The ninhydrin reaction, one of the most important method of detecting amino acids, both technically and historically, has been conventionally used to detect their microgram amounts. When amino acids with a free alpha amino groups are treated with an excess of ninhydrin, they yield a purple colored product.
Update January 19: Amazon has increased the monthly price of Amazon Prime from $10.99 to $12.99 for those who opt for the month-to-month plan. However, the annual price remains untouched at $99 per year, which makes it the better option for avid Amazon shoppers.
A.: Amazon Prime is a paid service ($99 per year, plus a free 30-day trial or $10.99 per month) that gives Amazon shoppers a few distinct advantages. Members of Amazon Prime are eligible for free one- or two-day shipping on most items, among several other perks. Free two-day shipping on eligible items to addresses in the contiguous U.S. and other shipping benefits. For more information, go to Amazon Prime Shipping Benefits.