Analytical tools for identification of non-intentionally added substances (NIAS) coming from polyurethane adhesives in multilayer packaging materials and their migration into food simulants

Adhesives used in food packaging to glue different materials can provide several substances as potential migrants, and the identification of potential migrants and migration tests are required to assess safety in the use of adhesives. Solid-phase microextraction in headspace mode and gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) and ChemSpider and SciFinder databases were used as powerful tools to identify the potential migrants in the polyurethane (PU) adhesives and also in the individual plastic films (polyethylene terephthalate, polyamide, polypropylene, polyethylene, and polyethylene/ethyl vinyl alcohol). Migration tests were carried out by using Tenax(?) and isooctane as food simulants, and the migrants were analyzed by gas chromatography coupled to mass spectrometry. More than 63 volatile and semivolatile compounds considered as potential migrants were detected either in the adhesives or in the films. Migration tests showed two non-intentionally added substances (NIAS) coming from PU adhesives that migrated through the laminates into Tenax(?) and into isooctane. Identification of these NIAS was achieved through their mass spectra, and 1,6-dioxacyclododecane-7,12-dione and 1,4,7-trioxacyclotridecane-8,13-dione were confirmed. Caprolactam migrated into isooctane, and its origin was the external plastic film in the multilayer, demonstrating real diffusion through the multilayer structure. Comparison of the migration values between the simulants and conditions will be shown and discussed.     

High‐efficiency sample preparation approach to determine acrylamide levels in high‐fat foods

An improved sample preparation method was developed to enhance acrylamide recovery in high‐fat foods. Prior to concentration, distilled deionized water was added to protect acrylamide from degradation, resulting in a higher acrylamide recovery rate from fried potato chips. A Chrome‐Matrix C₁₈ column (2.6 μm, 2.1 × 100 mm) was used for the first time to analyze acrylamide levels using ultra high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry, displaying good separation of acrylamide from interference. A solid‐phase extraction procedure was avoided, and an average recovery of >89.00% was achieved from different food matrices for three different acrylamide spiking levels. Good reproducibility was observed, with an intraday relative standard deviation of 0.04–2.38%, and an interday relative standard deviation of 2.34–3.26%. Thus, combining the improved sample preparation method for acrylamide analysis with the separation on a Chrome‐Matrix C₁₈ column (2.6 μm, 2.1 × 100 mm) using ultra high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry is highly useful for analyzing acrylamide levels in complex food matrices.     

Development of a LC–MS/MS method for the determination of isomeric glutamyl peptides in food ingredients

A liquid chromatography with tandem mass spectrometry method was developed for the determination of 27 glutamyl di‐ and tripeptides in food ingredients. Such compounds are of importance for the food industry, as they can modulate the perception of basic tastes (sweet, salty, and umami). Due to their high polarity, the hydrophilic interaction chromatography mode was selected to have sufficient retention on the column and the best separation was obtained on an amide hybrid silica stationary phase packed with 1.7 μm particles. Thorough optimization of the mobile phase was performed as the start‐composition had to be free of ammonium to avoid on‐column cis–trans isomerization of the first eluting proline dipeptide. A baseline separation was achieved for all α and γ isomers whereas only a partial resolution was obtained for γ‐Glu‐Leu and γ‐Glu‐Ile, for which only the position of a methyl group differs. A fast sample preparation, based on successive dilutions, was performed before injection into the liquid chromatography with tandem mass spectrometry system. The developed method was then applied for the semi‐quantification of glutamyl di‐ and tri‐peptides in four different food ingredients. The methodology will further support the optimization of production processes to select the conditions for which the peptide concentrations would be the highest.     

