Separations, Volume 8, Issue 2 (February 2021) – 13 articles

(1) Background: ZIF-67 is one of the most intriguing metal–organic frameworks already applied in liquid adsorption. To increase its adsorption performance, dual ionic liquids were immobilized on ZIF-67 in this research; (2) Methods: The obtained sorbent was used to adsorb aristolochic acid I (AAI) in standard solutions. Then, the sorbent was applied in solid-phase extraction to remove AAI from Fibraurea Recisa Pierre extracted solution. (3) Results: By analyzing the adsorption models, the highest adsorption capacity of immobilized sorbent (50.9 mg/g) was obtained at 25 °C within 120 min. In the SPE process, 0.02 mg of AAI was removed per gram of herbal plant, the adequate recoveries were in the range of 96.2–100.0%, and RSDs were 3.5–4.0%; (4) Conclusions: The provided experimental data revealed that ZIF-67@EIM-MIM was an excellent potential sorbent to adsorb and remove AAI from herbal plant extract, and the successful separation indicated that this sorbent could be an ideal material for the pretreatment of herbal plants containing AAI. Full article

Tramadol (TRM) and pregabalin (PGB) are frequently used in combination for neuropathic pain management. Accordingly, a selective and sensitive high-performance liquid chromatography–electrospray ionization–mass/mass spectrometric (ESI–LC–MS/MS) method is presented for determination of TRM and PGB, whether in pure forms or human biological fluids (plasma/urine), using gabapentin (GBP) (IS) as the internal standard. Chromatographic separation was effected in total run time of 2.5 min, on Phenomenex Luna^® Omega 1.6 um polar C¹⁸ (LC 150 × 2.1 mm) column with a mobile phase of methanol/water (70:30, v/v), 0.1% (v/v) formic acid at a flow rate of 0.3 mL/min. Ionization of the analytes was obtained using electrospray in the positive ion mode (ESI+). The MS/MS detection was performed by monitoring the fragments for TRM, PGB and GBP on a triple quadrupole mass spectrometer. Assay calibration was over the range of 10–1000 ng mL⁻¹ for TRM and PGB with the correlation coefficients over 0.999 in pure form, human plasma and urine spiked with the studied compounds. Validation data showed the inter-run relative standard deviations (RSDs) were less than 4.3% for TRM and 3.8% for PGB, whereas the intra-run RSDs were less than 3.7% for TRM and 3.6% for PGB. The mean extraction recoveries for TRM and PGB were in the ranges of 86.51–93.38% and 86.20–92.42%. This method was successfully performed on real plasma and urine samples taken from neuropathic patients and proved to be an applicable method for routine therapeutic drug monitoring of the proposed drug combination. Full article

Adenine nucleotides—adenosine monophosphate, diphosphate, and triphosphate—are of utmost importance to all living organisms, where they play a critical role in the energy metabolism and are tied to allosteric regulation in various regulatory enzymes. Adenylate energy charge represents the precise relationship between the concentrations of adenosine monophosphate, diphosphate, and triphosphate and indicates the amount of metabolic energy available to an organism. The experimental conditions of adenylate extraction in freshwater amphipod Gammarus fossarum are reported here for the first time and are crucial for the qualitative and quantitative determination of adenylate nucleotides using efficient and sensitive ion-pair reverse phase LC. It was shown that amphipod calcified exoskeleton impeded the neutralization of homogenate. The highest adenylate yield was obtained by homogenization in perchloric acid and subsequent addition of potassium hydroxide and phosphate buffer to achieve a pH around 11. This method enables separation and accurate detection of adenylates. Our study provides new insight into the complexity of adenylate extraction and quantification that is crucial for the application of adenylate energy charge as a confident physiological measure of environmental stress and as a health index of G. fossarum. Full article

Natural products with antimycobacterial adjuvant potential may be utilized to address the rise of multidrug-resistant tuberculosis (TB). The antioxidant-rich oil palm (Elaeis guineensis) fruit (OPF) was investigated for antimycobacterial activity against Mycobacterium tuberculosis (MTB) H37Ra using bio-guided fractionation techniques, followed by determination of fractional inhibition index (FIC) with first-line anti-TB drugs. In vitro screening using microplate Alamar blue assay showed n-hexane and chloroform partitions of OPF mesocarp had a minimum inhibitory concentration (MIC) of 400–800 µg/mL. The n-hexane fraction contained nonanoic acid (C₉H₁₈O₂), decanoic acid (C₁₀H₂₀O₂), and dodecanoic acid (C₁₂H₂₄O₂), identified by gas chromatography-mass spectrometry, which all had an MIC of 50 µg/mL. Nonanoic and decanoic acids had additive effects when combined with streptomycin (FIC index: 0.625) and rifampicin (FIC index: 0.75), respectively. Isoniazid had a 16-fold increase in activity when combined with nonanoic acid and decanoic acid. The combination of nonanoic acid with streptomycin was bactericidal to 99.9% of MTB H37Ra by Day 7 of the time-kill assay, with structural damage of the cell wall observed using electron microscopy. Cytotoxicity assessment using Vero cells confirmed nonanoic acid had low toxicity with LC₅₀ of > 200 µg/mL. The bio-guided fractionation of OPF shows the presence of fatty acids with anti-TB adjuvant potential. Full article

