Abstract: In this paper, the effect of process analyzer selection and positioning on plant-wide process monitoring is investigated. A fundamental problem in process analytical chemistry is the incomparability of different instrument characteristics. A fast but imprecise instrument is incomparable to a slow but precise instrument. Theory is developed to overcome this problem by using an abstract definition of a process analyzer. This, definition allows us to. put all instrument characteristics for a particular monitoring task on an equal footing. This results in a measurability factor M that expresses monitoring performance of any process measurement by combining instrument characteristics such as precision, sampling rate, grab size, response correlation, and delay time. Both the choice of location and the performance characteristics of different process analyzers can be evaluated busing the measurability factor. The unifying nature of the measurability factor allows for a rational decision between completely different process analyzers and locations (Smilde et at., in this issue). The theory is illustrated and validated with an experiment. A tubular reactor for free-radical bulk polymerization of styrene is monitored by in-line short-wave near-infrared spectroscopy at different positions. Alternatively, product samples are collected for at-linle near-infrared analysis. Both analyzers measure styrene monomer concentration. The analysis results are used, to predict conversion as well as number and weight average molecular mass of the polystyrene reactor product. The theoretical measurability factors for this, case study correspond well with the experimental findings. An ever-increasing number of process analyzers are implemented in the chemical in uistr. At the same time, the diversity in techniques suitable for harsh process conditions-e.g., chromatography (near)-infrared, and Raman or (low-field) nuclear magnetic resonance spectroscopy, mass spectrometry, flow injection analysis, an ultrasonic analysis, to name just a few grows steadily. The implementation and operation of analytical in process measurements is, however, still relatively expensive.

Abstract: With the current popularity of second-order (or hyphenated) instruments, there now exists a number of chemometric techniques for the so-called second-order calibration problem, i.e. that of quantifying an analyte of interest in the presence of one (or more) unknown interferent(s). Second-order instruments produce data of varying complexity, one particular phenomenon sometimes encountered being that of rank overlap (or rank deficiency), where the overall rank of the data is not equal to the sum of the ranks of the contributing species. The purpose of the present work is to evaluate the performance of two second-order calibration methods, a least squares-based and an eigenvalue-based solution, in terms of their quantitative ability and stability, as applied to flow injection analysis (FIA) data which exhibits rank overlap. In the presence of high collinearity in the data, the least squares methods is found to give a more stable solution. Two-mode component analysis (TMCA) is used to investigate the reasons for this difference in terms of the chemical properties of the species analyzed. The success of second-order calibration of this data is found to depend strongly on the collinearity between the acidic and basic time profiles and the reproducibility of the pH gradient in the FIA channel, both of which are shown to be related to the pK(a) values of the species.

Abstract: In this paper, different three-way methods are tested for their power and shortcomings to solve complex second-order calibration problems. The generic calibration problem is quantifying for an analyte in the presence of an unknown interferent: a second-order calibration problem. Due to rank restrictions of the data, standard second-order calibration methods like Generalized Rank Annihilation cannot be used to solve the type of complex second-order calibration problems shown in this paper. Different real examples are tested in which it is shown that the three-way methods can, to a certain extent, deal with the complex calibrations. This stresses the fact that all second-order calibration methods should be regarded as three-way methods, and when put in this framework, can be compared with respect to their performance.