ACOMP detector train

Any detector that has a flow cell can, in principle, be used in ACOMP. Conductivity and pH probes are simple, inexpensive examples of this. In facf these latter probes can often be inserted into the reactor, so that they need not be part of the ACOMP detector train and hence do not require flow cells. In such cases, it can be very valuable to add in situ data from these probes to the ACOMP data for determining other reaction characteristics. 

Comonomer Concentrations An important innovation made by the addition of a full spectrum UV spectrophotometer into ACOMP detector train led to the determination of the instantaneous concentration of each comonomer during the reaction, in the case of the copolymerization of comonomers with similar spectral characteristics [19, 20], The working assumption was that a UV spectrum at any instant is a Unear combination of the normalized basis spectra of the comonomers, the copolymer, and any other UV absorbing species, and that the unknown comonomer concentrations can be foimd by minimizing the error between measured and computed spectra over many wavelengths, even when spectral diffaences are small at any iven wavelength. 

The ACOMP detector train provides m(t), mjit) is computed via the previous equation. m (t) is then obtained from Equation 13.50, and c (t)=m (t)IV(t). Density changes, while measurable, are usually small (negligible in this section, due to the very low Am concentration), and are not corrected for in this work. They have been addressed in the ACOMP context earlier [49, 97]. 

The ACOMP front end is the ensemble of pumps, mixing chambers, filters, and conditioning steps that prepare the continuous highly dilute and conditioned stream and deliver it to the detector train. Lag times between withdrawal and detection are typically from 10s to 100s of seconds, with... 

Advantages of ACOMP include its versatility as a generalized approach, its ability to make fundamental measurements without recourse to empirical models and calibration, its capacity for providing a data-rich stream of complementary information from multiple independent detectors, yielding multifaceted characteristics of polymerization reactions, and its use of the front end to extract, dilute, and condition a sample stream that allows sensitive detectors to provide reliable data without exposing them to harsh reactor or sample conditions. Disadvantages include the mechanical complexity of the front end, the delay time between a continuous fluid element s extraction from the reactor and downstream measurement by the detector train, and a small but continuous waste stream. ACOMP is more invasive than probes that can be placed at an outside reactor window, but are no more invasive than in situ probes, in that in either case access to the reactor contents is required. 

ACOMP Delay Time and Response Time Because ACOMP involves continuous withdrawal, dilution, and conditioning of reactor liquid, there is inevitably both (i) a delay time between when a fluid element is withdrawn and when a measurement of its properties is made by the detector train, and (ii) a system response time associated with the various mixing processes involved. 

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