Dissolution hierarchy

In a typical multivitamin-mineral combination product consisting of 10-15 ingredients, it is neither practical nor necessary to require in vitro demonstration of each and every vitamin and mineral. Consequently, in a unique approach to establishing in vitro dissolution for multivitamin-mineral combination products, an index vitamin and an index mineral are identified as markers for dissolution. In an attempt to account for the many different permutations of vitamins and mineral combinations, a hierarchy of index vitamins and index minerals was arrived at and specified (5). Table 1 shows the hierarchy of index vitamins and minerals specified for demonstration of dissolution requirement in the nutritional supplements monographs in USP 25-NF20. 

In view of the reported growing importance ascribed to folic acid deficiency in the prevention of various disease conditions, such as neural tube defects, megaloblastic anemia, colon cancer, and colorectal cancer, a dissolution requirement is specified for folic acid when it is present in multivitamin-mineral combination products. Currently, the dissolution standard required in the official articles of dietary supplements (including vitamin-mineral combination products) places folic acid outside the index vitamin hierarchy. Therefore, a mandatory dissolution test for folic acid is required that is independent of and in addition to the mandatory index vitamin test for multivitamin preparations containing folic acid. 

In contrast to the dissolution criteria used for water-soluble vitamins, the hierarchy for index minerals is based on their importance in public health. For example, iron was chosen as the number one index mineral because iron deficiency is the most prevalent condition in the United States and because iron is present in almost all the multivitamin-mineral combination products currently available on the... 

For doping-dependent anodic etch stops in HF, a general hierarchy of dissolution is observed [La5] illuminated n-doped and n+-doped areas are most easily dissolved, followed by p+-doped areas. Next likely to be dissolved are p-type areas. Moderately n-type doped areas kept in the dark are least likely to be etched. This hierarchy corresponds to the potential shift of the I-V curve in the regime of PS formation [Gal, Zh5]. 

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