Ractopamine Hydrochloride Suspension
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C18H23NO3·HCl 337.84
Benzenemethanol, 4-hydroxy--[[[3-(4-hydroxyphenyl)-1-methylpropyl]amino]methyl]-, hydrochloride;    
(±)-all-rac-p-Hydroxy--[[[3-(p-hydroxyphenyl)-1-methylpropyl]amino]methyl]benzyl alcohol, hydrochloride     [90274-24-1].
DEFINITION
Ractopamine Hydrochloride Suspension contains NLT 10% and NMT 20%, by weight, of ractopamine hydrochloride (C18H23NO3·HCl) in water. [Note—The material partially precipitates out at room temperature to form a slurry, and redissolves when heated to 50–60. ]
IDENTIFICATION
•  Infrared Absorption 197K
Sample:  Dry a portion of Ractopamine Hydrochloride Suspension under vacuum for 3 h at 60.
ASSAY
•  Procedure
Solution A:  5.75 mg/mL solution of monobasic ammonium phosphate adjusted with 10% phosphoric acid to a pH of 4.0 ± 0.1
Solution B:  1.1 mg/mL solution of 1-heptanesulfonic acid sodium salt in Solution A
Mobile phase:  Stabilizer-free tetrahydrofuran and Solution B (3:17)
Diluent:  Stabilizer-free tetrahydrofuran and water (3:17). [Note—The Standard solutions and System suitability solution are stable for up to 72 h at room temperature. The Sample solution is stable for up to 90 h at room temperature. ]
System suitability solution:  100 µg/mL of USP Ractopamine Hydrochloride RS and 10 µg/mL of USP Raspberry Alcohol RS in Diluent
Standard solution A:  0.08 mg/mL of USP Ractopamine Hydrochloride RS in Diluent
Standard solution B:  0.1 mg/mL of USP Ractopamine Hydrochloride RS in Diluent
Standard solution C:  0.12 mg/mL of USP Ractopamine Hydrochloride RS in Diluent
Sample stock solution:  Stir Ractopamine Hydrochloride Suspension in a 60 water bath for up to 1 h, to ensure complete dissolution. While hot, transfer 700 mg of the Ractopamine Hydrochloride Suspension dropwise to a 100-mL volumetric flask, and dilute with Diluent to volume.
Sample solution:  Dilute a portion of the Sample stock solution with Diluent (1:10).
Chromatographic system 
Mode:  LC
Detector:  UV 226 nm
Column:  4.6-mm × 15-cm; 5-µm packing L1
Flow rate:  1 mL/min
Injection size:  20 µL
System suitability 
Samples:  System suitability solution and Standard solution B
Suitability requirements 
Resolution:  NLT 1.5 between raspberry alcohol and ractopamine, System suitability solution
Tailing factor:  NLT 0.7 and NMT 2.0 for the ractopamine peak, Standard solution B
Relative standard deviation:  NMT 2.0% for three replicate injections, Standard solution B
Analysis 
Samples:  Standard solutions and Sample solution
Prepare a calibration curve using the three ractopamine peak responses from Standard solutions A, B, and C and their corresponding concentrations. From the graph determine the concentration, C, in mg/mL, of ractopamine hydrochloride in the Sample solution.
Calculate the percentage (w/w) of C18H23NO3·HCl in the portion of Ractopamine Hydrochloride Suspension taken:
Result = (V/W) × CS × D × 100
V== volume of the Sample stock solution, 100 mL
W== weight of Ractopamine Hydrochloride Suspension taken (mg)
CS== concentration of ractopamine hydrochloride from the Sample solution
D== dilution factor to prepare the Sample solution, 10
Acceptance criteria:  10%–20% of C18H23NO3·HCl
IMPURITIES
Organic Impurities 
•  Procedure
Solution A:  5.75 mg/mL of monobasic ammonium phosphate in water; pH NLT 4.4
Solution B:  1.1 mg/mL of 1-heptanesulfonic acid sodium salt in Solution A
Solution C:  Acetonitrile and Solution B (1:9)
Solution D:  Acetonitrile and Solution B (17:33)
Mobile phase:  See the gradient table below.
Time
(min)
Solution C
(%)
Solution D
(%)
0 100 0
22 0 100
32 0 100
37 100 0
55 100 0
Diluent:  Acetonitrile and water (1:4)
System suitability solution:  9 µg/mL each of USP Raspberry Ketone RS and USP Ractopamine Hydrochloride RS in Diluent
Blank:  Diluent
Sample solution A:  Stir Ractopamine Hydrochloride Suspension in a 60 water bath for up to 1 h, to ensure complete dissolution. While hot, transfer 200 mg of the Ractopamine Hydrochloride Suspension dropwise into a 50-mL volumetric flask, and dilute with Diluent to volume.
