The Du Pont Co. reported record earnings for the first quarter of 1978 yesterday, but company officials downplayed the advances by citing inflation and recent large capital expenditures.

"Considering the effects of inflation and the sizeable amount of money we have spent on capital projects since 1973 (Du Pont's best year on record), we should be doing much better than 1973," said Du Pont President E. R. Kane at a news conference here following the company's annual meeting.

Chairman Irving S. Shapiro added, "in inflationary times, records measured in current dollars are not the source of pride they used to be," but he added that the company was heading toward a record year.

During the meeting, before an overflow crowd 1,300 stockholders, chairman Shapiro, painted a bright picture for stockholders. He called the gains "particularly gratifying," since foreign exchange losses in the quarter just ended penalized earnings by 13 cents per share, compared with a 16 cent gain in the first quarter of last year.

First-quarter profits rose to $168 million ($3.45 a share) from $121 million ($2.45) in the first quarter of 1977, while total sales for the quarter were a record $2.5 billion, up 12 percent from last year. The per share figure topped the previous high of $3.28 a share reached in both the second quarters of 1973 and 1977.

According to Shapiro, the strength of the company continued to be in what he called "CPS" - chemicals, plastics and specialty products. CPS earnings increased 16 percent over last year and 60 percent over 1973.

Specialty products and plastics were particularly strong, while the Miss. Already the domestic leader in production of the chemical - which is a lightening and brightening element in paint - Du Pont has been accused by the Federal Trade Commission of attempting to monopolize the market with artificially low prices.

He said the low prices were in response to a growing influx of imports in the field; Shapiro said the company would fight the government efforts.

During the meeting, Shapiro revealed that $750,000 was spent on Du Pont's fleet of ten corporate jets. He said the company would add a helicopter to the fleet this year.

He also revealed that the company would pay $15.5 million in capital gains taxes on the $60 million it netted from the sale of the Wilmington News-Journal newspaper to Gannett Newspapers earlier this year.

Annual corporate meeting gadfly Evelyn Y. Davis proposed an amendment to the DuPont by-laws that would have limited the terms of future chairmen and presidents to four years.

The motion, which would have also limited the terms of the directors of the company to four years, was defeated by a huge majority, even after Davis had cited a need for "younger and more handsome men on the board."