§ 436.324 - Polarographic analysis of cefamandole.

(a) Equipment—(1) Polarograph. Use a polarograph equipped with a dropping mercury indicating electrode, a platinum auxilliary electrode, and a saturated calomel reference electrode, such as Princeton Applied Research Model 174 1or equivalent.

(2) X-Y plotter. Use a suitable X-Y plotter, such as Houston Omnigraphic Model 2200-3-3 2or equivalent.

(3) Nitrogen. Use a nitrogen tank equipped with a pressure-reducing regulator and a filter to remove traces of oxygen, such as an oxisorb filter 1 or equivalent.

(b) Reagent. pH 2.3 Buffer: Dissolve 3.6 grams of dibasic sodium phosphate, 39.4 grams of citric acid, and 70.8 grams of potassium chloride in sufficient distilled water to make 1 liter.

(c) Operating conditions—(1) Operating mode: Differential pulse.

(2) Scan range: −0.3 volt to −1.05 volts.

(3) Scan rate: −2 millivolts per second.

(4) Sensitivity: 10 to 20 microamperes or equivalent to keep peak on scale.

(5) Mercury drop time: 1 second per drop.

(6) Modulation amplitude: 25 millivolts.

(7) Display direction: +

(8) Damping: None.

(d) Preparation of sample and working standard solutions. Use the cefamandole lithium working standard. Accurately weigh approximately 12 milligrams of sample or working standard into a 50-milliliter volumetric flask. Dissolve the sample or working standard in 4 milliliters of distilled water. Immediately prior to polarography, add 30 milliliters of pH 2.3 buffer, dilute to volume with distilled water, and mix.

(e) Procedure. Transfer a portion of the sample or working standard solution to the polarographic cell. Pass a stream of nitrogen through the solution for 5 minutes to remove the dissolved oxygen. After 5 minutes, disperse the nitrogen above the sample. Start the mercury dropping from the mercury dropping electrode, and, using the operating conditions described in paragraph (c) of this section, record the polarogram. Compare the polarogram of the sample to that of the working standard.

(f) Calculations. Calculate the potency of cefamandole as follows:

ER01JA93.046

The peak height is obtained from the polarogram by measuring the vertical distance from the peak to the baseline of the sample or working standard.