Automated Sample Preparation - Analytical Chemistry (ACS


Automated Sample Preparation - Analytical Chemistry (ACS...

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Instrumentation Donald A. Burns Technicon Industrial Systems 511 Benedict Avenue Tarrytown, NY 10591

Downloaded by UNIV OF CAMBRIDGE on September 10, 2015 | http://pubs.acs.org Publication Date: October 1, 1981 | doi: 10.1021/ac00235a810

Automated Sample Preparation Scene I: Analytical laboratory, mid-morning: Carl Chemist (scowling): "Blast! This analysis can be done in five minutes, but it takes 20 minutes to get each sample ready. I'll be here all night!" Anabelle Analyst (equally dejected): "You think that's bad? The cleanup procedure for these samples requires nine different steps and a ton of glassware to wash. There must be a better way!" Scene II: Same laboratory, several weeks later:

This brief dialogue addresses two important problems facing the analytical chemist: the labor-intensive aspect of sample cleanup prior to analysis and the inefficiency that results when sample preparation and sample analysis operate in different time frames. These two analysts, and most of their colleagues, surely have sufficient reason to squawk when they discover that many so-called fully automated methods have all but ignored the major effort required for manual sample treatment prior to sample introduction into the system. Analysts want access to an instrument that will accept unmeasured, untreated samples at one end and provide a full report, in correct concentration units, at the other end, requiring no operator involvement beyond keeping the reagent bottles full. Such instruments (see Figure la) do exist and have been described for gas chromatography (GC) (1), and more recently for high performance liquid chromatography (HPLC) (2). Inside these analyzers several types of operations may be performed, some examples of which are shown in Figure lb. But not all instruments are fully automated, nor should they be. It is often advisable to stop part way through the procedure and insert an additional step: temporary storage. Figure lc illustrates such a pause: a 0003-2700/81/A351-1403S01.00/0 © 1981 American Chemical Society

Carl (smiling): "Say, this off-line sample prep unit is great! The instrument processed 40 samples overnight, unattended, and the analyzer can now handle them at 12 per hour. They'll all be finished by noon!" Anabelle (equally ecstatic): "You think that's good? Take a look at this machine: It's doing the entire sample cleanup by itself, with no dirty glassware, and the RSDs are lower than I used to get. Thank goodness for automation!"

Figure 1 . A n a n a l y t i c a l i n s t r u m e n t : (a) t h e a n a l y s t ' s d r e a m ; (b) t y p i c a l o p e r a t i o n s ; (c) t w o m a j o r divisions (a) Sample-».

Analyzer

(b) Analyzer 1. 2. 3. 4. 5. 6. 7. 8.

Sample Definition Sample Reduction Physical Cleanup Chemical Modification Separation Chemical Modification Detection Data Manipulation