Simultaneous determination of 14 active constituents of Shengjiang Xiexin decoction using ultrafast liquid chromatography coupled with electrospray ionization tandem mass spectrometry

An effective herbal medicinal prescription of Shengjiang Xiexin decoction (SXD) was used in treating the inflammatory bowel disease in clinic. In this study, an ultrafast liquid chromatographytandem mass spectrometry (UFLCMS/MS) method was developed to separate and to simultaneously determine 14 major active ingredients in SXD. Chromatographic separation was successfully accomplished on an Acquity BEH C18 (100mm×2.1mm, 1.7μm) column using gradient elution with 0.1% (v/v) formic acid water (A) and 0.1% (v/v) formic acid in methanol (B). Negative and positive electrospray ionization tandem mass spectrometry was used to detect the 14 analytes using its selective reaction monitoring (SRM) mode. A good linear regression relationship for each analyte was obtained over the range from 3.88ng/mL to 4080ng/mL. The precision was evaluated by intra- and inter-day assays with a relative standard deviation (RSD) of less than 6.25%. The recovery measured at three concentration levels varied from 98.72% to 103.47%. The overall limits of quantification (LOQ) ranged from 2.05ng/mL to 4.72ng/mL. The method was successfully implemented in the qualitative and quantitative analyses of the 14 chemical constituents in SXD. The results showed that the developed UFLCMS/MS method was linear and accurate. The method could be used reliably as a quality control method for SXD.

Rapid and highly sensitive analysis of benzodiazepines and tandospirone in human plasma by automated on-line column-switching UFLC-MS/MS.

A high-throughput method was developed for the detection of 31 benzodiazepine drugs and tandospirone in human plasma by on-line column-switching ultra-fast liquid chromatography-tandem mass spectrometry. Plasma samples (100μl) spiked with the 32 drugs and oxazepam-d5 (internal standard) were diluted with 300μl of 13.3mM ammonium acetate/acetonitrile (33:67, v/v). After centrifugation and filtration, the clear supernatant was injected directly onto the extraction column (Oasis HLB cartridge column). The following procedure was fully automated. The analytes retained on the extraction column were eluted by backflushing of the extraction column and introduced into an analytical column (SUMIPAX ODS D-Swifter column, 30mm×3.0mm i.d.; particle size 2μm) by column switching. Quantification was performed by multiple reaction monitoring with positive-ion electrospray ionization. Distinct peaks appeared for each drug and the internal standard on each channel within 7min, including the extraction time. All drugs spiked into plasma showed recoveries of 83-95%. The regression equations for the 32 drugs showed excellent linearities in the range of 50-2000pg/ml of plasma and the limits of detection ranged from 20 to 50pg/ml. The lower and upper limits of quantitation were 50-100ng/ml and 2000pg/ml, respectively. Intra- and interday coefficients of variation for none of the drugs were greater than 13.6%. The accuracies of quantitation were 87-112%. The multiple reaction monitoring information-dependent acquisition of enhanced product ions method enabled the quantification and confirmation of diazepam, triazolam, and lorazepam obtained from actual plasma.

Simultaneous determination and pharmacokinetic study of four phenolic acids in rat plasma using UFLC–MS/MS after intravenous administration of salvianolic acid for injection

A simple, sensitive and selective ultra-fast liquid chromatography-tandem mass spectrometry (UFLC–MS/MS) method was established for simultaneous determination and pharmacokinetic study of rosmarinic acid (RA), salvianolic acid D (Sal D), lithospermic acid (LA) and salvianolic acid B (Sal B) in rat plasma after intravenous administration of salvianolic acid for injection (SAFI). Three doses of administration, containing 14, 28 and 56mg/kg, were investigated in this study. Plasma samples were pretreated using protein precipitation (PP) with pre-cooled acetonitrile. Chromatographic separation was achieved on a CORTECS™ UPLC C18 column (1.6μm, 2.1×100mm) with a mobile phase composed of 0.1% formic acid aqueous (V/V) and 0.1% formic acid acetonitrile (V/V). Analytes were detected using electrospray ionization (ESI) source in negative ionization mode and quantified in multiple reaction monitoring (MRM) mode. The validated method is stable and reliable. No significant difference of half lives (t1/2) of four analytes at three doses was observed. Area under the curve (AUC0-∞) and peak concentration (Cmax) of the four analytes demonstrated a linear increase in across the doses with the linear correlation r of each analyte at three doses were greater than 0.95. It indicated that the pharmacokinetic behavior of SAFI is positively related to dose at the range of 14–56mg/kg.

