Determination of trace level ions by high-volume direct-injection ion chromatography

Determination of Trace-Level Anions in High-Purity Water Samples by Ion Chromatography with an Automated On-Line Eluent Generation System

“…The 10 target anions were separated on a 2-mm IonPac AG-11 and AS-11 column set using the gradient IC method employing the large-volume direct injection technique (5,6). The volume of sample loop used in this study was 1000 l. In the gradient IC method used, the hydroxide concentration in the eluent was maintained at 0.5 mN during the sample injection step to concentrate the target anions, including weakly retained anions such as fluoride and acetate, from the sample.…”

“…To minimize contamination, we injected standards and samples by using a disposable plastic syringe at the injection valve waste port to draw the sample into the sample loop from the sample container (5,6).…”

“…The severe baseline shifts during the hydroxide gradients can compromise the quantitation of target analytes. To determine anions at sub-to low microgram-per-liter levels, precautions such as thorough degassing of the deionized (DI) water used in the eluent preparation and the use of anion trap columns to remove carbonate have been recommended to minimize the baseline shifts during the hydroxide gradients (5,6). Therefore, there is need for more convenient and reliable methods to generate high-purity and carbonate-free hydroxide solutions for use as eluents in ion chromatography.…”

“…More recently, it has been shown that gradient IC methods using direct injection of relatively large volumes of sample (e.g., 1000 l) can also be used to determine trace anions at sub-to low microgram-per-liter levels (5,6).…”

“…Over the past decade, ion chromatography (IC) with suppressed conductivity detection has emerged as the method of choice for determining trace anions in high-purity water samples (1)(2)(3)(4)(5)(6). Semiconductor Equipment and Materials International (SEMI) recommends the use of IC for monitoring anions at concentrations ranging from 0.025 to 0.5 g/liter in high-purity water used in semiconductor fabrication (7).…”