Detroit--M-Xchange.com, the b-to-b exchange co-founded by former General Motors Corp. sales chief Roy Roberts, has closed. Announced in March, M-Xchange.com was to link minority suppliers with Fortune 500 corporations. A statement on the company's home page www.M-Xchange.com
reads, ``The ability to charge transaction fees for Web-based commercial exchanges has declined, rendering it difficult for M-Xchange to achieve profitability in an adequate time frame using its business model.'' It continues to state that a decline in b-to-b venture capital financing led to M-Xchange's demise.