Ethanol calibration curve

Ethanol in the sample crosses the microporous meaibrane and enters the internal solution where NADH is produced. Conditions are maintained so that the rate of ethanol diffusion into the internal solution is rate limiting so that the rate of NADH production is first order with respect to the amount of ethanol in the sample solution. Figure 10 shows an ethanol calibration curve where the rate of NADH production is linearly related to the ethanol concentration. 

Figure 10. Ethanol calibration curve from the internal enzyme biosensor with alcohol dehydrogenase. (Reproduced with permission from ref. 13. Copyright 1988 Pergamon.)...

An alternative elution technique is to transfer the powder (e.g. for bromophenol blue) to a glass column fitted with a glass-wool plug or glass sinter, and elute the dye with ethanol containing a little ammonia. The eluted solution, made up to a fixed volume in a small graduated flask, may be used for colorimetric/ spectrophotometric analysis of the recovered dye (see Chapter 17). A calibration curve must, of course, be constructed for each of the individual compounds. 

Chromatograms of the ethanol-soluble fraction were obtained in THF on Toyo Soda Oligomer columns over a range of sample masses, as shown in Figure 5 The exclusion limit of these columns is 50,000 and Mp" values above 10,000 are inaccurate because the calibration curve is very steep in this region. Consequently, chromatograms were also obtained on the "Main Column" GPC with the results shown in Figure 6. 

After refluxing, disconnect the trapping tube, and transfer the yellow solution into a 25-mL volumetric flask. Rinse the mbe with ethanol, and adjust the solution to volume with ethanol. Measure the absorbance of the solution at 435 nm against a blank prepared by diluting 15 mL of color reagent to 25 mL with ethanol. Determine the carbon disulflde content from a calibration curve obtained by plotting carbon disulfide concentrations of different standard solutions on the abscissa versus the absorbance on the ordinate. 

An electron transfer type of enzyme sensor was thus fabricated by a electrochemical process. Although no appreciable leakage of ADH and MB from the membrane matrix was detected, NAD leaked slightly. To prevent this leakage, the ADH-MB-NAD/polypyrrole electrode was coated with Nation. A calibration curve is presented in Fig.25 for ethanol determination in an aquous solution with the enzyme sensor. Ethanol is selectively and sensitively determined in the concentration range from 0.1 nM to 10 mM. 

Protein concentration was determined using the Bradford assay at 595 nm. 100 pL of the sample were introduced into a cuvette containing 5 mL of Bradford solution (100 mg of Coomassie blue, 50 mL of ethanol and 100 mL of 85 % phosphoric acid dissolved in 850 mL of H2O). The solutions were incubated for 5 min at room temperature. The absorbance was measured at 595 nm. The protein concentration in the sample was determined using a calibration curve plotted with serum albumin (1 mg mL ) as a standard.)... 

Calibration. Most aldehydes, except formaldehyde, form two geometrical isomers of the derivatives and appear as two peaks in the chromatogram. The sum of these two peak areas was used in the calibration measurements. A six-point calibration curve for nine carbonyl compounds was measured. The calibration range was 0.1-50 ppb, except for (E)-2-nonenal, where the calibration range was 0.01-5 ppb. The matrix used for calibration solutions was 5% ethanol solution, pH 4.5. Correlation coefficient (Rh values indicate that this method can be used for analysis of aldehydes in a wide range of concentrations (Table 1). 

The density of the liquid mixture can be determined using a pyknometer or it can be derived from a previously determined calibration curve. For the determination of densities less than unity (e.g., polyethylene), ethanol/water mixtures are suitable for densities larger than unity one may use mixtures of water with aqueous salt solutions (40% CaCl2 solution = 1.40 g/ml 72% ZnCl2 solution = 1.95 g/ml). The density gradient method, which is an elegant var-... 

