High Pressure Liquid Chromatography

Salicylic acid is a major hydrolytic degradation product of aspirin, responsible especially for gastric irritation during oral aspirin administration. This impurity was investigated in 12 different brands of aspirin formulation readily available in our locality. A simple, rapid and sensitive high performance liquid chromatographic method was adopted for this investigation. The mobile phase was methanol/water (20/80, v/v) adjusted to pH 2.5 with phosphoric acid and was run on a 50 mm reversed-phase column monitored at 240 nm. The limit of detection for salicylic acid was 5 ng. Only three of these formulations showed the presence of salicylic acid impurity and all these contained salicylic acid in excess of the USP 1980 limit of 0.3% salicylic acid per tablet.

Root barks of Chionanthus virginicus L. are used in homeopathic medicines in the treatment of icterus and hepatitis. The objective of this study is to identify novel secoiridoids and lignans and to develop a simple and reliable HPLC method for the determination of oleuropein, phillyrin, total secoiridoids and total lignans for quality control and stability studies of C. virginicus herbal drug and preparations. Secoiridoids and lignans were purified by preparative HPLC. Compounds previously described were identified by HPLC according to their retention times and UV spectra. Structures of new compounds were determined by NMR. Two compounds namely excelside B and acetoxypinoresinol-4"-O-beta-D-glucoside are described for the first time in the drug. HPLC separation was performed on Symmetry C18 (Waters) by gradient elution using acetonitrile and 0.2% aqueous phosphoric acid. The method was validated for specificity, linearity, precision, accuracy, limits of detection and quantifica...

With the aim of developing a new enzyme-linked immunosorbent assay test to detect autoantibodies in the sera of rheumatoid arthritis patients with a high sensitivity and specificity using synthetic citrullinated peptides of fibrin (which is abundant in rheumatoid synovium) as antigenic substract, peptides belonging to α- and β-fibrin chains were selected by computer-aided prediction of antigenicity and epitope mapping and synthesized in solid phase. We analysed by enzyme-linked immunosorbent assay 133 sera from patients with well-characterized rheumatic diseases, including 67 patients with rheumatoid arthritis. The results of the immunoassays reported highlight the usefulness of fibrin-related peptides in rheumatoid arthritis diagnosis and, especially, the ability and specificity of the [Cit621,627,630]α-fibrin(617–631) (αfib617) peptide sequence to recognize the autoantibodies that are present in rheumatoid arthritis patients.

Abstract: The purpose of this work was to correlate the amount of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) determined in mouse fur with the number of intestinal tumours induced by PhIP, to further evaluate incorporation of PhIP into hair as ...

We describe an isocratic, reversed-phase high-performance liquid chromatographic method for the simultaneous measurement of fully oxidised, dihydro- and tetrahydropterins in cerebrospinal fluid. Tetrahydrobiopterin is detected electrochemically using an ESA Coulochem ...

A sensitive and specific HPLC–ESI-MS/MS method for the direct determination of glucosamine in human plasma has been developed and validated. Plasma samples were analyzed after a simple, one-step protein precipitation clean-up with trichloroacetic acid using a polymer-based amino high-performance liquid chromatography (HPLC) column and a water/acetonitrile mobile phase elution gradient, with d-[1-13C]glucosamine as the internal standard. Detection was performed by mass spectrometry, using an electrospray source and employing multiple reaction monitoring to separately monitor glucosamine and the internal standard. The limit of quantification of the method was 10 ng/ml of glucosamine and the calibration curve showed a good linearity up to 1000 ng/ml. The precision (R.S.D.) and the accuracy (bias) of the method at the limit of quantification were 13.8 and 4.0%, respectively, and the mean recovery of glucosamine at three concentration levels was 101.6 ± 5.7%. The method was applied for the determination of glucosamine concentrations in human plasma samples collected from untreated healthy volunteers and, in a separate bioavailability study, to evaluate plasma glucosamine pharmacokinetics profiles after oral administration of crystalline glucosamine sulfate.

Bisphenol A (BPA) is a toxic industrial chemical that affects the endocrine system even at low concentrations. A new method, based on capillary high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) analysis, has been developed to determine BPA in atmospheric samples. The method involves collection of air samples (typically 2 m3) on glass fiber filters, with ultrasonic extraction and sample concentration under vacuum before analysis. HPLC analysis was performed isocratically at a flow rate of 10 µL min−1 using a capillary reversed-phase column and MS/MS analysis in negative ion multiple reaction monitoring (MRM) mode, using BPA-d16 as internal standard. The present method provides linear response in the range 0.007–3.5 µg/filter (R2 > 0.999) and is characterized by high accuracy (mean bias 2%) and good reproducibility (mean RSD 5%). High sensitivity (LOD = 2 ng/m3 based on 2 m3 of air collected), specificity, and speed of the analysis make the present method suitable for routine determination of BPA in the atmosphere, both for ambient and personnel monitoring. Copyright © 2005 John Wiley & Sons, Ltd.

Racemic RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol, RD) was used as a topical skin-whitening agent until it was recently reported to induce leukoderma. We then showed that oxidation of RD with mushroom tyrosinase rapidly produces RD-quinone, which is quickly converted to RD-cyclic quinone and RD-hydroxy-p-quinone. In this study, we examined whether either or both of the enantiomers of RD can be oxidized by human tyrosinase. Using a chiral HPLC column, racemic RD was resolved optically to R(-)-RD and S(+)-RD enantiomers. In the presence of a catalytic amount of l-dopa, human tyrosinase, which can oxidize l-tyrosine but not d-tyrosine, was found to oxidize both R(-)- and S(+)-RD to give RD-catechol and its oxidation products. S(+)-RD was more effectively oxidized than l-tyrosine, while R(-)-RD was less effective. These results support the notion that the melanocyte toxicity of RD depends on its tyrosinase-catalyzed conversion to toxic quinones and the concomitant production of rea...