Comparison of ultra high performance supercritical fluid chromatography,ultra high performance liquid chromatography,and gas chromatography for the separation of synthetic cathinones

A comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones has been conducted. Nine different mixtures of bath salts were analyzed in this study. The three different chromatographic techniques were examined using a general set of controlled synthetic cathinones as well as a variety of other synthetic cathinones that exist as positional isomers. Overall 35 different synthetic cathinones were analyzed. A variety of column types and chromatographic modes were examined for developing each separation. For the ultra high performance supercritical fluid chromatography separations, analyses were performed using a series of Torus and Trefoil columns with either ammonium formate or ammonium hydroxide as additives, and methanol, ethanol or isopropanol organic solvents as modifiers. Ultra high performance liquid chromatographic separations were performed in both reversed phase and hydrophilic interaction chromatographic modes using SPP C18 and SPP HILIC columns. Gas chromatography separations were performed using an Elite‐5MS capillary column. The orthogonality of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography was examined using principal component analysis. For the best overall separation of synthetic cathinones, the use of ultra high performance supercritical fluid chromatography in combination with gas chromatography is recommended.     

Simultaneous determination of pyrametostrobin and its two metabolites in cucumber and soil using a quick,easy, cheap,effective, rugged,and safe method with HPLC–MS/MS

An easy, effective and sensitive analytical method for the simultaneous determination of a novel fungicide pyrametostrobin and its two metabolites pyrametostrobin‐M1 and pyrametostrobin‐M2 in cucumber and soil was developed using a quick, easy, cheap, effective, rugged, and safe method with high‐performance liquid chromatography and tandem mass spectrometry. The extraction solvent was acetonitrile, and cleanup sorbents were primary secondary amine and graphitized carbon black for cucumber samples and primary secondary amine for soil samples. The three target compounds were successfully separated between 3.2 and 3.9 min using a Waters CORTECS™ C₁₈ column connected to an electrospray ionization source. All the matrix‐matched samples at three fortified levels (10, 100 and 1000  μg/kg) provided satisfactory recoveries in the range of 78.8–93.8% with relative standard deviations below 6.9%. The limits of quantitation for the three compounds were below 0.183 μg/kg. The proposed method was validated by analyzing real samples.     

Chiral separation of quinolones by liquid chromatography and capillary electrophoresis

The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for preclinical or clinical trials, respective chiral separation methods are urgently needed. In this context, the present review discusses chromatographic and electrophoretic methods for the enantioseparation of chiral quinolones and provides some useful information on their physical and pharmaceutical properties. The drawbacks of currently used techniques are revealed and ways to overcome them are outlined. Moreover, recommendations for an optimal choice of a separation protocol are given.     

Simultaneous analysis of ten low‐molecular‐mass organic acids in the tricarboxylic acid cycle and photorespiration pathway in Thalassiosira pseudonana at different growth stages

A method using high‐performance liquid chromatography coupled with tandem mass spectrometry was developed for the simultaneous determination of organic acids in microalgae. o‐Benzylhydroxylamine was used to derivatize the analytes, and stable isotope‐labeled compounds were used as internal standards for precise quantification. The proposed method was evaluated in terms of linearity, recovery, matrix effect, sensitivity, and precision. Linear calibration curves with correlation coefficients >0.99 were obtained over the concentration range of 0.4–40 ng/mL for glycolic acid, 0.1–10 ng/mL for malic acid and oxaloacetic acid, 0.02–2 ng/mL for succinic acid and glyoxylic acid, 4–400 ng/mL for fumaric acid, 20–2000 ng/mL for isocitric acid, 2–200 ng mL⁻¹ for citric acid, 100–10000 ng mL⁻¹ for cis‐aconitic acid, and 1–100 ng mL⁻¹ for α‐ketoglutaric acid. Analyte recoveries were between 80.2 and 115.1%, and the matrix effect was minimal. Low limits of detection (0.003–1 ng/mL) and limits of quantification (0.01–5 ng/mL) were obtained except cis‐aconitic acid. Variations in reproducibility for standard solution at three different concentrations levels were <9%. This is the first report of the simultaneous analysis of ten organic acids in microalgae, which promotes better understanding of their growth state and provides reference value for high‐yield microalgae cultures.     

Chiral separation of novel diazenes on a polysaccharide‐based stationary phase in the reversed‐phase mode

Chiral high‐performance liquid chromatography separation of two recently synthesized liquid crystalline materials C1 and C2 was studied in the reversed‐phase mode. Both materials have an azo‐moiety and one chiral center in their molecular structures. They were available in racemic and pure S forms. For the enantiomeric separations, a Chiralpak AY‐RH stationary phase based on amylose tris(5‐chloro‐2‐methylphenylcarbamate) coated on 5 μm silica was used. The compounds were analyzed in both of their possible forms, the more thermodynamically stable E form and the labile Z form. The conditions and time scale of the UV‐induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate S and R enantiomers of both of the studied materials not only in their E forms, but also in their Z forms. In comparison to the separation in the normal‐phase mode, which we have reported recently, the resolution in the reversed‐phase mode is significantly better. Interestingly, peak reversal was noticed for the S and R enantiomers when the separation was carried out with E versus Z forms of both compounds.     

Analysis of microcystins using high‐performance liquid chromatography and magnetic solid‐phase extraction with silica‐coated magnetite with cetylpyridinium chloride

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid‐phase extraction and high‐performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC‐LR was 0.001 μg/L, and the limit of quantification was 0.0028 μg/L. The limit of detection of MC‐RR was 0.001 μg/L, and the limit of quantification was 0.003 μg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid‐phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid–liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.     

