Incremental addition technique

Figure 4.24. Estimated concentration of ion using the standard addition technique with an ion-selective electrode. The simulated signal traces are for DVM resolutions of 1, 0.1, 0.01, resp. 0.001 mV (left to right). For each resolution the added volume V2 is varied from 2.4 to 2.55 ml in increments of V2 = 10 /rl. The ordinate marks indicate the 95-105% SLs. The expanded traces for 0.1. .. 0.001 mV resolution are also given. The simulation was run for five different values of 0 = 300 + RND [mV]. The vertical drops (e.g., A B) occur at...

To prove that under these conditions, the IB polymerization is living, a monofunctional analogue of 1,2-p-methoxyphenyl-2-methoxypropane, was used to study the kinetics by incremental monomer addition technique. Results of this study indicated Hving polymerization with slow initiation [61,62]. 

The chemical speciation of copper in river water and model solutions was investigated by a titration technique in which cupric ion activities were measured at constant pH as the total copper concentration ([Cujoj]) was varied by incremental additions of CUSO4. pCu(-log cupric ion activity) was measured with a cupric ion-selective electrode (Orion 94-29) and pH with a glass electrode (Beckman 39301) both coupled to a single junction Ag/AgCl reference electrode (Orion 90-01) in a temperature controlled (25 + 0.5°C) water bath. Total copper concentrations in the titrated solutions were determined directly by atomic absorption spectrophotometry (Perkin Elmer 603) using a graphite furnace (Perkin Elmer 2200). Measurement of total copper concentrations is necessary because of adsorptive loss of copper from solution onto container and/or electrode surfaces. 

Quantitation by the standard addition technique Matrix interferences result from the bulk physical properties of the sample, e.g viscosity, surface tension, and density. As these factors commonly affect nebulisation efficiency, they will lead to a different response of standards and the sample, particularly with flame atomisation. The most common way to overcome such matrix interferences is to employ the method of standard additions. This method in fact creates a calibration curve in the matrix by adding incremental sample amounts of a concentrated standard solution to the sample. As only small volumes of standard solutions are to be added, the additions do not alter the bulk properties of the sample significantly, and the matrix remains essentially the same. Since the technique is based on linear extrapolation, particular care has to be taken to ensure that one operates in the linear range of the calibration curve, otherwise significant errors may result. Also, proper background correction is essential. It should be emphasised that the standard addition method is only able to compensate for proportional systematic errors. Constant systematic errors can neither be uncovered nor corrected with this technique. 

Gas adsorption is the standard technique to study the textural properties of porous solids (ref. 1). The classical technique is based on incremental additions of gas providing a discret set of points along the isotherm. This technique can be referred as a "discret technique. It appears to be limited and time consumming when high accuracy is required. This is especially true in the case of microporous solids. To overcome this intrinsec limitation, "continuous" adsorption techniques have been developed. In these techniques the adsorbate is admitted to the sample tube at a slow flow rate. As it is critical to maintain, at any given time, the adsorption equilibrium, very low adsorbate flow rates must be used. 

In the incremental or decremental technique, another designation for the standard addition (or subtraction) technique, one adds increments of standard solution to the sample, or vice versa. (In the decremental technique the standard precipitates or complexes the ion under test.) When the sample itself is incrementally added to the standard, the latter may have received a previous addition of ISA and/or pH adjuster, but in the reverse method this addition may be made to the sample. However, for the specific example of a univalent anion we shall show how the normal incremental method works38 and that in fact the addition of ISA is not necessary. 

As can be seen from the table, the number of AOs increases rapidly with the cardinal number X. Thus, with each increment in the cardinal number, a new shell of valence AOs is added to the cc-pVXZ set since the number of AOs added in each step is proportional to X2, the total number (Nbas) of AOs in a correlation-consistent basis set is proportional to X3. The core-valence sets cc-pCVXZ contain additional AOs for the correlation of the core electrons. As we shall see later, the hierarchy of correlation-consistent basis sets provides a very systematic description of molecular electronic systems, enabling us to develop a useful extrapolation technique for molecular energies. 

Karl Fischer reagent analy chem A solution of 8 moles pyridine to 2 moles sulfur dioxide, with the addition of about 15 moles methanol and then 1 mole iodine used to determine trace quantities of water by titration. karl fish-or re a-jont Karl Fischer technique analy chem A method of determining trace quantities of water by titration the Karl Fischer reagent is added in small increments to a glass flask containing the sample until the color changes from yellow to brown or a change in potential is observed at the end point. karl fish-or tek nek kauri-butanol value analychem The measure of milliliters of paint or varnish petroleum thinner needed to cause cloudiness in a solution of kauri gum in butyl alcohol. kail-re byut-3n,ol, val-yu ... 

In addition to ICP-MS for the multi-element analysis of aqueous solutions, LA-ICP-MS allows the direct determination of trace elements in biological samples and due to this feature it is a well suited analytical technique for microlocal analysis with spatial resolution. In 1995, Outridge el al.lg reported on the performance of an LA-ICP-MS analysis for studying incremental biological structures as archives of trace element accumulation. The use of LA-ICP-MS for several biological (and environmental) applications is reviewed by Durrant and Ward.19 Selected examples for determination of trace elements and species in biological samples are summarized in Table 9.25. 

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