Simultaneous determination of amantadine, rimantadine, and memantine in processed products, chicken tissues, and eggs by liquid chromatography with tandem mass spectrometry

Ultrasensitive SERS aptasensor using Au@Ag bimetallic nanorod SERS tags for the selective detection of amantadine in foods

Herein, a novel surface enhanced Raman spectroscopy (SERS) aptasensor was developed for amantadine (AMD) detection, based on magnetite nanoparticles coated with polyethylenimine, silver nanoclusters and aptamers (Fe3O4@PEI@AgNC-apt) as the capture probe and complementary DNA-modified gold nanorods (AuNRs@4-MPBA@Ag-c-DNA containing 4-mercaptophenylboric acid molecules) as the reporter probe. In the presence of AMD, the AMD and the reporter probe competed for the aptamer on the surface of the capture probe, resulting in the reporter probe detaching from the capture probe leading to a decrease in intensity of the SERS signal at 1067 cm-1 for 4-MPBA. Under optimal conditions, a good linear relationship was established between the SERS intensity at 1067 cm-1 and the logarithm of the AMD concentration over the range 10-6-102 mg L-1, with a LOD of 0.50 × 10-6 mg L-1. The AMD levels in spiked samples were evaluated using the SERS aptasensor, with good recoveries ranging from 90.57% to 113.49% being obtained.

Development and validation of rapid screening of 192 veterinary drug residues in aquatic products using HPLC-HRMS coupled with QuEChERS

The presence of veterinary drug residues in aquatic products represents a significant challenge to food safety. The current detection methods, limited in both scope and sensitivity, underscore the urgent need for more advanced techniques. This research introduces a swift and potent screening technique using high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) and a refined QuEChERS protocol, allowing simultaneous qualitative and semi-quantitative analysis of 192 residues. A comprehensive database, employing full scan mode and data-dependent secondary mass spectroscopy, enhances screening accuracy. The method involves efficient extraction using 90% acetonitrile, dehydration with Na2SO4, and acetic acid, followed by cleanup using dispersive solid-phase extract sorbent primary secondary amine. It is suitable for samples with varying fat content, offering detection limits ranging from 0.5 to 10 μg/kg, high recovery rates (60-120%), and low relative standard deviations (<20%). Practical application has validated its effectiveness for multi-residue screening, marking a significant advancement in food safety evaluation.

Selective determination of 2-aminobenzothiazole in environmental water and organic extracts from fish and dust samples

In the present study, a homemade mixed-mode ion-exchange sorbent based on silica with embedded graphene microparticles is applied for the selective extraction of 2-aminobenzothiazole (NH2BT) followed by determination through liquid chromatography coupled to high-resolution mass spectrometry. The sorbent was evaluated for the solid-phase extraction of NH2BT from environmental water samples (river, effluent wastewater, and influent wastewater), and NH2BT was strongly retained through the selective cation-exchange interactions. Therefore, the inclusion of a clean-up step of 7 mL of methanol provided good selectivity for the extraction of NH2BT. The apparent recoveries obtained for environmental water samples ranged from 62 to 69% and the matrix effect from -1 to -14%. The sorbent was also evaluated in the clean-up step of the organic extract for the extraction of NH2BT from organic extracts of indoor dust samples (10 mL of ethyl acetate from pressurized liquid extraction) and fish (10 mL of acetonitrile from QuEChERS extraction). The organic extracts were acidified (adding a 0.1% of formic acid) to promote the cation-exchange interactions between the sorbent and the analyte. The apparent recoveries for fish samples ranged from 22 to 36% depending on the species. In the case of indoor dust samples, the recovery was 41%. It should be highlighted the low matrix effect encountered in such complex samples, with values ranging from -7 to 5% for fish and dust samples. Finally, various samples were analyzed. The concentration in river samples ranged from 31 to 136 ng/L; in effluent wastewater samples, from 55 to 191 ng/L; in influent wastewater samples, from 131 to 549 ng/L; in fish samples, from 14 to 57 ng/g dried weight; and in indoor dust samples, from  Collapse

