122
ANALYTICAL CHEMISTRY APPLICATIONS AND INTERFERENCES
Table I.
Precision of Method in an Analysis of Variance
Error Blue sols a t 250 mp About regression
Sum of Squares
Degrees of Freedom
Mean Square, A
0.00110
4
0.000274
Within replications 0.00078 Total 0.00188 Blue sols at 287 mp About regression 0.00102
6 10
0.00013 0.000188
4
0.00026
Within replications 0.00159 Total 0.00261 Red sols a t 250 mp Aboutregression 0.000229
6 10
0.00027 0.00026
4
0.000067
Within replications 0.000194 Total 0.000423 Red sols a t 287 mp About regression 0.000314
6 10
0.000032 0.000042
4
0.000078
Standard Error, P.P.M.Te
F .
Z.l
0.32 i n
0.33
0.14
1.4 Within replications 0.000335 6 0,000057 Total 0,000549 10 0.000068 0.15 The error “about regression” represents deviations from Beer’s law (linearity). The error “within replications” represents errors not attributable to changes in tellurium concentration-e.g., errors in pipetting or reading absorbances. The “total” error includes both of the aforementioned errors and best represents the error in a determination in which a linear relationship (Beer’s law) is assumed for the data. The mean squares are variance estimates, 3’ for absorbances. The F values compare deviations from linearity with deviations within replications, a high F value indicating nonlinearity.
Elementary tellurium sols have been used in visible colorimetry and spectrophotometry for analysis of ores (12, IS), steels (a), industrial atmospheres ( 4 , 11) and biological material (4). Preliminary separations are usually indicated. Notable among methods for separating trace amounts of tellurium is coprecipitation of tellurium in selenium by hypophosphite followed by volatilization of selenium as the bromide (10). Reduction with stannous chloride is also useful (1, 2, 4, 7 ) . If stannous chloride is used, measurements should be made a t 280 to 290 mp, because of strong absorption by chloro t,in complexes a t shorter wave lengths. Other ions whose chloro complexes absorb in the ultraviolet are ferric, bismuth(III), vanadium(V), molybdenum( VI), titanic, cuprous, plumbous, mercuric, and thallous. rlbsorption spectra of these ions are given by Rogers et al. ( 3 , 9). In most cases, interferences can be eliminated by proper selechion of wave length for measurement. Alkaline earth ions and chloro complexes of chromic, nickelous, zinc, and aluminum ions do not absorb in the ultraviolet. Other general classes of interferences are strong oxidizing agents, agents which strongly complex tellurium, substances forming sols under similar conditions, and indifferent electroll-tes in concentrations greater than 0.5.W (8). LITERATURE CITED
shown in Figures 2 and 3. The wave length 287 mp is at the maximum; 250 mp is an arbitrarily chosen wave length not on an absorption plateau. There is no significant effect on reproducibility (standard deviation in parts per million of tellurium) from choice of wave length between 290 and 240 mp (Table I). Measurements made a t 260 and 240 mp further support this statement. In this greater freedom of choice of xave length lies a distinct advantage of the ultraviolet band over the visible band. The superior reproducibility of red sols recommends them for analytical purposes. All curves are linear according to analyses of variance-i.e., no significant F-values are found (Table I ) . Red sols give a negative intercept on the (soncentration axis, which becomes more negative with increase in wave length. In these sols, tellurium concentration of 2 p.p.m. or less tend to give low absorbances relative to the linear calibration curve. Reproducibility and linearity characteristics for the ultraviolet band are very similar to those for the visible band; the sensitivity is slightly less for the ultraviolet band.
(1) Brown, E. G., Analyst, 79,50 (1954). (2) Crossley, P. B., Ihid., 69,206 (1944). (3) DeSesa, 11. 4.,and Rogers, I,. B., Anal. Chim. Acta, 6, 534 (1952). (4) DeMeio, R. H., ANAL.CHEY., 20, 488 (1948). (5) “Inorganic Syntheses.” Vol. 2, p. 189, New York, 3IcGrawHill Book Co., 1946. ( 6 ) Johnson, R. A , , ANAL.CHEM.,25, 1013 (1953). , and Kwan, F. P., Ibid., 23, 851 (1951). (8) Johnson, R. A , , Kwan. F. P.. and Westlake, D., Ibid., 25, 1017 (1953). (9) AIerritt, C., Jr., Hershenson. H. &I., and Rogers, L. E., Ibid., 25, 572 (1953). (10) Southern, H. K., Rept. B:-606, May 31, 1915, cited in Natl. Nuclear Energy Ser.. Div. 1’111, 1, Anal. Chem. Manhattan Project, p. 318, New York, NcGraw-Hill Book Co., 1950. (11) Steinberg, H. H., Massari, S. C., Miner. A . C., and Rink, R., J . I n d . Hyg. Toxicol. 24, 183 (1942). (12) Volkov, S. T., Zavodskaya Lab.. 5, 1429 (1936). (13) Zemel, V. S., Ihid.. 5, 1433 (1936). RECEIVED for review June 9, 19
