Butylated Hydroxyanisole
(bue' ti lay'' ted hye drox'' ee an' i sole).
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C11H16O2 180.24
Phenol, (1,1-dimethylethyl)-4-methoxy-;    
tert-Butyl-4-methoxyphenol     [25013-16-5].
Butylated Hydroxyanisole contains NLT 98.5% of C11H16O2.
•  A. Procedure
Analysis:  To 5 mL of 0.1 mg/mL solution in 72% alcohol add 2 mL of 20 mg/mL sodium borate solution and 1 mL of 0.1 mg/mL solution of 2,6-dichloroquinone-chlorimide in dehydrated alcohol, and mix.
Acceptance criteria:  A blue color is produced.
B.  The retention times of 3-tert-butyl-4-hydroxyanisole and 2-tert-butyl-4-hydroxyanisole from the Sample solution correspond to those from the Standard solution, as obtained in the Assay.
•  Procedure
Solution A:  5% acetic acid
Mobile phase:  Acetonitrile and Solution A (45:55)
Standard solution:  90 µg/mL of USP 3-tert-Butyl-4-hydroxyanisole RS and 10 µg/mL of USP 2-tert-Butyl-4-hydroxyanisole RS in Mobile phase
Sample solution:  100 µg/mL of Butylated Hydroxyanisole in Mobile phase
Chromatographic system 
Mode:  LC
Detector:  UV 290 nm
Column:  4.6-mm × 75-mm; 3.5-µm packing L1
Column temperature:  30
Flow rate:  1.2 mL/min
Injection size:  20 µL
System suitability 
Sample:  Standard solution
[Note—The retention times of 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole are about 4.2 and 4.6 min, respectively. ]
Suitability requirements 
Resolution:  NLT 1.5 between the 3-tert-butyl-4-hydroxyanisole isomer and 2-tert-butyl-4-hydroxyanisole isomer peaks
Tailing factor:  NMT 1.5
Relative standard deviation:  NMT 2.0% for the 3-tert-butyl-4-hydroxyanisole isomer and 2-tert-butyl-4-hydroxyanisole isomer peaks
Samples:  Standard solution and Sample solution
Measure the peak areas for each isomer. Calculate the percentage of each isomer in the portion of Butylated Hydroxyanisole taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak area of the corresponding isomer from the Sample solution
rS== peak area of the corresponding isomer from the Standard solution
CS== concentration of the appropriate USP Reference Standard in the Standard solution (µg/mL)
CU== concentration of the Sample solution (µg/mL)
[Note—Calculate the percentage of C11H16O2 in the portion of Butylated Hydroxyanisole taken by adding the quantities of the two isomers. ]
Acceptance criteria:  NLT 98.5%
Inorganic Impurities 
•  Residue on Ignition 281: NMT 0.01%, determined on a 10-g specimen
•  Heavy Metals, Method II 231: NMT 10 ppm
•  Packaging and Storage: Preserve in well-closed containers.
•  USP Reference Standards 11
USP 2-tert-Butyl-4-hydroxyanisole RS
    C11H16O2        180.25
USP 3-tert-Butyl-4-hydroxyanisole RS
    C11H16O2        180.25
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 1717
Pharmacopeial Forum: Volume No. 35(6) Page 1503