Photodiode detection

We have looked in detail at the analysis of nutrients in natural water, as this is of considerable interest globally, in terms of the overall effect on water quality, and in particular, the prevention of algal blooms which have become an all-too familiar problem in many countries. Bearing in mind the need for inexpensive components and the requirement of low-power operation, we have focused on colorimetric detection using LED/photodiode detection in a microfluidic manifold as a generic... 

For lemon juice, the flavonoid composition was characterized by HPLC with photodiode detection at 287 nm (108), the HPLC condition based on a procedure proposed by Kirksey et al. (103) for the detection of fruit juice adulteration. Hesperidin and eriocitrin were the characteristic flavonoids of lemon juice. Flavonoid content by HPLC was used to study the effects of processing and pulp removal on flavonoid composition in lemon juice. Eriocitrin is also used in distinguishing lemon juice from grapefruit and orange juices, which do not contain this flavonoid. 

Many authors have concluded that the conjugated diene method might be used as an index of stability of lipids in place of, or in addition to PV. It is faster than iodometric PV determination, much simpler, does not depend on chemical reactions or color development, and requires a smaller sample size. However, the presence of compounds absorbing in the region of the conjugated diene formation may interfere with such determinations. It has been proposed that interference in complex systems can be minimized or eliminated by derivative spectroscopy, using photodiode detection of spectra and computer analysis of the data. ... 

H. Kano, H.T.M. van der Voort, M. Schrader, G.M.R van Kampen, S.W. Hell, Avalanche photodiode detection with object scanning and image restoration provides 2-4 fold resolution increase in two-photon fluorescence microscopy. Bioimaging 4, 187 (1996)... 

D. L. Spears and C. Freed, "HgCdTe Varactor Photodiode Detection of cw CO2 Laser Beats beyond 60 GHz," Appl. Phys. Lett. 23, 445 (1973). 

Hemmi, A., K. Yagiuda, N. Funazaki et al. 1995. Development of a chemiluminescence detector with photodiode detection for flow-injection analysis and its application to 1-lactate analysis. Anal. Chim. Acta 316 323-327. 

For detection in the UV-visible region, photomultipliers or other photoelectric devices are used. Some instruments may use a multi-channel diode array detector. An array of typically 300 silicon photodiodes detects all the wavelengths simultaneously with a resolution of about 1 nm. This provides a great saving in time and an improved signal/noise ratio. 

Four wave mixing via the third order nonlinear susceptibility of the medium produces two new waves of frequencies 03+6, travelling collinearly with the probe. A photodiode detects the resulting intensity modulation of the probe. The original probe beam serves thus as the local oscillator for sensitive heterodyne detection. 

Photodiode Detects the fluorescent signal and sends an electrical current proportional to the incident light to the lock-in amplifier. 

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