Shelf lives

The shelf life (t9(j) of a pharmaceutical product is the length of time the product may safely be stored on the dispensary shelf before significant decomposition occurs. This is important since, at best, drugs may 

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Hansen L D and Hart R M 1978 Shelf-life prediction from Induction period J. Electrochem. Soc. 125 842... 

Caro s acid, H2SO5 is used as a titrant for determining Fe +. Directions are given for exploring the method of end point detection, the titrant s shelf-life, the method s accuracy and precision, and the susceptibility of the method to interference from other species. 

In contrast to the extreme reactivity of the monomeric PX (1) generated from it, the dimer DPX (3) feedstock for the parylene process is an exceptionally stable compound. Because of their chemical inertness, dimers in general do not exhibit shelf-life limitations. Although a variety of substituted dimers are known in the Hterature, at present only three are commercially available DPXN, DPXC, and DPXD, which give rise to Parylene N, Parylene C, and Parylene D, respectively. 

Although the anionic polymerization mechanism is the predominant one for the cyanoacryhc esters, the monomer will polymerize free-radically under prolonged exposure to heat or light. To extend the usable shelf life, free-radical stabilizers such as quinones or hindered phenols are a necessary part of the adhesive formulation. 

The routine compositional and functional testing done on the adhesives includes gas chromatographic testing for purity, potentiometric titrations for acid stabilizer concentrations, accelerated thermal stabiUty tests for shelf life, fixture time cure speed tests, and assorted ASTM tests for tensile shear strengths, peel and impact strengths, and hot strengths. 

Antioxidants (qv) have a positive effect on oils when present in the proper concentration. Sterols and tocopherols, which are natural antioxidants, may be analy2ed by gas-Hquid chromatography (glc), high performance Hquid chromatography (hplc), or thin-layer chromatography (tic). Synthetic antioxidants maybe added by processors to improve the performance or shelf life of products. These compounds include butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), / fZ-butyUiydroquinone (TBHQ), and propyl gallate. These materials may likewise be analy2ed by glc, hplc, or tic. Citric acid (qv), which functions as a metal chelator, may also be deterrnined by glc. 

Fully Processed Foods. Fully processed foods are processed and packaged so that the ambient temperature shelf life can exceed three to six... 

Two other broad areas of food preservation have been studied with the objective of developing predictive models. En2yme inactivation by heat has been subjected to mathematical modeling in a manner similar to microbial inactivation. Chemical deterioration mechanisms have been studied to allow the prediction of shelf life, particularly the shelf life of foods susceptible to nonen2ymatic browning and Hpid oxidation. 

Unpasteurized orange and grapefmit juices also are increasingly popular products in the United States. Emit must be extracted under strict sanitary conditions and the juice kept just above 0°C during its approximately 17 day shelf life. Year round juice supply is difficult because long-term storage of fmit or unpasteurized juice is not feasible. 

Hafnium Carbonate. Basic hafnium carbonate [124563-80-0], Hf2(0H)4C02 XH20, is prepared as a wet paste by reaction of a slurry of basic hafnium sulfate [139290-14-5], Hf 02(S0 2 XH20, and sodium carbonate, then filtering. The basic carbonate has a short shelf life and is preferably prepared as needed. It is a starting material for the preparation of various hafnium carboxylates. 

The peioxide and a2o thermal initiatois also aie photochemicady unstable and have been used as ladical sources at weU below thek nornial theimal decomposition tempeiatuies. Howevei, thek industiial use as photoinitiatois has been limited because thek light-absoiption chaiacteiistics fiequentiy aie unsuitable and because of the obvious potential complication owing to thek slow thermal decomposition, which leads to pool shelf-life and noniepioducible photoactivity in given formulations (88). Further information on photoinitiatois can be found in the Hteiatuie (92). 

The higher, long-chain dimers as weH as the tetramer dehydroacetic acid are far more stable and can be handled safely. The alkylketene dimers (AKDs) are shipped to the paper industry in tank tmcks in the form of ready-to-use aqueous emulsions with a total soHds content of 12—25% and a guaranteed shelf life of 30 days, as they have good hydrolytic stabHity. In this form they are not combustible Hquids, and are Hsted in the Canadian Domestic Substances List. 

MAA and EAA are stable Hquids, and are shipped in nonretumable 208-L (55-gal) polyethylene-lined dmms. For bulk shipments, insulated stainless steel tank containers and tmcks provide secure protection. 2-Acetoacetoxyethyl methacrylate is a Hquid stabili2ed with radical inhibitors such as BHT [128-37-0] and has a shelf life of approximately three months. Shipment is in 60- or 208-L polyethylene-lined dmms. Acetoacetaryhdes are nicely crystalline, stable soHds and are shipped in 208-L dmms with polyethylene liners. 

Chocolate (0.3—0.5% lecithin) lecithin is a wetting agent and emulsifier. It facihtates mixing, saves processiag time and power, saves cocoa butter, stabilizes viscosity, iacreases shelf life, counteracts moisture thickening, and aids release of molded goods (see Chocolate and cocoa). 

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