Best Instrument

First Generation UHPLC fittings developed by Best Instrument, Inc. 'First Generation' denotes the continued reliance on the cone shaped ferrule as the sealing mechansim. The 'second generation' is would then be the TSip™ type of fitting as described in issued patents.

Youtube video provides a good overview of the major 'first generation' styles.

Overview of first generation UHPLC fittings

Overview of first generation UHPLC fittings

Group of first generation UHPLC fittings
Figure 1: Group of major first generation UHPLC fittings
  • 1. 'Slip-Free' style
  • 2. 'Gemini' Patented style, standard length
  • 2A. 'Gemini' Patented style, extended length (for crowded ports)
  • 3. 'Better Nut'
  • 4. 'OEM' fitting, a 'Slip-Free' adaptation.

'First Generation' UHPLC fittings had been developed and patented by Richard A. Henry and others at Keystone Scientific as early as 1995. In 2006, in responce to tubing slippage failures causing loss of calibration of the Viscometric Flowmeter Dr. Henry suggested that such a fitting as the 'Slip-free' should be commercialized, and sold as a product. So, the original fitting developed at Best Instrument was as depicted in the figure, item 1.
Additional fittings were deveoped in the first two years. Those shown in the figure are about half of those that were commercialized and sold through Supelco as Supel-Connect high performance fittings and Supel-Connect high performance nuts. Variants were OEM branded and sold through a additional HPLC distributors.

"Slip-Free" style first generation UHPLC fittings

"Slip-Free" style first generation UHPLC fittings

First 'Slip-Free' derivative
Figure: Derivative of 'Slip-Free' design by Keystone

A very popular and effective implementation is shown in 1, of the figure. This is a derivative of the Henry-Boone patent, US5582723. The drawback in this approach is that it is necessary for a high degree of operator training or awareness regarding proper installation technique. That is, enough end-users tightened the 'cap' as the method of attaining a final seal. A review of the mechanics shows this flawed approach will not apply additional pressure to the intended sealing mechanism, i.e. the cone shaped ferrule. Rather, this approach, (final tightening by the cap) forces the tip of the tubing to the bottom of the port, where it cannot seal. No provisions had been made in the design of the initial CPI port by Parker Hannefin, and other manufacturers to use the idea of sealing at the tip as a sealing mechanism.

To alleviate (or partially alleviate) the potential damage to an HPLC system by overtightening with tools (such as vise-grip pliers). The Best Instrument implementation of US patent 5582723 patent contains features described in US patent 9217522. Nmely, the grip ring is attached in a breakaway fashion, such that excessive tightening force is very unlikely to result in a broken fitting which could ruin the HPLC instrument. Addittionally, the cap is of a smaller diameter, and having a fine knurl to imply to the customer the relative tightening forces. Additionally, the internal ferrule is crimped on, not soldered, or brazed, therefore, it will slide and ruing the fitting instead of damaging the HPLC instrument.

Alternate embodiment of 'Slip-Free' derivative
Figure: Prototype 'OEM fitting' manufactured for Dionex

Another type of 'Slip-Free' derivative is shown as item 4 in the figure above. This type was developed as a result of a request by Dionex Corporation in 2007 (prior to the Thermo acquisition of Dionex). The design objective was for small diameter fittings with the dispersion charachteristics ot the 'Slip-Free' technique. It was known by Dionex at this time the Ultimate 300 system (which was in early design phase) could not meet overall system design expectations due to the lact of adequatly low dispersion fittings. This OEM fitting was offered because Best Instrument could not bring the TSip™ method to validated high production volumes in the desired timeframe. The TSip™ method was available in 2007, and is described in patent applications which would lead to US patent 8006367. Nevertheless, the OEM style fitting did enjoy significant sales, and are still available through Supelco and other distributors.

'OEM fitting'
Figure: 'OEM fitting' post-prototype form

Labeled simply as the 'OEM fitting', the internal ferrule was crimped into place using a small drimping tool, shown, and available as a separate item. This ability to crimp the Slip-Free sytle of fitting on to any length of tubing desired, and to install in the field, is a feature which is viewed as too cumbersome for the average user. The product is seen as filling the original role (by system integrators) as a high pressure non-slip type fitting for HPLC, limited UHPLC, and 'PREP' applications.

Column switcher upgrade kit
Figure: Column switcher upgrade kit

These color coded first generation fittings were developed for a column switching application. Each color represents a column inlet, and the corresponding outlet. The fittings in this case are the fitting described in US patent 9217522. The selective use of aluminum for the grip ring and cap allows these components to be anodized and dyed in a variety of colors. Additionally, the anodizing technique is very conducive to laser engraving, allowing markings to meet the durability requirements of MIL-STD-130.

Nuts for column switch kit
Figure: Color coded HPLC nuts for column switcher application.

Additional 'First Generation' configurations were developed but in light of the Patent Pending status of the 'Gemini' styles (2 and 2A in the figure), and the notion that the entire first generation could become obsolete by the Tip Sealing teachings in the patent applications, most development work for the first generation was toward improved manufacturing speeds and cost reduction in order to supply demand. The more future-thinking product development work was toward the TSip™ method.

As of 2016, 'First Generation' configurations are available, but strongly discouraged for new method development, as TSip™ fittings are now available for HPLC, UHPLC, and other techniques.

Gemini holds PEEK and PEEKSil over 10,000 PSI

Gemini holds PEEK and PEEKSil over 10,000 PSI

Gemini Exploded View
Figure: Gemini fitting, exploded view
The 'Gemini' fitting, so called because it employs a pair of high performance ferrules, employs a unique tightening mechanism to acheive far greater holding force on PEEK and PEEKSil tubings with lessened chance of tubing deformation. This is considered to be a 'First Generation' fitting because there is a possibility of tightening, acheiving a leak free seal, and yet to retain the uncertainty of dispersion associated with the cylindrical volume about and below the tubing which extends below the primary (cone shaped) sealing ferrule. Despite this attribute, skilled operators can acheive certain high pressure bio-compatible separations which were previously impossible.

"Better Nut" fittings, a conventional 10-32 HPLC nut with additional features.

"Better Nut" fittings, a conventional 10-32 HPLC nut with additional features.

Better Nut
Figure: Better Nut

The 'Better Nut' style fitting is so named because it has two additional design features which are thought to make it 'better'.

The first feature is a wide flare where the tubing exits the nut, giving a wider bend radius, which reduces the likelyhood of a serious crimp in the tubing.

The second feature is the unique 'knurl-hex', or 'hex-knurl' portion of the nut. This allows installation by initial finger tightening using the hex portion, follwed by wrench tightening using the hex portion. While not a 'ground breaking' innovation, grippig a circular object for initial insertion porvides better tactile feedback during this crutial phase where 'cross-threading' is a possibility. In a pre-better-nut design, (without the knurled area), one would insert using the hex portion, which gives a slightly more confused tactile feedback.