Atomic absorption spectrophotometer, versus

Procedure Concomitantly determine the absorbance of each Standard Preparation and of the Sample Preparation at 422.7 nm, with a suitable atomic absorption spectrophotometer, following the operating parameters as recommended by the manufacturer of the instrument. Plot the absorbance of the Standard Preparations versus concentration of calcium, in micrograms per milliliter, and from the curve so obtained determine the concentration, C, in micrograms per milliliter, of calcium in the Sample Preparation. Calculate the quantity, in milligrams, of calcium in the sample taken by the formula... 

Procedure Concomitantly determine the absorbance values of the Test Solutions at the potassium emission line at 766.7 nm with a suitable atomic absorption spectrophotometer equipped with an air-acetylene flame, using water as the blank. Plot the absorbance values of the Test Solutions versus their contents of potassium, in micrograms per milliliter draw the straight line best fitting the three points and extrapolate the line until it intersects with the concentration axis. From the intercept, determine the amount, in micrograms, of potassium in each milliliter of Test Solution A. Calculate the percent potassium in the portion of sample taken by multiplying the concentration, in micrograms per milliliter, of potassium found in Test Solution A by 0.2. 

Procedure Concomitantly determine the absorbance values of the Test Solutions at the sodium emission line at 589.0 nm with a suitable atomic absorption spectrophotometer equipped with an air-acetylene flame, using water as the blank. Plot the absorbance values of the Test Solutions versus... 

Procedure Use a suitable atomic absorption spectrophotometer equipped with a sodium hollow-cathode lamp and an oxidizing air-acetylene flame. After using the Blank Solution to zero the instrument, concomitantly determine the absorbances of the Standard Solutions and the Test Solution at the sodium emission line of 589 nm. Plot the absorbances of the Standard Solutions versus concentration, in micrograms per milliliter, of sodium, and draw the straight line that best fits the plotted points. From the graph so obtained, determine the concentration, C, in micrograms per milliliter, of sodium in the Test Solution. Calculate the percentage of sodium in the portion of potassium lactate taken by the formula... 

Set a suitable atomic absorption spectrophotometer to a wavelength of 309.3 nm. Adjust the instmment to zero absorbance against water. Prepare and read the absorbance of four aqueous solutions containing 5, 10, 20, and 50 xg/mL of aluminum, in the form of the chloride, and plot the standard curve as absorbance versus concentration of aluminum. 

There are available also several kits for the assay of calcium, in 10 or 20 microliter samples by chelate formation colorimetrically or fluorimetrically. (Pierce Chem. Co., Rockford, 111.). These are read either with the spectrophotometer or by spectrofluorometry. In our experience, while these systems can be used for approximate results, the plot of concentration versus reading curves are rather flat and only an approximation of the values can be obtained. This may be very important late at night or at times when the atomic absorption machine is down, but if the atomic absorption instrument is available it should be used in preference to these procedures. 

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