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.
However, there are two catches to this. The first is that Amazon Prime is a little more expensive than some comparable streaming services, such as Netflix and Hulu ($7.99 per month) for movies and TV shows, or Pandora One ($4.99 per month) and Deezer Premium ($7.99 per month) for music.ou are charged annually, from the date you sign up to the same date next year. If you're looking to compare that to other per-month billing schemes, Amazon Prime's cost averages out to $8.25 per month.