Development and validation of a UFLC-MS/MS method for determination of 7'(Z)-(8″S, 8‴S)-epi-salvianolic acid E, (7'R, 8'R, 8″S, 8‴S)-epi-salvianolic acid B and salvianolic acid B in rat plasma and its application to pharmacokinetic studies.

7'(Z)-(8″S, 8‴S)-epi-Salvianolic acid E (compound 1) and (7'R, 8'R, 8″S, 8‴S)-epi-salvianolic acid B (compound 2), two novel analogs of salvianolic acid B (Sal B), have been recently isolated from Salvianolic acid for injection. They both show powerful antioxidant effects, including inducing NQO1 activity and scavenging DPPH free radical, and potential protecting effects for cerebral ischemia. However, no reports have been described the pharmacokinetic study of them. In this study, an ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method was developed and validated for the determination of compound 1, compound 2 and Sal B in rat plasma, respectively. Plasma samples were pretreated by liquid-liquid extraction with ethyl acetate. Chromatographic separation was achieved on a Waters Acquity UPLC(®) HSS T3 column (1.7μm particles, 2.1mm i.d.×100mm) with the mobile phase of 0.1% aqueous formic acid (A)-acetonitrile (B) (65:35, v/v). Quantification was performed on a triple quadruple tandem mass spectrometry with electrospray ionization (ESI) by multiple reaction monitoring (MRM) in the negative ion mode. Monitored transitions were set at m/z 717.0→519.0, 717.1→519.1, 717.2→518.9 and 320.9→152.1 for compound 1, compound 2, Sal B and chloramphenicol (internal standard, IS), respectively. Linear calibration curves were acquired over the concentration range of 2.0-1000ng/mL for the three analytes in rat plasma. The extraction recoveries, matrix effects, intra- and inter-day precisions and accuracies of the three analytes were all within acceptable limits. The validated method was successfully applied to the pharmacokinetic study of compound 1, compound 2 and Sal B after intravenous administration of 6.0mg/kg in rats, respectively. The results indicated that compound 1 and compound 2 were both eliminated more slowly than Sal B. Exposure levels of both compound 1 and Sal B were higher than compound 2 in the same dosage range. This study provided critical reference for the pharmacokinetic study of compound 1 and compound 2.

Development of a UFLC-MS/MS method for the simultaneous determination of seven tea catechins in rat plasma and its application to a pharmacokinetic study after administration of green tea extract

A rapid, sensitive and selective ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method was developed and validated for simultaneous determination of seven green tea catechins including catechin (C), (−)-epicatechin (EC), gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG), gallocatechin-3-gallate (GCG) and (−)-epigallocatechin-3-gallate (EGCG) in rat plasma. The plasma samples were firstly hydrolysed with the mixture of β-glucuronidase and sulfatase, which were then extracted by liquid-liquid extraction with ethyl acetate-isopropanol (1:1, v/v). The analytes were separated on a Venusil MP C18 column (Venusil, China) with a gradient elution at a flow rate of 0.4mL/min. The detection was performed in negative ionization and multiple reaction monitoring (MRM) mode. All the calibration curves exhibited good linearity (r>0.9943) with intra- and inter-day precisions of less than 14.3% and the accuracy deviations ranging from −8.8% to 7.5%. The extraction recoveries of the analytes and ethyl gallate (internal standard) were all more than 72%. The validated method was successfully applied to a pharmacokinetic study of seven catechins in rat plasma after oral administration of the green tea extract at different doses of 0.4, 1.2 and 2.0g/kg.

Simultaneous determination of four aflatoxins and ochratoxin A in ginger after inoculation with fungi by ultra-fast liquid chromatography-tandem mass spectrometry.

