Laboratory evaluation of twelve portable devices for medicine quality screening.

BACKGROUND: Post-market surveillance is a key regulatory function to prevent substandard and falsified (SF) medicines from being consumed by patients. Field deployable technologies offer the potential for rapid objective screening for SF medicines. METHODS AND FINDINGS: We evaluated twelve devices: three near infrared spectrometers (MicroPHAZIR RX, NIR-S-G1, Neospectra 2.5), two Raman spectrometers (Progeny, TruScan RM), one mid-infrared spectrometer (4500a), one disposable colorimetric assay (Paper Analytical Devices, PAD), one disposable immunoassay (Rapid Diagnostic Test, RDT), one portable liquid chromatograph (C-Vue), one microfluidic system (PharmaChk), one mass spectrometer (QDa), and one thin layer chromatography kit (GPHF-Minilab). Each device was tested with a series of field collected medicines (FCM) along with simulated medicines (SIM) formulated in a laboratory. The FCM and SIM ranged from samples with good quality active pharmaceutical ingredient (API) concentrations, reduced concentrations of API (80% and 50% of the API), no API, and the wrong API. All the devices had high sensitivities (91.5 to 100.0%) detecting medicines with no API or the wrong API. However, the sensitivities of each device towards samples with 50% and 80% API varied greatly, from 0% to 100%. The infrared and Raman spectrometers had variable sensitivities for detecting samples with 50% and 80% API (from 5.6% to 50.0%). The devices with the ability to quantitate API (C-Vue, PharmaChk, QDa) had sensitivities ranging from 91.7% to 100% to detect all poor quality samples. The specificity was lower for the quantitative C-Vue, PharmaChk, & QDa (50.0% to 91.7%) than for all the other devices in this study (95.5% to 100%). CONCLUSIONS: The twelve devices evaluated could detect medicines with the wrong or none of the APIs, consistent with falsified medicines, with high accuracy. However, API quantitation to detect formulations similar to those commonly found in substandards proved more difficult, requiring further technological innovation.

The optimization of total flavonoids from rhizoma drynariae by response surface methodology and the metal ion chelation activity assay.

Rhizoma Drynariae, the dried rhizome of Drynaria fortunei (Kunze), is rich in flavonoids and has varieties of pharmacological activities. To optimize the extract conditions for bioactive flavonoids, a response surface methodology (RSM) was utilized to assess the effects of three independent variables (liquid-to-solid ratio (mL/g), extract temperature (°C) and ethanol concentration (%) on the total flavonoids content (TFC). To test the chelation with metal ion, the UV-visible spectrophotometer was used to detect metal ion chelation of extracted flavonoids. Regression analysis displayed a good fit of the experimental data. The optimal condition was liquid-to-solid ratio with 50:1, extract temperature with 80 °C and ethanol concentration with 40.22%. The total flavonoids had a better chelation with metal ions Cu2+, Fe2+, Fe3+ than Zn2+. These results suggested that the model employed is suitable and the application of RSM in optimizing the extract conditions is successful. The experimental values were in fine agreement (the yield 24.05±0.69mg/g) with predicted values. The total flavonoids from the extract presented good chelation against four metal ions (Cu2+, Zn2+, Fe2+ and Fe3+), which provided a good evidence for Alzheimer's disease treatments.

Non-aqueous reversed phase liquid chromatography with charged aerosol detection for quantitative lipid analysis with improved accuracy.

