Is there are way to send notes when sending through a sample email to the approver. It would be helpful to add comments for the approver to note.
No, this isn't currently possible. I think there is probably an idea somewhere that you can vote on.
I know it's not ideal but I send the view email as webpage link in an email and within that same email I write up the notes. That way, there is no distortion from sending yourself a sample email and forwarding to the person with notes or sending them a test email and then having a second email with the notes.
But using the Web Page View as a preview for approval is itself a distortion.
If there's an HTML element in the email in which you'd want to display a comment, why not allocate that space in the template and add an email script token ({{my.approvalNotes}}) that only generates output for certain recipients?