Simultaneous determination of phenolic compounds in Equisetum palustre L. by ultra high performance liquid chromatography with tandem mass spectrometry combined with matrix solid‐phase dispersion extraction

A method based on matrix solid‐phase dispersion extraction followed by ultra high performance liquid chromatography with tandem mass spectrometry is presented for the extraction and determination of phenolic compounds in Equisetum palustre. This method combines the high efficiency of matrix solid‐phase dispersion extraction and the rapidity, sensitivity, and accuracy of ultra high performance liquid chromatography with tandem mass spectrometry. The influential parameters of the matrix solid‐phase dispersion extraction were investigated and optimized. The optimized conditions were as follows: silica gel was selected as dispersing sorbent, the ratio of silica gel to sample was selected to be 2:1 (400/200 mg), and 8 mL of 80% methanol was used as elution solvent. Furthermore, a fast and sensitive ultra high performance liquid chromatography with tandem mass spectrometry method was developed for the determination of nine phenolic compounds in E. palustre. This method was carried out within <6 min, and exhibited satisfactory linearity, precision, and recovery. Compared with ultrasound‐assisted extraction, the proposed matrix solid‐phase dispersion procedure possessed higher extraction efficiency, and was more convenient and time saving with reduced requirements on sample and solvent amounts. All these results suggest that the developed method represents an excellent alternative for the extraction and determination of active components in plant matrices.     

Determination of aminoglycoside residues in kidney and honey samples by hydrophilic interaction chromatography‐tandem mass spectrometry

Two methods based on liquid chromatography–tandem mass spectrometry were developed for the determination of ten aminoglycosides (streptomycin, dihydrostreptomycin, spectinomycin, apramycin, paromomycin, kanamycin A, gentamycin C1, gentamycin C2/C2a, gentamycin C1a, and neomycin B) in kidney samples from food‐producing animals and in honey samples. The methods involved extraction with an aqueous solution (for the kidney samples) or sample dissolution in water (for the honey samples), solid‐phase extraction with a weak cation exchange cartridge and injection of the eluate into a liquid chromatography–tandem mass spectrometry system. A zwitterionic hydrophilic interaction chromatography column was used for separation of aminoglycosides and a triple quadrupole mass analyzer was used for detection. The methods were validated according to Decision 2002/657/EC. The limits of quantitation ranged from 2 to 125 μg/kg in honey and 25 to 264 μg/kg in the kidney samples. Interday precision (RSD%) ranged from 6 to 26% in honey and 2 to 21% in kidney. Trueness, expressed as the percentage of error, ranged from 7 to 20% in honey and 1 to 11% in kidney.     

A rapid method for the determination of brominated flame retardant concentrations in plastics and textiles entering the waste stream

Due to new European legislation, products going to waste are subject to ‘low persistent organic pollutant concentration limits’. Concentrations of restricted brominated flame retardants in waste products must be determined. A rapid extraction and clean‐up method was developed for determination of brominated flame retardants in various plastics and textiles. The optimised method used vortexing and ultrasonication in dichloromethane followed by sulfuric acid clean‐up to determine target compounds. Poly‐brominated diphenyl ethers were determined by gas chromatography with mass spectrometry and hexabromocyclododecane by liquid chromatography with tandem mass spectrometry. Good recoveries of target analytes were obtained after three extraction cycles. The method was validated using poly‐propylene and poly‐ethylene certified reference materials as well as previously characterised textiles, expanded and extruded poly‐styrene samples. Measured concentrations of target compounds showed good agreement with the certified values indicating good accuracy and precision. Clean extracts provided low noise levels resulting in low limits of quantification (0.8–1.5 ng/g for poly‐brominated diphenyl ethers and 0.3 ng/g for α‐, β‐ and γ‐hexabromocyclododecane). The developed method was applied successfully to real consumer products entering the waste stream and it provided various advantages over traditional methods, including reduced analysis time, solvent consumption, minimal sample contamination and high sample throughput, which is crucial to comply with the implemented legislation.     

Comparison of pulse glow discharge‐ion mobility spectrometry and liquid chromatography with tandem mass spectrometry based on multiplug filtration cleanup for the analysis of tricaine mesylate residues in fish and water

Analytical methods based on multiplug filtration cleanup coupled with pulse glow discharge‐ion mobility spectrometry and liquid chromatography tandem mass spectrometry were developed for the analysis of tricaine mesylate residue in fish and fish‐raising water samples. A silica fiber holder and an appropriate new interface were designed to make the direct introduction of the fiber into the pulse glow discharge‐ion mobility spectrometry introduction mechanism. The multiplug filtration cleanup method with adsorption mixtures was optimized for the determination of tricaine mesylate in fish samples. Good linear relationships were obtained by the two methods. For fish samples, limits of detection were 6 and 0.6 μg/kg by ion mobility spectrometry and liquid chromatography with tandem mass spectrometry, respectively. The matrix effect of the established liquid chromatography tandem mass spectrometry method was negligible for fish samples but that of the ion mobility spectrometry method was not. The two methods were compared. The ion mobility spectrometry system could be used a rapid screening tool on site with the advantage of rapidity, simplicity, and portability, and the liquid chromatography tandem mass spectrometry system could be used for validation in laboratory conditions with the advantage of lower limit of detection, stability, and precision.     

