Trace determination of five triazole fungicide residues in traditional Chinese medicine samples by dispersive solid‐phase extraction combined with ultrasound‐assisted dispersive liquid–liquid microextraction and UHPLC–MS/MS

A novel and reliable method for determination of five triazole fungicide residues (triadimenol, tebuconazole, diniconazole, flutriafol, and hexaconazol) in traditional Chinese medicine samples was developed using dispersive solid‐phase extraction combined with ultrasound‐assisted dispersive liquid–liquid microextraction before ultra‐high performance liquid chromatography with tandem mass spectrometry. The clean up of the extract was conducted using dispersive solid‐phase extraction by directly adding sorbents into the extraction solution, followed by shaking and centrifugation. After that, a mixture of 400 μL trichloromethane (extraction solvent) and 0.5 mL of the above supernatant was injected rapidly into water for the dispersive liquid–liquid microextraction procedure. The factors affecting the extraction efficiency were optimized. Under the optimum conditions, the calibration curves showed good linearity in the range of 2.0–400 (tebuconazole, diniconazole, and hexaconazole) and 4.0–800 ng/g (triadimenol and flutriafol) with the regression coefficients higher than 0.9958. The limit of detection and limit of quantification for the present method were 0.5–1.1 and 1.8–4.0 ng/g, respectively. The recoveries of the target analytes ranged from 80.2 to 103.2%. The proposed method has been successfully applied to the analysis of five triazole fungicides in traditional Chinese medicine samples, and satisfactory results were obtained.     

Comparative analysis of main bio‐active components in the herb pair Danshen‐Honghua and its single herbs by ultra‐high performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry

A sensitive, reliable, and powerful ultra‐high performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry method was developed for simultaneous quantification of the 15 main bio‐active components including phenolic acids and flavonoids within 13 min for the first time. The proposed method was first reported and validated by good linearity (r ² > 0.9975), limit of detection (1.12–7.01 ng/mL), limit of quantification (3.73–23.37 ng/mL), intra‐ and inter‐day precisions (RSD ≤ 1.92%, RSD ≤ 2.45%), stability (RSD ≤ 5.63%), repeatability (RSD ≤ 4.34%), recovery (96.84–102.12%), and matrix effects (0.92–1.02). The established analytical methodology was successfully applied to comparative analysis of main bio‐active components in the herb pair Danshen‐Honghua and its single herbs. Compared to the single herb, the content of most flavonoid glycosides was remarkably increased in their herb pair, and main phenolic acids were decreased, conversely. The content changes of the main components in the herb pair supported the synergistic effects on promoting blood circulation and removing blood stasis. The results provide a scientific basis and reference for the quality control of Danshen‐Honghua herb pair and the drug interactions based on variation of bio‐active components in herb pairs.     

l‐Cysteine‐modified magnetic microspheres for extraction and quantification of saxitoxin in rat plasma with liquid chromatography and tandem mass spectrometry

Saxitoxin, which is one of the most typical paralytic shellfish poisoning toxins, ranks the highest intoxication rate of marine biological poisoning cases globally. Efficient clean‐up and extraction of saxitoxin from complex biological matrices are imperative for the analysis and concentration monitoring of the toxin when correlative poisoning cases happen. Herein, l ‐cysteine‐modified magnetic microspheres based on metal‐organic coordination were synthesized by a facile approach and applied for magnetic solid‐phase extraction of saxitoxin from rat plasma samples before liquid chromatography–tandem mass spectrometry detection. Parameters, including adsorbent amount, extraction time, desorption solution, and desorption time that could affect the extraction efficiency, were respectively investigated. The developed method demonstrated good linearity in the range of 5–300 ng/mL (R² = 0.9985) with a limit of quantification of 5 ng/mL and a limit of detection of 0.5 ng/mL, acceptable accuracy. and precision of within‐run and between‐run.     

