Uncertainty in modern spectrophotometers

Noise analysis for CCD-based ultraviolet and visible spectrophotometry

“…Source fluctuation noise behaves in a similar statistical manner to shot noise, being white noise with a Poisson distribution in the rate of arrival of photons [24]. Together source fluctuation and shot noise follow the generalised Equation (6). Unless the transmitted intensity is very low, source fluctuation noise tends to dominate shot noise.…”

“…An authoritative study into spectrometer noise was that of Rothman et al using a single beam molecular absorption spectrophotometer (EU-701A, GCA McPherson Corp.) [5]. It was still considered as such more than thirty years after publication [6,7]. More recently studies have been carried out to characterise spectrometer developments such as diode arrays, photomultiplier tubes and CCDs [6,8,9,10,11].…”

“…Noise phenomena from other parts of the system such as sample chamber repositioning error play a significant role [5,6], but this study predominantly deals with noise in the spectrometers themselves. Shot noise is included as it is fundamental to any light measurement system [9].…”

Uncertainty in CCD detectors with and without cooling devices when used for molecular fluorescence measurements

“…2a, inset), but also a very important systematic component. In uorescence measurements, the systematic component (spatial uncertainty) is compensated for by experimental operation according to eqn (3), whereas the random component (temporal uncertainty) follows eqn (6). Thus, only a part (but not the most important one) of the apparent uncertainty in Fig.…”

“…3,4 UV-visible absorption and uorescence have different working conditions; the former is usually used under high light level conditions in the detector, whereas low signals in the detector are commonplace in uorescence measurements. Thus, the factors affecting the uncertainty in the signal may be different in both cases, and uncertainty studies on absorption 5,6 may not apply to uorescence. The same theoretical bases dictate uncertainty in both situations, and they were established long ago; 1,[7][8][9][10][11] however, it is difficult to nd laboratory data to back them up in the case of uorescence.…”