Aflatoxins (AFs) and ochratoxin A (OTA) have been detected frequently in food, agricultural products and traditional Chinese medicines, and their presence poses serious health and economic problems worldwide. Ginger can easily be polluted with mycotoxins. In this study, ginger samples were cultivated for 15 days after inoculation with fungi and were prepared based on ultrasound-assisted solid-liquid extraction using methanol/water followed by immunoaffinity column clean-up and analysed by ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) for AFs and OTA. The limits of detection and quantification of AFs and OTA were 0.04-0.30 µg mL(-1) and 0.125-1.0 µg mL(-1) , respectively. The recoveries were 82.0-100.2%. After 15 days' cultivation, no macroscopic mildew was found in ginger. But, the content of AFB1 expressed an increasing trend in ginger, peel [less than the limit of quantification (LOQ)] to the innermost layer (51.86 µ mL(-1) ), AFB2 was only detected in the innermost layer at the level of 0.87 µ mL(-1) . A small amount (<LOQ) of OTA was found in the peel of ginger after the two fungi were inoculated on the surface of ginger. The developed method was successfully applied to analyse five mycotoxins, and has many advantages including rapid determination and high sensitivity. Meanwhile, in practice, more attention should be paid to the safety and quality of ginger. © 2016 Society of Chemical Industry.

PRiME pass-through cleanup for the fast determination of aflatoxins in human serum by using LC-MS/MS

A novel, simple and sensitive method based on the use of a PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure combined with ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) for the determination of 4 AFs, i.e., AFB1, AFB2, AFG1 and AFG2 in human serum, was developed and validated. The effective PRiME pass-through cleanup procedure using the Oasis PRiME HLB cartridge was optimized for the extraction of AFB1, AFB2, AFG1 and AFG2 in human serum. The obtained results demonstrated the higher extraction capacity of the PRiME pass-through cleanup procedure with recoveries between 92.1% and 102%. The limits of detection (LODs) for AFB1, AFB2, AFG1 and AFG2 were 0.048 μg L−1, 0.069 μg L−1, 0.043 μg L−1 and 0.14 μg L−1, respectively. Validation results on linearity, specificity, accuracy and precision, as well as on application to the analysis of AFs in 10 liver cancer volunteers demonstrated the applicability to clinical studies.

Study on pharmacokinetics of 3,4-divanillyltetrahydrofuran in rats by ultra-fast liquid chromatography/tandem mass spectrometry.

3,4-Divanillyltetrahydrofuran is the main active ingredient of nettle root which can increase steroid hormones in the bloodstream for many of bodybuilders. To better understand its pharmacological activities, we need to determine its pharmacokinetic profiles. In this study, a rapid and sensitive ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method has been developed for the determination of 3,4-divanillyltetrahydrofuran in the plasma of rats. Chromatographic separation was performed on a C18 column at 40°C, with a gradient elution consisting of methanol and water containing 0.3% (v/v) formic acid at a flow rate of 0.8mL/min. The detection was performed using an electrospray triple-quadrupole MS/MS via positive ion multiple reaction monitoring mode. The lower limits-of-quantification determined were 0.5ng/mL. The intra- and inter-day precision (RSD%) was found to be within 15% and the accuracy (RE%) ranged from -4.0% to 7.0%. This simple yet sensitive method was fully validated and could be successfully applied to the study on pharmacokinetics of 3, 4-divanillyltetrahydrofuran.

Determination of a novel phosphodiesterase-4 inhibitor chlorbipram in mouse plasma and brain by UFLC-MS/MS: Application in pharmacokinetic studies after intravenous administration.

In this study, we evaluated a simple and sensitive method for determination of a novel phosphodiesterase-4 (PDE4) inhibitor, chlorbipram, in mouse plasma and brain using ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS). Separation was achieved using an Acquity UPLC BEH C18 column (50mm×2.1mm, particle size 1.7μm) with a gradient mobile phase consisting of water and methanol at a flow rate of 0.25ml/min. Detection was performed in the multiple reaction monitoring (MRM) mode using electrospray ionization (ESI) in the positive ion mode. The liquid-liquid extraction method with ethyl acetate was used for both pretreatment of plasma and brain homogenates. The calibration curves of chlorbipram showed good linearity over the concentration range of 0.5-200ng/ml (R(2)>0.994) for mouse plasma and over the range of 0.25-100ng/ml (R(2)>0.994) for mouse brain homogenate. The extraction recovery was in the range of 78.3-84.8% for chlorbipram and the internal standard (IS) ZXI14 in two different biological matrices. The intra- and inter-day precision values were less than 13.0% and the accuracy ranged from 97.8% to 106.0% for quality control samples. No noteworthy matrix effects and instability were observed for chlorbipram. This validated method was successfully applied to a pharmacokinetic study of chlorbipram in mice after intravenous administration. The results show that this novel drug crosses the blood-brain barrier and provides the basis for further studies on chlorbipram.