Supercritical fluid chromatography coupled with tandem mass spectrometry: A high‐efficiency detection technique to quantify Taxane drugs in whole‐blood samples

We present a technique to rapid determine taxane in blood samples by supercritical fluid chromatography together with mass spectrometry. The aim of this study was to develop a supercritical fluid chromatography with mass spectrometry method for the analysis of paclitaxel, cabazitaxel, and docetaxel in whole‐blood samples of rats. Liquid‐dry matrix spot extraction was selected in sample preparation procedure. Supercritical fluid chromatography separation of paclitaxel, cabazitaxel, docetaxel, and glyburide (internal standard) was accomplished within 3 min by using the gradient mobile phase consisted of methanol as the compensation solvent and carbon dioxide at a flow rate of 1.0 mL/min. The method was validated regarding specificity, the lower limit of quantification, repeatability, and reproducibility of quantification, extraction recovery, and matrix effects. The lower limit of quantification was found to be 10 ng/mL since it exhibited acceptable precision and accuracy at the corresponding level. All interday accuracies and precisions were within the accepted criteria of ±15% of the nominal value and within ±20% at the lower limit of quantification, implying that the method was reliable and reproducible. In conclusion, this method is a promising tool to support and improve preclinical or clinical pharmacokinetic studies with the taxanes anticancer drugs.     

Determination of several synthetic cathinones and an amphetamine‐like compound in urine by gas chromatography with mass spectrometry. Method validation and application to real cases

Most routine practices for drugs‐of‐abuse testing do not include screening procedures for new psychoactive substances, despite their increasing diffusion, preventing clear knowledge of the real consumption of these drugs in the populations. To make up for this shortcoming, a gas chromatography with mass spectrometry method was developed for the simultaneous determination of 18 synthetic cathinones and one amphetamine‐like compound in human urine. The sample preparation was based on liquid–liquid extraction under alkaline condition followed by derivatization with trifluoroacetic anhydride. The separation of the 19 analytes was achieved in less than 10 min. The whole methodology was validated according to national and international guidelines. Selectivity, linearity range, limit of detection and limit of quantitation, precision and accuracy were evaluated. For all the analytes, the calibration curve was linear in the 100–1000 ng/mL concentration range. The limits of detection ranged from 10 to 30 ng/mL and limits of quantitation from 30 to 100 ng/mL. Precisions were in the ranges 0.1–10.4%, and 1.0–12.1% for low (100 ng/mL) and high (1000 ng/mL) concentration, respectively. The accuracy, expressed as bias% was within ±20% for all the analytes. The present method was successfully applied to urine samples originating from autopsies, drug abuse/withdrawal controls, clinical investigations, roadside controls, driving re‐licensing, and workplace testing.     

Dispersive solid‐phase extraction adsorbent of methamphetamine using in‐situ synthesized carbon‐based conductive polypyrrole nanocomposite: focus on clinical applications in human urine

Determination of methamphetamine is of great importance in clinical and forensic laboratories because there are low dosages of drugs in the biological media and social problems created due to the methamphetamine consumption. Polymeric carbon based‐nano composites are reasonable candidates for dispersive solid phase extraction method due to facial and affordable synthesis process and high selectivity and sensitivity. Nano graphene oxide polypyrolle composite was synthesized and employed as dispersive solid‐phase extraction adsorbent for methamphetamine extraction from complex urine matrix. Full characterization of the prepared nano graphene oxide polypyrolle composite was completed and the influential extraction parameters were investigated through one‐parameter‐at‐a‐time method. High‐performance liquid chromatography detectors were applied as detection and quantification instrument. The optimized extraction parameters included 300 µL of methanol, 10 min of extraction and desorption time, 6000 stirring rate, urine pH value of 10, 60 mg of adsorbent, and 6 mL of urine volume. After outlining the calibration curve, the linear range of the method was considered as 30–800 ng/mL. The detection limit for the suggested method was 9 ng/mL. The analysis of addicted subjects with the proposed method confirmed the utility of the method in different analytical and clinical laboratories.     