Sample solution B:  Dilute a portion of Sample solution A with Diluent (1:100). [Note—The Sample solutions are stable for up to 48 h if stored at 5. ]
Chromatographic system 
Mode:  LC
Detector:  UV 226 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  1 mL/min
Injection size:  20 µL
System suitability 
Sample:  System suitability solution
Suitability requirements 
Resolution:  NLT 2.0 between raspberry ketone and ractopamine
Analysis 
Samples:  Blank, Sample solution A, and Sample solution B
[Note—Disregard any peaks that correspond to those in the Blank. Correct the response of the ractopamine peak in Sample solution B by subtracting the peak response at the retention time of ractopamine in the Blank. ]
Calculate the percentage of each individual impurity in the portion of Ractopamine Hydrochloride Suspension taken:
Result = (rA/rB) × 100/D
rA= = peak response of each individual impurity from Sample solution A
rB= = corrected peak response for ractopamine from Sample solution B
D= = dilution factor to prepare Sample solution B, 100
Acceptance criteria 
Individual impurities:  See Impurity Table 1.
Total impurities:  NMT 3.5%
Impurity Table 1
Name Relative
Retention
Time
Acceptance
Criteria,
NMT (%)
Octopaminea 0.37 0.5
Tyramineb 0.55 0.5
N-Isopropyloctopaminec 0.63 0.5
Piperazinediphenold 0.74 0.5
Aminobutylphenole 0.76 0.5
Raspberry alcoholf 0.85 0.5
Raspberry ketoneg 0.96 1.0
Ractopamine 1.0
Deoxyractopamineh 1.1 0.5
Ractopamine O-methyli 1.2 1.0
Ractopamine N-hydroxybenzylj 1.26 1.0
Ractopamine cyclohexyl analogk 1.29 0.5
Ractopamine dimerl 1.4 1.0
Any individual unspecified impurity 0.2
a  4-(2-Amino-1-hydroxyethyl)phenol.
b  4-(2-Aminoethyl)phenol.
c  4-[1-Hydroxy-2-(isopropylamino)ethyl]phenol.
d  4,4¢-(Piperazine-2, 5-diyl)diphenol.
e  4-(3-Aminobutyl)phenol.
f  4-(3-Hydroxybutyl)phenol.
g  4-(4-Hydroxyphenyl)butan-2-one.
h  4-[3-(4-Hydroxyphenethylamino)butyl]phenol.
i  4-{3-[2-(4-Hydroxyphenyl)-2-methoxyethylamino]butyl}phenol.
j  4-(1-Hydroxy-2-{(4-hydroxybenzyl)[4-(4-hydroxyphenyl)butan-2-yl]amino}ethyl)phenol.
k  4-{1-Hydroxy-2-[3-(4-hydoxyphenyl)-5-methylcyclohexylamino]ethyl}phenol).
l  4,4¢-(1,1¢-Oxybis{2-[4-(4-hydroxyphenyl)butan-2-ylamino]ethane-1,1-diyl})diphenol.
SPECIFIC TESTS
•  Diastereomer Ratio
Solution A:  5.75 mg/mL of monobasic ammonium phosphate in water
Solution B:  Add 10 mL of triethylamine to 950 mL of Solution A, dilute with Solution A to 1000 mL, and adjust with phosphoric acid to a pH of 4.5.
Mobile phase:  Acetonitrile and Solution B (3:22)
Diluent:  Acetonitrile and Solution A (1:4)
System suitability solution:  0.4 mg/mL of USP Ractopamine Hydrochloride RS in Diluent
Sample solution:  Stir Ractopamine Hydrochloride Suspension in a 60 water bath for up to 1 h to ensure complete dissolution. While hot, transfer 275 mg of it dropwise into a 100-mL volumetric flask, and dilute with Diluent to volume.
[Note—The Sample solution is stable for up to 36 h when stored at ambient conditions. ]
Chromatographic system 
Mode:  LC
Detector:  UV 226 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  1 mL/min
Injection size:  20 µL
System suitability 
Sample:  System suitability solution
[Note—The elution order is RS,SR diastereoisomer followed by RR,SS diastereoisomer. ]
Suitability requirements 
Resolution:  NLT 1.25 between the diastereomers
Analysis 
Sample:  Sample solution
Calculate the RS,SR diastereomer content, in percentage:
Result = rA/(rA + rB) × 100
rA== peak response of the RS,SR diastereoisomer from the Sample solution
rB== peak response of the RR,SS diastereoisomer from the Sample solution
Acceptance criteria:  45%–49%
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Store at a temperature not exceeding 70.
•  Labeling: Label it to indicate that it is for veterinary use only.
•  USP Reference Standards 11
USP Ractopamine Hydrochloride RS Click to View Structure
USP Raspberry Alcohol RS
4-(3-Hydroxybutyl)phenol.
    C10H14O2        166.22
USP Raspberry Ketone RS
4-(4-Hydroxyphenyl)butan-2-one.
    C10H12O2         164.20
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Morgan Puderbaugh, B.S.
Associate Scientific Liaison
1-301-998-6833
(SM32010) Monographs - Small Molecules 3
Reference Standards RS Technical Services
1-301-816-8129
rstech@usp.org
USP35–NF30 Page 4513
Pharmacopeial Forum: Volume No. 35(5) Page 1171