Key Words

• Clean-up
• Complex water samples
• Dust
• Fish
• Homemade mixed-mode ion-exchange sorbent
• Selective solid-phase extraction

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MESH Headings

• Animals
• Tandem Mass Spectrometry/methods
• Wastewater
• Water/analysis
• Dust/analysis
• Water Pollutants, Chemical/analysis
• Solid Phase Extraction/methods
• Fishes
• Cations/analysis

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Grants

• 2020PMF-PIPF-33 Universitat Rovira i Virgili
• PID2020-114587GB-I00 Ministerio de Ciencia e Innovación

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Affiliation(s)

Alberto Moral Department of Analytical Chemistry and Organic Chemistry, Universitat Rovira i Virgili, Sescelades Campus, Marcel·lí Domingo 1, 43007, Tarragona, Spain
Francesc Borrull Department of Analytical Chemistry and Organic Chemistry, Universitat Rovira i Virgili, Sescelades Campus, Marcel·lí Domingo 1, 43007, Tarragona, Spain
Kenneth G Furton Department of Chemistry and Biochemistry, Florida International University, International Forensic Research Institute, Miami, FL, 33199, USA
Abuzar Kabir Department of Chemistry and Biochemistry, Florida International University, International Forensic Research Institute, Miami, FL, 33199, USA
Núria Fontanals Department of Analytical Chemistry and Organic Chemistry, Universitat Rovira i Virgili, Sescelades Campus, Marcel·lí Domingo 1, 43007, Tarragona, Spain.
Rosa Maria Marcé Department of Analytical Chemistry and Organic Chemistry, Universitat Rovira i Virgili, Sescelades Campus, Marcel·lí Domingo 1, 43007, Tarragona, Spain

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Highly Sensitive Magnetic-Nanoparticle-Based Immunochromatography Assay for Rapid Detection of Amantadine in Chicken and Eggs

Amantadine (AMD) is an antiviral drug that is prohibited for use in livestock and poultry. In this study, carboxyl-modified magnetic nanoparticles (MNPs) were synthesized using the solvothermal method in one step with harmless and inexpensive regents, and they were used to label monoclonal antibodies (mAbs) of AMD in microwells with electrostatic adsorption. Then, a magnetic immunochromatography assay (MICA) method was successfully established. Under optimal conditions, the MICA showed a good performance, with a linear range of 0.2~10.0 µg/L. The limit of detection (LOD) was 0.068 µg/L with the instrument, and the visual LOD (vLOD) was 0.5 µg/L. There was no cross-reaction with rimantadine and ribavirin. The vLOD in real samples was 1.0 µg/kg. The developed MICA has the advantages of convenience, speed, and sensitivity, which make it suitable for the on-site rapid detection of AMD residues in chicken tissues and eggs.

A novel method based on Ag-Au nanorings with tunable plasmonic properties for the sensitive detection of amantadine

To prevent the toxic effect of amantadine (AMD) on humans, a sensitive and direct detection method is required. The conventional enzyme-linked immunosorbent assay (ELISA) usually shows a monochromatic gradient color variation with the concentration of the target; hence, it is not a sensitive method for naked-eye detection. In this work, Ag-Au nanorings with highly tunable plasmon properties were synthesized as colorimetric nanosensors. The growth of Ag on the hollow nanorings led to rich color variations. Ag-Au nanorings were integrated into ELISA for the sensitive detection of AMD with the naked eye. The proposed method showed high sensitivity for the qualitative and quantitative detection of AMD, the visible cut-off value (0.2 ng mL^-1) and limit of detection (0.071 ng mL^-1) were 10-fold and 4.7-fold lower, respectively, than those of conventional ELISA. This method showed a linear range of 0.08-2 ng mL^-1 and 4-12 ng mL^-1. The detection results of this method on 100 samples (food samples and municipal water) agreed well with those of liquid chromatography-tandem mass spectrometry. The proposed plasmonic ELISA has high sensitivity, easy operation, and naked-eye readout.

