Current Chromatography - Volume 7, Issue 1, 2020

Green separation science involves extraction, pre-concentration and chromatographic analysis aiming at minimizing environmental impact by reducing energy and reagent usage and reducing or eliminating waste generation. However, the enrichment of trace analytes and/or the analysis of complex matrices most frequently require several steps before analysis, such as extraction, pre-concentration, clean up and preparative chromatography. Thus, alternative and greener separation techniques and solvents are replacing classical methods to diminish the carbon footprint and increase sustainability. Moreover, many innovations are also emerging to curtail the environmental impact of samples analysis; such as micro or nano analytical platforms, sensor-based systems and direct injection to high-resolution mass spectrometry. The current review provides an updated account of the green and sustainable separation science techniques. The current innovations on greener separations and their application in different fields of study are discussed.

Background: Eugenol is the main constituent of clove essential oil. Past studies have found that clove oil has diverse uses in the pharmaceutical field due to its antioxidant, antibacterial and anesthetic properties. Objective: This work compares the performance of different extraction methods and factors and identifies the effect of the treatments on oil yields and eugenol content. Materials and Methods: Maceration, Hydro distillation, microwave-assisted extraction (MAE), and Soxhlet were performed. The best technique was identified according to yield and content. Further studies were conducted to examine the effects of different factors, such as solvent types (ethanol and methanol) and sample-to-solvent ratio (1:10 and 1:15). HPLC UV-Vis was utilized in the analysis of eugenol concentration. Results and Discussion: Soxhlet extraction provided the highest yield (39.98%) and eugenol content (15.83%), compared to other methods. The results observed from several Soxhlet extraction factors showed that there is no significant difference between the different factors. In the meantime, methanol 1:15 provided the greatest amount of yields (57.83%) and eugenol content (22.21%). In this regard, the higher ratio resulted in higher eugenol content. Conclusion: The results obtained are less comparable because the processing time, the working solvent, and the separation technique were carried out differently for each method. In the meantime, as there is no past study that compared the selected methods and factors, this study’s findings will contribute substantially to fill the gap in this field.

Background: Carotenoids are natural plant pigments and precursors of vitamin A, which provide a health benefit, protect against chronic degenerative diseases, and contribute to immune functions. Utilization and identification of foods with a high content of carotenoids received greater attention nowadays. Objective: The present study was aimed at evaluating total carotenoids content (TCC) and carotene composition of unconventional leafy vegetables growing in Bangladesh. Materials and Methods: The samples were collected from different locations of Bangladesh and mixed together to ensure sample representativeness. Acetone–petroleum ether extraction followed by spectrophotometric measurement was utilized for quantification of TCC. High-performance liquid chromatography (HPLC- DAD) was used to separate and quantify carotene components. Results and Discussion: The TCC values ranged from 129.38 μg/100 g edible portion (EP) in Helencha to 12803.31 μg/100 g EP in Roktodrone. The study findings also revealed that the selected plant samples exhibited high content of β-carotene ranging from 120.99 μg/100 g EP in Parul to 11301.16 μg/100 g EP in Roktodrone. It was also observed that most of the vegetables analyzed did not have α-carotene, lycopene, β-cryptoxanthin or it was in such a small quantity that could not be detected with HPLC. Conclusion: It can be suggested that regular intake of these vegetables may provide pro-vitamin A. In order to address the vitamin A deficiency and to maintain biodiversity, the analysis of carotenoids composition of these unconventional plant foods is to be initiated and make it available to the mass population. It would also fill up the data gap in the existing food composition table of Bangladesh.

Background: The cost-effective and environmentally benign solvent of hydrophobic deep eutectic (DES) was prepared for the removal of Cu (II) from aqueous solution. Hydrophobic DES has been gaining increasing attention from researchers for the replacement of hazardous solvent consumption in liquid-liquid extraction (LLE). Objectives: To synthesize the hydrophobic DES and optimize the parameters for ligandless LLE using DES, and LLE with DES-LIG, respectively. Materials and Methods: The fatty acid-based DES was prepared using a mixture of capric acid (C10) and lauric acid (C12) as a potential solvent for the extraction of Cu (II). The DES was characterized via FT-IR, NMR, and TGA. The removal percentage of Cu (II) was compared between ligandless LLE and other conventional LLE techniques. DES was used as the solvent in the ligandless LLE, while 1,10-phenanathroline ligand with DES (DES-LIG) was used in the conventional LLE techniques. The optimized parameters such as pH, initial concentration, and contact time for Cu (II) removal were studied and analyzed using atomic absorption spectroscopy (AAS). Results and Discussion: The ligandless LLE with DES demonstrated the highest removal percentage of Cu (II) at optimum conditions of pH 8, initial concentration of 80 μg mL-1, and contact time of 45 minutes. Conclusion: The removal of Cu (II) was more effective in ligandless LLE using DES.

