Argentina is tightening its grip on credit card purchases in an effort to stem capital flight and tax evasion. One measure published Friday makes adds a 15 percent tax every time people make a purchase outside Argentina using a peso-denominated credit card. Another requires card-issuers to report every purchase to the government. Argentines have used their credit cards on trips to get around currency controls and shelter their wealth from inflation. These purchases soared 48 percent in June from the year before, obligating the central bank to send 289 million in precious dollars out of the country. Now the government can compare what travelers declare to customs and tax agencies with what their credit card bills say, and penalize people who live large while claiming to be paupers.