Evaluation of Accuracy in Photometric Analysis

Abstract

In light absorption spectrometry, plotting the data in the form of absorptancy against logarithm of concentration has important advantages over other plotting methods. For many instruments and operating techniques, the optimum range can be defined by inspection of the curve, as it is the concentration range in which it has its steepest slope. The maximum attainable accuracy is easily derived from the slope of the curve; the very flat portions of the curve at low and at high absorptancy emphasize the importance of selection of proper range if best accuracy is to be realized.Various methods of accomplishing measurement in the optimum range are discussed. For systems conforming to Beer's FROM time to time during the past several years, various authors have discussed the errors involved in photometric methods of analysis. Twyman and Lothian (30) showed that the minimum error occurs

Carotenoids in Man. The Distribution of Epiphasic Carotenoids in Atherosclerotic Lesions 1

“…Recoveries of added carotenoid to aortic powder ranged from 88 per cent to 93 per cent regardless of whether the initial content was low or high, respectively. The high range of analytical error found in samples with low carotenoid content resulted from production of insufficient color to stay in the effective range of the instrument (14).…”

Problems associated with the need for standardization in clinical spectrophotometric and fluorometric measurements

“…Near this tran s mittance Beer's law calculation s yi eld the lowest relativ e conce ntration e rror (IlC/C) for any give n uncertainty in tran s mission meas ure ment [18,19]. Willard , Merritt and De an [20] show the relative conce ntrati on e rror, res ultin g from a tran s mittan ce meas ure me nt un certainty of 0.4 pe rcent, to range from 8.2 percent at 0.95 T through 1.1 percent at 0.40 T to 8.7 percent at 0.01 T.…”

Development of Alternative Methods for Determining Soil Organic Matter

“…Thus, industries and other generators, such as Embrapa, have been seeking clean alternatives that eliminate or minimize the generation of chemical residues. This trend of clean innovation was called Green Chemistry, and among its main principles, it presents: (i) the prevention of residues generation; (ii) the economy of atoms or development of synthetic processes; (iii) the design of safe products; and (iv) intrinsically safe chemistry for accident prevention (Ayres, 1949;Lenardão et al, 2003;Prado, 2003;Silva et al, 2005).…”

“…By Ringbom curve (Ayres, 1949), set for x [Cr 3+ ] Absorbance, built with concentration samples of contrasting SOM, it was possible to identify the linear region of the method (Figure 1). Due to linearity deviations of Lambert-Beer Law at low and high concentrations (Harris, 2005), it was possible to set an equation of 3 rd order whose derivative is an equation of 2 nd order which has as the "x vertex" 0.089 mol L -1 of Cr 3+ , the point of maximum sensitivity.…”