Just saw this thread, and read the link that PMESguy provided, and was kinda concerned. Our products tend to be more natural, and more powerful than a lot of other companies, but of course, we just sell them, we don't make them. So, I went to the manufacturer, and I carefully questioned one of their nutritionists about Grapefruit Seed Crush. I don't think English was her first language, but I was able to get this from her. Yes, GSC is a synthetic compound, it is not found in nature. It is made in a lab by combining components different parts of the grapefruit. It results in a pharmaceutical grade antimicrobial. Now that right there might turn some people off, or make them want to do some more research.
I then questioned her very closely about preservatives in the GSC. I asked her if it contained benzethonium chloride. She said no. Then apparently she found the spot in her spec sheet about the product where it said, "Contains no preservatives". I wasn't done though. I asked her if it contained any triclosan or methyl paraben. She said no. I asked her again about the benzethonium chloride. She again said that it didn't have that and was preservative free.
Don't know if that helps anybody. Obviously I haven't sent this to a lab for testing and have only the word of the manufacturer's nutritionist. In the past that has proven to be very valuable and very trustworthy. But still, I'm not going to stake my reputation on GSC being free of preservatives, because frankly, I just don't know.
I'm not sure if I agree with the conclusion of the linked article that the antimicrobial properties of all grapefruit seed extracts are due to the relatively small percentage of preservatives. That is one possible explanation, but claiming that it is the only explanation is far-fetched. The scientific method demands that more testing be done with controls before any solid conclusion could be made.
Personally, we have had great experience with GSC. It does seem to have strong antimicrobial properties, despite reputedly being preservative free. Just thought I'd share what I found.