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.
MUST WATCH. Even with a $20 price increase in March that bumped its annual cost to $99, many users already considered Amazon Prime one of the Web's best bargains. For $8.25 per month, members get two-day shipping on many purchases and the ability to borrow Kindle books and watch streaming movies and TV shows for free.