A woman is brought into a Bay Area hospital. She’s having seizures, and lapses into a coma before she can tell anyone what happened to her. Her family reports that she used herbal sleep aids.

Could she have accidentally overdosed? Knowing the true cause behind the coma is critical. Giving the wrong antidote to a toxic substance can have potentially fatal consequences.

The clock was ticking. A sample of the patient’s blood and the suspect herbal remedy was sent to a lab at San Francisco General Hospital, where Dr. Roy Roberto Gerona set about analyzing it.

Gerona has been using UCSF’s time-of-flight mass spectrometer to solve mysterious cases referred to him by the Poison Control Center over the past two years.

A molecule’s “time of flight” is literally the length of time it takes for a molecule that is tossed up into the air inside a mass spectrometer to fall a given distance. That information provides Gerona with critical information about a chemical’s identity.

Gerona’s path to clinical chemistry was circuitous. As a young man growing up in the Philippines, he was fascinated by science. He began planning for his Ph.D. long before his peers even knew that such a degree existed.

Gerona longed to be an astronomer, and the pathway to astronomy in the Philippines was through physics. But on the road to physics he met a chemistry teacher who showed him how the patterns of the molecules that make up all living things are behind such basic phenomena as the color of the sky.

Gerona received a Ph.D. in biochemistry and settled down to doing basic research on the proteins involved in transmitting signals in our nervous systems. But he realized that he wanted to translate the meaning of molecular patterns in a way that would bring concrete benefits for people’s lives. Which is the story of how he came to UCSF’s Clinical Chemistry Laboratory at SFGH, where he began his work unlocking the names of mysterious chemicals that can make us sick.

More recently, Dr. Alan Wu, the Clinical Chemistry Laboratory’s chief, hit upon another chemical mystery that the time-of-flight machine might help solve — figuring out what environmental chemicals are in our bodies already, day in and day out.

Gerona is now testing samples from a study being conducted by Dr. Tracey Woodruff, the director of UCSF’s Program on Reproductive Health and the Environment.

In the study, pregnant women receiving prenatal care at SFGH have agreed to provide samples so that the levels of environmental chemicals in their system can be measured to help understand how environmental chemicals can harm reproductive health.

Before Gerona was involved in this research, Woodruff could only ask, are such and such environmental contaminants present in pregnant women?

And if you only inquire about a few suspects, there’s a good chance you might miss the real culprit, as those doctors might have.

The suspect herbal remedy taken by the coma patient turned out to be innocent. An hour after the samples arrived, Gerona had his answer. Instead of the herb, the culprit looked like diphenhydramine, an ingredient often used in over-the-counter allergy medications and sleeping pills.

Later that evening, the doctors administered an antidote for diphenhydramine overdose, and the patient woke up the next morning alive and well.