This paper describes the separation and detection of five inorganic anions (I - , BrO3 - , NO2 - , Br - , and NO3 -) by capillary ion chromatography using 1-alkyl-3-methylimidazolium-coated columns and UV detection at 210 nm. The salts of imidazolium (IM) ions (C2-, C4-, C6-, C8-, C10-, and C18-IMs) are a family of ionic liquids and were newly examined as permanent coating reagents on a triacontyl (C30) -bonded silica reversed phase column. When 40 mM NaCl aqueous solution was used as an eluent, the elution time of these anions was increased with the length of alkyl chain between C2- and C10-IMs, but turned to decrease with C18-IM. Good and faster separations were attained using a C18-IM-coated column with 150 mM NaCl in 25%(v/v) acetonitrile-75%(v/v) water. The method was successfully applied to the determination of nitrite, bromide, and nitrate in seawater and river water.
Herein, we evaluate the photostability of pranoprofen (PP) tablets (NIFLAN® 75 mg), its powdered and suspended forms. PP is a member of the 2-arylpropionic acid family of NSAIDs. The content of the active compound was monitored by high-performance liquid chromatography (HPLC) using an ODS column with ultraviolet light (UV) detector. The residual amount of PP in the powder was 86.5%, which was comparable to that of in the suspension (85.4%) after UV irradiation for 24 hr. Further UV irradiation (total irradiation time of 7 days) resulted in the significant photodegradation of PP in the suspension (residual amount: 55.5%), compared to that of 1 day irradiation. However, the residual amount of PP in the powder was 78.6% after 7 days irradiation as the same to that of 1 day irradiation. To identify the chemical structure of five photoproducts generated from the UV-irradiated PP dosage forms, electrospray ionization liquid chromatography mass spectrometry (ESI-LC/MS/MS) analysis was performed. From these results, photodegradation of PP was observed through changing dosage forms. This is the first report evaluating the generation of PP photoproducts induced by the UV irradiation in the formulation.
Simultaneous separation of 37 proteinogenic D/L-amino acids excluding proline with HPLC is generally difficult. In this study, two sets of o-phthalaldehyde (OPA)-based fluorescent diastereomers of D/L-amino acids were formed using two chiral thiols of N-acetyl-L-cysteine (NAC) and N-isobutyryl-L-cysteine (NIBC) independently. It is expected that obtained two sets of OPA-derivatized D/L diastereomers show different retention selectivity in reversed phase chromatography because NAC and NIBC have different hydrophobicities. The two independent HPLC methods were designed to obtain complementary separations for the two sets of fluorescent diastereomers of the proteinogenic D/L-amino acids. The obtained two complementary chromatograms provided complete determination for diastereomers of proteinogenic D/L-amino acids. After the optimization of HPLC separation conditions, two types of automated analytical procedures were investigated. One was for OPA/NAC and OPA/NIBC derivatization of amino acids using originally equipped pretreatment functions of auto-sampler. The other was for switching the two HPLC separation methods during the consecutive batch run. Through these re-consideration for automated procedures, finally obtained method afforded satisfactory peak area repeatability of 1.5%RSD or less and calibration curve linearity of 0.999 or greater for each diastereomers. The established methods were applied to the real liquor samples and successful results were obtained.
D-Amino acids have recently been found to be present in mammals, and their synthetic pathways require investigation. We analyzed D- and L-amino acids in HepG2 cells using the Nα-(5-fluoro-2,4-dinitrophenyl)-L-leucinamide (FDLA) chiral derivatization method for liquid chromatography-tandem mass spectrometry (LC/MS/MS). D-Asp and D-Ser were detected in HepG2 cells and their culture medium, and the concentrations of these amino acids increased in a time-dependent manner during culture. In addition, in the presence of the D-aspartate oxidase (DDO) inhibitor, 5-aminopyridine-3-carboxylic acid, the concentrations of D-Asp and D-Ser increased compared to those in the control cells. These results suggest that D-Asp and D-Ser are biosynthesized in HepG2 cells and that DDO is involved in the regulation of D-Asp and D-Ser concentration in these cells.
Enantioselective analysis of lactate (LA) in various fermented food/beverage samples including the Japanese traditional amber rice vinegars was performed using a newly designed three-dimensional high-performance liquid chromatographic (3D-HPLC) system. The enantiomers of LA are reported to be possible biomarkers for some diseases such as diabetic mellitus. To evaluate the diagnostic value, the dietary intake should be taken into consideration. Therefore, clarifying the presence of LA enantiomers in our environment is a matter of interest. In the present study, LA enantiomers in a variety of fermented food/beverage samples were determined after the pre-column derivatization with 4-nitro-7-piperazino-2,1,3-benzoxadiazole. Among the fermented products tested, high concentrations of LA enantiomers were observed in a Japanese traditional amber rice vinegar (sample SK, 13.1 and 22.8 μmol/mL for D-LA and L-LA, respectively). The developmental changes of the LA enantiomers during the fermentation/aging processes of the Japanese traditional amber rice vinegar were also studied. The concentrations of D- and L-LA drastically increased in the early stage of the fermentation and attained to the highest concentrations after 1 month, then gradually decreased thereafter. The present results help to illuminate the benefits of Japanese traditional vinegars in the health and food sciences.
A novel core-shell ion-exchange resin composed of an ion-exchanging porous shell layer formed on a hard polymer core was prepared for application to HPLC. The effect of various core-shell ratios on the retention time and theoretical plate number (N) in the separation of carbohydrates was examined. A mixed aqueous sample of inositol, glucose, fructose and sucrose was reasonably separated under alkaline conditions (100 and 150 mmol/L NaOH) at flow rates of 0.4-1.0 mL/min. The retention time was linearly related to the thickness of the porous layer. The values of theoretical plate number(N) of glucose, fructose, and sucrose depend on the shell thickness at a flow rate of 0.5 mL/min when using the 100 and 150 mmol/L NaOH eluent.