Identification and metabolite profiling of alkaloids in aerial parts of Papaver rhoeas by liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry

Papaver plants can produce diverse bioactive alkaloids. Papaver rhoeas Linnaeus (common poppy or corn poppy) is an annual flowering medicinal plant used for treating cough, sleep disorder, and as a sedative, pain reliever, and food. It contains various powerful alkaloids like rhoeadine, benzylisoquinoline, and proaporphine. To investigate and identify alkaloids in the aerial parts of P. rhoeas, samples were collected at different growth stages and analyzed using liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry. A liquid chromatography with mass spectrometry method was developed for the identification and metabolite profiling of alkaloids for P. rhoeas by comparing with Papaver somniferum. Eighteen alkaloids involved in benzylisoquinoline alkaloid biosynthesis were used to optimize the liquid chromatography gradient and mass spectrometry conditions. Fifty‐five alkaloids, including protoberberine, benzylisoquinoline, aporphine, benzophenanthridine, and rhoeadine‐type alkaloids, were identified authentically or tentatively by liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry in samples taken during various growth stages. Rhoeadine alkaloids were observed only in P. rhoeas samples, and codeine and morphine were tentatively identified in P. somniferum. The liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry method can be a powerful tool for the identification of diverse metabolites in the genus Papaver. These results may help understand the biosynthesis of alkaloids in P. rhoeas and evaluate the quality of this plant for possible medicinal applications.     

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 determination of niacin and pyridoxine at trace levels by using diode array high‐performance liquid chromatography and liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry

A highly sensitive and simple diode‐array high‐performance liquid chromatography and liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry method was developed for the simultaneous determination of niacin and pyridoxine in pharmaceutical drugs, tap water, and wastewater samples. To determine the in vivo behavior of niacin and pyridoxine, analytes were subjected to simulated gastric conditions. The calibration plots of the diode‐array high‐performance liquid chromatography and liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry method showed good linearity over a wide concentration range with close to 1.0 correlation coefficients for both analytes. The limit of detection/limit of quantitation values for liquid chromatography quadrupole time‐of‐flight tandem mass spectrometry analysis were 1.98/6.59 and 1.3/4.4 μg/L for niacin and pyridoxine, respectively, while limit of detection/limit of quantitation values for niacin and pyridoxine in high‐performance liquid chromatography analysis were 3.7/12.3 and 5.7/18.9 μg/L, respectively. Recovery studies were also performed to show the applicability of the developed methods, and percentage recovery values were found to be 90–105% in tap water and 94–97% in wastewater for both analytes. The method was also successfully applied for the qualitative and quantitative determination of niacin and pyridoxine in drug samples.     

Residue measurement of pendimethalin in tobacco by using heart‐cutting two dimensional liquid chromatography coupled with tandem mass spectrometry

A novel heart‐cutting two‐dimensional liquid chromatography coupled with tandem mass spectrometry method was developed for quantitative analysis of pendimethalin residue in tobacco. The strategy of reversed phase liquid chromatography coupled with another reversed‐phase liquid chromatography was employed for high column efficiency and excellent compatibility of mobile phase. In the first dimensional chromatography, a cyano column with methanol/water as the eluent was applied to separate pendimethalin from thousands of interference components in tobacco. By heart‐cutting technique, which effectively removed interference components, the target compound was cut to the second dimensional C18 column for further separation. The pendimethalin residue was finally determined by the tandem mass spectrometry under multiple reaction monitoring reversed‐phase liquid chromatography mode. Sample pretreatment of the new method was simplified, involving only extraction and filtration. Compared with traditional methodologies, the new method showed fairly high selectivity and sensitivity with almost no matrix interference. The limit of quantitation for pendimethalin was 1.21 ng/mL, whereas the overall recoveries ranged from 95.7 to 103.3%. The new method has been successfully applied to non‐stop measure of 200 real samples, without contamination of ion source. Detection results of the samples agreed well with standard method.     