Extraction of ochratoxin A in red wine with dopamine‐coated magnetic multi‐walled carbon nanotubes

A new, rapid, green, and cost‐effective magnetic solid‐phase extraction of ochratoxin A from red wine samples was developed using polydopamine‐coated magnetic multi‐walled carbon nanotubes as the absorbent. The polydopamine‐coated magnetic multi‐walled carbon nanotubes were fabricated with magnetic multi‐walled carbon nanotubes and dopamine by an in situ oxidative self‐polymerization approach. Transmission electron microscopy, dynamic light scattering, X‐ray photoelectron spectroscopy and vibrating sample magnetometry were used to characterize the absorbents. Ochratoxin A was quantified with high‐performance liquid chromatography coupled with fluorescence detection, with excitation and emission wavelengths of 338 and 455 nm, respectively. The conditions affecting the magnetic solid‐phase extraction procedure, such as pH, extraction solution, extraction time, absorbent amount, desorption solution and desorption time were investigated to obtain the optimal extraction conditions. Under the optimized conditions, the extraction recovery was 91.8–104.5% for ochratoxin A. A linear calibration curve was obtained in the range of 0.1–2.0 ng/mL. The limit of detection was 0.07 ng/mL, and the limit of quantitation was 0.21 ng/mL. The recoveries of ochratoxin A for spiked red wine sample ranged from 95.65 to 100.65% with relative standard deviation less than 8%. The polydopamine‐coated magnetic multi‐walled carbon nanotubes showed a high affinity toward ochratoxin A, allowing selective extraction and quantification of ochratoxin A from complex sample matrixes.     

Simultaneous determination of ginsenosides and bufadienolides in rat plasma after the oral administration of Shexiang Baoxin Pill for pharmacokinetic study by liquid chromatography tandem mass spectrometry following solid‐phase extraction

A sensitive and reliable bioanalytical method was established for quantitati\ve and pharmacokinetic investigation of nine ginsenosides and seven bufadienolides in rat plasma after the oral administration of Shexiang Baoxin Pill by liquid chromatography–electrospray ionization tandem mass spectrometry, using tinidazole and digoxin as internal standards (ISTDs). All of the analytes and ISTDs obtained satisfactory recoveries by solid‐phase extraction using an Oasis HLB μElution Plate, which was eluted with methanol and ethyl acetate successively, and chromatographic separation was achieved on a Shim‐pack XR‐ODSIIcolumn (75 × 2.0 mm, 2.2 μm) with gradient elution using a mixture of acetonitrile–0.1% formic acid solution (v /v) as the mobile phase at a flow rate of 0.3 mL/min. Detection was carried out by a triple‐quadrupole tandem mass spectrometry with positive/negative ion switching multiple reaction monitoring mode. All analytes showed good linearity over a wide concentration range (r ² > 0.99). The lower limit of quantification was in the range 0.625–12.5 ng/mL for bufadienolides and 2–5.5 ng/mL for ginsenosides, and the mean recoveries of all analytes were in the range 78.29–99.35%. The intra‐ and inter‐day precisions (RSD) were in the range 0.08–12.38% with the accuracies between 86.09 and 99.40%. The validated method was then successfully applied to pharmacokinetic study of the above 16 compounds in rat plasma. Pharmacokinetic results indicated that the developed extraction and analytical method could be employed as a rapid, effective technique for pharmacokinetic study of multiple components, especially various polarity that are difficult to extract simultaneously.     

Magnetic porous carbon derived from a metal–organic framework as a magnetic solid‐phase extraction adsorbent for the extraction of sex hormones from water and human urine

An iron‐embedded porous carbon material (MIL‐53‐C) was fabricated by the direct carbonization of MIL‐53. The MIL‐53‐C possesses a high surface area and good magnetic behavior. The structure, morphology, magnetic property, and porosity of the MIL‐53‐C were studied by scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and N₂ adsorption. With the use of MIL‐53‐C as the magnetic solid‐phase extraction adsorbent, a simple and efficient method was developed for the magnetic solid‐phase extraction of three hormones from water and human urine samples before high‐performance liquid chromatography with UV detection. The developed method exhibits a good linear response in the range of 0.02–100 ng/mL for water and 0.5–100 ng/mL for human urine samples , respectively. The limit of detection (S/N = 3) for the analytes was 0.005–0.01 ng/mL for water sample and 0.1–0.3 ng/mL for human urine sample. The limit of quantification (S/N = 10) of the analytes were in the range of 0.015–0.030 and 0.3–0.9 ng/mL, respectively.     