[Simultaneous Analysis of 7 Antiviral Agents in Chicken Tissues and Processed Products by LC-MS/MS]

Since amantadine, rimantadine, arbidol, laninamvir, oseltamivir, peramivir, and zanamivir may be used as antiviral agents to treat avian influenza, we herein developed a simultaneous assay using LC-MS/MS. This method was applied to chicken products (including yakitori (grilled chicken), fried chicken, chicken steak, and boiled eggs) as well as chicken tissues (muscle, fat, the liver, gizzards, and heart) and eggs.Samples were extracted with methanol-water (9 : 1), purified by a tandem column with an InertSep^® MAX cartridge (upper part) and InertSep^® MCX cartridge (lower part), and then measured by LC-MS/MS. The sample matrix had no effect on the identification of compounds. Chromatographic separation was performed on a ZIC-HILIC column using a mobile phase of 1% acetic acid solution and 1% acetic acid solution in acetonitrile, resulting in complete separation and other obstructive peaks from the sample matrices. An external solvent calibration curve was used for quantification.The application of the method to 6 samples of chicken tissues and eggs achieved good results of between 77.9 and 97.5% for trueness and between 1.7 and 9.2% for concurrent accuracy. The method was also applied to 9 samples of processed products, including grilled chicken and fried chicken, and achieved good results with true percentages ranging between 72.6 and 99.2% and concurrent accuracies between 3.0 and 11.2%. Therefore, the developed method may also be applied to processed products.The limit of quantification (LOQ) of the developed method was 0.01 mg/kg.The method was then applied to 42 types of commercial processed products, including yakitori, fried chicken, steamed chicken, chicken steak, and boiled eggs, and no antiviral agents were detected.Collectively, the present results confirmed that the method developed herein is applicable to not only chicken tissues, but also their processed products.

Development and validation of a quantitative method for 15 antiviral drugs in poultry muscle using liquid chromatography coupled to tandem mass spectrometry

The objective of this work was to develop a quantitative multi-residue method for analysing antiviral drug residues and their metabolites in poultry meat samples. Antiviral drugs are not licensed for the treatment of influenza in food producing animals. However, there have been some reports indicating their illegal use in poultry. In this study, a method was developed for the analysis of 15 antiviral drug residues in poultry muscle (chicken, duck, quail and turkey) using liquid chromatography coupled to tandem mass spectrometry. This included 13 drugs against influenza and associated metabolites, but also two drugs employed for the treatment of herpes (acyclovir and ganciclovir). The method required the development of a novel chromatographic separation using a hydrophilic interaction chromatographic (HILIC) BEH amide column, which was necessary to retain the highly polar compounds. The analytes were detected using a triple quadrupole mass spectrometer operating in positive electrospray ionization mode. A range of different sample preparation protocols suitable for polar compounds were evaluated. The most effective procedure was based on a simple acetonitrile-based protein precipitation step followed by a further dilution in a methanol/water solution. The confirmatory method was validated according to the EU 2021/808 guidelines on different species including chicken, duck, turkey and quail. The validation was performed using various calibration curves ranging from 0.1 µg kg^-1to 200 µg kg^-1, according to the analyte. Depending on the analyte sensitivity, decision limits achieved ranged from 0.12 µg kg^-1 for arbidol to 34.7 µg kg^-1 for ribavirin. Overall, the reproducibility precision values ranged from 2.8% to 22.7% and the recoveries from 84% to 127%. The method was applied to 120 commercial poultry samples from the Irish market, which were all found to be residue-free.

