The real question at hand (since I've never been observed) is whether or not QF 4.2 can or ever has been detected as synthetic.
Not as long as the batch is current and hasnt been stored in direct sunlight. Exposure to direct sunlight will ruin the QF batch, resulting in a "..sample not consistent with human urine.." ruling.

The same also applies to old/expired batches. But since you have QF 4.2 formula, its current. So no worrys there. :smokin:

For a peace of mind, run a home validity test on your QF batch so you can be assured that the creatinine, pH, and specific gravity are within acceptable ranges. You can find validity test kits online. Do a Google search for drug adulteration test kits.