The marriage of Thermo Fisher Scientific Inc. (NYSE:TMO) and Dionex Corp. (NSDQ:DNEX) will have to wait another month to be fully consummated.

Thermo Fisher officials released a statement today saying the deadline for the $2.2 billion deal would be pushed back to May 13 to satisfy the remaining anti-trust hurdles in the European Union.

“Thermo Fisher applied to the European Commission (EC) for jurisdiction, as previously disclosed. The EC took jurisdiction over the transaction on February 25, 2011, and accepted the company’s merger filing today, April 4,” according to a press release. “Under applicable law, the EC has 25 business days following the filing, or until May 13, 2011, to review the transaction. The company expects to complete the transaction in the second quarter of 2011.”

The Valentine’s Day hookup between the two companies was detailed in regulatory documents filed Feb. 14.

The debt offering for Thermo to acquire Dionex will consist of three series of senior notes — $1 billion in 10-year notes with a 4.5 percent coupon, $900 million in five-year notes paying 3.2 percent yearly interest and $300 million in three-year notes with a 2.05 percent coupon. A little derivatives dipsy-do will effectively trim the interest expense by more than half for the 2014 notes, as Thermo Fisher plans to use an interest rate swap to create a floating rate equal to the six-month LIBOR rate (currently 0.46 percent) plus 41.12 basis points.

U.S. anti-trust regulators signed off on the merger in early January, but Thermo Fisher CEO Marc Casper said Feb. 2 that the company was waiting on the European Commission to decide whether it will review the transaction, which would eliminate the need to win approvals in individual EU countries.