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.
Assuming the $2 increase, Netflix will soon cost $119.88 per year. Amazon Prime membership costs $99 per year (or about $8.25 per month), but also includes unlimited, free two-day shipping on many items. You also get access to the company's growing selection of streaming TV shows and movies. Hulu Plus costs $7.99 per month or $95.88 per year. We haven't heard of any upcoming price increases and don't expect to since Hulu can keep prices low by showing advertisements along with its programming. Netflix and Amazon don't show you ads.