Ion‐pair switchable‐hydrophilicity solvent‐based homogeneous liquid–liquid microextraction for the determination of paraquat in environmental and biological samples before high‐performance liquid chromatography

An approach involving ion‐pair switchable‐hydrophilicity solvent‐based homogeneous liquid–liquid microextraction coupled to high‐performance liquid chromatography has been applied for the preconcentration and separation of paraquat in a real sample. A mixture of triethylamine and water was used as the switchable‐hydrophilicity solvent. The pH was regulated using carbon dioxide; hence the ratio of the ionized and non‐ionized form of triethylamine could control the optimum conditions. Sodium dodecyl sulfate was utilized as an ion‐pairing agent. The ion‐associate complex formed between the cationic paraquat and sodium dodecyl sulfate was extracted into triethylamine. The separation of the two phases was carried out by the addition of sodium hydroxide, which changed the ionization state of triethylamine. The effects of some important parameters on the extraction recovery were investigated. Under the optimum conditions (500 μL of the extraction solvent, 1 mg sodium dodecyl sulfate, 2.0 mL of 10 mol/L sodium hydroxide, and pH 4), the limit of detection and the limit of quantification were 0.2 and 0.5 μg/L, respectively, with preconcentration factor of 74. The precision (RSD, n  = 10) was  <5%. The recovery of the analyte in environmental and biological samples was in the range of 90.0–92.3%.     

Ultra‐high performance liquid chromatography with tandem mass spectrometry method for the simultaneous quantitation of five phthalides in rat plasma: Application to a comparative pharmacokinetic study of Huo Luo Xiao Ling Dan and herb‐pair extract

A fast, sensitive, and reliable ultra‐high performance liquid chromatography with tandem mass spectrometry method has been developed and validated for the simultaneous quantitation and pharmacokinetic study of five phthalides (senkyunolide A, ligustilide, butylidenephthalide, 3‐butylphthalide, and levistilide A) in rat plasma after oral administration of Huo Luo Xiao Ling Dan (HLXLD) or Angelica sinensis‐‐Ligusticum chuanxiong herb pair (DG‐CX) between normal and arthritis rats. After extraction from blood, the analytes and internal standard were subjected to ultra‐high performance liquid chromatography with a Shim‐pack XR‐ODS column (75 × 3.0 mm², 2.2 μm particles) and mobile phase was composed of methanol and water (containing 0.05% formic acid) under gradient elution conditions, with an electrospray ionization source in the positive ionization and multiple reaction monitoring mode. The lower limits of quantification were 0.192–0.800 ng/mL for all the analytes. Satisfactory linearity, precision, accuracy, mean extraction recovery, and acceptable matrix effect have been achieved. The validated method was successfully applied to a comparative pharmacokinetic study of five bioactive components in rat plasma after oral administration of HLXLD or DG‐CX alone, respectively, between normal and arthritic rats. The results showed that there were unlike characters of pharmacokinetics among different groups.     

Comparative pharmacokinetic study of the components of Jia‐Wei‐Kai‐Xin‐San in normal and vascular dementia rats by ultra‐fast liquid chromatography coupled with tandem mass spectrometry

