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Lv D, Wang D, Li D, Guo D, Qi M, Zhang Y, Chai Y, Chen X, Cao Y. A novel standard-free detection of adulteration method for sildenafil derivatives in dietary supplements. Biomed Chromatogr 2024; 38:e5925. [PMID: 38837800 DOI: 10.1002/bmc.5925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 05/13/2024] [Accepted: 05/19/2024] [Indexed: 06/07/2024]
Abstract
The rapid and accurate detection of illegal adulteration of chemical drugs into dietary supplements is a big challenge in the food chemistry field. Detection of compounds without a standard reference is even more difficult; however, this is a common situation. Here in this study, a novel "standard-free detection of adulteration" (SFDA) method was proposed and phosphodiesterase-5 inhibitor derivatives were used as an example to figure out the possibility and reliability of this SFDA method. After analysis by quadrupole coupled time of flight-tandem mass spectrometry detection and multivariable statistics, six common fragment ions were chosen to indicate whether adulteration was present or not, while 20 characteristic fragment ions indicated whether adulteration was by nitrogen-containing heterocycles or by anilines. Furthermore, the quantitative methods were conducted by high-performance liquid chromatography-tandem mass spectrometry. In a word, this strategy allows for a quick determination of dietary supplement adulteration without any need for standard materials, improving the efficacy of food safety testing.
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Affiliation(s)
- Diya Lv
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Dongyao Wang
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Dan Li
- Eastern Hepatobiliary Surgery Institute, Naval Medical University, Shanghai, China
| | - Dandan Guo
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Minyu Qi
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Ying Zhang
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Yifeng Chai
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Xiaofei Chen
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
| | - Yan Cao
- Shanghai Key Laboratory for Pharmaceutical Metabolite Research, School of Pharmacy, Naval Medical University, Shanghai, China
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Kee CL, Ge X, Low MY, Gilard V, Malet-Martino M. Analytical methods for the detection and characterization of unapproved phosphodiesterase type 5 inhibitors (PDE-5i) used in adulteration of dietary supplements- a review. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2023; 40:1495-1530. [PMID: 38011602 DOI: 10.1080/19440049.2023.2279567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 10/31/2023] [Indexed: 11/29/2023]
Abstract
This article is an up-to-date review of 112 unapproved phosphodiesterase type 5 inhibitors (PDE-5i) found as adulterants in sexual enhancement dietary supplements and other products from 2003 to July 2023. Seventy-five of these unapproved PDE-5i are analogues of sildenafil (67%), followed by 26 analogues of tadalafil (23%), 9 analogues of vardenafil (8%) and 2 other type of compounds (2%). The products have been formulated in various packaging, primarily in capsule, tablet, and powder forms. Common screening techniques allowing detection of such analogues include high performance or ultra-high performance liquid chromatography in tandem with ultra-violet detector (HPLC-UV or UPLC-UV) (50%) and thin-layer chromatography in tandem with ultra-violet detection (TLC-UV) (7%). Screening by mass spectrometry (MS) is relatively less common with the use of single-, triple-quadrupole or time-of-flight (TOF) mass spectrometers (9%). Meanwhile, the combined detection by UV-MS has been recorded at 10% usage. Screening by proton nuclear magnetic resonance spectroscopy (NMR) (11%) has also been applied. For compound characterization, i.e. structural elucidation, NMR spectroscopy has been preferred (100 out of 112 compounds), followed by high-resolution mass spectrometry (HRMS) (74 out of 112 compounds) and Fourier-transform infrared spectroscopy (FTIR) (44 out of 112 compounds). Over the past two decades, analytical technology has been evolving with enhanced sensitivity and resolution. Despite this, structural elucidation of the new emerging analogues in adulterated dietary supplements remains a challenge, especially when the analogues involve complex structural modification. Therefore, the above-mentioned techniques may not be adequate to characterize the analogues. Additional work involving chiroptical methods, two-dimensional (2D) NMR experiments and X-ray crystallography are likely to be required in the future.
