Phenol calibration graph

The analytical performance of CC is demonstrated by extending the calibration graph of measured phenol with data found by CC. 

See Figure 8. HPLC equipment using reversed phase separation with fluorometric detection was used. Injection for correlation HPLC was accomplished with a newly developed device ( 4 ). The total range of phenol measured was five decades of concentration 0.01 -100 jug/L. The two higher concentrations (10 - 100 /i-g/L) were determined solely by conventional methods. The two lower concentrations (0.01 - 0.1 /xg/L) were determined by correlation HPLC with 16 and 3 sequences correlation time, respectively. Measurements at the 1 /xg/L level were carried out both by conventional and by correlation HPLC (1 sequence). The bars indicated on the calibration graph represent the peak area +3 (arbitrary units), where is the standard deviation... 

Figure 8. Calibration graph of phenol with fluorometric detection.

The advantages of CC in ultra trace analysis are shown to be unmistakable. The quantitative reliability of the method was demonstrated by the extension of a calibration graph for phenol to two decades of concentration more when compared with conventional chromatography. A considerable improvement of the signal-to-noise ratio can be achieved in a relatively short time. The method offers excellent prospects for ultra trace analysis in cases where preconcentration of the solute fails. 

Fig. 10. Calibration graph for phenol with fluorimetric detection for 5 concentrations (I0" to lO" gl ) s indicates single injection and c indicates correlation chromatography. The numbers below the data points indicate the correlation time (minutes) (ppt = ng 1" ). The bars represent 3 x standard deviation of the integrated noise (confidence interval).

Re archers are active in the field of correlation gaschromatography and correlation HPLC " the first application in trace analysis was introduced in 1970 A typical example of the noise reduction property is the determination of a calibration graph of phenol for the higher concentrations with conventional chromatography, and extended to very low concentrations by CC (Fig. 10). The detection limit achieved is about 3 ppt (Laeven et al. ). A correlogram of 10 ng/1 phenol mple is shown in... 

The selectivity profiles for a variety of phenols and diphenols obtained using HRP and CDH modified electrodes are presented in Table II. HRP showed similar responses to both mono- and diphenols. The responses to aromatic amines are generally higher compared with the corresponding phenols. The aromatic amines, however, showed a calibration graph with a lower Michaelis-Menten constant, than for the other compoimds. CDH showed high response for the tested diphenols, and virtually no response for the monophenols. 

Takahashi [12, 13] used gas liquid chromatography to determine BHA and BHT in breakfast cereals. He obtained quantitative recoveries of 20 to 30 ppm of the antioxidants added to cereals. To determine antioxidants and preservatives in soya sauce and other foods, Takemura [14] converted these compounds to trimethylsilyl derivatives and analysed the product by GC. The sample was shaken with the silation reagent (1 ml) for 30 seconds, then set aside for 5 minutes and 2 pi of the solution was analysed by GC on, for example 20% of SE-31 silicone on Celite 545 at 200 °C with helium as carrier gas (22 ml/min) and hexane as internal standard. The method was applied to 15 preservatives and 7 antioxidants well-separated peaks were obtained for 4-hydroxy benzoate estars, phenol, xylenol derivatives and salicylic acid. The calibration graphs for methyl, ethyl, propyl and butyl-4-hydroxybenzoates were rectilinear for the range 0.5 to 4 mg. The method was used to determine 4-hydroxybenzoates in soya sauce. 

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