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In this work, a fast analytical method based on hydrophilic interaction liquid chromatographic-Ultraviolet detection (HILIC-UV) using a short narrow bore cyano-bonded silica column packed with full...

Crude phosphatidylcholine (PC) was extracted with ethanol from egg yolk, and an L9(34) orthogonal array experimental design was set up to optimize the solvent extraction conditions. Subsequently, semipreparative hydrophilic interaction liquid chromatography (HILIC) was explored to purify the crude extract on a homemade silica column. The purity of PC prepared in this way can reach up to 93.96%, with rapid separation.

Volatile oil rich spices cannot be sterilised by pasteurisation because of the presence of thermal-sensitive components. In this article, we report the effect of irradiation on the volatile constituents of Monodora myristica. The samples were irradiated at ambient conditions at dose levels of 0 and 15 kGy using a linear accelerator at a dose rate of approximately 10(7) Gy s(-1). The volatile oil was extracted via headspace analysis and the quantification carried out with a HP-5MS fused silica column. Twenty-three constituents were identified with alpha-phellandrene as the major constituent (53%). Electron-beam irradiation of M. myristica did not significantly affect the volatile constituent profile at 15 kGy. Except alpha-thujene, which was increased from 7.18% to 16.76%, the most affected constituents were those that constitute less than 0.10% of the oil. Irradiation could be an effective way for decontamination of M. myristica.

WOS: 000237847500007, A capillary electrophoretic method for the determination of cetirizine is described in this study. The method was developed by using a running buffer consisting of 10 mM of 10% methanol with pH 8.5, employing a fused silica column with a total length of 85 cm, an effective length of 65 cm, and internal diameter of 75 mu m. 28 kV were applied, which produced signals that were detected at 200 nm. Under these conditions, cetirizine and phenobarbital sodium as an internal standard appeared at 6.7 and 8.9 minutes, respectively. The limits of detection and quantification were found to be 5.45 x 10(-6) M and 1.60 x 10(-5) M, respectively. The repeatability and linearity of the method were validated by intra-day and inter-day precision. Then, the proposed method was applied to Zyrtec trademark tablet, syrup, and oral drop. The results indicate that the method is simple, accurate, and precise for the analysis of cetirizine.

The potential of using tree bark as a passive sampling medium for detection of Polychlorinated dibenzo- p -dioxins and furans (PCDD/F) in an urban environment has been investigated. Bark samples (∼ 30 g) were extracted with toluene using accelerated solvent extraction. Extracts were then cleaned up via a multi-bed silica column and a Florisil column followed by GC-MS/MS analysis. It is shown that PCDD/F are present in tree bark collected from sites close to a municipal waste incinerator, a crematorium, a hospital and a chemical incinerator. Furthermore, characteristic patterns for dioxin congeners were observed for the suspected emission sources.

The synthetic route to (2E,4E,6E)-5-ethyl-3-methyl-2,4,6-nonatriene, the aggregation pheromone of the Freeman sap beetle, Carpophilus freemani Dobson (Coleoptera: Nitidulidae), has been improved in terms of 6E isomer selectivity by the use of tetra-n-propyltriphenylphosphonium bromide in the final Wittig reaction. Separation of the 6E-isomer from undesired 6Z-isomer can be accomplished on a preparative scale by HPLC using a silica column with hexane as the elution solvent. This chromatographic method was also used to purify the aggregation pheromone of the dusky sap beetle, Carpophilus lugubris Murray. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.

A simple isocratic reversed phase HPLC method for the separation of a series of barbiturates is described. The column used is a newly developed synthetic silica known as Symmetry Clg (Waters Corp., Milford, MA, USA) and the mobile phase consists of 50 mM KH2PO4 (pH 4.55): acetonitrile water (20:30:50:). The barbiturates studied are monitored by UV detection at 225 nm. Detailed methodology and the advantage of the Symmetry C18 reversed phase is presented.

The separation and the estimation of several main glycolipid classes as well as of some of these classes into main subclasses (or species) by reverse phase and normal phase high performance liquid chromatography and UV detection, is described. Two different gradient elutions onto a C18 column and onto a silica column, respectively, and an isocratic elution onto a strong cation exchange column were performed, with detection at 206nm. Separations were achieved within 30min. in the reverse phase and normal phase modes and within 10min. in the cation exchange mode. The following glycolipids standard classes were tested: gangliosides, sulfate cerebrosides (sulfatides), digalactosyl-diglycerides, galactosyl-cerebroside as well as ceramides (the backbone of sphingoglycolipids), N-palmitoyl-sphingosine (a synthetic ceramide) and a phospholipid, cardiolipin. Some species of digalactosyl-diglycerides and galactosyl-cerebrosides were also separated. Application of the present method on the separation of gly...