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Affiliation(s)
- Chee-Leong Kee
- Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, Singapore
| | - Xiaowei Ge
- Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, Singapore
| | - Min-Yong Low
- Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, Singapore
| | - Véronique Gilard
- Laboratoire IMRCP (UMR CNRS 5623), Université Paul Sabatier, Université de Toulouse, Toulouse cedex, France
| | - Myriam Malet-Martino
- Laboratoire SPCMIB (UMR CNRS 5068), Université Paul Sabatier, Université de Toulouse, Toulouse cedex, France
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Sheng Y, Xue Y, Wang J, Liu S, Jiang Y. Fast screening and identification of illegal adulteration in dietary supplements and herbal medicines using molecular networking with deep-learning-based similarity algorithms. Anal Bioanal Chem 2023:10.1007/s00216-023-04708-5. [PMID: 37119358 DOI: 10.1007/s00216-023-04708-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 04/18/2023] [Accepted: 04/19/2023] [Indexed: 05/01/2023]
Abstract
Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) is a powerful analytical tool used for adulteration inspection. Nevertheless, it is a challenging task to identify illegal adulterants that are not included in the library or are unexpected from large MS data. Molecular networking is a good tool for exploring, visualizing, and organizing MS/MS spectra, and moreover, it employs shifted peak match to calculate spectral similarity, making it capable of identifying adulteration that is not included in the library. The key of molecular networking is spectral similarity algorithms, and therefore, in this study, we compared the performance of four cutting-edge similarity algorithms, modified cosine similarity (shifted peak match), entropy similarity, and two deep-learning-based algorithms, MS2DeepScore and Spec2Vec, in building molecular networking for identification of adulteration that is not included in the library. We conducted an analysis of excluded-query-compound on all MS/MS spectra in test library and performed a large-scale false discovery rate estimation to investigate whether the spectral similarity calculated by each algorithm could represent the actual structural similarity well. The obtained results demonstrated Spec2Vec exhibited good performance in both detection capability and false discovery rate. Further comprehensive evaluation of the performance of Spec2Vec in the identification of adulteration that is not included in the library or is unexpected in different matrices and in application to real samples proved the approach studied here is a promising and powerful tool for adulterant inspection and improved the capability of analyzing large MS data.
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Affiliation(s)
- Yanghao Sheng
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, China
- Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Ying Xue
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, China
- Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Jue Wang
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, China
- Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Shao Liu
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, China.
- Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, China.
| | - Yueping Jiang
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, China.
- Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, China.
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Rapid screening of illegal additives in functional food using atmospheric pressure solids analysis probe coupled to a portable mass spectrometer. J Pharm Biomed Anal 2022; 214:114722. [PMID: 35325799 DOI: 10.1016/j.jpba.2022.114722] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 03/04/2022] [Accepted: 03/08/2022] [Indexed: 10/18/2022]
Abstract
Pharmaceutical drugs like Sildenafil are illegally added to functional food such as nutritional supplements and herbal remedies to deliver drugs without a regular prescription to consumers. Rapid screening of illegal additives is desirable for the public security department. The seized samples are often large in number and unknown in composition; methods are needed for qualitative screening of unknown samples. Here, a new approach is presented based on atmospheric pressure solids analysis probe (ASAP) coupled with single-quadrupole mass spectrometer to rapidly screen 42 common illegal additives in six categories of functional food. The ASAP-MS method could be applied to solid or liquid sample analysis with a very simple pre-treatment and no LC chromatographic separation, using a home-built library; the identification of suspicious additives could be obtained rapidly. More importantly, the approach is sensitive enough for complex matrix samples like coffee samples. 21 batches of seized unknown samples were tested by the ASAP-MS, and the positive results were confirmed by LC-MS/MS(QQQ), indicating that the ASAP-MS method is effective and reliable. The ASAP-MS with home-built library is a promising method for rapid screening of illegal additives in functional food, which could be widely used in the grassroots police station that lack professional laboratory environment.