Synthesis and characterization of tracers and development of a fluorescence polarization immunoassay for amantadine with high sensitivity in chicken

Fluorescence polarization immunoassay (FPIA) is a homogeneous and rapid analytical method that is suitable for high-throughput screening of large numbers of samples. However, FPIA typically suffers from lower sensitivity than the well-established enzyme-linked immunosorbent assay (ELISA), limiting its wide application as an analytical tool that can be run with trace levels of an analyte. Herein, a highly sensitive FPIA for detecting amantadine (AMD) in chicken is described. To achieve high sensitivity, nine chemical tracers of AMD that employ different fluoresceins, fluorescein derivatives, and haptens were synthesized and paired with four previously produced monoclonal antibodies (mAbs). The effect of the tracer structure on the sensitivity of FPIA was investigated and discussed. We found that the tracers with a linear and shorter bridge between adamantane and fluorescein generally provided higher sensitivity. After optimization, N'-(1-adamantyl) ethylenediamine (AEDA), an AMD structural analogue labeled with fluorescein isothiocyanate (FITC), achieved the lowest IC₅₀ value (1.0 ng/ml) in the FPIA, which was comparable to that of the heterologous ELISA format that used the same mAb7G2. We also investigated the possible recognition mechanism of mAbs in terms of conformational and electronic aspects. The developed FPIA was applied to chicken to detect AMD residue, demonstrating a limit of detection (LOD) of 0.9 µg/kg with recoveries of 76.5-89.3% and coefficients of variation (CVs) below 14.5%. These results show that the proposed FPIA is an efficient, accurate, and convenient method for the rapid screening of AMD residues in chicken. PRACTICAL APPLICATION: The fluorescence polarization immunoassay (FPIA) was developed to determine and quantify amantadine (AMD) in chicken samples with high sensitivity. This homogeneous method avoids coating and washing steps and may provide high-throughput AMD screening in chicken in 10 min with high accuracy and precision. FPIA can be used as a monitoring tool and contribute significantly to the rapid detection of AMD in chicken.

Dual mixed-mode poly (vinylpyridine-co-methacrylic acid-co-ethylene glycol dimethacrylate)-based sorbent for acidic and basic drug extraction from oral fluid samples

In this study, a dual mixed-mode polymer sorbent was prepared via one-step thermally initiated polymerization of 4-vinylpyridine (VP), methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) for the solid-phase extraction (SPE) of basic and acidic drugs. The use of VP and MAA as ionizable functional monomers allowed the tailoring of ion-exchange and hydrophobic features of the polymer. The obtained polymer was characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Next, the retention behavior of dual mixed-mode polymer towards basic and acidic drugs was investigated. Moreover, the practical capability of this novel material was tested for the extraction of relevant drugs such as cocaine, 3-methylmethcathinone, and diazepam in oral fluid samples. Recovery values (at different spiked levels in blank oral fluid samples), ranging from 69 to 99%, and limits of detection (LODs), between 0.10 and 0.25 μg L^-1, were obtained.

Simultaneous determination of five antiviral drug residues and stability studies in honey using a two-step fraction capture coupled to liquid chromatography tandem mass spectrometry

An effective sample pretreatment method followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) was first developed for simultaneous determination of five antiviral drug residues including ribavirin, moroxydine, amantadine, rimantadine and memantine in honey. To adsorb analytes with different binding properties and overcome the interference of sugars and uridine as endogenous ribavirin structural analogs in honey, the target drugs were extracted with 1% formic acid and then purified by a phenylboronic acid (PBA) solid phase extraction cartridge using two-step fraction capture prior to LC-MS/MS analysis. This method was validated by analyzing honey samples from nine floral origins including miscellaneous flowers, citrus, vitex, rape, acacia, sunflower, linden, buckwheat and jujube spiking at multiple levels, and the recoveries ranged from 82.46% to 116.34%, with relative standard deviations (RSDs) less than 14.58%. The limits of detection (LODs) and limits of quantitation (LOQs) of moroxydine, ribavirin, amantadine, rimantadine, and memantine were 0.1-2 µg/kg and 0.2-5 µg/kg, respectively. Depletion experiments of five antiviral drugs in honey at different storage and process temperatures demonstrated that moroxydine can potentially be used as a drug to cure sacbrood disease in honeybees.