A fast, sensitive, and reliable ultra‐high performance liquid chromatography coupled with tandem mass spectrometry method has been developed and validated for simultaneous quantification of geniposide, polygalaxanthone III, 3,6′‐disinapoyl sucrose, α‐asarone, β‐asarone, poricoic acid A, poricoic acid B, dehydrotumulosic acid, deoxyschizandrin, schizandrin B, and kaempferide in plasma after oral administration of extracts of Jia‐Wei‐Kai‐Xin‐San in normal and vascular dementia rats. The developed method was precise and accurate within the linearity range of the analytes. The lower limits of quantification were 1.04–2.68 ng/mL for all the analytes. Both intra‐ and inter day precision and accuracy of the analytes were all within accepted criteria. The mean extraction recoveries of the analytes and the internal standard from rat plasma were all >60.0%. The validated method had been successfully applied to compare pharmacokinetic profiles of the analytes in plasma of normal and vascular dementia rat treated with herbal extracts. Results indicated that differences existed between normal and vascular dementia model rats except dehydrotumulosic acid and kaempferide, which might be due to the pathology of vascular dementia and pharmacological effect of the analytes. These pharmacokinetic studies might benefit for the mechanism exploration and clinical use of traditional Chinese medicine formulae.     

LC–MS/MS analysis of metformin,saxagliptin and 5‐hydroxy saxagliptin in human plasma and its pharmacokinetic study with a fixed‐dose formulation in healthy Indian subjects

A specific and rapid liquid chromatography–tandem mass spectrometry method is proposed for the simultaneous determination of metformin (MET), saxagliptin (SAXA) and its active metabolite, 5‐hydroxy saxagliptin (5‐OH SAXA) in human plasma. Sample preparation was accomplished from 50 μL plasma sample by solid‐phase extraction using sodium dodecyl sulfate as an ion‐pair reagent. Reversed‐phase chromatographic resolution of analytes was possible within 3.5 min on ACE 5CN (150 × 4.6 mm, 5 μm) column using acetonitrile and10.0 mm ammonium formate buffer, pH 5.0 (80:20, v /v) as the mobile phase. Triple quadrupole mass spectrometric detection was performed using electrospray ionization in the positive ionization mode. The calibration curves showed good linearity (r ² ≥ 0.9992) over the established concentration range with limit of quantification of 1.50, 0.10 and 0.20 ng/mL for MET, SAXA and 5‐OH SAXA respectively. The extraction recoveries obtained from spiked plasma samples were highly consistent for MET (75.12–77.84%), SAXA (85.90–87.84%) and 5‐OH SAXA (80.32–82.69%) across quality controls. The validated method was successfully applied to a bioequivalence study with a fixed‐dose formulation consisting of 5 mg SAXA and 500 mg MET in 18 healthy subjects. The reproducibility of the assay was demonstrated by reanalysis of 87 incurred samples.     

Simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone,and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma by liquid chromatography with tandem mass spectrometry and its application to a pharmacokinetic study

A new liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma using chlorpropamide as an internal standard. Plasma samples (50 μL) were prepared using a simple deproteinization procedure with 150 μL of acetonitrile containing 100 ng/mL of chlorpropamide. Chromatographic separation was carried out on an Acclaim RSLC120 C₁₈ column (2.1 × 100 mm, 2.2 μm) using a gradient elution consisting of 7.5 mM ammonium acetate and acetonitrile containing 0.1% formic acid (0.4 mL/min flow rate, 7.0 min total run time). The detection and quantitation of all analytes were performed in selected reaction monitoring mode under both positive and negative electrospray ionization. This assay was linear over concentration ranges of 50–5000 ng/mL (trifolirhizin), 25–2500 ng/mL ((–)‐maackiain), 5–250 ng/mL ((–)‐sophoranone), and 1–250 ng/mL 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran) with a lower limit of quantification of 50, 25, 5, and 1 ng/mL for trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran, respectively. All the validation data, including the specificity, precision, accuracy, recovery, and stability conformed to the acceptance requirements. The results indicated that the developed method is sufficiently reliable for the pharmacokinetic study of the analytes following oral administration of Sophora tonkinensis extract in rats.     