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Hamidi S. Assessment of Undeclared Synthetic Drugs in Dietary Supplements in an Analytical View: A Comprehensive Review. Crit Rev Anal Chem 2021; 53:986-996. [PMID: 34756146 DOI: 10.1080/10408347.2021.1999787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Dietary supplements have gained widespread attention globally as they are supposed to be healthier than synthetic pharmaceutical compounds with fewer side effects. Unlike common prescription drugs, dietary supplements are readily available to the general public. However, over the past few years, all kinds of legal and illegal drugs, have been detected in dietary supplements without labeling to defraud consumers, resulting in serious public health consequences. Due to the increasing number of drug frauds in dietary supplements, their consumption will undoubtedly risk consumers. Therefore; the importance of high-tech analytical methods in their assessment for controlling food quality seems undeniable. The current review examines the analytical techniques that focus on adulterating health products with undeclared pharmaceuticals, including registered and banned drugs. The present study referred to a survey from 2004 to 2021 based on articles in the Scopus database.
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Affiliation(s)
- Samin Hamidi
- Food and Drug Safety Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
- Pharmaceutical Analysis Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
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Sansone A, Cuzin B, Jannini EA. Facing Counterfeit Medications in Sexual Medicine. A Systematic Scoping Review on Social Strategies and Technological Solutions. Sex Med 2021; 9:100437. [PMID: 34619517 PMCID: PMC8766274 DOI: 10.1016/j.esxm.2021.100437] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/13/2021] [Accepted: 08/20/2021] [Indexed: 12/24/2022] Open
Abstract
Introduction The counterfeit phenomenon is a largely under-reported issue, with potentially large burden for healthcare. The market for counterfeit drugs used in sexual medicine, most notably type 5 phosphodiesterase inhibitors (PDE5i), is rapidly growing. Aims To report the health risks associated with the use of counterfeit medications, the reasons driving their use, and the strategies enacted to contain this phenomenon. Methods A systematic scoping review of the literature regarding counterfeit PDE5i was carried between January and June 2021, then updated in August 2021. Main Outcome Measure We primarily aimed to clarify the main drivers for counterfeit PDE5i use, the health risks associated, and the currently available strategies to fight counterfeiters. Results One hundred thirty-one records were considered for the present scoping review. Production of fake PDE5i is highly lucrative and the lacking awareness of the potential health risks makes it a largely exploitable market by counterfeiters. Adulteration with other drugs, microbial contamination and unreliable dosages make counterfeit medications a cause of worry also outside of the sexual medicine scope. Several laboratory techniques have been devised to identify and quantify the presence of other compounds in counterfeit medications. Strategies aimed at improving awareness, providing antitampering packaging and producing non-falsifiable products, such as the orodispersible formulations, are also described. Clinical implications Improving our understanding of the PDE5i counterfeit phenomenon can be helpful to promote awareness of this issue and to improve patient care. Strengths & Limitations Despite the systematic approach, few clinical studies were retrieved, and data concerning the prevalence of counterfeit PDE5i use is not available on a global scale. Conclusion The counterfeit phenomenon is a steadily growing issue, with PDE5i being the most counterfeited medication with potentially large harmful effects on unaware consumers. Sansone A, Cuzin B, and Jannini EA. Facing Counterfeit Medications in Sexual Medicine. A Systematic Scoping Review on Social Strategies and Technological Solutions. Sex Med 2021;9:100437.