Lotus Leaf Alkaloid Extract Displays Sedative-Hypnotic and Anxiolytic Effects through GABAA Receptor.

Lotus leaves have been used traditionally as both food and herbal medicine in Asia. Open-field, sodium pentobarbital-induced sleeping and light/dark box tests were used to evaluate sedative-hypnotic and anxiolytic effects of the total alkaloids (TA) extracted from the herb, and the neurotransmitter levels in the brain were determined by ultrafast liquid chromatography-tandem mass spectrometry. The effects of picrotoxin, flumazenil, and bicuculline on the hypnotic activity of TA, as well as the influence of TA on Cl(-) influx in cerebellar granule cells, were also investigated. TA showed a sedative-hypnotic effect by increasing the brain level of γ-aminobutyric acid (GABA), and the hypnotic effect could be blocked by picrotoxin and bicuculline, but could not be antagonized by flumazenil. Additionally, TA could increase Cl(-) influx in cerebellar granule cells. TA at 20 mg/kg induced anxiolytic-like effects and significantly increased the concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and dopamine (DA). These data demonstrated that TA exerts sedative-hypnotic and anxiolytic effects via binding to the GABAA receptor and activating the monoaminergic system.

Determination of nonsteroidal anti-inflammatory drugs in human tear and plasma samples using ultra-fast liquid chromatography-tandem mass spectrometry.

To evaluate a new rapid and sensitive method for analyzing human tears and plasma for nonsteroidal anti-inflammatory drugs (NSAIDs) and investigate the influence of the transfer of NSAIDs in an ocular lesion. In this cross-over study, a single dose of 200 mg of ibuprofen and 60 mg of loxoprofen sodium were orally administered to six healthy Japanese subjects. Collected samples were analyzed by ultra-fast liquid chromatography tandem mass spectrometry (UFLC-MS/MS). Recoveries of the two drugs spiked in the tears and plasma were 96.0-117.0 % in the tears and 99.0-105.7 % in the plasma. Regression equations for both NSAIDs showed excellent linearity from 0.02-1.0 μg/ml for the tears and 0.1-5.0 μg/ml for the plasma, with the limits of detection at 0.02 μg/ml for tears and 0.1 μg/ml for plasma. This new high-throughput NSAID determination method only requires a small tear amount (10 μl) and plasma volume (20 μl) and thus will be useful in clinical and toxicological analyses. Analytical results also showed the presence of ibuprofen and loxoprofen in the actual tears and plasma, which confirms the transition of NSAIDs from the tears to the plasma.

Very-long-chain fatty acid sphingomyelin in nuclear lipid microdomains of hepatocytes and hepatoma cells: can the exchange from C24:0 to C16:0 affect signal proteins and vitamin D receptor?

Lipid microdomains localized in the inner nuclear membrane are considered platforms for active chromatin anchoring. Stimuli such as surgery, vitamin D, or glucocorticoid drugs influence their gene expression, DNA duplication, and RNA synthesis. In this study, we used ultrafast liquid chromatography-tandem mass spectrometry to identify sphingomyelin (SM) species coupled with immunoblot analysis to comprehensively map differences in nuclear lipid microdomains (NLMs) purified from hepatocytes and hepatoma cells. We showed that NLMs lost saturated very-long-chain fatty acid (FA; C24:0) SM in cancer cells and became enriched in long-chain FA (C16:0) SM. We also found that signaling proteins, such as STAT3, Raf1, and PKCζ, were increased and vitamin D receptor was reduced in cancer cells. Because recent researches showed a shift in sphingolipid composition from C24:0 to C16:0 in relation to cell life, we performed a comparative analysis of properties among C16:0 SM, C24:0 SM, and cholesterol. Our results led us to hypothesize that the enrichment of C16:0 SM could determine enhanced dynamic properties of NLMs in cancer cells with an increased shuttling of protein signaling molecules.

