J Leonard Dixon

After Ali left Ren said to Liz, “I need a tea break. Let’s sit and discuss this before we get started. I don’t want to screw this up.”

Ren and Liz went down the hall to his office and Ren put two mugs of water in the microwave. When they were done Ren popped in the tea bags.

Ren said to Liz, “What do you think?”

Liz looked out the window and replied, “It is a nice day.”

Ren laughed as he responded, “Yes, but you know what I was asking about.”

Liz said, “Oh, do you mean the painting by Vincent van Gogh that we just cut into? Do you think I didn’t notice? You want me comment on that?”

“Yes!” Ren replied, still laughing.

“Well, I was shaking in my boots hoping that you wouldn’t slip and gouge out a whole section of what must be a $20 million dollar art work! Why are you measuring the composition of the paint in a Van Gogh painting? And why are we getting involved in another crazy project?”

Ren answered, “Those are very good questions. First I have to say that I was shaking a little bit when I cut into the paint layers. A little slip and what a mess it would have been. But luckily everything worked out. Concerning why we are measuring the paint? Ali is an old friend and he asked me to help him. I would prefer not to but I couldn’t turn him down. For now all I can say is that he would like us to get a basic composition of the paint for him for insurance purposes. I really can’t say much more. Concerning why we are involved in another crazy project? It is because we are scientists and we need to explore. That’s what we do. Artists create. Scientists generate new knowledge. We have the tools and know how to do this. Yes, it is one more crazy project, with all of its details and intricacies. And we are already involved in too many crazy projects. But I couldn’t say no to him. I promise you that I will not dive into another project without a really good reason.”

Liz commented, “That’s what you always say.” After a few moments Liz continued, “Look, this is your lab and you’re the boss. But we have a long line of research samples that we need to run and this will set us back a bit. I just wanted to let you know.”

Ren replied, “I am aware of that. And I realize that machine time is not the weak link here. It is the data analysis and the thinking that takes the most time and gets us backed up. OK, the damage to our schedule has been done. Let’s discuss the scan modes for Ali’s samples and then we can start them. I’ll do the majority of the analysis once the scans are completed.”

Liz said, “I’ll help. Someone has to check up on you!” Then she laughed.

While they drank their tea they discussed how to extract and prepare the samples for the mass spectrometer. The paint was oil based so they needed to use organic solvents to extract it. The materials in the paint had been exposed to the atmosphere for many years and therefore many of the components had oxidized and cross-linked, thus forming huge molecular masses. In order to ionize the chemicals within the samples, they needed to hit them with high voltage in the ionization source. Then the chemicals would be scanned for high molecular masses in the first mass filter. After passing through the first filter, the chemicals would be blown to pieces in the collision cell. Then the chemicals would pass through the second mass filter and hopefully, readable spectrum of the masses would be obtained from the paint samples. From this information each chemical in the paint would be identified by comparison of the spectra with that in the library of the National Bureau of Standards, outside of Washington, D.C.

Liz suggested the scan modes and program details to analyze the paint. She was amazingly skilled at programming these very complicated instruments. After discussing the strategy it was time to get back to work. Ren washed his hands and put on a lab coat and walked into the ultra clean room. Liz was already working on the samples. She performed sequential organic and aqueous solvent extractions on each. This took about 3 hours- most of this due to waiting for the extractions to occur. While this was happening, Liz started both mass spectrometers, the liquid chromatograph mass spectrometer (also known as LCMS) and the older gas chromatograph mass spectrometer (GCMS). These were located in the main instrument room, which was a large open space about 40 x 50 feet in size. This room was the equivalent of an artist’s studio. Besides housing the instruments, there were workbenches, blackboards, space for spare parts, and shelves holding hundreds of books and binders. After the extractions and making the final dilutions, Liz loaded the samples into the auto-sampler of the LCMS, which we would utilize first. Compounds in each sample would be separated first and then fed one at a time into each mass spectrometer where the precise mass of each ingredient would be measured. Since the instruments were programmed and would run unaided by further human direction, Ren went home to rest. Ali had made him a nervous wreck and he was exhausted.

Ren went back into the lab later that night. He arrived just as the last few runs of the first site in the painting were finishing. He immediately called up the spectra from the computer. They were pretty complicated so Ren needed to concentrate on one sample at a time. He chose the middle region from the first cut into the painting, made in a section that consisted mostly of purple paint. The spectra showed a series of large, complex compounds. These were still too large mass wise and would be difficult to identify, so the samples needed to be rerun. Ren programmed the instrument for greater voltage in the collision cell to fragment the large components into smaller ones. He also changed the chromatographic elution conditions to better separate major chemicals from each other before they flowed into the mass spectrometer. Basically, they were analyzing for both the smaller size pigments and the components of the oils they were suspended in. The oil, most likely linseed oil, was made up primarily of triacylglycerol molecules, also known as fat. Over time the triacylglycerols had oxidized and cross-linked to form very large polymers. With luck the cross-linked structures would be broken down and they would be able to identify pigments, the base oil, and any additives in the paint. Any modern ingredients in the samples, such as acrylic molecules or their polymers, should be easily identified if they were present. Ren waited around for next round of runs to finish. The spectra from these runs showed smaller, less complex molecules and more of them. The signals were stronger than those seen in the original runs. The peak shapes were more symmetrical than before. By 3 in the morning Ren had the first preliminary composition list of the chemicals from the first sampling site of the painting. It looked reasonable and he started running all the other samples from all the cuts using the same instrument conditions worked out for the purple region.

Ren pushed the run icon on the instrument and headed home. Liz would be in at 8 am to check on things. In 24 hours all the different levels of the paint would be analyzed. The major chemicals extracted from each layer of each cut would be available. Quite amazingly, the analysis of the paint was turning out to be more straightforward than Ren had expected. Hopefully, the data would point to Van Gogh as the artist who painted Ali’s “masterpiece.” But being certain would be the hard part. Most likely, the results would need to be interpreted, and that’s where Ren would need help. The more he thought about it, the more Ren wondered what a nexus of craziness he had gotten himself into. He turned off the lights and walked down the dark hallway to the basement exit.