Dionex shareholders will receive $118.50 per share, representing a 21 percent premium over Friday's closing price.
Thermo expects the deal to increase its adjusted earnings per share by 13 cents to 15 cents in the first 12 months after closing, which is projected for the first quarter of 2011.
Dionex specializes in chromatography systems, which allow components of a mixture to be separated before they are put into a mass spectrometer for analysis. Thermo is a major player in mass spectrometry.
Dionex, which is based in Sunnyvale, California, and has more than 1,600 employees, introduced the first ion chromatography system for water analysis shortly after its founding in 1975, the companies said in announcing the deal on Monday.
In addition to increasing its lab-equipment offerings, the acquisition will also allow Thermo to expand its presence in the Asia-Pacific region. Dionex generates more than 35 percent of its revenue in Asia-Pacific and other emerging markets. It reported nearly $420 million in sales for its most recent fiscal year.
Thermo reported revenue of $10.1 billion last year.
Thermo shares were up 2.3 percent to $54.25 in premarket trading. Dionex shares rose to $117.75.
Dionex also serves customers in food safety, environmental analysis and other industrial sectors, where Thermo sees growth potential beyond its main customer base in the biotechnology and pharmaceutical research sector.
Last March, Thermo lost out to German-based Merck KGaA (MRCG.DE) in a bid to buy Millipore Corp and its biotechnology production business. Merck bought Millipore for $6 billion.
At the time, analysts said Thermo would continue to hunt for deals, though not necessarily those the size of Millipore.
Barclays Capital and J.P. Morgan Securities LLC are Thermo's financial advisers, while its legal counsel is Wachtell, Lipton, Rosen & Katz. Goldman Sachs and Cooley LLP are advising Dionex.
(Reporting by Lewis Krauskopf; Editing by Lisa Von Ahn and John Wallace)