Page 102 - Application Handbook - Liquid Chromatography

LAAN-A-LC-E233

Application High Performance Liquid Chromatography

News Ion Analysis in Drugs (Part 3)

Determination of Counterions (Cations) by Ion
No.L456 Chromatography

In Application News No.L387, we introduced examples Table 2 Analytical Conditions
of impurity ion analysis and counterion analysis in Column : Shim-pack IC-C4 (150 mm L. × 4.6 mm I.D.)
pharmaceuticals using ion chromatography. Typically, a Mobile Phase : A : 3.0 mmol/L Oxalic acid
variety of counterions are used to selecting the B : Acetonitrile
optimum salts in the development stage of a Flowrate A : B = 95 : 5 (v/v)
: 1.0 mL/min
pharmaceutical product because the physicochemical Column Temp. : 40 ˚C
and pharmacokinetic properties associated with the Injection Volume : 20 μL
active pharmaceutical ingredients (API) will vary Detection : Conductivity (Non-suppressor mode)
depending on differences in counterions. Furthermore,
as inorganic substances such as catalysts and ions used
during synthetic process may affect such properties as
solubility and stability, it is very important to conduct
analysis of ionic contaminants. High-sensitivity analysis uv
of these ionic contaminants, even when present at 10000
trace levels in pharmaceutical products, can be ˙Peaks
conducted using ion chromatography. Further, by 1.Na
adding an organic solvent to the eluent, the principle 2.K
component can be eluted more quickly, thereby 3.Mg
shortening the analysis time. 8000 4.Ca
Here, we introduce examples of analysis of sodium,
potassium, magnesium and calcium as the principal
counter cations found in pharmaceuticals. 1
6000

n Analysis of Trace Amounts of Cations
We conducted low-concentration analysis of a standard
solution of sodium, potassium, magnesium and 4000
calcium. Table 1 shows the area reproducibility and 3
retention time (n = 6), and Table 2 shows the analytical 2
conditions used. The results of analysis of the cation
standard solution are shown Fig. 1. 2000 4

Table 1 Repeatability
0
Conc (mg/L) R.T. %RSD Area %RSD
Sodium 2.5 0.02 0.07 0.0 2.5 5.0 7.5 10.0 12.5 min
Potassium 2.5 0.02 0.07
Magnesium 2.5 0.01 0.27
Calcium 2.5 0.02 0.28 Fig. 1 Chromatogram of a Four-Cation Standard Mixture