Liquid Chromatographic Separation of Isoniazid, Pyrazinamide and Rifampicin on a Reversed-Phase Silica Column

A gradient liquid chromatographic method which can separate isoniazid, pyrazinamide and rifampicin is described. A Hypersil C18, 5 mm, 250 mm x 4.6 mm internal diameter column was maintained at 40°C. The method was developed by systematic evaluation of the influence of the buffer concentration, column temperature and the mobile phase pH. The method proposed uses isocratic elution with potassium phosphate buffer (pH 6.0; 0.05 M) for 10 min, followed by linear gradient to potassium phosphate buffer (pH 6.0; 0.05 M)-methanol (40:60, v/v) in 5 min, isocratic elution at the same composition for a further 15 min and then linear gradient back to potassium phosphate buffer (pH 6.0; 0.05 M) in 5 min. The flow-rate was 1 ml/min and UV detection was at 254 nm. The method was validated and it has been used for routine analysis of tablets containing isoniazid, pyrazinamide and rifampicin. Analysis time is 35 minutes. (E & C Afr Jnl Pharm Sci: 2002 5(1): 8-14

Loss of DPP6 in neurodegenerative dementia: a genetic player in the dysfunction of neuronal excitability

Emerging evidence suggested a converging mechanism in neurodegenerative brain diseases (NBD) involving early neuronal network dysfunctions and alterations in the homeostasis of neuronal fring as culprits of neurodegeneration. In this study, we used paired-end short-read and direct long-read whole genome sequencing to investigate an unresolved autosomal dominant dementia family signifcantly linked to 7q36. We identifed and validated a chromosomal inversion of ca. 4 Mb, segregating on the disease haplotype and disrupting the coding sequence of dipeptidyl-peptidase 6 gene (DPP6). DPP6 resequencing identifed signifcantly more rare variants—nonsense, frameshift, and missense—in early-onset Alzheimer’s disease (EOAD, p value=0.03, OR=2.21 95% CI 1.05–4.82) and frontotemporal dementia (FTD, p=0.006, OR=2.59, 95% CI 1.28–5.49) patient cohorts. DPP6 is a type II transmembrane protein with a highly structured extracellular domain and is mainly expressed in brain, where it binds to the potassium channel Kv4.2 enhancing its expression, regulating its gating properties and controlling the dendritic excitability of hippocampal neurons. Using in vitro modeling, we showed that the missense variants found in patients destabilize DPP6 and reduce its membrane expression (p<0.001 and p<0.0001) leading to a loss of protein. Reduced DPP6 and/or Kv4.2 expression was also detected in brain tissue of missense variant carriers. Loss of DPP6 is known to caus

Relationship between content limits and assay methods : an interlaboratory statistical evaluation

It has been statistically demonstrated, by means of interlaboratory acquired experimental results, that the prescribed content limits in a pharmacopoeial monograph should be critically reconsidered if one volumetric assay method is systematically substituted by another. Three different volumetric methods, prescribed as assays in phenothiazine monographs and ensuring the same content limit intervals, reveal different repeatabilities or reproducibilities. Analysis of variance and box-plot presentations confirm that for some of the three methods examined, interlaboratory variations contribute significantly to the total variances. For one particular method, however, this contribution is obviously less pronounced. Important contributions of method-to-method variations to the total variance are also established for three of the four participating laboratories

Determination of uncertainty in a liquid chromatographic method for erythromycin from Interlaboratory study results

Projet NM 12/2