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Capillary IC Columns

Less Becomes More

Thermo Scientific Dionex IonPac capillary columns (0.4 mm i.d.) are packed with the same material as the equivalent analytical scale version, thus producing the same separation performance as a 4 mm column. This is ideal for method transfer as the user does not need to redevelop or validate the method. Scaling the cross-sectional area down to 0.4 mm brings many additional benefits.

IC Capillary Columns

Lower Eluent Usage and Waste Disposal

The typical flow rate is only 1/100th the eluent flow rate of an analytical format. Analytical column formats typically run at  flow rates of 1 mL\min. Due to the smaller cross-sectional area, the flow rate on a capillary format can be scaled down to 10 µL\min. This reduces the eluent usage to just 5.25 L per year, compared to 525 L. While the low eluent usage saves time and labor in eluent preparation, it also has a dramatic effect on waste production and disposal, reducing operating costs.

Increased Mass Sensitivity

Chromatography detectors are generally either mass sensitive or concentration sensitive. A mass-sensitive detector responds to the mass of the target analyte passing through the detector per unit time. The conductivity detector used commonly in ion chromatography is a concentration-sensitive detector.

If we inject 0.4 μL of a six cation standard onto a 0.4 mm and a 4 mm Dionex IonPac™ CS12A column, the same amounts of analytes are injected onto both columns. However, the flow rate for the 0.4 mm column is 10 μL /min and for the 4 mm column is 1.0 mL/min. Because of the difference in the separation flow rates, the volume passing through the conductivity detector at a specific time is 100 times lower with the capillary system than the standard system. Because the retention times are identical, the concentrations of separated analytes passing through the conductivity detector in the 0.4 mm column systems are 100 times those in the 4 mm column system. As shown in Figure 1, there is a 100-fold increase in conductivity response because the conductivity detector is a concentration-sensitive detector. Therefore a capillary column provides increased mass sensitivity. This is beneficial for applications where the volumes of samples are limited when compared to standard bore using the 4 mm columns. This is also of benefit when performing ultratrace-level analysis as a 10 μL injection on a capillary column is equivalent to a 1000 μL injection on a standard bore system.

Figure 1. Comparison of chromatograms obtained using 0.4 mm and 4 mm IonPac CS12A columns and 0.4 µL injection volumes

Increased Sensitivity and Selectivity with IC × IC (2D-IC) for High Ionic Strength Samples

By combining a first-dimension standard bore column (4 mm) with a second-dimension capillary column (0.4 mm), an increase in sensitivity down to detection limits in the low ng/L range can be achieved easily for high-ionic-strength samples. By combining columns with different resin properties, greater selectivity for ions can be realized for better resolution or for conformation.

IC On Demand

With capillary columns the eluent flow rate is typically 10 μL/min, translating into 15 mL per day. Under these conditions the system can be operated continuously, and is thus always ready to run samples. This eliminates start-up and equilibration times, and provides more stable responses, leading to less frequent calibration requirements and improved performance. When used as a Reagent-Free IC (RFIC) system, the eluents are generated after the pumps, so the pump parts are not exposed to caustic chemicals, only water. This means less frequent maintenance is required, providing less down time and increased productivity.

Greater Flexibility and Lower Costs with Eluent Generation Technology

With an RFIC eluent generation system, the eluent is electrolytically generated from deionized water, consistently and conveniently. The system uses only 15 mL of water per day with continuous operation in the capillary format. Gradient elution is as easy as isocratic elution, all precisely computer controlled, allowing you to save time and money by accelerating your separations. The capillary eluent cartridge will last for up to 18 months of continuous operation under typical conditions (75 mM average concentration). The capillary format also increases the maximum generated eluent concentration to 200 mM, further accelerating difficult separations.

Reduced Sample Sizes for Low Volume Sampling

Capillary systems using the 0.4 mm columns provide increased mass sensitivity. This is beneficial for applications where the volume of sample is limited, such as biological samples, or for samples which are hazardous to handle.

Lower Cost of Ownership

There is no eluent preparation, no start-up time, no system equilibration once the system is up and running. The waste produced is dramatically reduced from 520 L to 5.2 L per year. As the system only uses water as the eluent, there is less frequent preventive maintenance required resulting in less down time and increasing your productivity. The Eluent Generator Cartridge also lasts for up to 18 months under continuous operation. All these factors contribute to lowering your overall cost of ownership of the system, saving you time and money and increasing your productivity.