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Affiliation(s)
- Andrea Sansone
- Chair of Endocrinology and Medical Sexology (ENDOSEX), Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Béatrice Cuzin
- Division of Urology and Transplantation, Edouard Herriot Hospital, Lyon, France
| | - Emmanuele A Jannini
- Chair of Endocrinology and Medical Sexology (ENDOSEX), Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
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Efficient Matrix Cleanup of Soft-Gel-Type Dietary Supplements for Rapid Screening of 92 Illegal Adulterants Using EMR-Lipid dSPE and UHPLC-Q/TOF-MS. Pharmaceuticals (Basel) 2021; 14:ph14060570. [PMID: 34203614 PMCID: PMC8232078 DOI: 10.3390/ph14060570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/11/2021] [Accepted: 06/13/2021] [Indexed: 11/17/2022] Open
Abstract
An efficient matrix cleanup method was developed for the rapid screening of 92 illegal adulterants (25 erectile dysfunction drugs, 15 steroids, seven anabolic steroids, 12 antihistamines, 12 nonsteroidal anti-inflammatory drugs (NSAIDs), four diuretics, and 17 weight-loss drugs) in soft-gel-type supplements by ultra-high performance liquid chromatography-quadrupole/time of flight-mass spectrometry (UHPLC-Q/TOF-MS). As representative green chemistry methods, three sample preparation methods (dispersive liquid-liquid microextraction (DLLME), “quick, easy, cheap, effective, rugged, and safe” dispersive solid-phase extraction (QuEChERS-dSPE), and enhanced matrix removal-lipid (EMR-Lipid) dSPE) were evaluated for matrix removal efficiency, recovery rate, and matrix effect. In this study, EMR-Lipid dSPE was shown to effectively remove complicated matrix contents in soft-gels, compared to DLLME and QuEChERS-dSPE. For the rapid screening of a wide range of adulterants, extracted common ion chromatogram (ECIC) and neutral loss scan (NLS) based on specific common MS/MS fragments were applied to randomly collected soft-gel-type dietary supplement samples using UHPLC-Q/TOF-MS. Both ECICs and NLSs enabled rapid and simple screening of multi-class adulterants and could be an alternative to the multiple reaction monitoring (MRM) method. The developed method was validated in terms of limit of detection (LOD), precision, accuracy, recovery, and matrix effects. The range of LODs was 0.1–16 ng/g. The overall precision values were within 0.09–14.65%. The accuracy ranged from 81.6% to 116.6%. The recoveries and matrix effects of 92 illegal adulterants ranged within 16.9–119.4% and 69.8–114.8%, respectively. The established method was successfully applied to screen and identify 92 illegal adulterants in soft-gels. This method can be a promising tool for the high-throughput screening of various adulterants in dietary supplements and could be used as a more environmentally friendly routine analytical method for screening dietary supplements illegally adulterated with multi-class drug substances.
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Wan L, Gao H, Gao H, Yan G, Wang F, Wang Y, Chen M. Dummy molecularly imprinted solid phase extraction in a nylon membrane filter for analysis of vardenafil in health care products. Microchem J 2021. [DOI: 10.1016/j.microc.2021.106157] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Nguyen TO, Tran CS, Do TTH, Nguyen TMH, Bui QD, Bui CT, Nguyen HN, Dang TH, Dinh VC, Nguyen TAH, Le THH. Rapid Screening and Quantitative Determination of Illegal Phosphodiesterase Type 5 Inhibitors (PDE-5i) in Herbal Dietary Supplements. JOURNAL OF ANALYTICAL METHODS IN CHEMISTRY 2021; 2021:5579500. [PMID: 34035975 PMCID: PMC8116155 DOI: 10.1155/2021/5579500] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 04/07/2021] [Accepted: 04/26/2021] [Indexed: 06/12/2023]
Abstract
Phosphodiesterase type 5 inhibitors (PDE-5i) are the first-line medication for oral erectile dysfunction, which are used according to the prescription of doctors. However, these substances have been found illegally in supplementary foods. The quality and safety of dietary supplements for enhancing male sexual performance have been questioned, raising the need for continual development of analytical methods. Liquid chromatography coupled with high-resolution mass spectrometry has become one of the most effective methods to identify and measure PDE-5i concentration. In this research, we focused on (i) developing and validating an effective screening and quantitation method for more than 53 PDE-5i in ingredients and supplementary products using LC-Q-Exactive after a simple sample extraction and (ii) assessing PDE-5i content in natural-based supplementary products available in Vietnam market. The extraction method used a small amount of organic solvent, which makes it more environmentally friendly (greener). The developed method has a limit of detection of 0.4 mg/kg, a limit of quantitation of 1.2 mg/kg, recoveries from 80 to 110%, and repeatability lower than 15%. Ninety-two herbal supplementary foods and ingredients used for enhancement of male sexual performance available in Vietnamese markets were collected. Fourteen PDE-5i including conventional and novel analogous were detected and measured in eighteen food supplements and two formulation ingredient samples.
