Determination of micro and macro elements in waters with the ELAN DRC-e

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Courtesy of PerkinElmer, Inc.

The ability of reaction cell technology to reduce the effects of spectral interferences is well-known, but another, lesser-known capability also exists: extending the dynamic range. This is accomplished by adjusting the bandpass parameters with no gas in the cell. Because the bandpass parameters can be adjusted on a per-mass basis, sensitivity can be reduced on selected isotopes without affecting other elements in the method. This advantage is seen when analyzing samples for both trace and high-level elements, as shown previously.1

This work demonstrates the ability of the ELAN® DRC™-e to analyze drinking and saline waters for both major and minor elements in a single run.

Experimental
Reagents and Sample Preparation
Samples were analyzed without any pre-treatment. Drinking waters were analyzed directly, while saline waters were diluted 12.5 times with 1% (v/v) HNO3 (Suprapur®, Merck®).

Internal standards were used to compensate for possible matrix effects during sample introduction. An internal standard mix (Y, Rh and Re) was added on-line by using orange/green peristaltic pump tubing and an internal standard addition kit.

External calibration curves were applied using standards ranging from 5 μg/L to 400 mg/L, depending on the element and expected levels. For example, elements likely to be present at low concentrations (i.e. As, Se, Pb) used calibration curves established with 5, 10, 50, and 100 μg/L standards, while high-level elements (i.e. Na, Mg, K, Ca) used standards at mg/L concentrations.

Instrumentation
All analyses were performed on an ELAN DRC-e ICP-MS equipped with Peltier cooled spray chamber and a Meinhard® C-type glass concentric nebulizer. In the method, the elements were grouped into 3 modes: standard mode, extended dynamic range mode (i.e. standard mode with the application of bandpass parameters), and DRC mode using oxygen as a reaction gas. Instrumental parameters are reported in Table 1, while DRC cell conditions appear in Table 2.

The samples were also analyzed for comparison by ICP-OES, using an Optima™ 5300 DV. Taking advantage of the Optima 5300 DV flexibility, macro elements were determined radially and micro elements axially. Several wavelengths were used for each element to check for possible spectral interferences; the preferred wavelengths, along with analysis mode and instrumental conditions, are reported in Tables 3 and 4.

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