The independent measurements of surface tension were obtained by the tedious Wilhelmy plate method. Figure 3 illustrates such a calibration curve for one set of orifices and for five types of test fluids (methanol-water, ethanol-water, acetone-water, sodium lauryl sulfate in water saturated with methyl methacrylate, and polymethylmethacrylate latices). This is a "universal" calibration curve independent of the fluid being monitored. For the 63 data points shown in Figure 3, the least squares regression line is given by... 

Fig. 2 Calibration curve in Round No. 73. Calibration data are shown by dots, the calibration curve obtained by the ordinary least squares technique, by the solid regression line 5 the limits of the regression corridor by dotted lines 4 and 6 the result of the ethanol determination in the sample by the dotted lines 1 and 8 the calibration curve for 3-times increased uncertainty of the certified value by the solid regression line 3, and the limits of its corridor by thin lines 2 and 7...

The free enzymes FIA system permitted analysis in a linear range of 0.05-1.0 g of ethanol/L, a sampling frequency of 15 analyses/h, and a relative SD of 3.5%. The total volumetric flow was 5 mL/min, and the six-channel injection valve permitted the introduction of 0.185 mL (loop volume) of enzymes-reagents solution per analysis (4). Ethanol solutions of different concentrations were used to determine the linear working range and for the calibration curve construction (Fig. 4), presenting a linear relation up to 1 g of ethanol/L with a correlation factor of 0.9899 for six samples. 

Fig. 9. Calibration curve for phosphate buffer standard ethanol solutions with integrated biosensor-FIA system.

For the substitute food simulants 95 % ethanol and iso-octane a precision experiment has not been carried out. However, from experience with establishment of calibration curves, r-values can be expected to be in the same range as with the other food simulants. 

Standardization The molar absorption coefficient of hydroxyalkenals in water and ethanol or methanol is 13 750 at 223 nm and 13 100 at 221 nm, respectively (Esterbauer, 1982). Calibration curves of peak height versus concentration are linear in the range 0.1-500 /iM. 

Figure 4. Calibration curve for octylphenoxypoly (ethoxy) ethanol.

Fig. 4.20. Calibration curves for ethanol obtained at a pervaporation time of ( ) 8 min and (O) 4 min.

RETINOIC ACID ASSAY. Calibration curves were obtained by adding known amounts of 13-cis (40 /il) and all trans (40 /il) retinoic acid in ethanol to 1 ml of phosphate buffered saline... 

The Index of refraction was measured at 15°C using Abbe-3L Bausch and Lomb refractomer and a Haake FK constant temperature bath. Refractive Index was first measured for ethanol, Indolene HO-III, and mixtures of both components of known concentrations. From this data calibration curves were obtained to relate component concentration with refractive Index. These calibration curves were used to determine whether or not preferential absorption of one component of the mixture takes place during elastomer swelling due to permeability considerations, or after equilibrium swell Is established due to solubility considerations. 

Recoveries also depend on the wine matrix white and red wines differ for volatiles and polyphenols, and contents of alcohol and sugars. For quantitative analysis, internal standards have to be spiked to the sample in suitable concentration, such as dimethyl sulfide-d6 (d6-DMS) 25 pg/L, dipropyl disulfide (DPDS) 25 pg/L, 4-methylthiazole (MT) lOpg/L, and 3-(methylthio)-l-hexanol (MTH) 50pg/L. A white wine matrix can be used [e.g., 10% v/v ethanol, sugar content <4g/L, and a polyphenolic content of 115mg/L expressed as (+)-catechin] for preparation of standard solutions to calculate the calibration curve for analytes, containing total S02 corrected to 100 g/L and previously treated twice with charcoal 3 g/L to remove sulfur and less polar volatile compounds (higher alcohols are not removed). 

In an analysis to determine the ethanol content of a wine by gas chromatography, an internal standard of isopropanol is used to account for the variability in the volume injected between tests. In the measurement of a four-point calibration curve and the repeated analysis of the wine sample, six injections in all are performed. Each injection contained 1% v/v of the internal... 

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