Momilactones, allelochemicals from rice plants, exhibit diverse effects, including functioning as crop-friendly pesticides, and possessing antifungal and anticancer properties. The present study aimed to optimize the isolation of momilactones A (MA) and B (MB) using high-speed countercurrent chromatography (HSCCC), prioritizing the minimization of organic solvent waste and utilizing discarded rice husk. By employing techniques such as solvent reuse and HSCCC, we successfully isolated the highly purified fractions of MA and MB (>95% purity, as verified by HPLC) from rice husk. The optimized two-phase solvent system (n-hexane/ethyl acetate/methanol/water, 7/3/5/5, v/v/v/v) was specifically chosen for its efficiency in HSCCC, applied to extracts from 2 kg of rice husk. The separation was performed using the lower mobile phase of the two-phase solvent system at a flow rate of 1.0 mL/min after rotating the multilayer coiled column at the revolution speed of 1000 rpm. The retention of the stationary phase was observed to be 77%. The purity of isolated MA (3.0 mg) and MB (2.0 mg) was determined to be 99.0% and 98.2% via LC-UV chromatogram, respectively. Significantly, the organic solvents used in the extraction and HSCCC processes were redistilled and recycled, leading to an over 80% reduction in solvent consumption. This study demonstrates the feasibility of a sustainable, economical, and effective chromatographic method for isolating allelochemicals from waste plant materials.

A novel fiber-packed column was developed with a fibrous polyimide (PI) as the separation medium in liquid chromatography (LC), and the retention behavior for various aromatic compounds on the stationary phase was investigated in reversed-phase conditions. A retention trend was observed on the PI phase, which strongly retained certain types of analytes with long alkyl chain(s) in the chemical structure. However, the retention factor of analytes with short alkyl chains exceeded that expected from hydrophobic interaction between the analytes and stationary phase. Several solute pairs with and without polar functional groups were employed as the sample probe. The separation factor for these analyte pairs on the PI phase was significantly better than that on typical conventional stationary phases such as octadecylsilica phases. The fibrous PI stationary phase exhibited a unique retention tendency in that the retention time of toluene increased with an increase in the column temperature, and the trends differed from that observed on typical LC stationary phases.

Monolithic materials having 3D-network structure are now widely used for the separation such in liquid chromatography and solid-phase extraction. Additionally, monolithic materials showed several functionalities, we previously discovered that epoxy monoliths, which were prepared with epoxy compounds and amine curing agents using suitable porogens, showed antibacterial potency when quaternized by hydrogen halides and alkyl halides and immersed in coli suspension. Antibacterial activity was enhanced by lowering pH of the aqueous phase with the former and cell membrane disruption triggered by cell contact with the latter. As well as the epoxy monoliths with nitrogen (N) at the high content rate enhance antibacterial activity. We consider that these actions may be effective for molds. In this study, we synthesize epoxy monoliths, conducting quaternization with hydrochloric acid and butyl bromide. Alternaria alternate, one of the genera in sooty mold, is employed for an evaluation. We examine effects of the epoxy monoliths on spores and hyphal growth. With the effects on spores, unquaternized monoliths and ones quaternized with hydrochloric acid and/or butyl bromide were immersed in coli suspension, and after predetermined time, the suspension was cultured in potato dextrose agar. Consequently, the monoliths quaternized with butyl bromide inhibited the growth of the spores. With the effects on the hyphal growth, we observed mold growth by placing the fabricated epoxy monolith in PDA and injecting molds to the surface of the monolith. The monoliths quaternized with hydrochloric acid inhibited the hyphal growth most by lowering pH of the culture medium. The quaternized monoliths with butyl bromide could inhibit the hyphal growth due to the positively charged surface of the monolith. Besides, we successfully achieved antimold with inhibiting the fungal growth by raising the N content rate and increasing degree of quaternization.