Simultaneous determination of selected estrogenic endocrine disrupting chemicals and bisphenol A residues in whole milk using fabric phase sorptive extraction coupled to HPLC‐UV detection and LC‐MS/MS

A simple and sensitive analytical methodology is developed for rapid screening and quantification of selected estrogenic endocrine disrupting chemicals and bisphenol A from intact milk using fabric phase sorptive extraction in combination with high‐performance liquid chromatography coupled to ultraviolet detection/tandem mass spectrometry. The new approach eliminates protein precipitation and defatting step from the sample preparation workflow. In addition, the error prone and time‐consuming solvent evaporation and sample reconstitution step used as the sample post‐treatment has been eliminated. Parameters with most significant impact on the extraction efficiency of fabric phase sorptive extraction including sorbent chemistry, sample volume, extraction time have been thoroughly studied and optimized. Separation of the selected estrogenic endocrine disrupting chemicals including α‐estradiol, hexestrol, estrone, 17α‐ethinyl estradiol, diethylstilboestrol, and bisphenol A were achieved using a Zorbax Extend‐C18 high‐performance liquid chromatography column (15 cm × 4.6 mm, 5 μm particle size). The limit of detection values obtained in fabric phase sorptive extraction with high‐performance liquid chromatography with ultraviolet detection ranged from 25.0 to 50.0 ng/mL. The method repeatability values were 3.6–13.9 (relative standard deviation, %) and intermediate precision values were 4.6–12.7 (relative standard deviation, %). The fabric phase sorptive extraction method was also coupled to liquid chromatography with tandem mass spectrometry for identifying each endocrine disrupting chemical at 10 ng/mL.     

Simultaneous quantification and rat pharmacokinetics of formononetin‐7‐O‐β‐d‐glucoside and its metabolite formononetin by high‐performance liquid chromatography–tandem mass spectrometry

Formononetin‐7‐O‐β‐d ‐glucoside has been proved to have significant anti‐inflammatory effect. To evaluate its rat pharmacokinetics, a rapid, sensitive, and specific liquid chromatography–tandem mass spectrometry method has been developed and validated for the quantification of formononetin‐7‐O‐β‐d ‐glucoside and its main metabolite formononetin in rat plasma. Samples were pretreated using a simple protein precipitation and the chromatographic separation was performed on a C₁₈ column by a gradient elution using a mobile phase consisting of water and acetonitrile both containing 0.1% formic acid. Both analytes were detected using a tandem mass spectrometer in positive multiple reaction monitoring mode. The assay showed wide linear dynamic ranges of both 0.10–100 ng/mL, with acceptable intra‐ and inter‐batch accuracy and precision. The lower limits of quantification were both 0.10 ng/mL using 50 μL of rat plasma for two analytes. The method has been successfully used to investigate the oral pharmacokinetic profiles of both analytes in rats. After oral administration of formononetin‐7‐O‐β‐d ‐glucoside at the dose of 50 mg/kg, it was rapidly absorbed in vivo and metabolized to its metabolite formononetin. The plasma concentration‐time profiles both showed double‐peak phenomena, which would be attributed to the strong enterohepatic circulation of formononetin‐7‐O‐β‐d ‐glucoside.     

LC–MS/MS method for simultaneous determination of flavonoids and physalins in rat plasma: Application to pharmacokinetic study after oral administration of Physalis alkekengi var. franchetii (Chinese lantern) extract

A rapid and sensitive liquid chromatography with tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the simultaneous determination of luteolin, luteolin‐7‐O ‐β ‐D‐glucopyranoside, physalin A, physalin D and physalin L in rat plasma. Scutellarein and dexamethasone were used as the internal standards (IS). Plasma samples were prepared by liquid‐liquid extraction with ethyl acetate. The five constituents were separated on an Acquity UPLC BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm). A gradient elution procedure was used with acetonitrile (A)‐0.1% aqueous formic acid (B). Mass spectrometric detection was performed in negative ion multiple reaction monitoring mode with an electrospray ionization (ESI) source. This method showed good linearity (r ² > 0.997) over a concentration range of 2.0–500 ng/mL with a lower limit of quantification of 2.0 ng/mL for all five compounds. The inter‐ and intra‐day accuracy ranged from 91.7 to 104%, and precisions (RSD) were <6.46% for all analytes. The extraction recoveries of all analytes were >85%. This validated method was successfully applied for the first time to the pharmacokinetic study of five ingredients after oral administration of 70% ethanol extract of Chinese lantern in rats.     