In situ derivatization–liquid liquid extraction as a sample preparation strategy for the determination of urinary biomarker prolyl‐4‐hydroxyproline by liquid chromatography–tandem mass spectrometry

Polar analytes that possess protic functional groups have often been treated with alkyl chloroformates to decrease their polarity and increase their volatility prior to gas chromatography–mass spectrometry analysis. This derivatization reaction has two distinct advantages. It proceeds smoothly in aqueous media, and the desired reaction products are efficiently separated from interfering ionic components by their extraction into a water‐immiscible organic phase. In the present work, the derivatization–liquid liquid sample preparation was examined in detail for analysis of a potential urinary dipeptide biomarker l ‐prolyl‐4‐l ‐hydroxyproline (PHP) by downstream liquid chromatography coupled to electrospray mass spectrometry. PHP was treated with a series of alkyl and fluoroalkyl chloroformates in aqueous media, and the detected reaction products were investigated. Smooth conversion of PHP into the N‐isobutyloxycarbonyl isobutyl ester was accomplished by the coupled action of isobutanol, isobutyl chloroformate and the pyridine catalyst. This derivative afforded a highest detector response from all the derivatized forms examined, including the nonderivatized PHP. A simple isocratic elution on a common RP‐C18 HPLC column coupled with tandem mass spectrometry, and use of the synthesized heptadeuterated analog (D7‐PHP) as an internal standard, enabled validation of the method and determination of PHP in human urine in less than 5 min. The in situ derivatization–liquid liquid extraction has thus been demonstrated to be a useful sample preparation strategy for the analysis of polar metabolites by liquid chromatography–tandem mass spectrometry in the complex urine matrix. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of organophosphate esters in water samples by mixed‐mode liquid chromatography and tandem mass spectrometry

A simple and sensitive method for the determination of organophosphate esters in water samples by mixed‐mode liquid chromatography with electrospray ionization tandem mass spectrometry coupled with solid‐phase extraction is developed. Using seven alkyl phosphates, three chlorinated alkyl phosphates, and four aryl phosphates as the targets, the developed method was systematically evaluated on the basis of the influence of the solid‐phase extraction cartridge, eluting solvent, sample‐loading volume, mobile phase condition, and the separation of reversed‐phase chromatography and mixed‐mode liquid chromatography. Under the optimal conditions, these organophosphate esters can be extracted by ENVI‐18 cartridge, eluted by 6 mL of 25% dichloromethane in acetonitrile, and then qualified and quantified by mixed‐mode liquid chromatography with tandem mass spectrometry in the multiple reaction‐monitoring mode. The application of mixed‐mode liquid chromatography endows the separation with reasonable retention for both hydrophilic and hydrophobic organophosphate esters regardless of their polarity, which is hardly achieved by reversed‐phase chromatography. Good linearity (from 0.9877 to 0.9969), low quantification limits (1–35 ng/L after extraction of 100 mL of river water), and acceptable recovery rates (58.6–116.2%, with the relative standard deviation <18.0%) were obtained. Finally, the established method was used for analyzing surface water samples, and the good applicability of this method was demonstrated.     

Analysis of lignans in Magnoliae Flos by turbulent flow chromatography with online solid‐phase extraction and high‐performance liquid chromatography with tandem mass spectrometry

In this study, a method coupling turbulent flow chromatography with online solid‐phase extraction and high‐performance liquid chromatography with tandem mass spectrometry was developed for analyzing the lignans in Magnoliae Flos. By the online pretreatment of turbulent flow chromatography solid‐phase extraction, the impurities removal and analytes concentration were automatically processed, and the lignans were separated rapidly and well. Seven lignans of Magnoliae Flos including epieudesmin, magnolin, 1‐irioresinol‐B‐dimethyl ether, epi‐magnolin, fargesin aschantin, and demethoxyaschantin were identified by comparing their retention behavior, UV spectra, and mass spectra with those of reference substances or literature data. The developed method was validated, and the good results showed that the method was not only automatic and rapid, but also accurate and reliable. The turbulent flow chromatography with online solid‐phase extraction and high‐performance liquid chromatography with tandem mass spectrometry method holds a high potential to become an effective method for the quality control of lignans in Magnoliae Flos and a useful tool for the analysis of other complex mixtures.     