A complementary HPLC method for the determination of 37 proteinogenic D/L-amino acids excluding proline by analyzing each sample twice while automatically switching between the two separation methods using two chiral thiols of N-acetyl-L-cysteine (NAC) and N-isobutyryl-L-cysteine (NIBC) was previously reported. In this study, separation of o-phthalaldehyde (OPA)/NIBC-derivatized proteinogenic D/L-amino acids with higher hydrophobicity under a single analytical method was investigated. By increasing the methanol ratio of the mobile phase and setting the column temperature to 20 °C, it was possible to separate the 37 fluorescent diastereomers of the proteinogenic D/L-amino acids in a single analysis within 66 minutes, with an analysis cycle of 87 minutes. The peak area repeatability for each diastereomer was 1.6% RSD or less because of automating the OPA/NIBC derivatization of proteinogenic D/L-amino acids. The calibration curve linearity was 0.999 or greater for each diastereomer. As a result of applying this method to liquor samples, it was found that the overall ratio of D-amino acid to D/L-amino acid was 6% or less, but it was quantifiable. Principal component analysis of the five liquor samples showed that these samples were classified by type of liquor. The established method has the potential to be applied to liquor profiling.

A method for isolating each enantiomer of synephrine from the racemate using chiral chromatography was investigated, and a simple and highly sensitive analytical method for determining synephrine enantiomers in commercial dietary supplements was constructed using chiral liquid chromatography-fluorescence detection (LC/FL). For isolating each enantiomer, synephrine was derivatized with the 9-fluorenylmethyl chloroformate (FMOC-Cl) and separated by chiral LC after removing excess FMOC-Cl by solid-phase extraction (OASIS MCX cartridge). Deprotection was performed with piperidine, with excess piperidine removed using an HLB cartridge. A sample solution extracted from a dietary supplement was cleaned by solidphase dispersive extraction with MCX, after which each enantiomer was derivatized using FMOC-Cl. Chiral LC was performed using a TCI Chiral MB-S column with a 75:25 mixture of 50 mM aqueous phosphoric acid solution/acetonitrile as the mobile phase. The limit of detection and limit of quantification values of 0.03 and 0.1 μg/mL, respectively, were recorded, along with a repeatability of < 15%, an intermediate precision of < 20%, and an accuracy of > 80%. Analysis of 17 commercial dietary supplements revealed that some exhibited enantiomeric excesses of less than 70% for the l-isomer, which suggests that partial racemization occurred in the manufacturing process. The developed method can be used to clarify the synephrine-isomerization mechanism in the food-hygiene field.

For the quantitative determination of organic compounds in particulate matter less than 2.5 μm (PM2.5), it is first collected on a filter paper using a high-volume air sampler and the organic compounds are eluted with an organic solvent. However, a positive error occurs in the quantitative results owing to the adsorption of gaseous organic compounds onto the filter paper and PM2.5. This study investigates the adsorption of gaseous organic compounds onto PM2.5. The adsorption of these compounds was evaluated by air sampling using two filter papers: one on which the target organic compounds were spiked (upstream filter) and another on which PM2.5 was adsorbed (downstream filter). Results obtained using n-alkanes clearly indicated a large amount of gaseous n-C₂₆ adsorption onto PM2.5. In contrast, octadecyl benzene, which has a boiling point similar to that of n-C₂₆H₅₄, did not show specific adsorption onto PM2.5. These results suggested that the adsorption of gaseous organic compounds onto PM2.5 may be affected by the volatility and chemical structure of the organic compound. Furthermore, in the component analysis of organic compounds in PM2.5, a large positive error may occur for a specific organic compound with low volatility due to its gas adsorption onto PM2.5.

Quantification of the circulating thyroid hormones helps in the diagnosis and evaluation of therapy efficacy for thyroid diseases. When only a small volume of serum/plasma can be used, the quantification of triiodothyronine (T₃), an active thyroid hormone, is no easy task due to its low concentration. In this study, a procedure enabling the multiple methylations of T₃ in one step was developed to enhance its detectability during electrospray ionization (ESI)-tandem mass spectrometry (MS/MS). The combined use of trimethylsilyldiazomethane and iodomethane provided the quaternized derivative, which was completely methylated in the carboxy, phenolic hydroxy and amino groups in T₃, within 60 min. This derivative demonstrated a higher ESI efficiency due to the permanent positive charge and a good fragmentation behavior during MS/MS to produce a product ion containing the T₃-specific moiety. When this methylation procedure was applied to the serum analysis by liquid chromatography (LC)/ESI-MS/MS, T₃ was detected with a sufficient signal-to-noise ratio (S/N) using only a 20-μL serum aliquot. The S/N-based sensitivity was increased four-fold by the multiple methylations in the serum assay. Thus, the developed procedure satisfactorily worked for the trace analysis of the serum T₃ by LC/ESI-MS/MS.