Emission spectrophotometer detection limits

The samples were first run on the Jarrell-Ash instrument, with the three burner set and the same instrument was used as a flame emission spectrophotometer for the determination of sodium and potassium. A statistical summary of analytical precision for eight elements in the eight samples are shown in Table 1. Here the precision is expressed as the % standard deviation (coeflBcient of variation), which is defined as one hundred times the ratio of standard deviation to the mean concentration (9). It can be seen from this data that the last three elements, which are present in a quantity near the limit of detection, have large deviations. It is clear that these figures could be lowered if the analysis were run using higher concentrations. But our purpose was to evaluate the usefulness of the technique for routine determinations. 

For routine HPLC analysis, the detection of flavins is carried out either spectro-photometrically, using variable- or fixed-wavelength HPLC detectors in the ultraviolet (e.g., 254 nm) or visible (e.g., 405 nm) region, or fluorimetrically. For riboflavin, the excitation wavelength for fluorimetric detection is usually 440 to 450 nm, and the emission wavelength 530 nm. The detection limit for fluorescence detectors is >1 pmol (0.38 ng) riboflavin, whereas <30 pmol (11 ng) can be detected spectrophotometrically at 254 nm. Photodiode array detectors are significantly less sensitive than normal HPLC spectrophotometers (38). 

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