In the last few years, the flavored beer market has increased significantly. In particular, consumers showed a growing interest in citrus-flavored beers. Citrus fruits contain, among other class of compounds, terpenes and terpenoids and oxygenated heterocyclic compounds. The absence of a specific legislation concerning beer flavored production and ingredients reported on the labels makes these beers subject to possible adulterations. Solid phase micro extraction (SPME) followed by gas chromatographic–mass spectrometry (GC-MS) and gas chromatographic-flame ionization detector (GC-FID) analysis of the volatile profile together with the characterization of the oxygen heterocyclic compounds through high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) demonstrated to be a powerful analytical strategy for quality control. In this study, we combined the volatile and non-volatile profiles of “citrus flavored mainstream beers”, in order to evaluate the authenticity and determine markers to prevent food frauds. The changes in the aroma composition of the unflavored types after the addition of peel, or citrus essential oil were also evaluated. The linear retention index (LRI) system was used for both techniques; in particular, its application in liquid chromatography is still limited and represents a novelty. The coupling of the high sensitivity of the HPLC MS/MS method with the LRI system, it has made possible for the first time a reliable identification and an accurate quantification of furocoumarins in citrus-flavored beers. Full article

Purified extracts from different types of berries and medicinal plants are increasingly used as raw materials for the production of nutraceuticals and dietary supplements, mainly due to their high content in bioactive substances. This is, for instance, the case of phenolic compounds such as flavonoids, which exhibit a wide range of beneficial properties, including antioxidant, anti-inflammatory, antineoplastic and antimicrobial activities. This paper tackles the characterization of several kinds of nutraceuticals based on hydrophilic interaction liquid chromatography (HILIC) with fluorescence detection (FLD). The study focused on the determination of flavanols and related compounds such as condensed tannins. Analytes were recovered by solvent extraction using methanol:water:hydrochloric acid (70:29:1 v:v:v) as the extraction solvent under sonication for 30 min at 55 °C. Experimental design with response surface methodology was used to optimize the HILIC separation to achieve good resolution of the main components, using acetonitrile:acetic acid (99:1 v/v) (solvent A) and methanol:water:acetic acid, (95:3:2 v/v/v) (solvent B) as the components of the mobile phase. For the assessment of the elution gradient, factors under study were solvent B percentage and gradient time. The best conditions were achieved with 10% solvent B as the initial percentage and 30 min of linear gradient to reach 25% solvent B. Principal component analysis and partial least square-discriminant analysis were used to characterize and compare the compositional features of dietary supplements based on both targeted and non-targeted approaches. Results revealed that the sample distribution relied on the oligomeric nature of descriptors. Full article

In the environment, pharmaceutical residues are a field of particular interest due to the adverse effects to either human health or aquatic and soil environment. Because of the diversity of these compounds, at least 3000 substances were identified and categorized into 49 different therapeutic classes, and several actions are urgently required at multiple steps, the main ones: (i) occurrence studies of pharmaceutical active compounds (PhACs) in the water cycle; (ii) the analysis of the potential impact of their introduction into the aquatic environment; (iii) the removal/degradation of the pharmaceutical compounds; and, (iv) the development of more sensible and selective analytical methods to their monitorization. This review aims to present the current state-of-the-art sample preparation methods and chromatographic analysis applied to the study of PhACs in water matrices by pinpointing their advantages and drawbacks. Because it is almost impossible to be comprehensive in all PhACs, instruments, extraction techniques, and applications, this overview focuses on works that were published in the last ten years, mainly those applicable to water matrices. Full article

The association between humans and cats (Felis catus) is well known. This domestic animal is also known for its malodorous urine and feces. The complexity of the odorous urine and feces impacts human life by triggering the human sensory organ in a negative way. The objective of this research was to identify the volatile organic chemicals (VOCs) and associated odors in cat urine and feces using gas chromatography–mass spectrometry and simultaneous sensory analysis of fresh and aged samples. The solid-phase microextraction (SPME) technique was used to preconcentrate the VOCs emitted from urine or feces samples. Twenty-one compounds were identified as emitted from fresh urine, whereas 64 compounds were emitted from fresh feces. A contrasting temporal impact was observed in the emission of VOCs for urine and feces. On aging, the emission increased to 34 detected chemicals for stale urine, whereas only 12 chemicals were detected in stale feces. Not all compounds were malodorous; some compounds had a pleasant hedonic smell to the human nose. Although trimethylamine, low-molecular-weight organic acids, and ketones were contributors to the odor to some extent, phenolic compounds and aromatic heterocyclic organic N compounds generated the most intense odors and substantially contributed to the overall malodor, as observed by this study. This work might be useful to formulate cat urine and feces odor remediation approaches to reduce odor impacts. Full article