Quality assessment of crude and processed Arecae semen based on colorimeter and HPLC combined with chemometrics methods

Raw Arecae Semen, the seed of Areca catechu L., as well as Arecae Semen Tostum and Arecae semen carbonisata are traditionally processed by stir‐baking for subsequent use in a variety of clinical applications. These three Arecae semen types, important Chinese herbal drugs, have been used in China and other Asian countries for thousands of years. In this study, the sensory technologies of a colorimeter and sensitive validated high‐performance liquid chromatography with diode array detection were employed to discriminate raw Arecae semen and its processed drugs. The color parameters of the samples were determined by a colorimeter instrument CR‐410. Moreover, the fingerprints of the four alkaloids of arecaidine, guvacine, arecoline and guvacoline were surveyed by high‐performance liquid chromatography. Subsequently, Student's t test, the analysis of variance, fingerprint similarity analysis, hierarchical cluster analysis, principal component analysis, factor analysis and Pearson's correlation test were performed for final data analysis. The results obtained demonstrated a significant color change characteristic for components in raw Arecae semen and its processed drugs. Crude and processed Arecae semen could be determined based on colorimetry and high‐performance liquid chromatography with a diode array detector coupled with chemometrics methods for a comprehensive quality evaluation.     

Preparation of magnetic mesoporous silica composite for the solid‐phase microextraction of diazinon and malathion before their determination by high‐performance liquid chromatography

A novel magnetic mesoporous silica material was synthesized and used as the sorbent for the magnetic solid‐phase microextraction of diazinon and malathion before their quantification by high‐performance liquid chromatography with UV detection. The sorbent was synthesized by a surfactant‐templated one‐pot sol–gel procedure using SiO₂‐coated Fe₃O₄ as the magnetic support, cetyltrimethylammonium bromide as the template and tetraethyl orthosilicate as the silicon source. The characteristics of the prepared sorbent were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction. The sorbent exhibited a high maximum adsorption capacity of 19.2 and 9.4 mg/g for diazinon and malathion, respectively. The parameters affecting the microextraction were optimized by the MultiSimplex method. Under the optimized conditions, the calibration graphs were linear in the concentration ranges of 0.3–50.0 and 0.5–50 μg/L with the limits of detection of 0.09 and 0.14 μg/L for diazinon and malathion, respectively. The relative standard deviations (n = 5) at a concentration level of 10.0 μg/L of analytes were less than 2.5 and 4% for intra and interday, respectively. The developed method was successfully used for the determination of diazinon and malathion in apple, tomato, cucumber, tap water, and well water samples.     

Development of a novel hollow‐fiber liquid‐phase microextraction based on oil‐in‐salt and its comparison with conventional one

A novel hollow‐fiber liquid‐phase microextraction based on oil‐in‐salt was proposed and introduced for the simultaneous extraction and enrichment of the main active compounds of hesperidin, honokiol, shikonin, magnolol, emodin, and β,β′‐dimethylacrylshikonin in a formula of Zi‐Cao‐Cheng‐Qi decoction and the single herb, Fructus Aurantii Immaturus , Cortex Magnoliae Officinalis , Radix et Rhizoma , and Lithospermum erythrorhizon , composing the formula prior to their analysis by high‐performance liquid chromatography. The results obtained by the proposed procedure were compared with those obtained by conventional hollow‐fiber liquid‐phase microextraction, and the proposed procedure mechanism was described. In the procedure, a hollow‐fiber segment was first immersed in organic solvent to fill the solvent in the fiber lumen and wall pore, and then the fiber was again immersed into sodium chloride solution to cover a thin salt membrane on the fiber wall pore filling organic solvent. Under the optimum conditions, the enrichment factors of the analytes were 0.6–109.4, linearities were 0.002–12 μg/mL with r ² ≥ 0.9950, detection limits were 0.6–12 ng/mL, respectively. The results showed that oil‐in‐salt hollow‐fiber liquid‐phase microextraction is a simple and effective sample pretreatment procedure and suitable for the simultaneous extraction and concentration of trace‐level active compounds in traditional Chinese medicine.     

Multiconstituent identification in root,branch, and leaf extracts of Juglans mandshurica using ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry

As a traditional medicinal plant, Juglans mandshurica has been used for the treatment of cancer. Different organs of this plant showed anti‐tumor activity in clinic and laboratory. Comparative identification of constituents in different plant organs is essential for investigation of the relationship between chemical constituents and pharmacological activities. For this aim, the roots, branches, and leaves of J. mandshurica were extracted with 50% v/v methanol and then subjected to ultra‐high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry analysis conducted under low and high energy. As a result, we have to date identified 111 compounds consisting of 56 tannins, 29 flavonoids, 13 organic acids, 8 naphthalene derivatives, and 5 anthracenes. Five compounds, namely, diquercetin trihydroxy‐truxinoyl‐glucoside, two quercetin kaempferol dihydroxy‐truxinoyl‐glucosides, syringoyl‐tri‐galloyl‐O‐glucose, and dihydroxy‐naphthalene syringoyl‐glucoside, were tentatively identified as new compounds. Of the compounds identified, 76 were found in the root extract, 67 in the branch extract, and 37 in the leaf extract. Only six compounds including four organic acids and two tannins were found in all three extracts. We developed a rapid and sensitive ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry approach to identify multiple constituents of complex extracts without separation and ion selection. The results presented provide useful information on further research of the bioactive compounds of J. mandshurica .