Stability indicating

A selective, sensitive and stability indicating reversed phase-HPLC method was developed for the determination of clarithromycin antibiotic in human plasma. 

Each of the following carbocations can rearrange to a cation with special stabilization. Indicate likely routes for the rearrangement to a more stable species for each ion. 

Both experimental studies on gas-phase ion stability and MO calculations indicate that the two vinyl cations shown below benefit fiom special stabilization. Indicate what stmctural features present in these cations can provide this stabilization. 

The caliper is used to correct the density and neutron porosity measurements for borehole effects and also can be used as a borehole stability indicator. Figure 4-289 shows an example of comparison between the MWD ultrasonic caliper and the four-arm wireline caliper run five days later. 

V.A. Strunin et al, FizGoreniyaVzryva 7 (4), 498-501 (1972) CA 77, 64201 (1972)/ Equations relative to stationary burning stability indicate that such stability is greater at... 

Chemical Testing. Adequate instrumentation for a variety of different test methods should be available. Most stability-indicating chemical assays are performed by high-performance liquid chromatography. Occasionally, gas chromatography, infrared spectrophotometry, or spectrofluorimetry are used. Test... 

Stability of a drug substance and product is monitored throughout the development and clinical phases. This monitoring requires stability-indicating assay methodology, and this is a subject that is separate from performulation per se. In most instances, the major, feasible decomposition products are identified early [51], and as such it is known if the pathways are hydrolytic, oxidative, or photochemical. 

A stability-indicating HPLC method has been described for niclosamide in artificial gastric and intestinal juices [68],... 

Table. Expansion coefficients and stability indices of modified graphite nitrates. 

Despite a wide range of the modifiers used, there is a clear symbasis between the calculated proton affinities and the experimental stability indices Kst (Figure 3). The decrease in concentration of nitric acid in the interlayer space will give rise to a poorer stability of GICs, if the proposed stabilization mechanism is valid. To verify this assumption, the treatment of graphite nitrate with 25-fold excess of acetic acid, compared to that used in the above procedure, was carried out in a glass column. Most of the molecules of nitric acid are probably removed from the interlayer space under such a treatment. It turns out that this procedure reduces the expansion... 

Figure 3. Comparison between the calculated proton affinities and stability indices. Numerals correspond to the line numbers in the Table.

XRPD as a stability-indicating assay method When the phase identity, or degree of crystallinity (or lack thereof), of a drug substance is important to its performance in a drug product, XRPD can serve as a vital stability-indicating assay method. There is no doubt that XRPD can be validated to the status of any other stability-indicating assay, and that one can use the usual criteria of method validation to establish the performance parameters of the method. This aspect would... 

If DSC data have been obtained for a pure material or a reaction mixture, several thermal stability indicators (ASTM E 1231-96) may be estimated from the data. These are adiabatic temperature rise, explosion potential, instantaneous power density, time to maximum rate, and NFPA instability index (Leggett 2002). 

Finally, the protein assay for the drug product will also be used for realtime and accelerated stability testing if it has been validated to be stability indicating. A stability-indicating protein concentration method usually translates to a method that can reveal how much protein can be recovered from the dosage form. Many protein instabilities result in precipitation of the protein and adsorption to the container. An instability that results in only a modification of the protein structure but not in loss of protein from solution will not be detected by a sequence-independent protein assay such as a colorimetric assay. 

If a MAb was available that could differentiate between the native and denatured forms of a protein product, an ELISA could be used as a stability-indicating assay. The antibody could also be used for purification of the native molecule by removal of the denatured form.21 A MAb specific for the denatured protein can detect small amounts of the denatured protein in the presence of the native form.21... 

Bioassays can be used to assess the effect of molecular heterogeneity due to glycosylation, whereas ELISA cannot. The sensitivity of the bioassay and ELISA are often comparable. Both methods can be used as stability-indicating test methods. 

An important consequence of thermostability is the attainable level of stability indicated by the Tm. For example, different solution environments can cause the Tm to shift.23 27 A shift to higher temperatures by adding different excipients and/or changing the pH of the solution can be extremely helpful in... 

Theoretical considerations and observations for neutral stability indicate for small x that, where o-J is determined for averaging times... 

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