There is a great need for efficient analysis of the composition of vegetable oils and fats, since it affects the physical and technical properties. However, due to the complex nature of these kind of samples, it is often difficult and costly. In the present study, we developed a Non-Aqueous Reversed-Phase HPLC method that can be used to separate and quantify different free fatty acids, fatty acid esters, monoacylglycerides, diacylglycerides and triacylglycerides, including regioisomers such as SOS/SSO and 1,2- and 1,3-diolein. Two 25 cm Nucleodur C18 Isis columns in series, sub-ambient column temperature and a mobile phase gradient composed of acetonitrile, acetic acid, isopropanol and heptane were used for the separation. The lipids were detected and quantified using a charged aerosol detector and it was found that the peak shape highly affected the detector response as well as the response uniformity, even when inverse gradient compensation was employed. Thus, calibration and determination of response factors were necessary for reliable quantification. A correlation between response factors and peak width at half peak height was found and used for quantification of non-calibrated components. A quantification approach was suggested including an appropriate selection of calibrated components, depending on sample composition and the accuracy required. It was shown in a complex oil sample that the reduced calibration approach, using only 6 instead of 33 calibrated components, resulted in virtually the same composition, but yielded a more accurate result compared to using relative area that neglects response factors. The method validation showed good reproducibility and accuracy, making it an excellent tool for extensive analysis of complex lipid mixtures.

Selective uptake of thorium(IV) from nitric acid medium using two extraction chromatographic resins based on diglycolamide-calix[4]arenes: Application to thorium-uranyl separation in an actual sample.

Two novel extraction chromatography resins (ECRs) containing two diglycolamide (DGA) -functionalized calix[4]arenes with n-propyl and isopentyl substituents at the amide nitrogen atom, termed as ECR-1 and ECR-2, respectively, were evaluated for the uptake of Th(IV) from nitric acid feed solutions. While both the resins were having a quite high Th(IV) uptake ability (Kd >3000 at 3 M HNO3), the uptake was relatively lower with the resin containing the isopentyl DGA, which appeared magnified at lower nitric acid concentrations. Kinetic modeling of the sorption data suggested fitting to the pseudo-second order model pointing to a chemical reaction during the uptake of the metal ion. Sorption isotherm studies were carried out showing a good fitting to the Langmuir and D-R isotherm models, suggesting the uptake conforming to monolayer sorption and a chemisorption model. Glass columns with a bed volume of ca. 2.5 mL containing ca. 0.5 g lots of the ECRs were used for studies to assess the possibility of actual applications of the ECRs. Breakthrough profiles obtained with feed containing 0.7 g/L Th(NO3)3 solution resulted in breakthrough volumes of 8 and 5 mL, respectively, for the ECR-1 and ECR-2 resins. Near quantitative elution of the loaded metal ion was possible using a solution of oxalic acid and nitric acid. A method for the separation of Th-234 from natural uranium was demonstrated for the possible application of ECR-1.

Chemical Composition and Antioxidant Activity of Essential Oils from Eugenia patrisii Vahl, E. punicifolia (Kunth) DC., and Myrcia tomentosa (Aubl.) DC., Leaf of Family Myrtaceae.

Essential oils (EOs) were extracted from Eugenia patrisii, E. punicifolia, and Myrcia tomentosa, specimens A and B, using hydrodistillation. Gas chromatography coupled with mass spectrometry (GC/MS) was used to identify the volatile constituents present, and the antioxidant capacity of EOs was determined using diphenylpicryl-hydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays. For E. patrisii, germacrene D (20.03%), bicyclogermacrene (11.82%), and (E)-caryophyllene (11.04%) were identified as the major constituents of the EOs extracted from specimen A, whereas specimen B primarily comprised γ-elemene (25.89%), germacrene B (8.11%), and (E)-caryophyllene (10.76%). The EOs of E. punicifolia specimen A contained ß-Elemene (25.12%), (E)-caryophyllene (13.11%), and bicyclogermacrene (9.88%), while specimen B was composed of (E)-caryophyllene (11.47%), bicyclogermacrene (5.86%), ß-pinene (5.86%), and γ-muurolene (5.55%). The specimen A of M. tomentosa was characterized by γ-elemene (12.52%), germacrene D (11.45%), and (E)-caryophyllene (10.22%), while specimen B contained spathulenol (40.70%), α-zingiberene (9.58%), and γ-elemene (6.89%). Additionally, the chemical composition of the EOs was qualitatively and quantitatively affected by the collection period. Furthermore, the EOs of the studied specimens, especially specimen A of E. punicifolia, showed a greater antioxidant activity in DPPH rather than TEAC, as represented by a significantly high inhibition percentage (408.0%).