Background: Polyphenolic compounds are known to provide health benefits and protect against degenerative chronic diseases. Utilization and identification of foods with a high content of these compounds are gaining greater attention nowadays. Objective: The present study reports the total phenolic content (TPC), polyphenolic composition and antioxidant activity (DPPH, FRAP and TEAC) of 10 commonly consumed leafy vegetables growing in Bangladesh. Materials and Methods: The samples were collected from different locations of Bangladesh and mixed together to ensure sample representativeness. Folin-Ciocalteu method was used for the analysis of TPC, and quantification of polyphenolic components was done by high-performance liquid chromatography (HPLC- DAD). Additionally, antioxidant activities of the selected vegetables were also analysed by utilizing DPPH, FRAP & TEAC. Results and Discussion: TPC ranged from 23.64 ± 1.20 to 45.59 ± 3.04 mg gallic acid equivalent (GAE)/g freeze-dried sample (fds). The polyphenolic spectrum ranged from 0.30 ± 0.02 to 647.42 ± 147.12 mg/100 g fds; quantity and spectrum of which varied in the vegetables. Among the studied vegetables, Centella asiatica contained the highest amount of TPC (45.59 ± 3.04 mg GAE/g fds) and also exhibited high antioxidant capacities, as documented by DPPH, FRAP and TEAC assays. Moreover, Principal component analysis (PCA) of investigated variables clearly separated Centella asiatica from other samples. Conclusion: Phenolic compounds being strong antioxidants reduce the risk of chronic diseases and the finding of this study would aware the people to take vegetables rich in phenolics. It would also fill up the data gap in the existing food composition table of Bangladesh.

Background: The application of enantioselective capillary electrophoresis approach for the assessment of the enantiomeric purity of chiral molecules is receiving increased attention. Abscisic acid is one of the chiral sesquiterpenic plant growth regulators that regulate various ecological and physiological roles in higher plants. Enantiomeric determination of ABA is of great concern because of the different biological activity of its enantiomers. Materials and Methods: In this study, we investigated the enantioseparation selectivity of ABA by incorporating native β-cyclodextrins (β-CD) and its derivatives as chiral modifiers in the background electrolyte of an enantioselective capillary zone electrophoresis system. Electrophoretic aspects that affect the enantiomeric separation, such as pH, types of β-CD and its concentration, applied voltage, injection pressure and time, were studied and optimised. Results and Discussions: An enhancement in enantioseparation was achieved in a bare fused-silica capillary (64.5 cm x 50 mm i.d.) using a background electrolyte solution consisting of (2-hydroxypropyl)- β-CD (80 mM) solubilised in 100 mM phosphate buffer adjusted to pH 5.9 with NaOH, operated under normal polarity mode (25 kV) at 25°C, and using hydrodynamic injection (75 mbar for 10s). Relative standard deviations of (intra- and inter-day) ≤ 3.23% and ≤ 1.39% for migration times and enantiomeric fractions (EF) were achieved using the proposed method. Conclusion: The proposed chiral capillary electrophoretic method offers advantages in terms of enantioselectivity and analysis times, which can serve as a reliable platform for the stereoisomeric analysis of ABA.

Background: Cationic surfactants (CSs) such as quaternary ammonium compounds are used as fabric softeners, anti-bacterial agents, and human hair cosmetics. Accurate determination of CSs in environmental water samples is very difficult because of their very low concentration and strong adsorptivity to not only glassware but also to plasticware due to strong hydrophobic and electrostatic attractions. Linear alkylbenzene sulfonates (LASs), anionic surfactants, are produced in the largest quantity as the main components of laundry detergents, dishwashing liquids, and other cleaning formulations. In this study, a liquid chromatography/mass spectrometry (LC/MS) method was developed for simultaneous determination of CSs, cetyltrimethylammonium ion (CTMA) and trimethylstearylammonium ion (TMSA), and LASs in environmental water samples. Materials and Methods: This method involves a solid-phase extraction of CSs and LASs from the water samples using a solid-phase extraction cartridge, InertSep Slim-J PLS-3. A hydrophilic polymer column, Shodex MSpak GF-310 4D was used for the separation of CSs and LASs with a mobile phase gradient from 36 to 44 % (v/v) acetonitrile-water containing 0.8 mM di-nbutylammonium acetate and 0.2 M acetic acid. Di-n-butylammonium ion acts as the ion-pair reagent for retention of LASs on the column, while it makes the retention of CSs moderate. Positive and negative electrospray ionization modes were used for the MS detection for CSs and LASs, respectively. Results and Discussion: Instrument detection limits of the developed method based on selected ion monitoring technique for the mixed standard solutions of CSs and LASs were 3 and 6 ng L-1 for CTMA and TMSA, respectively and 13 – 47 ng L-1 for the C10-C14 LASs. The total concentration of the CSs was determined to be 6.6 μg L-1 for river water (Ebi river, Japan) and 0.028 μg L-1 for seawater (Tokyo Bay, Japan) samples. The concentration of total LAS was determined to be 1122 μg L-1 for the river and 10.8 μg L-1 for the seawater samples. Conclusion: These results demonstrate that the solid-phase extraction and the LC/MS method developed in this study are useful for the simultaneous determination of trace amounts of CSs and LASs in environmental water samples.