The silylated pyrimidine bases IIa-d were condensed with the benzyl 3,5-di-O-benzyl-2-deoxy-1,4-dithio-d-erythro-pentofuranoside III in acetonitrile under activation by N-iodosuccinimide, giving ca 1.5: 1/α: β anomeric mixtures of the blocked nucleosides IVa-d and Va-d. in yields of 55–58%. After the separation on a silica column the pure anomers were deprotected by BCI3 or TiCI4, providing the free nucleosides VIa-d and VIIa,c,d in moderate to good overall yields. The β- or α-anomeric configuration, anti-glycosidic conformation and prevailing C2′endo(S) thiosugar pucker in the synthesized compounds were established by the combined use of the 1H, 13C NMR and X-ray crystallography. Dedicated to Dr. Yoshihisa Mizuno on the occasion of his 75th birthday

An assay of atenolol in human serum is described using a 3 μm silica column with a 60:40 v/v 6.25 mM sodium dihydrogen phosphate pH 3.0-acetonitrile mobile phase at 1 mL/min; the ultraviolet detector was set at 254 nm. Minimum detectability of the drug was estimated to be 20 ng/mL (S/N = 2). The method is linear in the 100–1000 ng/mL range (r = 0.9992, n = 9). An ethylsilane solid phase extraction column was used for sample cleanup and recovery of atenolol from serum was 103 ± 4% (n = 3). Retention times for atenolol and metoprolol (internal standard) were 6.6 and 7.5 min, respectively, and typical theoretical plates were 17,583 and 22,680, respectively. Resolution between internal standard and atenolol peaks was calculated to be 4.5. A typical analysis was completed in less than 45 min. The good sensitivity and reproducibility of the method should render it useful for the assay of atenolol levels in serum.

Mercury-substituted chlorophylls, i.e., (pheophytin a)mercury(ll) and (pheophytin b)mercury(ll), were separated by reversed-phase HPLC with a C18-bonded silica column and a mobile phase of acetone-methanol. Their spectroscopic and chromatographic characteristics strongly suggest that both (pheophytin a)mercury(ll) and (pheophytin b)mercury(ll) form 1: 1 (metal ion: chlorin ring) complexes.

Sensitive methods for the determination of ferulic acid and 4-vinyl guaiacol in beers and worts are described. Samples were analyzed by direct-injection high-performance liquid chromatography using an octadecyl silica column. Detection was by either fluorescence monitoring (for 4-vinyl guaiacol alone) or electrochemical detection (for simultaneous determination of ferulic acid and 4-vinyl guaiacol). The methods were applied mainly to the analysis of production beers but were used also to monitor the decarboxylation of ferulic acid to 4-vinyl guaiacol in wort during a small-scale fermentation deliberately contaminated with a wild yeast strain.

The pharmacological activity of seven β-blockers was evaluated based on retention time on high performance liquid chromatographv with an internal surface reversed-phase silica column (Pinkcrton column). Significant relationships were found between the adjusted retention times for β-blockers and their pharmacological effects, such as affinity for the β1 heart receptors (r = -0.714) and the β2 lung receptors (r = -0.937). Thus retention time on high performance liquid chromatography may be a rapid and replicable approach to the prediction of pharmacological effects.

The retention indices (RI) of 47 selected acidic, neutral and basic drugs were determined on 7 reversed-phase (octyl- and octadecylsilica) columns in two laboratories in the 1-nitroalkane scale, using either 1-nitroalkane homologues or selected drugs, whose RI values were previously determined on the reference column. Obtained values were compared with the library values, determined previously on the reference column. Retention indices, calculated with drugs as RI markers, showed distinctly lower deviations from the library values and lower inter-column variability: The mean standard deviation of RI for all drugs analyzed on all columns in the 1-nitroalkane scale was 44.3 RI units, against 10.3 units when selected drugs were used as RI markers. The deviations from the listed values, calculated for each column separately with drugs as markers, were in 95% of cases smaller than 20 RI units, and in 80 % smaller than 10 units. The largest differences between the experimental and listed values were ob...

The mechanism of retention of several pharmaceutical drugs with basic, neutral and acidic properties have been examined on a cyano bonded silica stationary phases (Ultrasphere cyano). Clenbuterol, bromhexine, terphenadine, pirenzepine, astemizol, betamethasone, acetaminophen, indomethacin, diclofenac and nimesulide were chosen for this study. Methanol-phosphate buffer mixtures with low water levels were used as mobile phases. Different pH values and ionic strengths were considered. Under experimental conditions, the chromatographic behavior of basic drugs is more complex than the behavior of acidic and neutral ones. The predominant silanophilic interactions observed for drugs of basic characteristics may become quite useful in optimizing selectivity.

SummaryA fast method for the determination of the carotene fraction from commercially purchased bee-collected pollen by isocratic HPLC is described, using ultraviolet detection at 453 nm and direct injection of the sample into a silica column. The mobile phase was n-hexane:2-propanol:acetic acid (100:0·5:0·1), using flow 1 ml/min. The mean value for carotene was 46·7 mg β-carotene/100 g lipids.

