Queensland country trainer John Patterson has been disqualified for 18 months after being found guilty of four charges involving cobalt.

Queensland Racing Integrity Commission stewards opened an inquiry into four post-race urine or blood samples taken from runners trained by Patterson at Roma, in western Queensland, during July last year.

The samples were from Zapata Falls on July 15, and Zapata Falls, Florida Road and Cuban Fury all on July 29.

The inquiry heard the Queensland Government Racing Science Centre found cobalt was detected in each of the samples in excess of the allowable threshold.

Patterson pleaded guilty and was sentenced at a resumed inquiry.

In sentencing Patterson, stewards took into account the trainer was made aware of the discrepancy in the sample collected from Zapata Falls on July 15 and was given the chance to scratch Zapata Falls, Florida Road and Cuban Fury from the July 29 meeting.

Patterson was disqualified for 12 months on the July 15 charge and for 18 months on the other three charge to be served concurrently.