Values below the limit of detection winnonlin

For any given instrument suitable fortransmission measurements, the sensitivity depends upon themedium, the wavelength, and the path length of the radia-tion through the medium. The latter is the slope of acalibration graph at the concentration of interest, while theformer is the minimum concentration at which an analytecan be detected. Accepted criteria in instrumental analysis, thatdescribe these necessities are the detection limit and cali-bration sensitivity of a method. In every chemical analysis, it is important and desirableto detect and determine as low as possible concentrations ofan analyte. Keywords: Limit spectrophotometry Beers law 1,10-PhenanthrolineД¬onventional spectrophotometry, based upon measure-ment of light transmission through appropriate solvents andanalyte solutions, is a well known and widely applicableinstrumental technique in analytical chemistry and otherbranches of science in which chemical analysis informationis required. Also discussed is why and to what extent molecular fluorescence methods are more sensitivethan molecular absorption methods. Determination of iron in a reference material,using 1,10-phenanthroline as the chromogenic reagent, was chosen as an example to demonstrate the suitability of the proposed method andclarify several important statistical questions. The analyte concentration is found from a calibration graph, based uponBeers law or the approximate formula P0P = 2.303P0bc, which is valid for dilute solutions.

The source of the radiant power (P0) is not the xenon lamp but the fluorescence or scatteredradiation from the holder cuvette filled with an appropriate solution.

One cell only is used to measure standards or unknown solutions, placed between the standard holder cuvetteand the emission monochromator of the instrument. Transmission measurements (incident light power, P0, or transmitted, P) are performedwith a fluorescence spectrometer. DemertzisДepartment of Chemistry, Analytical Chemistry Laboratory, University of Ioannina, Ioannina 45110, GreeceReceived 23 October 2002 received in revised form 18 March 2003 accepted 16 April 2003ДЄn efficient, more sensitive and accurate spectrophotometric process is possible and can be used to obtain qualitative or quantitative resultsfor analytes at limiting concentrations lower than usual. Low detection limit spectrophotometryMavroudis A.

Values below the limit of detection winnonlin