A method has been developed to effect the separation of Fischer-Tropsch products, predominately hydrocarbons, into, first, alkane and alkene fractions, and, secondly, each of these fractions into their normal and branched components. Conditions for methods using a “dry” silica column for the first separation and molecular sieves for the second separation have identified that permit collection of sufficiently large samples for subsequent separations. The first separation has been effected so the normal to branched chain ratio has not been altered. Liquid chromatographic conditions have been found whereby the n-alkane fraction can then be separated to provide a pure sample of each alkane in the C8 - C24 carbon number range. The alkane fractions have been collected so that the 14C activity can be determined for each alkane.

A new procedure has been developed to measure nicotine in blood plasma by high-performance liquid chromatography (HPLC). Nicotine is extracted from plasma by elution with cholorform. Final determination is achieved by isocratic HPLC with ultraviolet detection. Twenty microliters of plasma extract is deluted over a silica column at a flow rate of 1.0 ml/min with a dioxane:isopropanol:NH4OH (80:3.0:0.4) mobile phase. The procedure is sensitive to 0.05 ug of nicotine per ml of plasma and is linear within the range of 0.05 to 10.0 ug/ml of plasma. When a known amount of nicotine was added to plasma, the concentration of nicotine measured averaged 99.9 + 3.9 (S.D.)% of the known concentration. The within-sample coefficient of variation was 3.9%

The potential of a previously reported on-line reversed-phase liquid chromatography-thermionic detector (LC–TID) system has been further evaluated. Several trialkyl (trimethyl to tri-octyl) and triaryl (triphenyl and tri-o-cresyl) phosphates were chosen as model compounds. LC was done on an alkyl-bonded silica column with methanol-water (80:20) at a flow-rate of 35—70μ/min as eluent. The band broadening in the interface-TID unit increased with decreasing volatility of the compounds and for the relatively non-volatile compounds, the band broadening decreased with increasing eluent flow-rate. For most of the test compounds, detection limits of 40–100pg were obtained. As an illustration of the high selectivity of the LC[sbnd]TID system, the trace-level determination of two aryl phosphates in sediment samples is reported.

Separation of vitamin D3, its four metabolites and their corresponding isotachysterol3 derivatives was studied using four HPLC systems: two reverse phase columns, a silica column and a cyanopropyl silica column. Most of them gave a good separation between the compounds studied, although both reverse phase systems were less efficient in the separation of dihydroxylated vitamin D3 metabolites and isotachysterol compounds. Isotachysterol3 derivatives behaved analogously to their vitamin D3 counterparts on all four systems, but their retention times were different. This indicates that chemical derivatization to isotachysterols can be used as a part of chromatographic identification of unknown vitamin D3 metabolites as well as in the determination of major vitamin D3 compounds in biological samples.

An electron spin resonance (esr) spectrometer is applied as a novel specific detector for liquid chromatography of stable free radicals. A uv and a visible optical detector are used simultaneously with the esr detector. The method is employed for detection of several organic radicals eluted from a prepacked silica column. Esr spectra of the eluant are measured repeatedly each minute during the chromatographic separation.

Chloroform extraction of Co-PAR, Fe-PAR, and Cu-PAR complexes in a pH 6.5 phosphate buffer implied the first two species were primarily monoanions, but the latter was a dianion. Examination of the literature and retention data of these complexes on C-18 and amino columns confirmed the more anionic nature of Cu-PAR. The Co+3 and Cu+2 complexes were slightly resolved from each other, but the Fe+3 complex was retained longer on the C-18 silica. In contrast, the Co+3 and Fe+3 complexes were not resolved, but the Cu+2 complex was well-retained on the weak anion exchange amino silica column. Use of short amino and C-18 columns in series provided a good separation of all three complexes. Detection of the metal complexes at 546 nm instead of 254 nm avoided interference by PAR and good detection limits were still maintained.

The p-bromophenacyl esters of saturated C35–56 fatty acids from Mycobacterium tuberculosis H37Ra were separated according to structural classes on a silica column by high performance liquid chromatography (HPLC). The sample was cycled five times during HPLC. Highly purified C35–38 esters were obtained by this method. Further HPLC fractionation on a reverse-phase column (C18-bonded silica) gave complete separation of most of the remaining fractions. By combining mass spectrometry with HPLC separations, many of the fatty acid esters were tentatively identified.

The separation of the syn and anti conformers of a selected group of nitrosamines was achieved only after the temperature of the cyclodextrin bonded silica column was lowered to −20°C. In certain cases it was apparent that a lower temperature is required for baseline separations. The mobile phases used were 90% acetonitrile/10% triethylammonium acetate, pH 5 for the nitrosamino acids, and tetrahydrofuran for the cyclic nitrosamino isomers.

A normal-phase HPLC system using a microparticulate silica column and a modified butyl chloride mobile phase was applied to the determination of acetaminophen in various dosage forms. The method is accurate, precise, stability-indicating and takes less than 30 minutes for most samples. Sample preparation consists of dissolving the drug from the matrix and dilution to an appropriate volume.