Boron is NOT our Friend
Since 1994, we had operated the cosmogenic nuclide lab without boron issues. Sure, there was that one batch of samples from Boliva that was loaded with boron (where the hell did that come from?) but all the rest were fine. Then, in November 2006, we carried over 100 targets to LLNL, all the lab production between July and the end of October. Every sample processed before the end of August was perfect; every sample processed after the end of August was unmeasurable. Boron was the culprit. B-10 masquerades as Be-10 and overloads the AMS detector. Bottom line, no data, for a little while. LLNL savvy came to the rescue with the installation of a final stripper foil and all but 4 samples were salvaged. The lab shut down immediately so we could figure out what went wrong.The real question was...where did all the boron come from? It took us several weeks to figure out that two things had happened during the summer of 2006. First, the synthetic, boron-free filters specified for our HVAC system had been replaced with borosilicate glass filters and those filters were not tightly seated on their racks. Second, during re-roofing of our new building, boron-bearing insulation had been stripped, pulverized, and injected into the air supply system as it was ripped off the roof. With gaps between the filters, this material had gone all the way to the cosmogenic lab where it plugged the ULPA final filters on our hoods and...since boron has a tendency to become volatile, degassed, and permeated every sample processed between August and November 2006. You can see some pictures of this mess, here. We spent 6 months figuring out what went wrong, replacing all the filters, cleaning the ducts, and cleaning the lab. Three 3 days after bringing the lab back on line in May 2007, it was destroyed by an electrical fire on Memorial Day. The fire vaporized a sheetrock wall (sheet rock contains boron both naturally and as an added fire retardant) and the fiberglass insulation behind the wall (yes, fiberglass is made from borosilicate glass). Test samples run in an adjacent lab after the fire showed extremely high boron levels. We did learn loads about boron in the process and share that information in the links below. Those interested in boron, might enjoy the information (Powerpoint) (PDF file) that we put together for the construction team rebuilding the laboratory.
Air Filters are Critical
Source of boron-free minipleat HVAC filters
Air handling...the reason for anomalously high boron background levels
Water Quality Matters
Ultrapure water blank for boron trace analysis
Ultrapure Water for Boron and Silica Sensitive Laboratory Applications
Boron Chemistry and Sources, Background Information
Supresion of Boron Volitilization...
Boron as a tracer for material transfer...
Microwave Digestion and Ultrasonic Nebulization for Determination of Boron...
Use of Inductively Coupled Plasma-Mass Spectrometry in Boron Stable Isotopes