A strategy for screening trypsin inhibitors from traditional Chinese medicine based on a monolithic capillary immobilized enzyme reactor coupled with offline liquid chromatography and mass spectrometry

A novel strategy was successfully developed for screening trypsin inhibitors in traditional Chinese medicines based on monolithic capillary immobilized enzyme reactors combined with liquid chromatography‐tandem mass spectrometry. Organic polymer based monolithic enzyme reactors were firstly prepared by covalently bonding trypsin to a poly(glycidyl methacrylate‐co‐poly (ethylene glycol) diacrylate) monolith by the ring‐opening reaction of epoxy groups. The activity and kinetic parameters of the obtained monolithic trypsin reactors were systematically evaluated using micro‐liquid chromatography. Fourier transform infrared spectroscopy and scanning electron microscopy were also used to characterize the monolithic trypsin reactors. The resulting functional and denatured monolithic trypsin reactors were applied as affinity solid‐phase extraction columns, and offline coupled with a liquid chromatography‐tandem mass spectrometry system to construct a binding affinity screening platform. Subsequently, the proposed platform was applied for screening trypsin binders in a Scutellaria baicalensis Georgi extract. Three compounds, namely scutellarin, baicalin, and wogonoside were identified, and their inhibitory activities were further confirmed via an in vitro enzymatic inhibition assay. Additionally, molecular docking was also performed to study the interactions between trypsin and these three compounds.     

Poly[(2‐(acryloyloxy) ethyl]trimethylammonium chloride‐co‐ethylene dimethacrylate monolith on‐line solid‐phase extraction coupled with liquid chromatography and tandem mass spectrometry for the fast determination of salicylic acid in foodstuffs

We report the fabrication of an anion‐exchange monolithic column in a stainless‐steel chromatographic column (10 mm × 2.1 mm i.d.) using [2‐(acryloyloxy) ethyl]trimethylammonium chloride as the monomer and ethylene dimethacrylate as the crosslinker. The prepared monolith was developed as the adsorbent for the on‐line solid‐phase extraction of salicylic acid in various animal‐origin foodstuffs combined with liquid chromatography and tandem mass spectrometry. The monolith was characterized by using Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption analysis, and elemental analysis. Potential factors affecting the on‐line solid‐phase extraction and liquid chromatography with tandem mass spectrometry analysis were studied in detail. Under the optimized conditions, the total analysis time including cleanup and liquid chromatography with tandem mass spectrometry separation was 17 min. The developed method gave the linear range of 15–750 μg/kg, detection limits (S/N = 3) of 5 μg/kg, and quantification limits (S/N = 10) of 15 μg/kg. The recoveries obtained by spiking 10, 20, and 100 μg/kg of salicylic acid in the animal‐origin food samples were in the range of 85.2–98.4%. In addition, the monolith was stable enough for 550 extraction cycles with the precision of peak area ≤11.6%.     

Simultaneous analysis by Quadrupole‐Orbitrap mass spectrometry and UHPLC‐MS/MS for the determination of sedative‐hypnotics and sleep inducers in adulterated products

Adulterated products are continuously detected in society and cause problems. In this study, we developed and validated a method for determining synthetic sedative‐hypnotics and sleep inducers, including barbital, benzodiazepam, zolpidem, and first‐generation antihistamines, in adulterated products using Quadrupole‐Orbitrap mass spectrometry and ultrahigh performance liquid chromatography with tandem mass spectrometry. In Quadrupole‐Orbitrap mass spectrometry analysis, target compounds were confirmed using a combination of retention time, mass tolerance, mass accuracy, and fragment ions. For quantification, several validation parameters were employed using ultrahigh performance liquid chromatography with tandem mass spectrometry. The limit of detection and limit of quantitation was 0.05–53 and 0.17–177 ng/mL, respectively. The correlation coefficient for linearity was more than 0.995. The intra‐ and interassay accuracies were 86–110 and 84–111%, respectively. Their precision values were evaluated as within 4.0 (intraday) and 10.7% (interday). Mean recoveries of target compounds in adulterated products ranged from 85 to 116%. The relative standard deviation of stability was less than 10.7% at 4°C for 48 h. The 144 adulterated products obtained over 3 years (2014–2016) from online and in‐person vendors were tested using established methods. After rapidly screening with Quadrupole‐Orbitrap mass spectrometry, the detected samples were quantified using ultrahigh performance liquid chromatography with tandem mass spectrometry. Two of them were adulterated with phenobarbital.     

