To be certain, check the balance of seasoning of not only the vinaigrette, but the finished product as well. A simple vinaigrette due to the nature of oil and vinegar isn't expected to stay blended very long. Therefore, its important to mix a simple vinaigrette immediately before serving. The culinary solution to separating oil and vinegar is to emulsify the vinaigrette with egg or egg yolks. This is the essence of making mayonnaise.
Oil is formed into tiny droplets by gradually adding it to the other ingredients while whipping.
These tiny droplets are suspended in the water contained in the vinegar and egg. Lecithin in the yolks keeps these suspended droplets of oil and water from separating. Mustard is a common ingredient in many vinaigrettes since compounds found in mustard seed also aid in maintaining an emulsion. Traditionally, the egg product used in mayonnaise and other emulsified dressings was not cooked. This presents a sanitation problem today.