FED-STD-791D
Method 3500.1
September 30, 1986
MONOBASIC ACID COMPONANTS OF SYNTHETIC ESTER LUBRICANTS
BY GAS CHROMATOGRAPHY
1. SCOPE
1.1 This method covers the determination of monobasic acid components of ester
lubricants by gas chromatography. The method is intended for use on any neopentyle
polyol ester lubricants where the acid components contain from 4 to 10 carbon atoms.
2. SUMMARY OF METHOD
2.1 The lubricant to be analyzed is hydrolyzed with potassium hydroxide,
followed by hydrochloric acid treatment to evolve the acids. After ether extraction of the
acids, the acids are physically separated by gas chromatography and are identified by
comparing them to corresponding acids separated under identical operating conditions
from a reference standard acid mixture of known composition. The acids are determined
quantitatively by also using the chromatogram of the sample which is interpreted by
comparing peak heights with those obtained on the reference standard mixture of pure
acids of known concentration.
3. SAMPLE SIZE
3.1 Approximately 20 g of sample are required for duplicate determination.
4. REFERENCES,STANDARDS, AND APPARATUS
4.1 Chromatograph and Recorder- A chromatograph with a thermal conductivity
detector and a strip type recorder may be used provided that the butyric and isovaleric
acid components in the standard acid mixture (see 5.21 can be satisfactorily resolved
when the column of 6.1.1 is used and the conditions of 6.1.2 are met. In addition, the
equipment shall have sufficient sensitivity to meet the precision requirements of section
9.
Two columns, stainless steel. 183 cm( 6ft) long, 0.635 cm(0.25in) O.D packed with the
mixture and in the manner described in section 6.11
Erlenmeyer flask, wide mouth 3.7 cm(1.46 in) I.D 250mL
1.1 Reflusk condenser, spiral, block tin
1.2 Electric hot plate
1.3 Steam bath or flash evaporator
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