High Throughput Instrumentation

Funded in part by the NSF

comments? Paul F. Endres

• Modern chemistry is dependent on instruments and our courses should reflect that
• Most instruments are expensive-- typically $10,000-25,000 for a basic instrument
• Instruments are generally not portable
• Instruments typically need about 5-6 foot of bench space

• Other universities often have smaller labs but will have several such rooms operating simultaneously
• ultimately, we need to provide for relatively large numbers of students

• class size is typically 8-12 students, working in pairs
• projects are sequenced so only one or two instruments of a given type are needed

If we are to provide instrumentation in the larger labs we need to select one of these situations

• limit our lab to relatively low cost instrumentation (pH, LED colorimeters) and provide separate equipment for each student or four each pair of students. This also implies small instruments which do not require much bench area.
  • We might note the a 2001-2003 project along this line-- the use of small, low cost handheld computers for laboratory data collection and analysis.
  • Information is available at the web site devoted to that project
• limit student exposure to an instrument demonstration or to the use of an instrument as part of a large group
• find instrumentation that can accommodate relatively large numbers of students per unit-- that is, high throughput devices.
  • we see this in a number of applications elsewhere-- the use of auto samplers on GC-MS or NMR instrumentation. This allows relatively large numbers of students samples to be run by a single instrument.

• Miniature diode array spectrometers
• Atomic Absorption Spectrometry
• Gas Chromatography with rapid columns

• This has turned out to be a very versatile form of instrumentation
• Cost is very modest when compared to conventional spectrometers
• These units are quite portable

The Atomic Absorption Spectrophotometer was a modest instrument (Buck 210SGV.)

• A given reading takes about 30 seconds, permitting relatively large numbers of students to use the instrument in a 30 minute period.
• Realistically, a class probably needs to produce a composite calibration curve, rather than having each student make 5 solutions and 5-15 measurements.
• This instrument could be moved (cycled) to areas of use, but this is awkward. It requires air, gas (acetylene) and ventilation facilities in each potential area of use.

• Altech produces a multibore capillary column, with approximately 1000 parallel channels on a single column.
• Each column has the resolution of a small bore capillary column
• The column can handle relatively large samples without the need for a split injector
• The sample is comparable with TC detectors (comparable to a packed column in sample size)
• High resolution allows good separation in relatively short periods. Retention times of 1-4 minutes are realistic.
• Temperature programming is traditionally the way of accommodating samples with a wide mixture of components. Unfortunately, such runs often involve considerable lost time during the post run, cool down cycle.
• The multibore column provides comparable changes in retention time by varying column head pressure and flow rate. (The van't demeter curve is relatively flat.) This enables a run to be performed at low flow rates and then stepped to a higher flow rate with a few timed valves. A simple pressure venting can prepare the GC for another run.
• This could allow up to 20 students per hour to get useful results from the same instrument.
  • the biggest difficulty has been the mismatch of components.
  • the intended GC's all had a detector volume that was too large for the column specifications and would degrade the capillary column resolution.
  • other GC's with suitable low volume TC detectors were are not available for testing of the pressure cycling plan
  • we could use the column on an instrument with Flame Ionization, but that's not a good choice of detector for introductory courses.
  • We were unable to provide a realistic test of these columns in a classroom environment.
    • concerns include the lifetime of the column with typical samples (these are expensive columns at about $750 each)
    • it is not obvious that a multibore column will age evenly. If difference occur between the various channels, we can expect to see serious peak broadening.
    • it is not clear from the literature if the pressure programming can be made to function in a manner that is as versatile as temperature programming.

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