Isotachophoresis of β‐blockers in a capillary and on a poly(methyl methacrylate) chip

Analysis of the β‐blockers oxprenolol, atenolol, timolol, propranolol, metoprolol, and acebutolol in human urine by a combination of isotachophoresis (ITP) and zone electrophoresis (ZE) was investigated. Methods were developed with a conventional capillary electrophoresis (CE) apparatus and a poly(methyl methacrylate) (PMMA) microchip system. With CE the separation of oxprenolol, atenolol, timolol, and acebutolol from a standard solution containing 5 μg/mL of each compound was accomplished by performing ZE with transient ITP. The electrolyte system consisted of 10 mM sodium morpholinoethane sulfonate (pH 5.5) and 0.1% methylhydroxyethylcellulose as the leading electrolyte and 30 mM ortho‐phosphoric acid (pH 2.0) as both the terminating and the ZE background electrolyte. With the microchip system the separation of oxprenolol and acebutolol from a standard solution containing 10 μg/mL of each compound was accomplished by a coupled‐channel ITP‐ZE device using the same leading electrolyte solution as the CE system but 5 mM glutamic acid (pH 3.4) as terminating and background electrolytes. The systems were used for analyses of patient urine samples. Water‐soluble hydrophilic matrix compounds were removed from the urine samples by solid‐phase extraction (SPE). Limits of quantification below 5 μg/mL could be achieved. The PMMA ITP‐ZE chip has not earlier been used for analyses of any drugs from urine samples.