Top Of The Glass: Bottletop Burettes are Indispensable in Today's Laboratory

Date: March 1, 1999 Table of Bottletop Burettes Dispensing precise quantities of aqueous solutions has always been one of the more frustrating and messy jobs in the laboratory. Limited by manual operations that require careful attention and a steady hand, dispensing and titrating fluids remains one of the least sophisticated and most common procedures in the laboratory, responsible for introducing margins of error that are not insignificant when considered over the course of multiple readings. Only recently, with the advent of bottletop burettes, could scientists dispense liquid while making precise measurements of fluid volume. Previously a four-step process was required: dispense the desired amount of liquid, carefully measure the given quantity, add or subtract the desired portion, and pour the remainder into the reaction vessel. This complicated and time-consuming process, which frequently results in drips and spills, has been reduced to a single step with the use of bottletop burettes. One needs only run the burette until the titrating endpoint is reached and then simply read how much has been dispensed. The combination of measuring and dispensing in a single stage significantly reduces the time it takes to run experiments. The following profile provides an overview of seven manufacturers and their respective contributions to mechanical burette technology. BrandTech Scientific's Digital Buret™ III BrandTech Scientific is the Essex, Conn. supplier of the Digital Buret™ III made by BRAND GmbH + CO, in Wertheim, Germany. This newest generation burette incorporates the reliability of its predecessors with the latest technology in liquid handling. One of the primary advantages of digital burettes over their glass counterparts is the ability to accurately measure meniscus levels. Gone are the days of pesky meniscus reading errors. With the Digitial Buret III, a digital readout ensures results with a resolution of 0.01 ml. The display can also be cleared to start a new titration without having to refill the cylinder. Sharon Dougherty, the laboratory director at Klein Family Vineyards, found that the techniques for reading meniscus levels varied considerably depending on the training and background of her technicians. "Leaky glass burettes with stopcocks that didn't completely hold fluid were unacceptable," said Dougherty. And despite the training of some of her technicians, there seemed to be an inherent difference in the way that some people read meniscus levels. She used the BrandTech Digital Buret to standardize meniscus readings and reduce variables. Her efforts have led to more reliable numbers and a consistent protocol that has been implemented at rival wineries Simi and Clos du Bois. Another distinct benefit of using the Digital Buret III is that it is untethered by lengthy power cords or recharging units. The lithium battery that powers the instrument is capable of performing over 60,000 titrations without charging. That amounts to 50 titrations a day for 5 years. The longevity of the battery is assisted by an adjustable sleep mode that shuts off the display when not in use. The Easy Calibration™ system is another innovation that enhances the speed and convenience of running an experiment. Instead of requiring laborious recalibration after a change in viscosity, or a visit to the nearest calibration lab for product support, the Digital Buret III is equipped with its own calibrating system. Calibration adjustments take place in seconds, allowing users to run their experiments rather than needlessly bothering with instrumentation. All units are shipped with a serial-numbered calibration certificate. BrandTech has also included a new SafetyPrime™ valve that eliminates the spurting of fluids that can occur when air and reagents are mixed. The valve removes bubbles from the instrument without wasting reagents and reduces the possibility of contaminating the work area with overspray. The removal of air bubbles from the line also ensures that the correct amount of reagent will be accurately dispensed. The Digital Buret III comes in 25 and 50 mL models, with adapters to fit most bottle threads, as well as an adjustable filling tube. Brinkmann Instruments Bottletop Buret The Brinkmann Bottletop Buret is manufactured by Walu Labortechnik GmbH and distributed by Brinkmann of Westbury, N.Y. The Brinkmann Bottletop Buret Models 25 and 50 have been designed from the ground up, in order to keep pace with the advancing field of liquid handling devices. Officially released in the first quarter of 1998, the Brinkmann burettes are some of the newest instruments to become available to a market that is growing increasingly sophisticated in its technology. The advantage that continuous fluid operation offers to researchers is the benefit of maintaining a safe and environmentally sound work environment. In the spirit of improving the general safety conditions of laboratory research, Brinkmann Bottletop Burets include a recirculating valve that eliminates wasting reagents by priming the burette internally. The dispensing volume is viewed on a digital display powered by standard alkaline batteries. This eliminates the errors of reading the meniscus and volume graduations of conventional burettes. The Bottletop Buret is easy to calibrate for fine adjustment of the volume when working with viscous or high-density solutions. In addition, the compact size of the instrument makes it an effective tool for use under vacuum hoods, unlike most glass burettes. One of Brinkmann's newest design features is a telescopic discharge tube that can be adjusted to easily fit into any vessel of all sizes. This low-tech solution to one of the nagging problems typical of burettes has made the instrument accessible from stirrers and hot plates that can be placed at a distance and connected by the burette's umbilical. The penlike tip of the filling tube can also be used at close quarters for narrow vessels and tubes. Jencons Scientific's Digitrate Digital Burette Jencons Scientific in Bridgeville, Pa., is the maker of the Digitrate™ Digital Burette. The Digitrate is available in two configurations, a 30 and a 50 ml model, both of which can be adapted to 33, 38, and 45 mm reservoirs using adapter accessories included in the basic purchase price of the instrument. Perhaps the most fundamental aspect of any measuring device is the assurance that it has been properly calibrated. Each Digitrate comes with a calibration test certificate that guarantees the instrument's accuracy at the time of delivery. In addition, the burette can be calibrated by the user and can be reset to factory default calibration. Precautions such as these can prevent costly mistakes. One feature unique to the Digitrate is a gearing mechanism that uses a piston. Unlike so-called plunger systems, the piston method reduces