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.
Amazon Prime and Netflix cost (roughly) the same per month. Amazon Prime is either Â£5.99 per month, for just its video on demand service, but most subscribers pay Â£79 per year for access to its video content, as well as other extras such as free shipping for products bought from its store.