Determination of glycosylation degree for glycoconjugate vaccines using a solid‐phase extraction combined with liquid chromatography and tandem mass spectrometry method

In this study, a solid‐phase extraction with liquid chromatography and tandem mass spectrometry method was developed to determine the degree of glycosylation of glycosylation sites and the ratio of free carrier protein to total carrier protein for glycoconjugate vaccines. To remove and enrich the glycosylated peptides, a solid‐phase extraction method was developed, optimized, and hyphenated to liquid chromatography?tandem mass spectrometry. The developed solid‐phase extraction with liquid chromatography?tandem mass spectrometry method was shown to possess a wide linear dynamic range (0.03?100 μg/mL), a high sensitivity (0.03 μg/mL for CRM197), good interday and intra‐day precision (relative standard deviation of peak area < 3.3%), and good recoveries from vaccine matrix (90?105%). Finally, the method was utilized to determine the degree of glycosylation and free carrier protein to total carrier protein ratio for pneumococcal conjugate vaccines and meningococcal vaccines. For quality evaluation of glycoconjugate vaccines, the method could provide more information than the traditional size exclusion chromatography method. Fourteen and twelve reported glycosylation sites for CRM197‐ and tetanus toxin‐based vaccines can be detected, respectively.     

Covalently bonded aptamer‐functionalised magnetic mesoporous carbon for high‐efficiency chloramphenicol detection

A novel aptamer‐modified magnetic mesoporous carbon was prepared to develop a specific and sensitive magnetic solid‐phase extraction method through combination with ultra‐high performance liquid chromatography‐tandem mass spectrometry for the analysis chloramphenicol in complex samples. More specifically, the chloramphenicol aptamer‐modified Mg/Al layered double hydroxide magnetic mesoporous carbon was employed as a novel magnetic solid‐phase extraction sorbent for analyte enrichment and sample clean‐up. The extraction solvent, extraction time, desorption solvent, and desorption time were investigated. It was found that the mesoporous structure and aptamer‐based affinity interactions resulted in acceptable selective recognition and a good chemical stability toward trace amounts of chloramphenicol. Upon combination with the ultra‐high performance liquid chromatography‐tandem mass spectrometry technique, a specific and sensitive recognition method was developed with a low limit of detection (0.94 pmol/L, S/N = 3) for chloramphenicol analysis. The developed method was successfully employed for the determination of chloramphenicol in complex serum, milk powders, fish and chicken samples, giving recoveries of 87.0‐107% with relative standard deviations of 3.1‐9.7%.     

Determination and purification of sesamin and sesamolin in sesame seed oil unsaponified matter using reversed‐phase liquid chromatography coupled with photodiode array and tandem mass spectrometry and high‐speed countercurrent chromatography

In Asian countries, sesame seed oil unsaponified matter is used as a natural food additive due to its associated antioxidant effects. We determined and purified the primary lignans sesamin and sesamolin in sesame seed oil unsaponified matter using reversed‐phase liquid chromatography coupled with photodiode array and tandem mass spectrometry and high‐speed countercurrent chromatography. Calibration curves showed good correlation coefficients (r² > 0.999, range 0.08 and/or 0.15 to 5 μg/mL) with a limit of detection (at 290 nm) of 0.02 μg/mL for sesamin and 0.04 μg/mL for sesamolin. Sesame seed oil unsaponified matter contained 2.82% sesamin and 2.54% sesamolin, respectively. Direct qualitative analysis of sesamin and sesamolin was achieved using quadrupole mass spectrometry with positive‐mode electrospray ionization. Pure (>99%) sesamin and sesamolin standards were obtained using high‐speed countercurrent chromatographic purification (hexane/ethyl acetate/methanol/water; 7:3:7:3). An effective method for determining and purifying sesamin and sesamolin from sesame seed oil unsaponified matter was developed by combining these separation techniques for standardized food additives.