Think about your old manual Spectronic 20, or your guide reading spectrophotometer which you use in your laboratory. You line up your samples in a row. In front of these, you put a few small sample cups or perhaps even a string of cuvettes, and you pipette a known quantity of sample to each cup. Then you add a reagent and mix the reagent and sample. You do this for each sample. You could have more reagents to include so that you repeat the entire procedure until all reagents are added. Then you start a timer.
When the timer beeps you know you have got a specific time window to read the absorbance or concentration of your own samples. You read by manually shifting the color-developed sample into a spectrometer cuvette, using a peristaltic pump to move the sample into a stream cell already in the spectrometer, or by adding the tube or cuvette which you used to create the sample color in. Then, you press a button to send the reading to a printer, a computer program, or you manually record the scanning on a laboratory worksheet. Can you shake and mix every sample precisely the same way each time? Are you going to mix them the exact same way daily? Will every analyst conduct them exactly the same way you have? Can there be color or turbidity in the samples? In case you zero your device with every sample, or just with reagent water blanks?
Is the Specific time you read the final absorbance critical?
The procedure described is what you are automating by using a different analyzer. Rather than lining up samples, you are pouring aliquots into sample cups that are set on an auto sampler tray. Rather than transferring a known quantity of sample what is hplc, the different analyzer does. Rather than adding reagents and mixing, the different analyzer does. Rather than starting a timer, the different analyzer does. Rather than reading the absorbance, recording the reading, and calculating a result the different analyzer does.
The analyzer has automated Just about all of the simple colorimetric techniques for you. Sample volume is measured and dispensed the exact same way, every time. Reagents are added and blended the same way each time. The timer is set and absorbance is measured the exact same way each time. Results are calculated precisely the same way each time. The different analyzer pipettes, dilutes, adds reagents, mixes, calibrates measures, calculates, and reports all for you. You pick a method by computer keyboard. There’s not any hardware to manually switch, no cartridge to rinse out, no baselines to track, no markup filters to change. Sample and reagent volumes are determined by a choice in a computer application, not by the inner diameter of a peristaltic pump tube.