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Boost Precision, Reproducibility for Critical LC Methods

Chromatographers who learned their craft twenty years ago may not have been familiar with autosamplers then, but today nearly every high performance liquid chromatography(HPLC) instrument includes an autosampler as standard equipment.

Chromatographers who learned their craft twenty years ago may not have been familiar with autosamplers then, but today nearly every high performance liquid chromatography(HPLC) instrument includes an autosampler as standard equipment.

“Autosamplers existed in the early days of HPLC but many scientists preferred manual injection,” notes Simon Robinson, HPLC product manager at Shimadzu Scientific Instruments (Columbia, MD). When sample was plentiful, manual injection was a convenient way to flush the injection loop between runs, an operation most easily accomplished (at the time) by hand.

But the main reason most lab workers preferred manual injection was that early autosamplers were not very reliable. Robinson recalls horror stories where analysts set up a tray of twenty labile samples or so, then returned the next day to find the instrument stuck on sample number two and all the remaining samples “wrecked.” However, “There’s been so much engineering focused on improving these instruments that it’s safe to say autosamplers are 100 percent reliable,” Robinson adds.

Autosamplers spare lab analysts from uninteresting, repetitive work. Even more time is saved when they are coupled with robotic sample preparation. Their major contributions to HPLC are reproducibility, repeatability, precision, and accuracy in delivering precise injection volumes.

So who would not routinely use an autosampler? According to Robinson, academic labs still rely heavily on manual sampling and injection because their primary objective, aside from data quality, is cost-effectiveness.

Another area where autosamplers are often impractical, observes Helmut Schulenberg-Schell, Ph.D., worldwide LC marketing manager for Agilent Technologies (Waldbronn, Germany), is in preparative HPLC. Prep work tends to be specialized, one-off, non-routine, and does not require the sensitivity or accuracy of analytical HPLC.

Autosamplers provide a level of automation, throughput, and productivity that is multiplicative. Using an autosampler, one chromatographer can operate multiple HPLC systems simultaneously, injecting many hundreds of samples after spending just a few minutes with the control software. This frees workers to perform other tasks like making mobile phases or analyzing data.

Speed, throughput, and reduced sample volumes are critical for most analytical laboratories, and autosamplers play prominently among the various “fast” techniques adopted toward achieving those goals. Autosamplers have become critical enablers—like columns, pumps, and detectors—of these trends, and in doing their part they have required substantial re-engineering for both stand-alone performance and integration. As such, autosamplers have been a primary target of engineering efforts to shorten cycle times vs. simply run times. After all, an HPLC or UPLC system does not add much in the way of throughput or speed in reducing analysis time if the slowest link in the cycle still requires several minutes to re-equilibrate. The wider adoption of UHPLC underscores the “need for speed” and the role of autosamplers within that scheme. “Now, suddenly,” says Schulenberg-Schell, “you can run ten times as many samples on an HPLC instrument, and the question of automation in sampling, injection, sample prep, and sample tracking becomes more urgent.”

Model AS-2059

• High-speed, direct fill, fully automatic sample injection system
• Features up to 768 well positions (two 384-well microplates)
• Offers reproducibility less than 0.2% RSD for 5.1 to 100 μl injection
• Less than 0.002% sample contamination for 10 μl injections



• Features special needle treatment: masks active sites and minimizes ionic interactions
• One-piece injection port/needle seal at valve center eliminates sample transfer tubing
• Ultra-high-speed sample processing: 10 seconds for a 10 μL injection
• 12-plate capacity ensures convenient processing of more than 1,000 samples

Shimadzu Scientific Instruments

1260 Infinity

• Designed for capillary and nanoflow LC, allowing injection of sample volumes from nL to μL from well plates and vials
• Rheodyne® valve, needle seat, loop and seat capillaries minimize dispersion
• Variable injection volume and flow through design prevents sample waste
• Features Peltier temperature control from 4 to 40°C for thermally labile samples

Agilent Technologies


• Features high-resolution syringe control for high-precision injections
• Includes interchangeable fixed-volume sample loops
• Offers optional sample cooling for consistent results
• Able to use plates or vials, alone or in combination, for varied sampling formats