Active pharmaceutical assay

Borman, P. J., Chatfield, M. J., Crowley, E. L., Eckers, C., Elder, D. P., Francey, S. W., Laures, A. M-F., Wolff, J-C. Development, validation and transfer into a factory environment of a liquid chromatography tandem mass spectrometry assay for the highly neurotoxic impurity FMTP (4-(4-flurophenyl)-l-methyl-l,2,3,6-tetrahydropyridine) in paroxetine active pharmaceutical ingredient (API). J. Pharm. Biomed. Anal., 48, 2008, 1082-1089. 

For those scientists who had to perform quantitation, the linearity of the A/D was also critical. Linearity is the condition in which the detector s response is directly proportional to the concentration or amount of a component over a specified range of component concentrations or amounts. It is imperative that the A/D not add any additional error or variability to the performance of the detector. The resulting calibration curve now becomes dependent on the combined linearity of the detector and the /VD. Accurate quantitation requires that the system is linear over the range of actual sample concentrations or amounts. Many pharmaceutical assays, like degradation and stability studies, require that the system be able to identify and quantitate very disparate levels of peaks. In many cases, this translates into a 3 to 4 order of magnitude difference between the main active component and the impurities that need to be quantitated. 

More than 220 producers of CRMs throughout the world produce today 12,000 20,000 materials with dif ferent matrixes, analytes and properties [4]. However, many testing (analytical) laboratories cannot find suitable CRMs in the market and develop in-house reference materials (IHRMs) themselves. Often IHRMs are developed in a laboratory to conserve the corresponding expensive CRMs. For example, a pharmaceutical company Chemagis Ltd. produces 30 active pharmaceutical ingredients steroids, benzodiazepines, antihistamines, hipolipidaemics, blood flow reactants, etc. Only for a few of them Mo-metasone Furoate, Fluticasone Propionate and Dobutamine Hydrochloride are of fi-cial reference standards for assay supplied by US, British and European Pharmacopoeias with prices of about 180 per unit (50 200 mg). Thus, to support its customers Chemagis is forced to develop IHRMs for assay as well as for impurities and related substances of each produced compound. Therefore, certification of such IHRMs that leads to traceable values is very important. 

The authors of this review have used I-human serum albumin for determining proteolytic activity in various types of foodstuffs, enzymatic preparations (determination of the contaminating proteolytic activity), pharmaceuticals and other materials Proteolytic activity assays using radioactively labeled substrates... 

P. W. Wrezel, I. Chion, and M. S. Hussain, Validation and implementation of in-process control HPLC assays for active pharmaceutical ingredients, LC-GC North Am. 22 (2004), 1006-1009. 

For pharmaceutical analyses, it is necessary to have reliable methods. Results obtained using ion-selective membrane electrodes are the best because of the simplicity, rapidity, and accuracy of direct and continuous measurement of the activity of the ions in the solution. Another very important reason for the selection of electrochemical sensors for pharmaceutical assay is non-interference of by-products when the purity of a raw material is to be determined. 

Unstable compounds are problematic. A sample purified in the laboratory might have a short shelf-life and poor performance as a standard. Compounds altered by assays are also inconvenient. For example, substituted benzylic alcohols can dehydrate under acidic HPLC conditions, or carboxylic esters can hydrolyze in aqueous mobile phase. An impurity isolated from an active pharmaceutical ingredient as an organic salt of an organic compound poses two problems at once. The analyst must account for both the acid and the base. In the case of a toluenesulfonic acid salt of an aliphatic amine, two different methods of detection might be needed. The toluenesulfonic acid in a reverse-phase HPLC assay can by monitored by UV light, but the aliphatic amine, with no chromophore, must be measured by a different technique. 

Analytical method goals are often defined as method acceptance criteria for peak resolution, precision, specificity, and sensitivity. For instance, pharmaceutical methods for potency assays of an active pharmaceutical ingredient (API) typically require the following resolution >1.5 from the closest eluting components precision of retention time and peak area, <1-2% RSD and linearity in the range of 50-150% of the label claim. Other desirable characteristics include ... 

Some pharmaceutical companies employ entire departments of B.S., M.S., and Ph.D. organic chemists to screen natural products for novel, pharmacologically active compounds. These natural products may originate in plants, fermentation broths, or animal matter. Scientists make the extractions and prepare the extracts for screening. Working in these departments, they also isolate, purify, characterize, and identify the compounds responsible for the activity. Biological assays direct the work, so that inactive substances squander no efforts or resources. 

Assay of pharmaceutical substances and formulated products is one of the most important and regulated activities in the pharmaceutical analysts laboratory. Regulatory authorities require strict validation standards to show that analytical assay methods are robust, accurate, repeatable, and suitable for their intended purpose. In the pharmaceutical industry, HPLC has dominated most analytical assay determinations and it is well established as the method of choice in most laboratories. In addition, pharmacopoeia monographs specify HPLC and titrimetric methods for the majority of pharmaceutical assays. To date, CE is not used extensively in QC work despite displaying excellent efficiencies, resolution, asymmetry factors, and signal-to-noise ratio. This is mainly due to the fact that CE can suffer from insufficient sensitivity and repeatability to control impurities in pharmaceutical substances at the levels required. These issues have been addressed somewhat with sensitivity... 

Pharmaceutical assays, including qualitative analysis, quantitative analysis, determination of actives in tablets and capsules, and considerations for intact dosage form analysis... 

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