The development of suspect or non-target screening methods to detect xenobiotics in biological fluids is essential to properly understand the exposome and assess its adverse health effects on humans. In order to fulfil that aim, the biomonitorization of human fluids is compulsory. However, these methods are not yet extensively developed, especially for polar organic xenobiotics in biofluids such as milk, as most works are only focused on certain analytes of interest. In this work, a multi-target analysis method to determine 245 diverse xenobiotics in milk by means of Ultra High Performance Liquid Chromatography (UHPLC)-qOrbitrap was developed. Under optimal conditions, liquid milk samples were extracted with acetonitrile in the presence of anhydrous Na₂SO₄ and NaCl, and the extracts were cleaned-up by protein precipitation at low temperature and Captiva Non-Drip (ND)—Lipids filters. The optimized method was validated at two concentration-levels (10 ng/g and 40 ng/g) obtaining satisfactory figures of merit for more than 200 compounds. The validated multi-target method was applied to several milk samples, including commercial and breast milk, provided by 4 healthy volunteers. Moreover, the method was extended to perform suspect analysis of more than 17,000 xenobiotics. All in all, several diverse xenobiotics were detected, highlighting food additives (benzothiazole) or phytoestrogens (genistein and genistin) in commercial milk samples, and stimulants (caffeine), plasticizers (phthalates), UV filters (benzophenone), or pharmaceuticals (orlistat) in breast milk samples. Full article

A solid-phase extraction (SPE) procedure was developed for simultaneous monitoring of sixteen different phenolics of various polarity, quantified by high-performance liquid chromatography (HPLC). The procedure allowed screening the accumulation of intermediates in different metabolic pathways that play a crucial role in plant physiology and/or are beneficial for human health. Metabolites mostly involved in phenylpropanoid, shikimate, and polyketide pathways comprise chlorogenic acid, gentisic acid, vanillic acid, caffeic acid, protocatechuic acid, ferulic acid, rutin, quercetin, epicatechin, gallic acid, sinapic acid, p-coumaric acid, o-coumaric acid, vanillin; two rarely quantified metabolites, 2,5-dimethoxybenzoic acid and 4-methoxycinnamic acid, were included as well. The procedure offered low cost, good overall efficiency, and applicability in laboratories with standard laboratory equipment. SPE recoveries were up to 99.8% at various concentration levels. The method allowed for routine analysis of compounds with a wide range of polarity within a single run, while its applicability was demonstrated for various model plant species (tobacco, wheat, and soybean), as well as different tissue types (shoots and roots). Full article

A simple and efficient method has been developed for the simultaneous determination of eight flavonoids (orientin, hyperoside, rutin, myricetin, luteolin, quercetin, kaempferol, and apigenin) in Sonchus arvensis by high-performance liquid chromatography diode array detector (HPLC-DAD). This method was utilized to differentiate S. arvensis samples based on the plant parts (leaves, stems, and roots) and the plant’s geographical origin. The chromatographic separation was carried out on a reverse-phase C18 column by eluting at a flow rate of 1 mL/min using a gradient with methanol and 0.2% aqueous formic acid. In the optimum conditions, the developed method’s system suitability has met the criteria of good separation. The calibration curve shows a linear relationship between the peak area and analyte concentration with a correlation coefficient (r²) > 0.9990. The ranges for the analytes’ limits of detection and quantitation were 0.006–0.015 and 0.020–0.052 µg/mL, respectively. Intra-day and inter-day precision expressed in terms of RSD values were <2%, and the accuracy range based on recovery was 97–105%. The stability of all analytes within 48 h was about 2%. By combining HPLC-DAD fingerprint analysis with chemometrics, the developed method can classify S. arvensis samples based on the plant parts and geographical origin. Full article

Betonica bulgarica is an endemic species distributed in Bulgaria. The chemical composition of the essential oil analysed by GC–MS (Gas chromatography–mass spectrometry) and the content of trace elements analysed by ICP–MS (Inductively coupled plasma mass spectrometry) were determined. Additionally, a study on the types and distribution of trichomes was done using a microscope with a camera. The essential oil was characterized using a high concentration of sesquiterpene hydrocarbons, whose major compounds are β-caryophyllene (17.4%), germacrene D (9.9%), and β-bourbonene (6.7%). The contents of manganese (177.2 µg/g) and strontium (156.8 µg/g) were highest among the investigated micronutrients. Two types of trichomes were identified on the adaxial and abaxial epidermises of the leaves of B. bulgarica—covering and glandular. Peltate stacked glandular trichomes with a four-celled head of type B were observed on the leaf surface. Full article