A new method of coupling capillary columns improves gas chromatography analyses.

The Editors’ Choice Silver Award at the 59th Pittsburgh Conference on Analytical Chemistry and Applied Spetroscopy (Pittcon) in March 2008 went to a product that utilizes a new method for coupling capillary columns in gas chromatography (GC), GCxGC, and capillary zone electrophoresis (CZE): the Meltfit One, from NLISIS Chromatography, Veldhoven, The Netherlands. Using the Meltfit One, coupling capillary columns becomes simple, stable, secure, and fast, resulting in more successful and reliable analyses and lower costs of ownership. The Meltfit One establishes stable and solid connections between capillary columns with the help of the Meltfit tube. It is a unique small glass tube, which is gently positioned around the columns as a ‘second skin’, leaving no room for dead volume or leaks.

“We started out only two years ago, with the goal to develop and launch products that make GC technology easier to use and decrease the total cost of ownership through faster and better performance,” explains Wil van Egmond, CEO of NLISIS. “The Meltfit One is our first proof of that mission. This [Editors’ Choice] Award stimulates us to intensify our development efforts and step forward with additional products that help solve other remaining nuisances of chromatography analysts around the world.”

The need for coupled columns

The Meltfit tube goes in the center of the Meltfit One tool. One capillary column goes in the left side of the tool, one goes in the right side of the tool, and then the user closes all parts of the tool. When the start button is pressed, heat and pressure connect the capillary columns. Image: NLISIS Chromatograhy

Modern separation systems frequently use coupled-column set-ups. This is the case in advanced applications as GCxGC, but also in more standard situations, such as the simple coupling of a pre-column or a retention gap to the analytical column. Conventional coupling of capillary columns is considered a difficult task, frequently leading to imperfect couplings and substantial down time.

Current glass connectors are relatively easy to install but are prone to leakage, especially at higher temperatures. They are cheap to purchase, but too often deliver unsatisfactory results. Metal connectors are difficult to install, inflexible in terms of possible column inner diameters and outer diameters, and they have a high risk of degradation, a high thermal mass, and are expensive.

Based on these weaknesses, NLISIS developed the Meltfit One, a solution that has a low cost of ownership, absolute leak tightness, no dead volume, no adsorption, no band broadening, and no thermal degradation, leading to a much higher sample throughput for the lab.

Creating a seamless connection

The Meltfit One has solved connection issues with the help of a unique small glass tube. The glass has been developed, tested, and produced at NLISIS and is chemically deactivated, so the glass will not interact with its environment.

In five simple steps, the Meltfit One establishes an automated and standardized connection between two capillary columns with the deactivated Meltfit tube. A combination of heat and air pressure fixes the columns in the glass tube, establishing a seamless connection. Connections are established in little more than 1 min, and they remain intact after frequent usage, even at high temperatures. The Meltfit technology has been tested with up to 11 connections in series, without showing any noticeable band broadening or leakage. Meltfit tubes can be used for coupling columns with inner diameters of 0.53 mm, 0.32 mm, 0.25 mm, and 0.1 mm.

Meltfit connectors can be used in isothermal and temperature programmed operation up to 385°C. The development of Meltfit connectors allowing GC oven temperatures up to 450°C is currently under development.

Meltfit connections can be used for many applications, including:

• Column-to-column connections: to connect columns with different stationary phases for improved selectivity, to make longer columns, or to mend broken columns.

• Guard column/retention gap: to protect the analytical column from dirt and to allow on-column injections onto 320 or 250 µm columns.

• GCxGC: to fit the various connectors in a tiny modulator space or small second dimension oven.

• GC-MS: to avoid having to vent the MS every time a new column needs to be installed (if a narrow transfer capillary is used) or to avoid careful repositioning of the column in the ion source with every column replacement.

The Meltfit One will find use in many industries, including petrochemical, pharmaceutical, environmental, and for quality assurance/quality control (QA/QC) in any of these industries.

Testing the technology

A Meltfit tube connects two columns seamlessly. Image: NLISIS Chromatography

An extensive scientific test program was run at the Univ. of Amsterdam to assess the performance of the Meltfit connector. Standardized test methods were used. The Grob test was used to probe the inertness of the connections. Even with up to 11 connections, no adverse effects were found. The Donike test was used to study the thermal degradation behavior, and the Meltfit connections performed excellently here as well. Finally, dead-volume and band broadening were quantified from the bandwidth and symmetry of methane. Even 11 connections did not produce any significant effect.

These research results were presented at the 10th International Symposium on Hyphenated Techniques in Chromatography and Chromatographic Analyzers (HTC-10) in Bruges, Belguim, in February 2008, and generated a lot of interest from the attending scientists.

With these results, van Egmond is confident that the Meltfit One has the potential to become the new standard for column coupling in the market. “Having worked with this technology for a year now and listening to the overwhelmingly positive reactions of the beta users, we feel it is fair to say that the Meltfit One is the most reliable and user-friendly GC column connection in the world,” he says. “The Meltfit One should enable chemical analysts around the globe to make perfect connections between capillary columns without the nuisances from the past.”