Related compounds
Diluent, Solution A, Solution B, Mobile phase, and System suitability solution
Proceed as directed in the Assay.
Quantitation limit solution
Dissolve an accurately weighed quantity of
USP Hydrochlorothiazide RS in
Diluent, sonicate if necessary, and dilute quantitatively, and stepwise if necessary, with
Diluent to obtain a solution having a known concentration of about 0.16 µg per mL.
Test solution
Proceed as directed for the Assay preparation in the Assay.
Chromatographic system (see Chromatography
621
)
Prepare as directed in the
Assay. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the resolution,
R, between benzothiadiazine related compound A and chlorothiazide is not less than 2.0 and the resolution,
R, between chlorothiazide and hydrochlorothiazide is not less than 1.5; the tailing factor for the benzothiadiazine related compound A, chlorothiazide, and hydrochlorothiazide peaks is not more than 1.5; and the relative standard deviation for replicate injections determined from benzothiadiazine related compound A and chlorothiazide is not more than 5.0%. Chromatograph three replicate injections of the
Quantitation limit solution, and record the peak responses as directed for
Procedure: the relative standard deviation is not more than 25%.
[NOTEThe relative retention times for benzothiadiazine related compound A, chlorothiazide, hydrochlorothiazide, 5-chlorohydrochlorothiazide, and hydrochlorothiazide dimer [6-chloro-
N-[(6-chloro-7- sulfamoyl-2,3-dihydro-4
H-1,2,4-benzothiadiazine-4-yl 1,1-dioxide)methyl]3,4-dihydro-2
H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide] are about 0.5, 0.8, 1.0, 2.1, and 2.6, respectively.
]
Procedure
Inject a volume (about 10 µL) of the
Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the portion of Hydrochlorothiazide taken by the formula:
100(ric / rsc),
in which
ric is the ratio of the peak area for each impurity to its response factor; and
rsc is the sum of ratios of all the peak areas to their respective response factors, the response factors being 0.54, 0.63, and 1.0 for benzothiadiazine related compound A, chlorothiazide, and all other peaks, respectively: not more than 1.0% of benzothiadiazine related compound A is found; not more than 0.5% of any other impurity is found; and not more than 0.9% of total other impurities excluding benzothiadiazine related compound A is found.
Assay
Sodium phosphate solution
Transfer 2.76 g of monobasic sodium phosphate, accurately weighed, into a 1000-mL volumetric flask, and add about 990 mL of water. Adjust with phosphoric acid to a pH of 2.7 ± 0.1, and dilute with water to volume. Make adjustments if necessary (see
System Suitability under
Chromatography
621![](images/chars/rang.gif)
).
Diluent
Prepare a mixture of Sodium phosphate solution and acetonitrile (7:3).
Solution A
Prepare and degas a mixture of acetonitrile and methanol (3:1).
Solution B
Prepare and degas a solution of anhydrous formic acid in water (5 in 1000).
Mobile phase
Use variable mixtures of
Solution A and
Solution B as directed for
Chromatographic system. Make adjustments if necessary (see
System Suitability under
Chromatography
621![](images/chars/rang.gif)
).
Standard preparation
Dissolve an accurately weighed quantity of
USP Hydrochlorothiazide RS in
Diluent, sonicate if necessary, and dilute quantitatively, and stepwise if necessary, with
Diluent to obtain a solution having a known concentration of about 0.32 mg per mL. Pass a portion through a filter having a 0.45-µm or finer porosity before injection.
Assay preparation
Transfer about 32 mg of Hydrochlorothiazide, accurately weighed, to a 100-mL volumetric flask. Add about 70 mL of Diluent, sonicate for 10 minutes if necessary to dissolve, and allow to cool to ambient temperature. Dilute with Diluent to volume, mix, and pass a portion through a filter having a 0.45-µm or finer porosity before injection.
Chromatographic system (see Chromatography
621
)
The liquid chromatograph is equipped with a 275-nm detector and 4.6-mm × 5-cm column that contains 3.5-µm packing L1. The flow rate is about 1.0 mL per minute. The column temperature is maintained at 35
![](images/chars/deg.gif)
. The chromatograph is programmed as follows.
Time (minutes) |
Solution A
(%) |
Solution B
(%) |
Elution |
0 |
3 |
97 |
equilibration |
05 |
3 |
97 |
isocratic |
514 |
3®36 |
97®64 |
linear gradient |
1418 |
36®3 |
64®97 |
linear gradient |
1820 |
3 |
97 |
re-equilibration |
Chromatograph the
Diluent to check for interference by system related peaks. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the relative retention times are about 0.5 for benzothiadiazine related compound A, 0.8 for chlorothiazide, and 1.0 for hydrochlorothiazide; the resolution,
R, between benzothiadiazine related compound A and chlorothiazide is not less than 2.0 and the resolution,
R, between chlorothiazide and hydrochlorothiazide is not less than 1.5; and the tailing factor for the benzothiadiazine related compound A, chlorothiazide, and hydrochlorothiazide peaks is not more than 1.5. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 1.0%.
Procedure
Separately inject equal volumes (about 10 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the hydrochlorothiazide peaks. Calculate the quantity, in mg, of C
7H
8ClN
3O
4S
2 in the portion of Hydrochlorothiazide taken by the formula:
100C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Hydrochlorothiazide RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.