On-line screening of indoleamine 2,3-dioxygenase 1 inhibitors by partial filling capillary electrophoresis combined with rapid polarity switching.

Indoleamine 2,3-dioxygenase 1 (IDO1) has been shown to play an important role in the immune escape process of tumors, and therefore is considered as a promising target for tumor immunotherapy. In this study, off-line and on-line capillary electrophoresis methods were developed for IDO1 inhibitors screening from natural product extracts. The optimized separation conditions of CE were achieved with 32 mM sodium tetraborate (pH 9.22) as background electrolyte, using a separation voltage of 21 kV. The off-line CE method was verified by the determination of enzymatic kinetic parameters and inhibitory mechanisms of two known inhibitors. A partial filling on-line CE method combined with rapid polarity switching was used for rapid screening of IDO1 inhibitors. The whole reaction and separation process was completed within 5 min. The on-line CE screening results showed that six of 18 natural products had inhibitory effect on IDO1, namely Carthamus tinctorius, Schisandra chinensis, Raisin, Coffee, Hawthorn and Radix angelicae sinensis. The results of on-line CE experiments were consistent with the off-line results, which proved the practicability and effectiveness of the method for inhibitors screening.

Classification-based strategies to simplify complex traditional Chinese medicine (TCM) researches through liquid chromatography-mass spectrometry in the last decade (2011-2020): Theory, technical route and difficulty.

The difficulty of traditional Chinese medicine (TCM) researches lies in the complexity of components, metabolites, and bioactivities. For a long time, there has been a lack of connections among the three parts, which is not conducive to the systematic elucidation of TCM effectiveness. To overcome this problem, a classification-based methodology for simplifying TCM researches was refined from literature in the past 10 years (2011-2020). The theoretical basis of this methodology is set theory, and its core concept is classification. Its starting point is that "although TCM may contain hundreds of compounds, the vast majority of these compounds are structurally similar". The methodology is composed by research strategies for components, metabolites and bioactivities of TCM, which are the three main parts of the review. Technical route, key steps and difficulty are introduced in each part. Two perspectives are highlighted in this review: set theory is a theoretical basis for all strategies from a conceptual perspective, and liquid chromatography-mass spectrometry (LC-MS) is a common tool for all strategies from a technical perspective. The significance of these strategies is to simplify complex TCM researches, integrate isolated TCM researches, and build a bridge between traditional medicines and modern medicines. Potential research hotspots in the future, such as discovery of bioactive ingredients from TCM metabolites, are also discussed. The classification-based methodology is a summary of research experience in the past 10 years. We believe it will definitely provide support and reference for the following TCM researches.

Potency testing of cannabinoids by liquid and supercritical fluid chromatography: Where we are, what we need.

Hemp and cannabis industry is undergoing a renewed interest due to legalization of marijuana (a topic that all countries are discussing, especially in recent years) and the growing importance of therapeutic properties of cannabinoids. Together with an increment in the production of hemp and recreational cannabis, there has been an increasing demand for accurate potency testing of products (i.e. quantification of main cannabinoids present in the plant in terms of weight percentage) prior commercialization. This translates in an urgent need of reliable analytical methods to characterize cannabis and hemp samples. Cannabis and hemp preparations are commercialized under various forms (e.g., flowers, oils, candies or even baked goods) usually containing a large number of often very similar compounds making their separation very challenging. Strictly connected to this, another emerging topic concerns the need for the developing of large scale separation techniques for the purification of cannabinoids from complex matrices and for the preparation of analytical-grade standards (including the chiral ones). This paper reviews the most recent achievements in both these aspects. Cutting-edge applications and novel opportunities in potency testing by high performance liquid chromatography (HPLC) with UV detection (which is becoming the golden standard, according to several pharmacopeias, for this kind of measurements) are discussed. The focus has been given to the very important topic of enantio-discrimination of chiral cannabinoids, for which supercritical fluid chromatography (SFC) appears to be particularly suitable. The last part of the work covers the purification of cannabinoids through preparative chromatography. In this regard, particular attention has been given to the most innovative multi-column techniques allowing for the continuous purification of target molecules. The most recent advancements and future challenges in this field are discussed.

