The phrase "a substantial difference however" is correct and usable in written English.
It can be used to introduce a contrast or exception to a previously stated idea or fact.
Example: "The results were similar in many aspects; a substantial difference, however, was noted in the final outcomes."
Alternatives: "a significant difference nonetheless" or "a considerable difference, on the other hand."
There is a substantial difference, however, between the six-figure models that are coming to market now and many of the high-priced pre-recession offerings.
The microcosms from the two sites showed a substantial difference, however, in the relative dominance of subsequent dichloroelimination of 112TCA.
If there was no longer a substantial difference, however, we concluded that the independent variables added in that step might account for the difference in ratings compared with white respondents.
There are substantial differences, however.
The two competing bills sponsored by leaders in the House of Representatives and the Senate have substantial differences, however, that have proven difficult for their sponsors to reconcile, even after a month of wrangling.
Results show that, there is no significant difference in groundwater recharge between the four landscape positions under shallow-rooted vegetation (p > 0.05); however, there is a substantial difference between different slope positions along the other transect (p < 0.05).
There was, however, a substantial difference in how people voted based on their responses to this question.
However, a substantial difference was found in discharge performance when using a molecular gas.
However, a substantial difference in carbonate (calcite and dolomite) content between the weathered and fresh tailings was found.
However, a substantial difference between the groups was identified in terms of the median cumulative cost at different time points over the follow-up: both the HIP and PEP groups cost substantially less than the conventional home care HACC group.
However, a substantial difference between the two districts occurred across the 8 aspects of daily living with 18.5% and 45.5% of children in Kinondoni and Temeke having experienced any oral impact during the 3 months preceding the survey.
