A coupling system of capillary gel electrophoresis with inductively coupled plasma-mass spectrometry for the determination of double stranded DNA fragments

Abstract

The coupling system of capillary gel electrophoresis (CGE) and inductively coupled plasma-mass spectrometry (ICP-MS) was newly developed and successfully applied to the double-stranded (ds) DNA quantification. The developed system combines the separation technique for large biomolecules and element selective detection of ICP-MS. This coupling was achieved by using the modified high performance concentric nebulizer (HPCN) with the PTFE tube (HPCN-PT), which can produce the liquid jet by the flow focusing effect. The HPCN-PT effectively nebulizes the highly viscous solution containing gel buffer even at a low flow rate. At a liquid flow rate of 0.010 mL min⁻¹ and a nebulizer gas flow rate of 1 L min⁻¹, the Sauter mean diameter (D_3,2) of primary aerosols generated by the HPCN-PT was 3.4 μm, and over 90% (v/v) of the aerosol droplets were less than 10 μm in diameter. The electrophoresis capillary filled with gel buffer was connected to the HPCN-PT via the interface. This interface has two connectors and an electrode that can connect CE and ICP-MS. After the electrophoretic separation at atmospheric pressure, the samples were transferred to the ICP-MS through the interface by applying additional pressure. Fragments of dsDNA, which were commercially available as a ladder marker solution, were successfully separated and analyzed by measuring ³¹P⁺ with CGE-ICP-MS, and a linear calibration curve of the phosphorus standard solution (R² = 0.999) was obtained from 2.7 to 27 mg kg⁻¹. The detection limit (LOD) and absolute detection limit of P were 3.7 μg kg⁻¹ and 0.6 pg (equivalent to 6 pg of DNA), respectively. This absolute detection limit value was equal to the conventional fluorescence determination of DNA.