Iron, determination

Ionization chamber pulses, 51, 59, 60 Ionization chambers, 49-52, 93 Ion pairs, 48-50 Ion tubes, characteristics, 3, 4 Ion yield in counter tubfes, 50, 51 Iridium, determination by x-ray emission spectrography, 328 Iron, determination by x-ray emission spectrography, 222, 328 in cements, 260, 261 in domestic ores, 200, 202, 203 in hi h-temperature alloys, 179-183 in solution, 185, 255... 

A second unusual EPR spectrum was observed in the oxidized (as-isolated) protein (Fig. 3). This spectrum, which was assigned to an S = z system, was not reminiscent of any Fe-S cluster. Indeed, with g-values of 1.968, 1.953, and 1.903, it looked more like a molybdenum or tungsten spectrum. However, chemical analysis ruled out the possibility that this EPR spectrum arose from Mo or W, and the spectrum was assigned to an Fe-S center instead. The spin concentration, however, was sub stoichiometric and sample-dependent. Furthermore, when the as-isolated protein was oxidized with ferricyanide, it became EPR silent. This, together with the iron determination and the fingerprint of the reduced protein, led Hagen and colleagues to the... 

Finally, a disagreement was noted between the iron determination results, which showed the existence of only 5 to 8 iron atoms/mole-cule, and the above analysis. As a solution to this discrepancy, it was proposed that the samples could contain a mixture of holo- and apoprotein. 

Figure 14 also demonstrates the principle that sometimes extraction into an organic solvent increases the intensity of the color. This is true, for example, for ferric thiocyanate, where extraction into an organic solvent will increase the sensitivity of iron determination to that obtainable with the phenanthrolines. The advantage of the iron ferric thiocyanate method in organic solvents is the fact that it is insensitive to pH changes, which is not true for the phenanthroline procedures (19). 

Fischl, J Serum iron determination using direct color... 

This can be done with the use of a gravimetric factor. Examples include the sulfate and iron determinations in the experiments at the end of this chapter (see Experiments 6 and 7). 

Dr. Spijkerman I still feel we should have a doublet because it is so time consuming to set up a spectrometer for iron, determine the velocity calibration, and then have to take oflF the source, change the detector and everything around to do a tin measurement. If we can get a standard for tin I think we should have a doublet that makes a velocity calibration possible. I would like to see a doublet that has approximately 3 or 4 mm./sec. (quadrupole) splittings—artificial if need be. 

Monitoring Serum iron determinations (especially by colorimetric assays) may not be meaningful for 3 weeks serum ferritin peaks after about 7 to 9 days and slowly returns to baseline after about 3 weeks. 

S. Salomon, P. Giamarchi and A. Le-Bihan, Desirability approach for optimisation of electrothermal atomic absorption spectrometry factors in iron determinations, Analusis, 28(7), 2000, 575-586. 

In the preceding iron determination, the results would be about 10% high because serum copper also forms a colored complex with ferrozine. Interference is eliminated if neocuproine or thiourea is added. These reagents mask Cu+ by forming strong complexes that prevent Cu+ from reacting with ferrozine. 

Figure 18-6 Calibration curve showing the validity of Beer s law for the (ferrozine)3Fe(ll) complex used in serum iron determination. Each sample was diluted to a final volume of 5.00 mL. Therefore, 1.00 pg of iron is equivalent to a concentration of 3.58 x 10 6 M.

D. C. Harris, Serum Iron Determination A Sensitive Colorimetric Experiment, J. Chem. Ed 1978, 55, 539. 

Figure 2. Iron determination illustrating silicon interference...

Resistance towards Acids.—1 gram of the material is digested with a litre of 1% sulphuric acid with occasional shaking, a few c.c. of the clear liquid being withdrawn every 24 hours and the dissolved iron determined. 

If a new sample is used for the determination of pyrite iron, the iron determined by these procedures represents the combination of the pyrite and nonpyrite iron. The amount of nonpyrite iron must then be determined separately and subtracted from the amount determined. If the residue from the sulfate determination was used, the iron determined by the foregoing procedures represents the pyrite iron. Once the correct value for the pyrite iron is determined, the pyrite sulfur is calculated using the following expression ... 

But there was such iron determination in his posture, sat up there, flicking the reins and urging the horses on a little faster, that Alexander could not imagine any fear in the familiar lines of his face, currently blocked from view. 

The Pacific Scientific (PSCO) simple regression analysis, based on Draper and Smith (il) was applied to the absorbance data itself and to the 1st and 2nd derivative data using as constituent data total iron determined by XRF, and water by gravimetric measurement. Regressions reported here were performed at the wavelength selected by the computer as giving the best correlation and also at a number of additional wavelengths associated with prominent spectral features. 

For some iron determinations used in soil science, extracts may contain high dissolved solids contents or organic extractants which may cause a change in sensitivity. Careful matrix matching should always be used with such extractants. 

The lattice constant of a-iron determined from patterns of Armco-iron was found to be... 

Total iron determination by atomic absorption spectroscopy... 

Volumetric methods are largely employed for the rapid estimation of iron in solution. As a rule, the iron must be present in the ferrous condition, and any ferric iron must first be reduced, the reagents employed varying somewhat with the method of titration. If both the ferrous and ferric contents of a solution are required, the ferrous iron is first determined by titration, then the whole is reduced, and the total iron determined. Subtraction gives the amount of ferric iron originally present. 

The square data points show the ppb iron determined by ICP-MS, whereas the circular data points show the % phenol formed in each lot from visible ICH exposure (Table 5). The agreement between the two is excellent. Additionally, the % of drug A loss was examined for solutions of formulation 1 as a function of added Fe up through 1000ppb levels after full ICH visible light exposure (Fig. 10). 

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