Evaluating Laboratory Performance of Spectrophotometers
A group of concentration-related absorbance curves reports give idonnation about the perfomawe of individual for solutions of potassium dichromate were examined btnments. Measurements from different spectrophotomi n order to evaluate the performance of a single spece h s have been compared using wire screens (16, 17, 18) trophotDmeter or a number of instruments The abfilters (l9-26), and solutions of absorbing materials (27-47). sorbance measurementsfor a set of 2OIlavrlengths in the interval Pot0 400 mF are arranged in the form d a The objective of such cooperative experiments has been to matrix and characteristic vector analysis i s used to ewmine the variability of malting spectrophotometrc masdetermine its rank. The matrix rill be rank one if measurementsare made with a single 7 menents under laboratoxy working conditions; and useful eschmatg of precision within and among instruments have eter i n good working condition and rank two if the beenobtainedfromsuchstudies. Usuallythemeasuranents measurements come from two or more instruments. Improperly adjusted spectrophobm&ws and unhave been made at a few isolated wademgths corresponding controlled experimental techniques mil produce tothemaximum or minimum in an absorbance curve. Measlnatrias of greater rank. The first characterislic ummmts 011 the sides of an absorbance band have seldom vector is related to an absorbance shift d the a b been studied, probably becaw they are more sensitive to sorbancec u m and transformed variates, using this vector, are used totest Beer's law nlatioashipr The valia~inwa~caliitions. second characteristic vector is relatedto a w a d e q f h This paper explaim a procedure for examining& behavior shii of the absorbance curves and is used tm check of complete absorbance curves from a single spctrophofor deviations i n warekngth calibration. taneteroragroupof- . ts. Theproceduredepends rrpon the fact that certain matrix algebra opepations can be psed to deted abnormal variations in a set of con cent ratio^ rplated absorbance curves. other matrix operations check cadto Beer's law and deviations in wavelength caliition.
(16) F. R Bryan, Appl. Sprcfry., 17,19 (1%3). (17)J. M.VatrdenbeH,J. Opt. Soe. Am., 52,284 (1%2). (18) W.slavin,Z M . 52,1399(1962)(19) M.E Auabacb, E L.Bauer, and E C. Nachrod, Z n L Q d W conhol,20 (11X 45 (1%). (20) C X Dodd and T. W.West, J. Opt. k. Am., 51,915 (l%l).
(21) J. Fog and E
