Poorly connected flow path fittings are one of the top reasons for peak tailing, peak broadening, split peaks, and carryover. That is because dead volume or micro-leakage can cause extra-column volume, which hinders the performance and reproducibility of HPLC and UHPLC. Conventional fittings are non-adjustable, require specialized wrenches to install, and are incompatible with different column brands. They are also subject to over-tightening which can cause the fitting to stick in the column.
Several manufacturers offer finger-tight fittings, but these fittings usually have polymeric ferrules that lack grip strength at high pressures. As a result, you must constantly check for leaks and re-tighten the fittings to avoid tubing slippage and dead volume. Agilent has completely redesigned their column fitting to overcome these problems. The A-line Quick Connect fitting uses a lever-operated and spring-loaded mechanism to provide zero dead volume and an easy-to-use, tight connection – even after hundreds of reconnections up to 1,300 bar.
Reusable and robust flow path fittings
We assessed the performance of the A-Line fittings using an Agilent 1290 Infinity Binary LC equipped with an Agilent ZORBAX RRHD Eclipse Plus C18 column. First, we disconnected and reconnected an Agilent A-Line Quick Connect fitting 200 times at the column inlet. The chromatogram in Figure 1 compares performance before and after the reconnections. A newly installed Swagelok stainless steel fitting was also tested to provide a chromatogram benchmark. The tailing factor of naphthalene – and the theoretical plates of uracil and phenol – stayed constant within the experimental allowance. This proves that the fitting connection was free from dead volume and leaks after 200 uses (Figure 2).
Figure 1. Even after 200 reconnections, there was no visible change to the chromatogram with the Agilent A-Line Quick Connect fittings. Results were also identical to those obtained with the newly installed Swagelok fitting.
Figure 3. Deteriorated peak shape, including larger peak tailing and lower peak height, after 30 reconnections of a UHPLC finger-tight fitting from another vendor.
We repeated the experiment using a reusable finger-tight UHPLC fitting with a polymeric ferrule from another vendor. After only 30 reconnections, the polymeric ferrule locked onto the capillary and could not be adjusted, resulting in dead volume. Comparing the chromatograms demonstrated the effects of dead volume, as shown in Figure 3. You can see deterioration of peak shape, including larger peak tailing and lower peak height.
Full details of this analysis are freely available in Agilent publication 5991-5525EN.
Fittings withstand ultra-high pressure environments and garner scientific award
In this article, we have demonstrated the Agilent A-Line Quick Connect fitting and how it delivers usability, robustness, and UHPLC performance in terms of tailing factor, number of theoretical plates, and peak height that remained constant through 200 reconnections of the fitting. What’s more, the unique spring-loaded design guarantees zero-dead-volume connection and compatibility with columns from other manufacturers. The benefits of these advanced fittings were recently recognized by the Analytical Scientist Innovation Award (TASIA), which highlights innovations delivered by transformative technology, game-changing software, or benchmark-breaking instruments. The Agilent A-Line Quick Connect fitting was recognized for its highly innovative approach in successfully simplifying the connection of fittings in ultra-high pressure environments.
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Even after 200 reconnections, there was no visible change to the chromatogram with the Agilent A-Line Quick Connect fittings. Results were also identical to those obtained with the to those obtained with the tting.
Reliable and robust performance without leaks even after reconnecting the Agilent A-Line Quick Connect fitting 200 times.
Deteriorated peak shape, including larger peak tailing and lower peak height, after 30 reconnections of a UHPLC finger-tight fitting from another vendor.