Analytical implications of different methods for preparing plant cell wall material.

Almost all plant cells are surrounded by a wall constructed of co-extensive networks of polysaccharides and proteoglycans. The capability to analyse cell wall components is essential for both understanding their complex biology and to fully exploit their numerous practical applications. Several biochemical and immunological techniques are used to analyse cell walls and in almost all cases the first step is the preparation of an alcohol insoluble residue (AIR). There is significant variation in the protocols used for AIR preparation, which can have a notable impact on the downstream extractability and detection of cell wall components. To explore these effects, we have formally compared ten AIR preparation methods and analysed polysaccharides subsequently extracted using high-performance anion exchange chromatography (HPAEC-PAD) and Micro Array Polymer Profiling (MAPP). Our results reveal the impact that AIR preparation has on downstream detection of cell wall components and the need for optimisation and consistency when preparing AIR.

"Force iteration molecular designing" strategy for the systematic characterization and discovery of new protostane triterpenoids from Alisma Rhizoma by UHPLC/LTQ-Orbitrap-MS.

Comprehensive analysis and identification of chemical components are of great significance for evaluating the efficacy and safety of herbal medicines, as well as for drug exploitation and development. Here we developed a "force iteration molecular designing" strategy, by combing a database-based in-house software for a precursor ion list (PIL) and PIL-triggered collision-induced dissociation-MS2 and high-energy C-trap dissociation-MS2 (PIL-CID/MS2-HCD/MS2) on an LTQ-Orbitrap mass spectrometer, aiming for the systematic characterization and discovery of new protostane triterpenoids (PTs) from Alisma Rhizoma (AR). AR was a well-known herbal remedy widely used for diarrhea, but its systematic characterization and comparison between two botanical origins have not been reported. Firstly, in-house software was developed based on force iteration, to generate a PIL that contains 483 accurate precursor ions. Secondly, to facilitate the acquisition of rich fragments and diagnostic ions sufficient for the structural elucidation of different types of PTs, a hybrid data acquisition method, namely PIL-CID/MS2-HCD/MS2, was generated. Thirdly, a total of 473 PTs were rapidly characterized from two botanical origins of AR according to an established four-step interpretation method, and the common constituents were 277 with ratio 70% (277/395) and 78% (277/355) in the rhizome of Alisma plantago-aquatica and A. orientale, respectively. Finally, two new PTs were isolated and unambiguously identified by NMR verifying the feasibility of this combined data acquisition strategy. This integrated strategy could improve the efficiency in the detection of new compounds in a single run and is practical to comprehensively characterize the complex components in herbal medicines.

Rapid Screening α-Glucosidase Inhibitors from Natural Products by At-Line Nanofractionation with Parallel Mass Spectrometry and Bioactivity Assessment.

In this study, a novel at-line nanofractionation screening platform was successfully developed for the rapid screening and identification of α-glucosidase inhibitors from natural products. A time-course bioassay based on high density well-plates was performed in parallel with high resolution mass spectrometry (MS), providing a straightforward and rapid procedure to simultaneously obtain chemical and biological information of active compounds. Through multiple nanofractionations into the same well-plate and comparisons of the orthogonal separation results of hydrophilic interaction liquid chromatography (HILIC) and reversed-phase liquid chromatography (RPLC), the α-glucosidase inhibitors can be accurately identified from co-eluates. The screening platform was comprehensively evaluated and validated, and was applied to the screenings of green tea polyphenols and Ginkgo folium flavonoids. After accurate peak shape and retention time matching between the bioactivity chromatograms and MS chromatograms, ten α-glucosidase inhibitors were successfully screened out and identified. The proposed screening method is rapid, effective and can avoid ignoring low abundant/active inhibitors.

Selective extraction of bioactive compounds from plants using recent extraction techniques: A review.

