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.
You Can Now Get Amazon Prime by the Month, With or Without Shipping. You can now pay for Amazon Prime month by month, with or without shipping. Starting today, the company is launching two new subscription plans: a monthly Prime membership plan for $10.99 and a monthly Prime Video membership plan for $8.99. Neither subscription requires an annual commitment.