The older LAS data system used for this analysis made it difficult to automate a sequence of injections. As a result, analysts had to spend much of their time performing manual injections and monitoring analyses. Simultaneously, other projects within the company needed additional analytical equipment, but the laboratory had neither budget nor space to accommodate all.

The Move to Fast GC
The purchase of the new data handling system, combined with routine replacement of GCs, created the opportunity for faster sample turnaround time and improved laboratory efficiency. "We decided to try fast GC, since we now had the capability," explains Dr. Golob.

The laboratory's original method used a 30-m column with a 0.25-mm inner diameter. The new column is 20 m long and has a 0.100-mm i.d.; column film thickness is less to maintain the same phase ratio.

The fast GC method requires a higher column head pressure (50 psi), a higher split ratio, and a faster temperature program rate (35ºC/min). Dr. Golob also employed a pressure program to improve the resolution of low-boiling peaks. Hewlett-Packard offers free software to assist customers in converting existing methods to fast GC.

Run Time Reduced to 13 Minutes
"We tried it and it worked! We realized that with these two instruments, we will have the sample throughput per shift that we need to control our processes." The team, which includes chemists Adam Howard and Lewis Tunnell, determined that total run time will fall from 31 minutes to 13 minutes, without loss of sensitivity and resolution. "The critical thing is having the HP 6890, because we can limit our sample size to maintain peak resolution and still get very good sensitivity," Dr. Golob points out. In addition, the HP 7683 automatic liquid samplers will enable dual simultaneous injection, doubling sample throughput.

Although it was not among the team's original objectives, having only two GCs and reducing the split flow will reduce carrier gas consumption dramatically. The HP 6890 Plus GC's gas saver feature can save even more.

The conversion to fast GC has been so beneficial, notes Dr. Golob, that her laboratory has converted six other methods used in a different product group. Her team is currently investigating the possibility of increasing the speed of another set of methods for a third product group. The team is also evaluating the compact HP 6850 GC, because it has only half the width of the HP 6890 GC and offers much faster oven programming rates.

"Pull Off Results and Walk Away"
Dr. Golob appreciates the advantages of the new system. "Now we can set up a sequence to run all the samples, so analysts don't have to spend time walking to the unit, injecting samples. With this change, they will be able to pull off results and walk away to deal with the data, while the instruments keep operating. And we're gaining space."

Going from seven to two GCs frees a lot of bench space. The HP 6890 Plus GC is also three inches narrower than the HP 5890A. In addition, the HP 6890 has built-in automatic liquid sampler and LAN interfaces that eliminate separate interface boxes.

"With these changes," adds Dr. Golob, "we are projecting immense improvements in productivity and efficiency."

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