Plasma lipid analysis by hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A novel method for the analysis of endogenous lipids and related compounds was developed employing hydrophilic interaction liquid chromatography with electrospray ionization tandem mass spectrometry. A hydrophilic interaction liquid chromatography with carbamoyl stationary phase achieved clear separation of phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, ceramide, and mono‐hexsosyl ceramide groups with good peak area repeatability (RSD% < 10) and linearity (R² > 0.99). The established method was applied to human plasma assays and a total of 117 endogenous lipids were successfully detected and reproducibly identified. In addition, we investigated the simultaneous detection of small polar metabolites such as amino and organic acids co‐existing in the same biological samples processed in a single analytical run with lipids. Our results show that hydrophilic interaction liquid chromatography is a useful tool for human plasma lipidome analysis and offers more comprehensive metabolome coverage.     

Recyclable Ligands for the Non‐Enzymatic Dynamic Kinetic Resolution of Challenging α‐Amino Acids

Structurally simple and inexpensive chiral tridentate ligands were employed for substantially advancing the purely chemical dynamic kinetic resolution (DKR) of unprotected racemic tailor‐made α‐amino acids (TM‐α‐AAs), enabling the first DKR of TM‐α‐AAs bearing tertiary alkyl chains as well as multiple unprotected functional groups. Owing to the operationally convenient conditions, virtually complete stereoselectivity, and full recyclability of the source of chirality, this method should find wide applications for the preparation of TM‐α‐AAs, especially on large scale.     

Immobilization of noble metal nanoparticles on the surface of TiO2 by the sonochemical method: photocatalytic production of hydrogen from an aqueous solution of ethanol

Sonochemically prepared Pt, Au and Pd nanoparticles were successfully immobilized onto TiO2 with the assistance of prolonged sonication. Their photocatalytic activities were evaluated in H2 production from aqueous ethanol solutions. Beside the sonochemical method, the conventional impregnation method was also employed to prepare photocatalysts. The sonochemically prepared catalysts showed higher activities than did the conventional ones. Their photocatalytic activities depended on the work functions and the dimensions of supported noble metal nanoparticles. Smaller Pt nanoparticles effectively restricted recombination of electrons and holes and provided H2 at a higher rate.     

Synthesis and chiroptical property of C2-symmetric cyclohexapyrrole

Condensation reaction of gem-dimethyldipyrrylmethane-5,5′-dicarbinol and 4,4′-dimethyl-3,3′-di-iso-butyl-2,2′-bipyrrole under the catalysis by trifluoroacetic acid gave a hexapyrrolic macrocycle 6 in 15% yield after DDQ oxidation. X-ray crystallography of 6 shows that three parts of highly planar dipyrrylmethene unit are assembled by two sp³ hybridized gem-dimethyl carbon bridges and one direct linking at the pyrrole α-positions, leading to C₂ molecular symmetry. The complexation of 6 with (S)-(+)- and (R)-(−)-mandelic acid induced a CD Cotton effect at 461 and 650 nm.     

An ultrasound-assisted digestion method for the determination of toxic element concentrations in ash samples by inductively coupled plasma optical emission spectrometry

A method of ultrasound-assisted digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) used for the determination of toxic element concentrations (arsenic, barium, cobalt, copper, lead, nickel, strontium, vanadium and zinc) in ash samples was developed. All the measurements were performed in robust plasma conditions which were tested by measuring the Mg(II) 280.270 nm/Mg(I) 285.213 nm line intensity ratios. The highest line intensity ratios were observed when a nebulizer gas flow of 0.6 L min⁻¹, auxiliary gas flow of 0.2 L min⁻¹ and plasma power of 1400 W were used for radially viewed plasma. The analysis of SRM 1633b showed that the ultrasound-assisted method developed is highly comparable with the microwave digestion method standardized by the United States Environmental Protection Agency (EPA-3052). The ultrasound-assisted digestion with a digestion solution of aqua regia and hydrofluoric acid (HF) resulted in recovery rates of over 81%. One exception is arsenic which resulted in recoveries of about 60% only; however, it could be digested with good recovery (>90%) using a digestion solution of 5 mL of water and 5 mL of aqua regia. The major advantage of the ultrasound-assisted digestion over microwave digestion is the high treatment rate (30 samples simultaneously with a sonication time of 18 min).     

Solvatochromic studies of ionic liquid/organic mixtures

Room-temperature ionic liquids (ILs) have potential for many different applications, including catalysis and synthesis. Organics are often present during IL applications; therefore, a more fundamental understanding of the interactions between IL and organics is necessary. A systematic study of the effects of organic cosolvents, cations, and anions on the solvent strength of IL/organic mixtures will allow for a greater understanding and potential for tuning of ILs for specific purposes. Solvent strength is commonly quantified using spectroscopic probes. We report the solvent strength of IL/organic mixtures using Reichardt's dyes 30 and 33, Kamlet-Taft parameters, and phenol blue. The results show that the polarity of ILs is largely unaffected by the organic cosolvent; that is, the probes are preferentially solvated by the ILs. However, more specific solvation forces, such as hydrogen bonding, can be influenced indirectly by the strength of the anion/cation interaction, giving counterintuitive results.     

Reduction of cephalosporanic acids with chromium(II) salts : Synthesis of 3-methylenecepham derivatives

7-Acylaminocephalosporanic acid derivatives (1) were converted into 7-acylamino-3-methylenecepham-4-carboxylic acids (2) by treatment with chromium(II) salts in aqueous media. The esters (4a or 4b) of 7-acylamino-3-methylenecepham compounds were readily isomerized to the 3-methyl-3-cephem compounds (5a or 5b) under basic conditions. The reaction mechanism is discussed.     

Calorimetry to Evaluate Inclusion Mechanism in the Complexation Between 2-hydroxypropyl-β-cyclodextrin and Barbiturates in Aqueous Solution

Two different types (structures) of inclusion complexes with a 1:1 stoichiometry between barbiturates and 2-hydroxypropyl-β-cyclodextrin (HPCyD) were realized in aqueous solution using isothermal titration calorimetry and molecular dynamics simulation. The first type of complex with a higher association constant was entropy driven and the substituent R ₂ was inserted into the HPCyD cavity by hydrophobic interaction. The barbituric acid ring contributed to the second type of complex, which was characterized by large negative values of ΔH and small positive ΔS reflecting van der Waals interaction and/or hydrogen bonding formation between the hetero atoms in the barbituric acid ring and the secondary hydroxyl groups of HPCyD. This revised version was published online in July 2006 with corrections to the Cover Date.