Acetyltributyl Citrate
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C20H34O8 402.48
Acetyltributyl Citrate contains NLT 99.0% of C20H34O8, calculated on the anhydrous basis.
•  B. The retention time of the Sample solution corresponds to that of a similar preparation of USP Acetyltriethyl Citrate RS, as obtained in the Assay.
•  Procedure
System suitability solution:  30 mg/mL each of USP Acetyltributyl Citrate RS and USP Tributyl Citrate RS in toluene
Sample solution:  30 mg/mL of Acetyltributyl Citrate in toluene
Chromatographic system 
Mode:  GC
Detector:  Flame ionization
Column:  0.32-mm × 30-m, bonded with a 0.5-µm layer of phase G42
Injector:  240
Detector:  280
Column:  See the temperature program table below.
Hold Time at Final
80 80 0
80 20 230 15
Flow rate:  1.9 mL/min
Carrier gas:  Helium
Injection type:  Split, 30:1
Injection size:  1 µL
System suitability 
Sample:  System suitability solution
[Note—The relative retention times for tributyl citrate and acetyl tributyl citrate are 0.9 and 1.0, respectively. ]
Suitability requirements 
Resolution:  NLT 1.5 between tributyl citrate and acetyl tributyl citrate
Relative standard deviation:  NMT 2.0% determined from both the tributyl citrate and acetyl tributyl citrate peaks, based on area percent calculation
Sample:  Sample solution
[Note—Measure all of the peak areas, excluding the solvent peak. ]
Calculate the percentage of C20H34O8 in the portion of Acetyltributyl Citrate taken:
Result = (rU/rT) ×100
rU== peak area of the Sample solution
rT== sum of all the peak areas
Acceptance criteria:  NLT 99.0% on the anhydrous basis
Inorganic Impurities 
•  Heavy Metals, Method II 231: NMT 10 ppm
•  Specific Gravity 841: 1.045–1.055
•  Refractive Index 831: 1.4410–1.4425
•  Acidity
Neutralized isopropyl alcohol:  To a suitable quantity of isopropyl alcohol add 2–3 drops of bromothymol blue TS and just sufficient 0.10 N sodium hydroxide dropwise to produce a faint blue color. [Note—Prepare Neutralized isopropyl alcohol just before use. ]
Sample solution:  32.0 g of Acetyltributyl Citrate in 30 mL of Neutralized isopropyl alcohol
Analysis:  Add bromothymol blue TS. Titrate with 0.10 N sodium hydroxide to a faint blue endpoint.
Acceptance criteria:  NMT 1.0 mL of 0.10 N sodium hydroxide is required.
•  Packaging and Storage: Preserve in tight containers.
•  USP Reference Standards 11
USP Acetyltributyl Citrate RS Click to View Structure
USP Tributyl Citrate RS Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
(EXC2010) Monographs - Excipients
Reference Standards RS Technical Services
USP35–NF30 Page 1683
Pharmacopeial Forum: Volume No. 35(6) Page 1495