On-line multi-residue analysis of fluoroquinolones and amantadine based on an integrated microfluidic chip coupled to triple quadrupole mass spectrometry

An on-line multi-residue qualitative and quantitative analysis method for fluoroquinolones and amantadine using an integrated microfluidic chip was developed prior to directly coupling to triple quadrupole mass spectrometry (QQQ-MS). Six parallel channels consisting of sample filtration units and micro solid phase extraction (micro-SPE) columns were present in the specifically designed microfluidic device. Firstly, the impurities in the sample solution were trapped by the micropillars in the filtration units. The solution passed through the micro-SPE units packed with hydrophilic-lipophilic balanced (HLB) particles, and then the two classes of drugs were enriched. After washing, the targets were eluted and immediately electrosprayed for MS analysis. This approach allowed effective filtration, enrichment, elution, and MS detection without the introduction of an additional separation step after SPE. Direct electrospray ionization (ESI)-MS in multiple reaction monitoring (MRM) mode could not only ensure the high sensitivity of quantitative analysis, but also achieved accurate qualitative analysis towards targets using the MRM ratios, reducing the possibility of false positives. Good linear relationships were obtained by the internal standard (IS) method with a linear range of 1-200 ng mL^-1 (R² > 0.992). The mean recoveries of the eight target analytes were from 85.2% to 122% with the relative standard deviation (RSD) ranging from 5.6% to 20.3%. All this demonstrated that the developed microfluidic device could be a useful tool for rapid detection in the field of food safety.

Nanochannel sensor for sensitive and selective adamantanamine detection based on host-guest competition

The abuse of adamantanamine (ADA) and its derivatives as veterinary drugs in the poultry industry could cause severe health problems for humans. It is of great need to develop a rapid, cheap and ultrasensitive method for ADA detection. In this study, a sensitive conical nanochannel sensor was established for the rapid quantitative detection of ADA with the distinctive design of the host-guest competition. The sensor was constructed by functionalizing the nanochannel surface with p-toluidine and was then assembled with Cucurbit [7]uril (CB [7]). When ADA is added, it could occupy the cavity of CB [7] due to the host-guest competition and makes CB [7] to release from the CB [7]-p-toluidine complex, resulting in a distinct change of hydrophobicity of the nanochannel, which could be determined by the ionic current. Under the optimal conditions, the strategy permitted sensitive detection of ADA in a linear range of 10-1000 nM. The nanochannel based ADA sensing platform showed both high sensitivity and excellent reproducibility and the limit of detection was 4.54 nM. For the first time, the rapid and sensitive recognition of an illegal medicine was realized based on the host-guest competition method with the nanochannel system and the principle and feasibility of this method were described at length. This strategy provides a simple, reliable, and effective way to apply host-guest system in the development of nanochannel sensor for small-molecule drug detection.

Comparative review of respiratory diseases caused by coronaviruses and influenza A viruses during epidemic season

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to sweep the world, causing infection of millions and death of hundreds of thousands. The respiratory disease that it caused, COVID-19 (stands for coronavirus disease in 2019), has similar clinical symptoms with other two CoV diseases, severe acute respiratory syndrome and Middle East respiratory syndrome (SARS and MERS), of which causative viruses are SARS-CoV and MERS-CoV, respectively. These three CoVs resulting diseases also share many clinical symptoms with other respiratory diseases caused by influenza A viruses (IAVs). Since both CoVs and IAVs are general pathogens responsible for seasonal cold, in the next few months, during the changing of seasons, clinicians and public heath may have to distinguish COVID-19 pneumonia from other kinds of viral pneumonia. This is a discussion and comparison of the virus structures, transmission characteristics, clinical symptoms, diagnosis, pathological changes, treatment and prevention of the two kinds of viruses, CoVs and IAVs. It hopes to provide information for practitioners in the medical field during the epidemic season.