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Affiliation(s)
- Thi Oanh Nguyen
- Vietnam Food Administration, 135 Nui Truc, Ba Dinh, Hanoi 10000, Vietnam
- University of Science, Vietnam National University, 334 Nguyen Trai, Thanh Xuan, Hanoi 10000, Vietnam
| | - Cao-Son Tran
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Thi Thu Hang Do
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Thi Minh Hoa Nguyen
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Quang-Dong Bui
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Cao-Tien Bui
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Hong-Ngoc Nguyen
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Thu-Hien Dang
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Viet-Chien Dinh
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
| | - Thi Anh Huong Nguyen
- University of Science, Vietnam National University, 334 Nguyen Trai, Thanh Xuan, Hanoi 10000, Vietnam
| | - Thi Hong Hao Le
- University of Science, Vietnam National University, 334 Nguyen Trai, Thanh Xuan, Hanoi 10000, Vietnam
- National Institute for Food Control, 65 Pham Than Duat, Cau Giay, Hanoi 10000, Vietnam
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Ma B, Lou T, Wang T, Li R, Liu J, Yu S, Pei H, Tian S, Li Y, Guo Y, Wang Z, Lin Z, Wang Z, Wang J, Gao Y. Development of a UHPLC-MS/MS-based data-mining method for rapid profiling and characterization of magnolol metabolites in rat urine and plasma. ARAB J CHEM 2021. [DOI: 10.1016/j.arabjc.2020.102954] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Novel synthesized attapulgite nanoparticles-based hydrophobic monolithic column for in-tube solid-phase microextraction of thiosildenafil, pseudovardenafil, and norneosildenafil in functional foods. Anal Bioanal Chem 2021; 413:1871-1882. [PMID: 33469710 DOI: 10.1007/s00216-021-03155-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 12/17/2020] [Accepted: 01/04/2021] [Indexed: 10/22/2022]
Abstract
In this study, a novel method which involved in-tube solid-phase microextraction (SPME) using an attapulgite (ATP) nanoparticles-based hydrophobic monolithic column was successfully developed. It was coupled with high-performance liquid chromatography-ultraviolet detection for the determination of three phosphodiesterase-5 (PDE-5) inhibitors, including thiosildenafil, pseudovardenafil, and norneosildenafil, in functional foods. The monolithic column was prepared by one-step polymerization, using 3-trimethoxysilylpropyl methacrylate-modified ATP nanoparticles and 1-butyl-3-vinylimidazolium bromide (VBIMBr) as the functional monomers, and ethylene glycol dimethacrylate (EDMA) as the cross-linker. The obtained poly(ATP-VBIMBr-EDMA) monolith was characterized by scanning electron microscopy equipped with energy-dispersive analysis of X-ray, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The adsorption capacity, up to 2.00 μg/cm calculated by the Langmuir isotherm model, was about six times that of the poly(VBIMBr-EDMA) monolith. Crucial factors affecting the extraction efficiency, including sample solvent, elution solvent, flow rates of sampling loading and elution, sample loading volume, and elution volume, were investigated in details. Under the optimal in-tube SPME conditions, the proposed method showed good reproducibility with run-to-run, column-to-column, and batch-to-batch relative standard deviations less than 7.2%, and low limits of detection of 0.5-0.9 ng/mL in real samples. Thiosildenafil was detected in four types of functional foods with the contents of 1.30-4.78 μg/g. This newly proposed in-tube SPME method based on poly(ATP-VBIMBr-EDMA) monolith may provide a simple, efficient, and promising alternative to daily monitoring of PDE-5 inhibitors in functional foods.
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