Simultaneous quantification of fosinopril and its active metabolite fosinoprilat in rat plasma by UFLC-MS/MS: Application of formic acid in the stabilization of an ester-containing drug.

Fosinopril is an angiotensin-converting enzyme inhibitor containing a phosphate ester group which undergoes esterase hydrolysis to its active metabolite, fosinoprilat. EDTA was utilized as an anticoagulant to inhibit the hydrolysis of fosinopril in whole blood during blood collection and processing. To prevent the ex vivo conversion to fosinoprilat, formic acid was added to rat plasma to effectively stabilize fosinopril. A sensitive, rapid and robust ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method was developed and validated for simultaneous determination of fosinopril and fosinoprilat in rat plasma. Protein precipitation was employed for plasma sample clean-up. Chromatographic separation was achieved on a Welch Ultimate XB-C18 column using gradient elution with a total run time of 5min. Analytes and their stable isotope labeled internal standards were detected by positive ion electrospray tandem mass spectrometric assay. The assay involves quantitation of both analytes in small-volume (50μL) plasma, with the lower limit of quantification of 0.1 and 1ng/mL for fosinopril and fosinoprilat, respectively. The method was fully validated in linear calibration ranges of 0.1-150ng/mL for fosinopril and 1-1500ng/mL for fosinoprilat with acceptable accuracy and precision. Assay recoveries were high (>95% for fosinopril and >91% for fosinoprilat) and matrix effect was negligible. Both analytes were found to be stable in stabilized rat plasma for 6h at room temperature, 30 days at -80°C, and following three freeze-thaw cycles and were also stable in processed samples for 36h at 4°C. The validated method was successfully applied to sample analyses for pharmacokinetic study of fosinopril and can be extended to the measurement of fosinopril in other biological samples.

Simultaneous determination of four Sudan dyes in rat blood by UFLC–MS/MS and its application to a pharmacokinetic study in rats

A rapid and sensitive method based on ultrafast liquid chromatography–tandem mass spectrometry was developed and validated for simultaneous determination of Sudan I, Sudan II, Sudan III, and Sudan IV levels in rat whole blood. Cleanert C18 mixed-mode polymeric sorbent was used for effective solid-phase extraction cleanup. Separation was carried out on a reversed-phase C18 column (100mm×2.1mm, 1.8μm) using 0.1% (v/v) formic acid in water/0.1% (v/v) formic acid in acetonitrile as the mobile phase in gradient elution. Quantification was performed by an electrospray ionization source in the positive multiple reaction monitoring mode using D5-Sudan I as the internal standard. Calibration curves showed good linearity between 0.2 and 20.0μg/L, with correlation coefficients higher than 0.9990. The average recovery rates were between 93.05% and 114.98%. The intra- and inter-day relative standard deviations were within 6.2%. The lower limit of quantification was 0.2μg/L. All the analytes were found to be stable in a series of stability studies. The proposed method was successfully applied to a pharmacokinetic study of four Sudan dyes after oral administration to rats.

Rapid method for quantification of seven synthetic pigments in colored Chinese steamed buns using UFLC-MS/MS without SPE.

Synthetic pigments are still used instead of natural pigments in many foods and their residues in food could be an important risk to human health. A simple and rapid analytical method combining the low-cost extraction protocol with ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) was developed for the simultaneous determination of seven synthetic pigments used in colored Chinese steamed buns. For the first time, ethanol/ammonia solution/water (7:2:1, v/v/v) was used as extraction solution for the synthetic pigments in colored Chinese steamed buns. The results showed that the property of the extraction solution used in this method was more effective than critic acid solution, which is used in the polyamide adsorption method. The limits of quantification for the seven synthetic pigments ranged from 0.15 to 0.50 μg/kg. The present method was successfully applied to samples of colored Chinese steamed buns for food-safety risk monitoring in Zhejiang Province, China. The results found sunset yellow pigment in six out of 300 colored Chinese steamed buns (from 0.50 to 32.6 μg/kg).