Plant extraction has existed for a long time and is still of interest. Due to technological improvements, it is now possible to obtain extracts with higher yields. While global yield is a major parameter because it assesses the extraction performance, it can be of interest to focus on the extraction of particular compounds (specific metabolites) to enrich the sample and to avoid the extraction of unwanted ones, for instance the primary metabolites (carbohydrates, triacylglycerols). The objective then is to improve extraction selectivity is then considered. In solid-liquid extraction, which is often called maceration, the solvent has a major impact on selectivity. Its polarity has a direct influence on the solutes extracted, related to the chemical structure of the compounds, and modelling compound/solvent interactions by using various polarity or interaction scales is a great challenge to favor the choice of the appropriate extracting liquid. Technical advances have allowed the development of recent, and sometimes green, extraction techniques, such as Microwave-Assisted Extraction (MAE), Ultrasound-Assisted Extraction (UAE), Pressurized Liquid Extraction (PLE) and Supercritical Fluid Extraction (SFE). This review focuses on the specificity of these recent techniques and the influence of their physical parameters (i.e. pressure, intensity, etc.). In addition to the solvent selection, which is of prime interest, the physical parameters applied by the different techniques influence the extraction results in different ways. Besides, SFE is a versatile and green technique suitable to achieve selectivity for some compounds. Due to its properties, SC-CO2 allows tailoring conditions to improve the selectivity.

Targeted isolation of 1,1-diphenyl-2-picrylhydrazyl inhibitors from Saxifraga atrata using medium- and high- pressure liquid chromatography combined with online high performance liquid chromatography-1,1-diphenyl-2- picrylhydrazyl detection.

Traditional Tibetan medicine (TTM) is a valuable source of novel therapeutic lead molecules inspired by natural products (NPs). The health benefits of Saxifraga atrata are well documented in TTM, but reports on its chemical composition are limited, most likely due to the complicated purification process. Herein, target separation and identification of 4 main radical scavenging compounds from the methanolic extract of S. atrata was were performed using medium- and high-pressure liquid chromatography coupled with online HPLC-DPPH detection. The sample was pretreated using medium pressure liquid chromatography with MCI GELⓇ CHP20P styrene-divinylbenzene beads as a stationary phase, yielding 1.4 g of the target DPPH inhibitors (Fr4, 11.9% recovery). The compounds were further purified and isolated using HPLC on RP-C18 (ReproSil-Pur C18 AQ) followed by HILIC (Click XIon) column separation, resulting in 2.8 mg of fraction Fr4-1-1, 6.8 mg of fraction Fr4-2, 244.9 mg of the Fr4-3-1 sample, and 38.3 mg of Fr4-4-1. The structure and purity of the target compounds were determined, and four compounds (ethyl gallate, 11-O-galloylbergenin, rutin and isoquercitrin) were isolated with >95% purity. The developed methodology is efficient for targeted isolation of high-purity radical scavengers from NP extracts and could be used for rapid identification and isolation of DPPH inhibitors from various NPs.

Actinide ion uptake from acidic radioactive feeds using an extraction chromatographic resin containing a branched dialkyl amide.

A dialkyl amide with branched alkyl group, viz. N,N-di(2-ethylhexyl)-propionamide (D2EHPrA) was used as the organic extractant in an extraction chromatographic resin prepared for the first time and evaluated for the separation of uranium from acidic feeds. The distribution coefficient measurements, carried out at varying HNO3 concentrations, indicated an increase in the UO22+ ion sorption with increasing nitric acid concentration. The UO22+ ion sorption kinetics and sorption isotherms with this resin were investigated in details. The column studies indicated that 8.3 mg of uranium could be loaded on a 2.1 cm3 column bed volume containing 0.35 g resin. Batch distribution data for other actinides such as Np4+ and Pu4+ indicated that the resin can also be used for effective separation of these metal ions from acidic feeds. Though the resin showed effectiveness for Np and Pu, detailed investigations dealing with macro concentrations of metal ions (in gm quantities) were restricted to uranium only due to hazardous nature of plutonium and limited availability of neptunium. The encouraging results reported in this work is an indication of the possible application of this resin for the recovery or pre-concentration of UO22+, Np4+ and Pu4+ ions from large volumes of aqueous solutions of moderate acidity.

