Standards quantum-counter

Quantum-Yield and Quantum-Counter Standards. The materials recommended as quantum-yield and quantum-counter standards are summarized In Table IV. As can be seen, several of the materials suggested as spectral responslvlty standards have also been suggested as quantum-yield and quantum-counter standards. The materials listed In Table IV cover the wavelength range from 200 to almost 800 nm, giving an excellent choice for the researcher. Quantum counters that operate further Into the red are still needed, especially for the area of... 

Table IV. Quantum Yield and Quantum Counter Standards...

One of the best known and most studied of the fluorescent alkaloids is the isoquinoline alkaloid, quinine, which is responsible for the bluish hue of tonic water. Much of the early research defining the fluorescence phenomenon was carried out on solutions containing quinine (Lakowicz, 2006). Quinine sulfate (ex 331 nm/em 382 nm) is often used as a quantum counter to correct EEMs spectra (Lakowicz, 2006). Its use as a standard to quantify fluorescence response in DOM studies has been proposed to properly correct DOM spectra and improve comparability of results between different instruments and analysts (Hoge et al., 1993, Murphy et al., 2010). 

Conventional scintillation counters such as the Microbeta (Wallac/Perkin Elmer, Turku, Finland) or the TopCount (Packard, Meriden, USA) use photomultiplier detection systems that count 8 or 12 wells at a time, resulting in a readout time of 40 minutes per 384-well microplate. Bialkali photocathodes (Sb-Rb-Cs or Sb-K-Cs) used in standard photomultipliers have a maximum spectral response at about 420 nm, with a quantum efficiency for detection of up to 30%. Thus, the aforementioned instruments are ideally suited for filtration assays and SPA assays with the blue-emitting YSi and PVT beads. 

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