Single-element optimum condition

In order to obtain the optimum power of detection, the analyte density in the plasma, the ionization and the ion transmission must be maximized. The power will thus be between 0.6 and 2 kW and the sampler at about 10-15 mm above the tip of the injector. The detection limits, obtained at single element optimum conditions differ considerably from those at compromise conditions, but are still significantly lower than in ICP-AES (Table 17). In general it can be said that for the heavy elements, which have complex atomic term schemes and accordingly very... 

Power of Detection. For optimum power of detection, the analyte density in the plasma, the ionization, and the ion transmission must be maximized. The necessary power is 0.6-2 kW with the sample ca. 10-15 mm above the tip of the injector. The detection limits, obtained at single element optimum conditions, differ considerably from those at compromise conditions, but are still considerably lower than in ICP-AES (Table 6). For most elements they are in the same range, but for some they are limited by spectral interference. This applies to As ( As" with Ar CF), Se ( Se with Ar Ar ), and Fe ( Fe with Ar O ). The acids present in the measurement solution and the material of which the sampler is made (Ni, Cu, etc.) may have considerable influence on these sources of interference and the detection limits for a number of elements. The detection limits for elements with high ionization potential may be even lower when they are detected as negative ions (for CF Cl = 5 ng/mL and for Cr Cl = I ng/mL). 

Highly diastereoselective alkylation at C-2 of benzo-l,4-diazepin-3-ones 41 was accomplished in 40-85% chemical yield using an (R)-phenylglycinol moiety at N-4, as the chirality-inducing element (Scheme 10) <2005EJ01590>. The optimum conditions involve deprotonation of 41 with 2 equiv of -BuLi at — 40 °C and alkylation at — 78 °C to give products 42 with 86-96% de. A single crystal X-ray diffraction analysis of the methylated derivative determined that the major product formed was the 2-(R)-isomer, as depicted in the product 42. 

In an element of catalyst dW the production rate per unit mass is FdxjdW. Hence Eq. (12-1) states that optimum performance is attained in the element when Tp is at a maximum. For the entire reactor to operate at optimum conditions the rate should have its maximum permissible value at every axial position. This concept has been used to predict optimum temperature profiles for single exothermic reversible reactions. ... 

Most commercial AAS systems have the monochromator, optics, and detector designed for the measurement of one wavelength at a time they are single-element instruments. There are a few systems available that do perform multielement determinations simultaneously, using an Echelle spectrometer (discussed in Chapter 2) and a bank of HCLs all focused on the atomizer. The limitation to this approach is not the sources or the spectrometer or the detector, but the atomizer. The atomizer can only be at one set of conditions, and those conditions will not necessarily be optimum for all of the elements being measured. There will be a tradeoff in detection limits for some of the elements. 

Blades and Horlick 1981a,b, Furuta and Horlick 1982). These latter lines are, therefore, used less often, although there are some elements (e.g., alkali metals) which do not have practical alternative lines. Nevertheless, there is no other excitation source for which a single set of operating conditions is so nearly optimum for such a wide range of elements. 

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