Orthogonality in the selection of biphasic solvent systems for off-line two-dimensional countercurrent chromatography from Polygonum cuspidatum Sieb. et Zucc.

Off-line two-dimensional countercurrent chromatography has been widely applied to the isolation of complex samples, but little research on the investigation of orthogonality in the selection of biphasic solvent systems is available. In the present work, the orthogonality in the selection of a biphasic solvent system for liquid-liquid chromatographic separation of aqueous extract and ether extract from the traditional Chinese medicinal plant Polygonum cuspidatum Sieb. et Zucc was evaluated by the correlation coefficient and space occupancy rate. In total, 25 different biphasic solvent systems were tested, and 313 system combinations were analysed. A convex hull methodology was used to determine the separation space and to optimize separation conditions. The correlation coefficient matrix was transformed into dendrograms and a colour map to visualize the dissimilarity between, and orthogonality for, all solvent systems. The aqueous extracts from Polygonum cuspidatum were separated using selected biphasic solvent systems with high orthogonality: ethyl acetate-ethanol-water (70:1:70, v/v) and petroleum ether-ethyl acetate-water (1:5:5, v/v). The ether extracts from Polygonum cuspidatum were also separated using selected biphasic solvent systems with high orthogonality: petroleum-ethyl acetate-methanol-aqueous 0.25 M NH3•H2O (5:5:5:5, v/v) and petroleum-ethyl acetate-methanol-water (5:5:5:5, v/v). Thirteen compounds were successfully obtained. The experimental results demonstrated that the evaluation of orthogonality provided an alternative strategy to select an applicable solvent system for the separation of complex samples using off-line two-dimensional countercurrent chromatography.

Separation of six antioxidants from Hypsizygus marmoreus by high-speed countercurrent chromatography utilizing an approach based upon the polarity parameter model.

For a successful high-speed countercurrent chromatography (HSCCC) separation of multiple components, the suitable solvent system selection is a critical operation. Despite the difference in separation mechanism between HSCCC and HPLC, K values of compounds in the solvent system and the retention factor of compounds in HPLC were connected with polarity, and the polarity mainly depended on the structure and chemical properties of compounds. On the basis of the concept of "like dissolves like", the average polarity of the solvent system is equal to the average polarity of multiple components at the "sweet point" log K = 0. The result of theoretical deduction showed a negative linear correlation between the polarity of each component and the logarithm of the gradient range of the organic phase. Therefore, the average polarity of unknown multiple components could be obtained through the polarity parameter model established in the HPLC analysis. The suitable solvent system composed of n-hexane-ethyl acetate-methanol-water (8:3:8:1, v/v) was selected through the average polarity of multi-components combining K values of the enriched samples. In the context of bioassay, an efficient HSCCC separation procedure was established, and two groups of analogue benzaldehyde derivatives (four main antioxidants, namely, isodihydroauroglaucin, isoaspergin, isotetrahydro-auroglaucin, and flavoglaucin; two minor antioxidants, namely, 6'-oxo-chaetopyranin and chaetopyranin) were obtained from Hypsizygus marmoreus. The predicted polarity values of multi-components were sufficient to meet the HSCCC experimental requirements. The HPLC analysis of reference compounds and multi-components showed a significant consistency with different chromatographic columns. Therefore, the polarity parameter model established in the HPLC analysis was a simple, rapid, and helpful tool for looking an appropriate solvent system, which was a forwarding step for the HSCCC separation of multiple components.

Comparison of Accelerated Solvent Extraction (ASE) and Energized Dispersive Guided Extraction (EDGE) for the analysis of pesticides in leaves.