Ion‐pair cloud‐point extraction: A new method for the determination of water‐soluble vitamins in plasma and urine

A novel, simple, and effective ion‐pair cloud‐point extraction coupled with a gradient high‐performance liquid chromatography method was developed for determination of thiamine (vitamin B₁), niacinamide (vitamin B₃), pyridoxine (vitamin B₆), and riboflavin (vitamin B₂) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion‐pair formation approach between these ionizable analytes and 1‐heptanesulfonic acid sodium salt as an ion‐pairing agent. Influential variables on the ion‐pair cloud‐point extraction efficiency, such as the ion‐pairing agent concentration, ionic strength, pH, volume of Triton X‐100, extraction temperature, and incubation time have been fully evaluated and optimized. Water‐soluble vitamins were successfully extracted by 1‐heptanesulfonic acid sodium salt (0.2% w/v) as ion‐pairing agent with Triton X‐100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r² > 0.9916) and precision in the concentration ranges of 1‐50 μg/mL for thiamine and niacinamide, 5–100 μg/mL for pyridoxine, and 0.5–20 μg/mL for riboflavin. The recoveries were in the range of 78.0–88.0% with relative standard deviations ranging from 6.2 to 8.2%.     

Solid‐phase extraction assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet to determine sildenafil and its analogues in dietary supplements

A novel analytical method for the simultaneous determination of the concentration of sildenafil and its five analogues in dietary supplements using solid‐phase extraction assisted reversed‐phase dispersive liquid–liquid microextraction based on solidification of floating organic droplet combined with ion‐pairing liquid chromatography with an ultraviolet detector was developed. Parameters that affect extraction efficiency were systematically investigated, including the type of solid‐phase extraction cartridge, pH of the extraction environment, and the type and volume of extraction and dispersive solvent. The method linearity was in the range of 5.0–100 ng/mL for sildenafil, homosildenafil, udenafil, benzylsildenafil, and thiosildenafil and 10–100 ng/mL for acetildenafil. The coefficients of determination were ≥0.996 for all regression curves. The sensitivity values expressed as limit of detection were between 2.5 and 7.5 ng/mL. Furthermore, intraday and interday precisions expressed as relative standard deviations were less than 5.7 and 9.9%, respectively. The proposed method was successfully applied to the analysis of sildenafil and its five analogues in complex dietary supplements.     

Online restricted‐access material combined with high‐performance liquid chromatography and tandem mass spectrometry for the simultaneous determination of vanillin and its vanillic acid metabolite in human plasma

An automated online solid‐phase extraction with restricted‐access material combined with high‐performance liquid chromatography and tandem mass spectrometry was developed and validated for the simultaneous quantification of vanillin and its vanillic acid metabolite in human plasma. After protein precipitation by methanol, which contained the internal standards, the supernatant of plasma samples was injected to the system, the endogenous large molecules were flushed out, and target analytes were trapped and enriched on the adsorbent, resulting in a minimization of sample complexity and ion suppression effects. Calibration curves were linear over the concentrations of 5–1000 ng/mL for vanillin and 10–5000 ng/mL for vanillic acid with a coefficient of determination >0.999 for the determined compounds. The lower limits of quantification of vanillin and vanillic acid were 5.0 and 10.0 ng/mL, respectively. The intra‐ and inter‐run precisions expressed as the relative standard deviation were 2.6–8.6 and 3.2–10.2%, respectively, and the accuracies expressed as the relative error were in the range of –6.1 to 7.3%. Extraction recoveries of analytes were between 89.5 and 97.4%. There was no notable matrix effect for any analyte concentration. The developed method was proved to be sensitive, repeatable, and accurate for the quantification of vanillin and its vanillic acid metabolite in human plasma.