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A method of ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) combined with modified QuEChERS purification technology was developed for the simultaneous determination of 25 veterinary medicine residues including four classes (sulfonamides, quinolones, chloramphenicols and amantidines) in chicken and egg. The samples were hydrolyzed by dilute hydrochloric acid, extracted by acetonitrile. Sodium chloride was added into the extracting solution to salt out. The acetonitrile was took out and degreased by n-hexanecyclohexane solution (1∶1,V/V) after stratification of acetonitrile and aqueous phase and concentrated to dry. The residues were dissolved with 0.2% formic acid ethyl acetate to remove the sodium chloride by filtrating and the filtrate was concentrated to dry again, then the sample was purified with a mixture of 30 mg of C18 and 60 mg PSA after adding 0.2% formic acid methanol. The target compounds were separated by ZORBAX C18 chromatography column (50 mm×2.1 mm×1.8 μm), the mass spectrometer data were acquired under multiple reaction monitoring (MRM) of positive and negative modes at the same time, and the residues were quantitated by isotope internal standard method. The results showed that the linear of 25 veterinary medicines is good in the range of 0.2~250 μg/L. The linear correlation coefficients are more than 0.99, and the detection limits are in the range of 0.1~0.9 μg/kg. The limits of quantification are 0.3~3.0 μg/kg. The average recoveries at three spiked levels (about 1, 5 and 20 folds of quantitative limits) are 79.5%~119% with the relative standard deviations of 0.9%~9.2%. The method is rapid,simple, accurate, sensitive and cheap, which is suitable for simultaneous determination of multiple vererinary medicine residues in eggs and chicken.

Three new thiohydantoins with a 2-thioxoimidazolidin-4-one nucleus, named macathiohydantoins P–R (1 – 3), along with one known analog (4) , were isolated from the roots of Lepidium meyenii. Their structures were elucidated by means of analysis of extensive spectroscopic data, including 1D NMR, 2D NMR and HRESIMS. The thiohydantoins (1 – 4) were isolated as racemic mixtures, which were further separated by chiral semi-preparative HPLC to afford the corresponding enantiomers. Their absolute configuration of C-5 was assigned by comparison of optical rotation values with those reported in the literature. All thiohydantoin derivatives were evaluated for their cytotoxicities against five human cancer cell lines. [Display omitted] • Three new thiohydantoins, named macathiohydantoins P–R (1 − 3), were isolated from the roots of Lepidium meyenii. • Their structures were characterised by means of extensive spectroscopic analyses. • The isolated compounds were evaluated for their cytotoxicities on five human cancer cell lines. [ABSTRACT FROM AUTHOR]

In this study, in order to protect the characteristic Dendrobium devonianum Paxt industry in the Longling area, and promote the healthy development of its characteristic Chinese herbal medicines in Yunnan Province, China, the identification of Dendrobium devonianum Paxt and Dendrobium officinale Kimura et Migo from Longling county was discussed using time of flight mass spectrometry. The data of 13 Dendrobium devonianum and 7 Dendrobium officinale in the Longling area were collected by TOF MS-IDA-15 MS/MS mode, and the collected data were analyzed by PCA and T-test using MarkerView software, and the difference markers were searched using the database to confirm their compound structures. In positive and negative ion modes, 3645 and 2344 peaks were detected, respectively; 64 positive ion compounds and 60 negative ion compounds, for a total of 124 compounds were identified, mainly including organic acids, polyphenols, alkaloids, amino acids and their derivatives, benzene and its derivatives, and other compounds. The score plot and loading plot analyzed by PCA show that Dendrobium devonianum and Dendrobium officinale collected in the Longling area can be effectively identified and differentiated by high-resolution mass spectrometry with the 15 different markers in positive ion mode and 17 markers in negative ion mode, respectively. The successful identification of Dendrobium devonianum and Dendrobium officinale fully demonstrates that TOF MS can be effectively used in the identification of Dendrobium and related Chinese herbal medicines with broadly application foreground. [ABSTRACT FROM AUTHOR]

A new natural product meyeniihydantoin A ( 1 ), and two new hydantoin derivatives, named meyeniihydantoins B–C ( 2 – 3 ) were isolated from the roots of Lepidium meyenii . Their structures were characterized by means of extensive spectroscopic analyses. The isolated meyeniihydantoins were evaluated for their cytotoxicities on NB4, A549, SHSY5Y, PC3 and MCF7 human cancer cell lines. [ABSTRACT FROM AUTHOR]

Four pesticides with a high detection rate in Pu'er tea have been determined by a QuEChERS (quick, easy, cheap, effective, rugged, safe) method with multiwalled carbon nanotubes (MWCNTs), and combined ultrahigh-performance liquid chromatography–triple quadrupole linear ion trap-tandem mass spectrometry (UHPLC-QTRAP-MS/MS). MWCNs have been compared with other common purification materials, and found to be superior. The matrix effect was systematically studied, and the results show that the MWCNs can quickly and effectively reduce matrix interference values, which were in the range from −17.8 to 13.8. The coefficients (R2) were greater than 0.99, with the limit of quantification ranging from 0.1 to 0.5 μg/kg, and the recovery rate ranging from 74.8% to 105.0%, while the relative standard deviation (RSD) ranged from 3.9% to 6.6%. A total of 300 samples, taken from three areas in which Yunnan Pu'er tea was most commonly produced, tested for four pesticides. The results show that the detection rate of tolfenpyrad in Pu'er tea was 35.7%, which is higher than other pesticides, and the lowest was indoxacarb, with 5.2%. The residual concentrations of chlorpyrifos, triazophos, tolfenpyrad and indoxacarb ranged from 1.10 to 5.28, 0.014 to 0.103, 1.02 to 51.8, and 1.07 to 4.89 mg/kg, respectively. By comparing with China's pesticide residue limits in tea (GB 2763-2021), the over standard rates of chlorpyrifos, tolfenpyrad, and indoxacarb were 4.35%, 0.87% and 0%, respectively. The risk assessment result obtained with the hazard quotient (HQ) method shows that the HQ of the four pesticides was far less than one, indicating that the risk is considered acceptable for the four pesticides in Pu'er tea. The largest HQ was found for tolfenpyrad, 0.0135, and the smallest was found for indoxacarb, 0.000757, but more attention should be paid to tolfenpyrad in daily diets in the future, because its detection rate, and residual and residual median were all relatively high. [ABSTRACT FROM AUTHOR]

Some racemates including alcohol, ketone, flavone, phenol, base, and amide racemates etc. were successfully separated by using a 3D chiral nanoporous metal–organic framework (MOF) as a new chiral stationary phase in HPLC. The experimental results show that the chiral MOF possesses excellent recognition ability for various racemates, and indicate that enantioseparation on the chiral MOF column is practicable. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) have recently attracted considerable attention because of their fascinating structures and intriguing potential applications in diverse areas. In this study, we developed a novel method for determination of enantiomeric excess (ee) of (±)-1,1′-bi-2-naphthol by solid-phase extraction (SPE) using a chiral MOF, [Co(l-tyr)]n(l-tyrCo), as sorbent. After optimization of the experimental conditions, a good linear relationship between the ee and the absorbance of the eluate (R2 = 0.9984) was obtained and the standard curve was established at the concentration of 3 mmol L−1. The ee values of (±)-1,1′-bi-2-naphthol samples can be rapidly calculated using the standard curve after determination of the absorbance of the eluate. The method showed good accuracy, with an average error of 2.26%, and is promising for ee analysis. [ABSTRACT FROM AUTHOR]