Analysis of amantadine in Laminaria Japonica and seawater of Daqin Island by ultra high performance liquid chromatography with positive electrospray ionization tandem mass spectrometry

A sensitive and validated method for determination of amantadine in Laminaria Japonica and seawater was established using ultra high performance liquid chromatography with positive electrospray ionization tandem spectrometry (UHPLC-ESI-MS/MS). Laminaria Japonica was extracted with acetonitrile containing formic acid (1%), then purified with 10.0 g anhydrous sodium sulfate, 0.50 g C18 and 0.50 g PSA powder. Seawater added 10.0 mL 0.20 mol/L hydrochloric acid was purified with MCX solid phase extraction (SPE) cartridge. After extraction and purification, the supernatant of Laminaria Japonica and eluate of seawater were evaporated to nearly dry under a gentle stream of nitrogen at 40 °C. Acetonitrile-0.1% formic acid in water (3/7, v/v) was adjusted to 1.00 mL final volume. An aliquot (10 μL) was injected into the C18 column for separation with the mobile phase of acetonitrile and 0.1% formic acid in water at 0.25 mL·min-1. Calibration curves were linear ranged from 1.00 ng/mL to 20.0 ng/mL. Mean recoveries were 73.5% to 95.8%, and limit of detection (LOD) and quantification (LOQ) were 0.50 μg/kg and 1.00 μg/kg for Laminaria Japonica. Mean recoveries were 75.8% to 93.4%, and LOD and LOQ were 0.50 ng/L and 1.00 ng/L for seawater. Based on the method above, Laminaria Japonica and seawater in Daqin Island were analyzed in February to June continuously, lgBAF3.71 (bioaccumulation factor), indicating a bioenrichment effect.

A Highly Selective and Strong Anti-Interference Host-Guest Complex as Fluorescent Probe for Detection of Amantadine by Indicator Displacement Assay

Amantadine (AMA) and its derivatives are illicit veterinary drugs that are hard to detect at very low concentrations. Developing a fast, simple and highly sensitive method for the detection of AMA is highly in demand. Here, we designed an anthracyclic compound (ABAM) that binds to a cucurbit[7]uril (CB[7]) host with a high association constant of up to 8.7 × 10⁸ M⁻¹. The host-guest complex was then used as a fluorescent probe for the detection of AMA. Competition by AMA for occupying the cavity of CB[7] allows ABAM to release from the CB[7]-ABAM complex, causing significant fluorescence quenching of ABAM (indicator displacement assay, IDA). The linear range of the method is from 0.000188 to 0.375 μg/mL, and the detection limit can be as low as 6.5 × 10⁻⁵ μg/mL (0.35 nM). Most importantly, due to the high binding affinity between CB[7] and ABAM, this fluorescence host-guest system shows great anti-interference capacity. Thus, we are able to accurately determine the concentration of AMA in various samples, including pharmaceutical formulations.

Simultaneous determination of amantadine and rimantadine in feed by liquid chromatography-Qtrap mass spectrometry with information-dependent acquisition

A sensitive method for simultaneous determination of amantadine and rimantadine in feed was developed using an ultra-high-performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UHPLC-Qtrap-MS) in the multiple reaction monitoring information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode, and employing the mixed cation exchange (MCX) solid-phase extraction column as sample cleanup and amantadine-d₁₅ and rimantadine-d₄ as internal standards, respectively. Compared to traditional MRM mode, for the targeted drugs in feed simultaneously both the secondary mass spectra and MRM information can be obtained using UHPLC-Qtrap-MS with MRM-IDA-EPI mode, and thus more accurate qualitative confirmation results achieved even at lower concentration of 0.2 μg/L in acceptable purity fit values. After optimization of sample preparation, good linearities (R > 0.9994) were obtained over the concentration range from 1 to 200 μg/L for amantadine and rimantadine. The precision was validated by intra-day and inter-day, and the relative standard deviations were all within 9.61%. Mean recoveries ranged from 76.1 to 112% at spiked concentrations of 0.5-100 μg/kg in three types of feed samples, including formula feed and complex concentrated feed for pigs and premix feed for chicken. The limits of detection (LODs) and quantification (LOQs) were 0.2 and 0.5 μg/kg for both drugs, respectively. The application in real feed samples further proved the accuracy and reliability of the developed method. This method provides an important tool to detect illegal uses of amantadine and rimantadine in feed. Graphical abstract Simultaneous quantitation and qualitative confirmation of amantadine and rimantadine in feed by MRM-IDA-EPI.

