Development and validation of a pre-column reversed phase liquid chromatographic method with fluorescence detection for the determination of primary phenethylamines in dietary supplements and phytoextracts

High-Performance Liquid Chromatography Methods for Determining the Purity of Drugs with Weak UV Chromophores - A Review

High-performance liquid chromatography (HPLC) is one of the most useful techniques for the separation and determination of new drugs with a complex nature. The selection of an HPLC detector depends on the chemical nature of molecules, potential impurities, matrix of the sample, sensitivity, availability, and/or cost of the detector. HPLC methods with UV/Vis detectors are the most used and simple analytical procedures in pharmaceutical applications, but it is limited to compounds that possess a chromophore. Hence, this review provides an overview on the development of analytical methods for compounds with weak chromophores. The review described selected papers about HPLC based methods in the PubMed, Scopus, Semantic Scholar and ScienceDirect databases, basically between 2006 and 2023. Of the analytical studies, the HPLC methods with UV-Vis, FLD, CAD, ELSD, RID, ECD, CLND and MS detection were found. This study is a comparison of different types of detection that are described in scientific literature and are routinely used for compounds with weak chromophores. It is expected that this review will be helpful for scientists in the analytical development fields to improve research related to the drug candidates and to ensure its quality according to regulatory levels.

Review of available "extraction + purification" methods of natural ceramides and their feasibility for sewage sludge analysis

Natural ceramide, a biologically active compound present in plants, has been used widely in food, cosmetics, and pharmaceutical industries. Abundant ceramide has been detected in sewage sludge, which has inspired the idea to recycle ceramide from it. Therefore, the methods of extracting, purifying, and detecting ceramides from plants were reviewed, with the aim to establish methods to get condensed ceramide from sludge. Ceramide extraction methods include traditional methods (maceration, reflux, and Soxhlet extraction) and green technologies (ultrasound-assisted, microwave-assisted, and supercritical fluid extraction). In the past two decades, more than 70% of the articles have used traditional methods. However, green extraction methods are gradually improved and showed high extraction efficiency with lower solvent consumed. The preferred technique for ceramide purification is chromatography. Common solvent systems include chloroform-methanol, n-hexane-ethyl acetate, petroleum ether-ethyl acetate, and petroleum ether-acetone. For structural determination of ceramide, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry are used in combination. Among quantitative analysis methods for ceramide, liquid chromatography-mass spectrometry was the most accurate. This review concludes that with our prilemenary experiment results it is feasible to apply the plant "extraction + purification" process of ceramide to sludge, but more optimization need to be performed to get better results.

Dietary supplement mislabelling: case study on selected slimming products by developing a green isocratic HPLC method for their quality control

Nowadays, a huge population consumes Dietary supplements for losing weight. Products are often claimed as botanical blends, yet they aren't necessarily safe. Misleading labels are also very common. Thus, validated analytical methods for a wide range of slimming compounds are highly needed. Herein, we present a simple HPLC/PDA method for the quantitation of seven popular slimming ingredients. Studied compounds were Caffeine, Raspberry Ketone, trans-Resveratrol, p-Synephrine, p-Octopamine, p-Hordenine and 2-phenethylamine. After optimization, separation was carried out on a C18 column and mobile phase was a mixture of Acetonitrile:Water containing 0.1% phosphoric acid (50:50, %v/v). The last compound was eluted at 9.76 min. Separation was efficient showing baseline- separated symmetric peaks, without using any gradient programs, organic mobile phase modifiers or modified stationary phases. Method validation was done following ICH guidelines. Calibration curves were linear over wide concentration ranges and calculated LOD values were in the range 0.02-0.09 µg/mL. Method greenness was assessed using Analytical Eco-scale, GAPI and AGREE metric tools. Further, four random sample products purchased from online supplement stores were assayed. Results proved some mislabeling actions. To support our findings, standard addition was carried out and average % recoveries were 96.67 - 101.44% with standard deviation ≤ 2.83 between measurements.

Linear-Dendritic Block Copolymer Containing Fluorescent Groups: An Effective and Environmentally Benign Inhibitor for Calcium Carbonate

A novel fluorescent-tagged scale inhibitor, the linear-dendritic double hydrophilic block copolymer [acrylic acid (AA)/allyloxy poly(ethylene glycol) polyglycerol (APEG-PG-(OH)n)/8-allyloxy-1,3,6-pyrene trisulfonic acid trisodium salt (PA) (AA/APEG-PG-(OH)n/PA)] was synthesized by polymerisation of AA, APEG-PG-(OH)n and PA. Structures of APEG, APEG-PG-(OH)n and AA/APEG-PG-(OH)n/PA were determined by 1HNMR. The experiments show that the dosage and the n value of AA/APEG-PG-(OH)n/PA play an important role on CaCO3 inhibition. The polymer AA/APEG-PG-(OH)5/PA displays a 90% inhibition of CaCO3 precipitate formation at a dosage of 8 mg/L. The relationship between the fluorescent intensity of AA/APEG-PG-(OH)5/PA and the dosage of this polymer was studied. The correlation coefficient R of AA/APEG-PG-(OH)5/PA's is 0.9995. The effect on formation of CaCO3 was investigated with combination of XRD and SEM analysis. Finally, the significant cause and mechanism for calcium carbonate inhibition were analysed in depth.

Fluorescent-Tagged Double-Hydrophilic Block Copolymer as a Green Inhibitor for Calcium Carbonate Scales

Allyloxy polyethoxy ether (APEG) and succinic anhydride were used to prepare allyloxy polyethoxy carboxylate (APEL). 8-Hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (PY) reacted with allyl chloride to produce fluorescent monomer 8-allyloxy-1,3,6-pyrene trisulfonic acid trisodium salt (PA). APEL and PA were copolymerized with maleic anhydride (MA) to synthesize the PA tagged, phosphate and nitrogen free CaCO3 inhibitor MA-APEL-PA. Structures of PA, APEG, APEL, and MA-APEL-PA were obtained by FT-IR and 1H-NMR measurements. The observation shows that the dosage of MA-APEL-PA plays an important role on CaCO3 inhibition. The effect on the formation of CaCO3 was investigated by a combination of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analysis. The relationship between MA-APEL-PA's fluorescent intensity and its dosage was also studied. Correlation coefficient '9 of MA-APEL-PA's fluorescent intensity and its dosage is 0.9997. MA-APEL-PA can be used to measure accurately the polymer consumption on line besides providing excellent CaCO3 inhibition.