vibration and agitation of the bottle's contents while ensuring that the Digitrate remains primed and ready. Though the Digitrate has an array of systems designed to make titrating easier, one of the best ways to ensure that the burette will work properly is to keep it clean. In this regard, the Digitrate has been constructed from autoclavable PTFE and borosilicate glass and can be disassembled in 15 seconds. National Labnet's Titramax Digital Buret The liquid handling line of National Labnet in Woodbridge, N.J., and Kimble/Kontes in Vineland, N.J., includes Witeg Labortechnik's Digital Buret, a safe and reliable alternative to traditional glass burettes. This instrument is sold as the Titramax Digital Buret and the Titrex 2000 Digital Buret. The bottletop unit screws onto the threads of reagent bottles and draws titrant directly from the bottles, eliminating pouring of reagent and chemical spills - and a one-way filter protects the unit from harsh chemicals that might be introduced from the sample into the bottle. The volume dispensed is read directly from the large LCD display--there are no meniscus readings to deal with. The 50 ml volume of the burette allows multiple titrations to be carried out without refilling. Between titrations, the display can be set to zero and the user can recalibrate for liquids of different viscosities. One of the innovations exclusive to this instrument is its downloadable memory. Up to 500 titration values may be stored in the unit's memory and later downloaded to a PC for further manipulation with the optional TitraLink software package. Memory is retained during recharging of the battery, and portability of the burette is enhanced by an AC adapter/recharger. The Titramax/Titrex is also simple to use. Four buttons control the microprocessor functions, while wheels on the sides of the unit control the flow of reagent. Both a fine and a coarse control wheel allow for larger-volume titrations as well as drop-by-drop additions. Before use, air is purged from the system without reagent loss by the recirculating valve system. The valves also prevent dripping and accidental discharge when the burette is not in use. Pegasus Scientifics Bibby Sterilin Digital Burette Pegasus Scientific is the exclusive distributor of Bibby Sterilin's Digital Burette in North America. The Bibby Digital Burette is designed primarily for pharmaceutical applications where the instrument is used repeatedly with the same solutions. The purpose of the instrument is to produce consistent results over a long series of tests, performing identical functions on a day-to-day basis. Ron Trent, who is the product manager for Pegasus Scientific, suggests that U.S. manufacturers that are in the business of producing bottletop burettes are basically on a level playing field as far as quality is concerned. On the other hand, he generally holds the German and Swiss manufacturers in high regard, as they were among the first to certify their instruments according to an international standard. Having conceded the essential equality of bottletop burettes produced in the United States and Europe, Trent did allow room for minor differences in design and materials that would tend to suggest perceptible advantages among these instruments. One issue in par-ticular that he thought deserving of attention was the difference between Teflon and ceramic plungers. According to Trent, Teflon plungers have the tendency to "creep and move" with changes in temperature. He offered the Bibby burette's ceramic plunger as the solution to this problem. With an extremely low coefficient of expansion, the ceramic plungers are resistant to extremes of both heat and cold, giving a consistency of titration over repeated operations. PolyScience's CAT Liquid Processor System PolyScience, a division of Preston Industries in Niles, Ill., is the exclusive distributor of CAT M. Zipperer's Contiburette® and Liquid Processor® bottletop burettes. The unique relationship between the two companies was formed from a friendship that started in the 1960s between the founders of the two companies. The resulting alliance between PolyScience and CAT M. Zipperer has brought one of Germany's most advanced burettes into the United States. The Contiburette Motorized Continuous Digital Burette is a motorized burette with an auxiliary connection for an optional unique remote control system. Although the basic unit performs titrations and dipensing, the C4 Controller offers expanded functions such as preset volumes, repeat dosing, and automatic setting of volume, as well as a "flow rate" mode and a "memory" mode. A foot or hand switch can also be connected with a 6 foot cable for remote operation. In addition, the Contiburette can be connected to a parallel printer port for interface to a PC. An even more advanced "Four-In-One" Liquid Processor is also available. When connected to a PC/486 this unit is capable of documenting and evaluating experimental data and can interface with several instruments for daisy-chain configurations. One of the features that sets the Contiburette apart from its competitors, according to Eugene Panhorst, product manager at PolyScience, is that it has a stepper motor fastened to a rotary-axial piston, which permits very accurate continuous pumping of discrete amounts of liquid. He suggested that this method was superior to the syringe, or "piston," type of burettes. The housing and rotary piston parts of the Contiburette are also made from alumina which protects the instrument from corrosion. Visco Alpha is the U.S. distributor of the Titronic® 97, which is manufactured by Schott GmbH in Germany. Having carefully examined the market for bottletop burettes, the company estimates that 60% of the people in the world performing titration are using manual burettes. Company officials believe that by offering a low-cost mechanical burette, they will be able to enhance the speed and efficiency of laboratory research. Since its release two years ago, the Titronic 97 has sold over 500 units, and the company anticipates an increasing share of sales both at home and abroad. According to Eric Weinstein, product manager for Visco Alpha, the Titronic 97 is one-third the cost of some of its competitors. He contends that the application of its Titrisoft 2.0 software is one of the most powerful systems in the world for titrating and dispensing fluid. Weinstein also emphasized the relative ease and safety with which the Titronic can be used--an issue of no small concern for him as the victim of a buretting accident that almost removed his thumb. Instead of wrestling with long glass burettes, users of Titronic's push-button system avoid the juggling with beakers and funnels that still occupies a majority of the research community. Table of Bottletop Burettes

Top Of The Glass: Bottletop Burettes are Indispensable in Today's Laboratory

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