Development of a new cyano-bonded column for high-performance liquid chromatography

Energy-efficient and environment-friendly method to prepare monodispersed silica stationary phases for simultaneous separation of compound drugs

An energy-efficient and environment-friendly approach to prepare porous monodispersed micro-sized silica particles with methyltrimethoxysilane (MTMS) as the precursor is described. The particles were synthesized by a two-step hydrolysis/condensation procedure, with post-synthetic aging and calcination for methyl group removal. They show uniform spherical morphology, narrow particle size distribution (D₉₀/₁₀, 1.2-1.6), tailored particle size (3, 5, 7 μm) and mesopore structure (10, 13 nm), which can be directly used as packing materials for HPLC without size classification. C₁₈, sulfonate, and C₁₈/sulfonate mixed-mode stationary phases were produced by a green vapor deposition method based on the synthesized silica particles. The newly synthesized C₁₈ phase exhibits mechanical stability, kinetic behavior and separation performance expected from the commercial C₁₈ column. The C₁₈/sulfonate phase exhibits prominent mixed-mode retention behavior which can be applied to the simultaneous separation of multiple substances in the compound drugs.

Taming C60 fullerene: tuning intramolecular photoinduced electron transfer process with subphthalocyanines

Two subphthalocyanine-C60 conjugates have been prepared by means of the 1,3-dipolar cycloaddition reaction of (perfluoro) or hexa(pentylsulfonyl) electron deficient subphthalocyanines to C60. Comprehensive assays regarding the electronic features - in the ground and excited state - of the resulting conjugates revealed energy and electron transfer processes upon photoexcitation. Most important is the unambiguous evidence - in terms of time-resolved spectroscopy - of an ultrafast oxidative electron transfer evolving from C60 to the photoexcited subphthalocyanines. This is, to the best of our knowledge, the first case of an intramolecular oxidation of C60 within electron donor-acceptor conjugates by means of only photoexcitation.

Simultaneous determination of OZ277, a synthetic 1,2,4-trioxolane antimalarial, and its polar metabolites in rat plasma using hydrophilic interaction chromatography

OZ277 is a synthetic 1,2,4-trioxolane antimalarial currently being evaluated in clinical trails. Biotransformation of OZ277 in rats results in the generation of metabolites with large differences in polarity which complicates the development of a method for the simultaneous analysis of all species. A simple, sensitive and selective hydrophilic interaction liquid chromatography-mass spectroscopy (HILIC/MS) method for simultaneous determination of OZ277 and its major metabolites in rat plasma was developed and validated. The method involves protein precipitation with acetonitrile followed by separation on a Waters Atlantis HILIC Silica column using gradient elution. The analytes were monitored using a positive electrospray ionization interface in selected ion monitoring mode. The calibration range for all of the analytes was 5-10,000ng/mL and the lower limit of quantitation was 5ng/mL using a 50microL rat plasma sample. The inter- and intra-day accuracy and precision was within 12%. The recovery of all analytes from rat plasma over a wide concentration range was 90% or greater. The method has been successfully used for quantifying OZ277 and its metabolites in plasma following intravenous administration to rats.

Column selectivity in reversed-phase liquid chromatography. VII. Cyanopropyl columns

Eleven cyanopropyl ("cyano") columns were characterized by means of a relationship developed originally for alkyl-silica columns. Compared to type-B alkyl-silica columns (i.e., made from pure silica), cyano columns are much less hydrophobic (smaller H), less sterically restricted (smaller S*), and have lower hydrogen-bond acidity (smaller A). Because sample retention is generally much weaker on cyano versus other columns (e.g., C8, C18), a change to a cyano column usually requires a significantly weaker mobile phase in order to maintain comparable values of k for both columns. For this reason, practical comparisons of selectivity between cyano and other columns (i.e., involving different mobile phases for each column) must take into account possible changes in separation due to the change in mobile phase, as well as change in the column.

LC methods for acyclovir and related impurities determination

Acyclovir, guanine, and impurity A have been baseline separated with isocratic conditions at pH=3.0 and run time under 15 min by employing a SB-CN column from Agilent (150 mm x 4.6mm and 3.5 microm). Moreover, when run time was increased to 40 min six impurities (guanine, impurities A, F, G, Vir 3/4 and N(7)) plus acyclovir were separated in the same conditions. The mobile phase consisted of buffer A/acetonitrile 96:4 (v/v), being buffer A:25 mM H(3)PO(4) (Milli-Q H(2)O) brought to pH 3.0 with KOH. The same column provided separation for all the seven impurities described in pharmacopoeia, including impurity C, which coeluted with acyclovir in the previous conditions with a mobile phase prepared with 25 mM phosphoric acid (pH=1.8)/acetonitrile 96:4 (v/v). The method has been validated following ICH guidelines and it has demonstrated to be reliable for acyclovir and its impurities determination.

Synthesis, Characterization, and Properties of Subporphyrazines: A New Class of Nonplanar, Aromatic Macrocycles with Absorption in the Green Region

Novel subphthalocyanine analogues that display strong absorption in the green region have been synthesized by using a boron template cyclotrimerization of maleonitrile derivatives. The spectroscopic properties of these macrocycles indicate that, like subphthalocyanines, they have 14 pi electrons and are aromatic compounds with a conical shape. The removal of the three fused benzene rings from the subphthalocyanine skeleton produces a 75-80 nm blue shift of the Q-band and a slight lowering of the absorption coefficients for this band. In addition, the reduction of the pi system from 18 to 14 electrons that accompanies progression from porphyrazines to subporphyrazines causes a hypsochromic shift of the Q-band of around 100 nm. Subporphyrazines that are peripherally functionalized with six thioether chains, and in which the sulfur atoms are attached directly to the pyrrole moieties, exhibit optical features that may be explained in terms of the extension of pi conjugation over the six thiolene groups, as well as strong pi donation from the sulfur lone pairs to the macrocycle. These two effects are quantitatively and qualitatively very similar to those observed for porphyrazines that possess the same type of substitution. In addition, the mesomorphic behavior at low temperatures of a macrocycle that is substituted with six thiododecyl chains was demonstrated by using differential scanning calorimetry and optical polarising microscopy.

Determination of zwitterionic and cationic surfactants by high-performance liquid chromatography with chemiluminescenscent nitrogen detection

The use of chemiluminescent nitrogen specific detection (CLND) combined with an HPLC separation allows for the identification and quantification of cationic and zwitterionic surfactants. The CLND provides equimolar responses, based on the amount of nitrogen within any compound. This allows for the detection of any nitrogen containing surfactant. Reversed-phase separation methods using cyano columns are developed for cationic and zwitterionic (sulfobetaine) surfactant mixtures. The limits of detection for these surfactants are in the single micromolar range (1 ng N). A linear response was obtained (R2=0.9981) between 50 microM and 5 mM. The methodology was then applied to the determination of an industrial zwitterionic surfactant, Rewoteric AM CAS U [coco(amidopropyl)hydroxyldimethylsulfobetaine].