Various techniques have been evaluated for the extraction and cleanup of pesticides from environmental samples. In this work, a Selective Pressurized Liquid Extraction (SPLE) method for pesticides was developed using a Thermo Fisher Scientific Accelerated Solvent Extraction (ASE) system. This instrument was compared to the newly introduced (2017) extraction instrument, the Energized Dispersive Guided Extraction (EDGE) system, which combines Pressurized Liquid Extraction (PLE) and dispersive Solid Phase Extraction (dSPE). We first optimized the SPLE method using the ASE instrument for pesticide extraction from alfalfa leaves using layers of Florisil and graphitized carbon black (GCB) downstream of the leaf homogenate in the extraction cell (Layered ASE method). We then compared results obtained for alfalfa and citrus leaves with the Layered ASE method to those from a method in which the leaf homogenate and sorbents were mixed (Mixed ASE method) and to similar methods modified for use with EDGE (Layered EDGE and Mixed EDGE methods). The ASE and EDGE methods led to clear, colorless extracts with low residual lipid weight. No significant differences in residual lipid masses were observed between the methods. The UV-Vis spectra showed that Florisil removed a significant quantity of the light-absorbing chemicals, but that GCB was required to produce colorless extracts. Recoveries of spiked analytes into leaf homogenates were generally similar among methods, but in several cases, significantly higher recoveries were observed in ASE extracts. Nonetheless, no significant differences were observed among pesticide concentrations in field samples when calculated with the isotope dilution method in which labelled surrogates were added to samples before extraction. The extraction time with the ASE methods was ~45 minutes, which was ~4.5 times longer than with the EDGE methods. The EDGE methods used ~10 mL more solvent than the ASE methods. Based on these results, the EDGE is an acceptable extraction instrument and, for most compounds, the EDGE had a similar extraction efficiency to the ASE methods.

A lab-developed interface for liquid-gas chromatography coupling based on the use of a modified programmed-temperature-vaporizing injector.

The main focus of the present research was the on-line coupling of two separation techniques, namely liquid chromatography (LC) and gas chromatography (GC). For such an analytical combination, a dedicated interface is required to remove solvent from the sample, leaving the latter in a sharp band at the head of the GC column. Considering such an objective, a lab-developed LC-GC interface is herein presented, based on the use of a six-port two-position valve and a programmed-temperature-vaporizing (PTV) injector. The PTV injector was derived from a commercial split/splitless injector body, heated using a resistance heating wire, and enabled a satisfactory recovery of low boiling compounds (≤ C13), working in the normal-phase mode. The lab-developed PTV injector allowed the use of a larger-volume liner (compared to the commercial one initially used), it being characterized by dimensions 95 mm length × 5.0 mm O.D. × 3.4 mm I.D. and a volume of 862 µL, thus facilitating the transfer of larger LC fractions. The developed system is fully automatized and controlled without the use of additional software. The interface was evaluated and used for the analysis of mineral oil saturated hydrocarbons in vegetable oils. Detection was carried out by using a flame ionization detector (FID), with quantification performed through external calibration, across the 5-1000 mg kg-1 range. The LC-GC-FID method linearity, limits of detection and quantification, accuracy and precision were measured. The resulting limits of detection and quantification values were 0.4 and 1.3 mg kg-1, respectively. The average accuracy at the 100 mg kg-1 level was 95.5% (ranging between 93.3 and 99.7%). Intra-day repeatability at levels of 5 and 100 mg kg-1 were 2.4% and 3.5%, respectively.

Adulterants in selected dietary supplements and their detection methods.

At present, there is a growing trend toward the intentional adulteration of dietary supplements (DS) with synthetic pharmaceuticals, which represents an alarming emerging risk to consumers and a serious problem for regulatory agencies. An amazing array of synthetic drugs and their analogues have been reported as adulterants in DS. Mainly, the presence of analogues represents a serious health risk as their efficacy and toxic effects have not been clinically assessed yet and may result in unpredictable adverse effects. The purpose of this review is to provide an overview, over the period 2009-2019, of the most frequently reported adulterants in DS for the treatment of erectile dysfunction, obesity/overweight, diabetes mellitus, and hypertension and the analytical methods used for their detection.