LOS ANGELES (AP) _ The chairman of Quotron Systems Inc. says a $680 million cash takeover bid by Citicorp is inadequate, but Quotron will continue to weigh the offer.

The directors of Quotron, a leading supplier of computerized stock quotations, ended two days of meetings Thursday without deciding whether to accept the $19 a share takeover bid by New York's Citicorp, the nation's biggest bank holding company.

''The developing concensus of the board was that the price offered by Citicorp was not adequate,'' Milton E. Mohr, chairman and chief executive of Quotron, said in a statement released Thursday.

Mohr said the board and its advisers will continue to evaluate the Citicorp offer as well as explore other opportunities for the company. The alternatives include the possibility of remaining independent or developing relationships with other companies and investors in an attempt to strengthen shareholders' value.

Quotron on Thursday closed unchanged at $18.62 1/2 in national over-the- counter stock trading, although it had been trading at $16.25 when Citicorp made its offer on March 18.

Wall Street analysts said they believe Quotron will be hard-pressed to oppose the offer because it provides a substantial premium over what the stock had been trading for.

Citicorp held merger talks with Quotron late last year, but those negotiations fell through. Analysts have speculated that Quotron dropped the talks because some of its largest customers, which include major Wall Street financial firms, threatened to drop the service if it was acquired by Citicorp, a competitor.

In reviving its proposal, Citicorp said it hoped the talks could be friendly but didn't rule out a possible hostile bid if Quotron spurns the plan.

The bank holding company said it would operate Quotron as a separate entity, the largest part of its expanding information division. Citicorp also said it hoped to retain Quotron's board and top management.