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.
Despite the appearance of a relatively large lump sum, that $99 per year comes to $8.25 per month. On a per-monthly basis, Amazon Prime is only 25Â¢ more than Hulu Plus ($7.99 per month) and 75Â¢ cheaper than Netflix NFLX Standard ($8.99 per month).mazon can increase its Prime membership by simply offering to pay for Prime services on a monthly basis. $8.25 per month is a much easier expense to handle than shelling out $99 upfront.