Sensitive and rapid determination of amantadine without derivatization in human plasma by LC-MS/MS for a bioequivalence study

A highly sensitive, rapid and rugged liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS) method was developed for reliable estimation of amantadine (AMD), an antiviral drug in human plasma. The analyte and internal standard (IS), amantadine-d6 (AMD-d6), were extracted from 200 µL plasma by solid phase extraction on Phenomenex Strata-X-C 33 µ cartridges. Chromatography was performed on Synergi™ Hydro-RP C₁₈ (150 mm × 4.6 mm, 4 µm) analytical column using a mixture of acetonitrile and 10 mM ammonium formate, pH 3.0 (80:20, v/v) as the mobile phase. Detection and quantitation was done by multiple reaction monitoring in the positive ionization mode for AMD (m/z 152.1 → 135.1) and IS (m/z 158.0 → 141.1) on a triple quadrupole mass spectrometer. The assay was linear in the concentration range of 0.50–500 ng/mL with correlation coefficient (r²) ≥ 0.9969. The limit of detection of the method was 0.18 ng/mL. The intra-batch and inter-batch precisions were ≤ 5.42% and the accuracy varied from 98.47% to 105.72%. The extraction recovery of amantadine was precise and quantitative in the range of 97.89%–100.28%. IS-normalized matrix factors for amantadine varied from 0.981 to 1.012. The stability of AMD in whole blood and plasma was evaluated under different conditions. The developed method was successfully applied for a bioequivalence study with 100 mg of AMD in 32 healthy volunteers. The reproducibility of the assay was determined by reanalysis of 134 subject samples.

Isomeric separation and quantitation of di-(2-ethylhexyl) trimellitates and mono-(2-ethylhexyl) trimellitates in blood by LC-MS/MS

A new and fast HPLC-method for the simultaneous determination of tri-(2-ethylhexyl) trimellitate (TOTM or TEHTM), its diesters 2,4-di-(2-ethylhexyl) trimellitate (2,4-DEHTM), 1,4-di-(2-ethylhexyl) trimellitate (1,4-DEHTM), 1,2-di-(2-ethylhexyl) trimellitate (1,2-DEHTM) and monoesters 1-mono-(2-ethylhexyl) trimellitate (1-MEHTM), 2-mono-(2-ethylhexyl) trimellitate (2-MEHTM) and 4-mono-(2-ethylhexyl) trimellitate (4-MEHTM) together with di-(2-ethylhexyl) phthalate (DEHP) and its primary metabolite mono-(2-ethylhexyl) phthalate (MEHP) in blood was developed and validated. The analytes are extracted from blood using liquid-liquid extraction and are chromatographically separated by reversed-phase HPLC using core shell material. Quantitative assessment was performed by ESI-tandem mass spectrometry in negative ionization mode using stable isotope dilution. In less than 30min six postulated primary metabolites of TOTM along with the DEHP metabolite MEHP can be selectively and sensitively quantified. Additionally, the method enables the determination of the parent plasticizers TOTM and DEHP. The detection limits in blood were found to range between 0.7-5.5μg/L for all TOTM analytes. Precision and repeatability of the method were proven by relative standard deviations between 0.9% and 8.7%. TOTM, an alternative plasticizer to DEHP, is already increasingly used for medical devices. Nevertheless, data about the human metabolism of TOTM are still limited. The presented method is the first one enabling the simultaneous determination of the parent plasticizers TOTM and DEHP together with their primary degradation products (DEHTM, MEHTM, MEHP) and can thus be applied manifold including the investigation of the human metabolism of TOTM.