Identification test

Reference Standards. Many of the identification tests and assays require the use of reference standards. These standards are available for purchase from the USPC. 

Testing of phthalocyanines includes crystallization (qv), flocculation, and appHcation in paints, plastics (qv), and printing inks (1). The ASTM standard specifications include CuPc in dry powder form for various appHcations (153). The specifications cover color (qv), character or tint, oil absorption, reactions in identification tests, and dispersions and storage stabiUty. Quantitative deterrninations are possible with ceric sulfate (30) or sodium vanadate (154). Identification methods are given (155), including tests for different appHcations. 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

An enzymatic method (45), which is specific for the citrate moiety, can be used as a combined assay and identification test for citric acid and its common salts down to 20 ppm. 

Aconitine produces an intense tingling sensation when a drop of a solution, 1 in 10,000, is applied to the tip of the tongue. It also gives a characteristic unstable, crystalline precipitate when a few drops of potassium permanganate solution are added to a solution of the alkaloid in dilute acetic acid. The formation of acetic acid when the alkaloid is heated dry, or of benzoic acid when it is hydrolysed by alkali, have also been suggested as identification tests. For the recognition of minute quantities a biological test is probably the best procedure. ... 

This solution is extracted several times with 5% acetic acid, until the silico-tungstate test (an identification test for alkaloids) yields a negative result, and the acetic solutions are washed with 10 ml ether. 

Guidance on specifications is divided into universal tests/criteria which are considered generally applicable to all new substances/products and specific tests/criteria which may need to be addressed on a case-by-case basis when they have an impact on the quality for batch control. Tests are expected to follow the ICH guideline on analytical validation (Section 13.5.4). Identification of the drug substance is included in the universal category, and such a test must be able discriminate between compounds of closely related structure which are likely to be present. It is acknowledged here that optically active substances may need specific identification testing or performance of a chiral assay in addition to this requirement. 

Purpose of analytical procedure Characteristics Identification Testing for impurities Quantitat. Limit Assay - dissolution (measurement only) - content/potency... 

The identification of plant models has traditionally been done in the open-loop mode. The desire to minimize the production of the off-spec product during an open-loop identification test and to avoid the unstable open-loop dynamics of certain systems has increased the need to develop methodologies suitable for the system identification. Open-loop identification techniques are not directly applicable to closed-loop data due to correlation between process input (i.e., controller output) and unmeasured disturbances. Based on Prediction Error Method (PEM), several closed-loop identification methods have been presented Direct, Indirect, Joint Input-Output, and Two-Step Methods. 

Where antioxidants or antimicrobial preservatives are used, the finished product release specification will need to include identification tests and assays for these two types of excipient. The shelf life specification should also include a specification for assay for antimicrobial preservatives. Stability data will be required for both antioxidants and antimicrobial preservatives in the finished product, and in addition the preservative efficacy of the formulated product should be examined over its shelf life and by means of appropriate in-use stability tests. Preservative efficacy data should also be presented at the lower limit of the preservative assay. 

Two identification tests for oxytetracycline hydrochloride are given in the USP 28 [1], one being an ultraviolet absorption test and the other a color test. European Pharmacopoeia [2], British Pharmacopoeia (BP) 2003 [4], International Pharmacopoeia [5], and Pharmacopoeia of the People s Republic of China [6] described a thin-layer chromatography and color tests for identification of oxytetracycline hydrochloride and oxytetracycline dihydrate. For identification of oxytetracycline calcium, USP 28 [1] used Method II under identification of tetracycline <193>, whilst BP 2003 [4] described a TLC, color test, and calcium test as the method of identification. 

Clarke recommended the following three identification tests [2] ... 

The most common types of analyses are the identification test, the quantitative determination of active ingredients or major component, and the determination of impurities. The identification test provides data on the identity of the compound or compounds present in a sample. A negative result signifies that the concentration of the compound(s) in sample is below the DL of the analyte(s). The quantitative method for the major component provides data of the exact quantity of the major component (or active ingredients) in the sample, and a reported concentration of the major component must be higher than the QL. In a Determination of impurities test, one obtains data regarding the impurity profile of a sample, and can be divided into a limit test or quantitative reporting of impurities (see Table 1, which has been modified from Refs. [1] and [8]). 

In another extensive series of studies, Clarke and coworkers developed sensitive microchemical tests for the determination of alkaloids [32-34], anesthetics [35], antihistamines [36], antimalarials [37], and analgesics [38]. One of the useful techniques introduced by Clarke was that of the hanging-microdrop [32], which permitted identification tests to be made on submicrogram quantities of analyte. Results obtained on the cinchona alkaloids are shown in Table 5 to illustrate the methodology. 

In addition to the ICDD, publications dealing solely with the powder patterns of drugs appear occasionally [12-15], In 1971, Sadik et al. pointed out that the identification test for kaolin (in NF XIII) was a test for the presence of aluminum, and therefore both kaolin and bentonite gave positive results [16]. Since the two compounds have different crystal structures, their x-ray diffraction patterns are different, and therefore XPD was recommended for identification of these compounds. In the current edition of USP, the identification of bentonite is based on its powder x-ray pattern [3]. 

NMR-spectroscopy has been extensively employed for the identification testing as well as quantitative analysis of pharmaceutical substances. These two aspects shall be discussed in the sections that follow ... 

The versatility and ability of NMR to distinctly differentiate nuclei in various intramolecular environments has placed it as the most reliable and dependable technique for carrying out the identification testing of a host of pure drugs. Hence, any apparent deviations of the spectrum of a sample under investigation vis-a-vis the spectrum of the pure and the authentic pharmaceutical substance usually give rise to an enormous information not only confined to the true identity of the substance but also the probable nature of the impurities it possesses. 

Can one make use of NMR-Spectroscopy as an identification testing method for pharmaceutical substances Explain with typical examples. 

Part—I has three chapters that exclusively deal with General Aspects of pharmaceutical analysis. Chapter 1 focuses on the pharmaceutical chemicals and their respective purity and management. Critical information with regard to description of the finished product, sampling procedures, bioavailability, identification tests, physical constants and miscellaneous characteristics, such as ash values, loss on drying, clarity and color of solution, specific tests, limit tests of metallic and non-metallic impurities, limits of moisture content, volatile and non-volatile matter and lastly residue on ignition have also been dealt with. Each section provides adequate procedural details supported by ample typical examples from the Official Compendia. Chapter 2 embraces the theory and technique of quantitative analysis with specific emphasis on volumetric analysis, volumetric apparatus, their specifications, standardization and utility. It also includes biomedical analytical chemistry, colorimetric assays, theory and assay of biochemicals, such as urea, bilirubin, cholesterol and enzymatic assays, such as alkaline phosphatase, lactate dehydrogenase, salient features of radioimmunoassay and automated methods of chemical analysis. Chapter 3 provides special emphasis on errors in pharmaceutical analysis and their statistical validation. The first aspect is related to errors in pharmaceutical analysis and embodies classification of errors, accuracy, precision and makes... 

Identification (ID) tests in Category IV require only specificity for their validation. Identification by HPLC usually involves comparison of the retention time (%) or relative retention time (RRT) of a sample and standard injection. The increasing use of photodiode array (PDA) detectors in HPLC methods also allows identification by comparison of UV spectra for standards and samples, in addition to retention characteristics. The information required for either ID test by HPLC can be gathered while performing any other HPLC method for a given sample. Identification tests are often incorporated into the assay method and the satisfactory completion of specificity for the assay will meet the requirements for ID as well. 

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