Analysis of Aqueous Solutions and Waters by ICP-OES with Twin Interface Plasma Observation

Inductively coupled plasma optical emission spectrometry (ICP-OES) is extensively used for the analysis of aqueous solutions due to its multi-element determination capability, sensitivity and high dynamic linear range.

This article describes the analysis of waters using the SPECTROBLUE with twin interface plasma observation (Figure 1). The application is explained in a number of ICP-OES standard procedures such as ISO 11885 and US-EPA Method 200.7. The article includes the detection limits, line selection and analyses on accuracy and precision.

SPECTROBLUE with twin interface plasma observation

Figure 1. SPECTROBLUE with twin interface plasma observation

Experimental Procedure

Instrumentation

SPECTRO Analytical Instruments’ SPECTROBLUE ICP-OES with twin interface plasma observation was used to perform all measurements. The twin interface option allows automatic radial and axial observation of the plasma with every measurement.

The SPECTROBLUE ICP-OES includes a Paschen-Runge spectrometer mount, using the proprietary ORCA (Optimized Rowland Circle Alignment) technique. Consisting of 15 linear CCD detectors and 2 hollow section cast shells, the wavelength range from 165 and 770nm can be investigated, enabling complete spectrum capture within 4s.

The system has unique reprocessing capabilities that eliminate the need for a new measurement, even if further lines or elements have to be determined at a later date.

The optic is filled with argon and hermetically sealed. The argon, which is continuously circulated through a filter, absorbs water vapor, oxygen and other species. High optical transmission in the UV is attained, enabling the determination of non-metals and also the use of major interference free lines in this region.

The state of the optical system is automatically monitored using SPECTRO’s Intelligent Calibration Logic (ICAL). An air-cooled ICP-generator, which is built on a 27.12MHz system, guarantees exceptional stability of the forward power even in the case of sample loads that change rapidly. All applicable ICP operating parameters are controlled by software, thus enabling easy selection of the optimum operating conditions.

To introduce the sample, a Sea Spray nebulizer with a cyclonic spray chamber was utilized, or a Modified Lichte nebulizer with a cyclonic spray chamber can also be utilized. Table 1 shows the operating conditions.

Table 1. Typical ICP operating conditions

Power 1450 W
Coolant flow 13 L/min
Auxiliary flow 0.8 L/min
Nebulizer flow 0.8 L/min
Plasma torch Quartz, demountable, 2.0 mm Injector tube
Spray chamber Cyclonic
Nebulizer Sea Spray
Sample aspiration rate 2 mL/min
Replicate read time 49 sec per replicate

Calibration Standards

Standard solutions that are commercially available on the market were used for calibration. Table 2 shows the concentrations of the elements.

Table 2. Calibration standards

Element Std.1 [mg/L] Std.2 [mg/L] Std.3 [mg/L] Std.4 [mg/L]
Ag 0 0.025 0.125 0.25
Al 0 0.1 0.5 1
As 0 0.1 0.5 1
B 0 0.1 0.5 1
Ba 0 0.1 0.5 1
Be 0 0.1 0.5 1
Ca 100 10.1 5.5 51
Cd 0 0.1 0.5 1
Co 0 0.1 0.5 1
Cr 0 0.1 0.5 1
Cu 0 0.1 0.5 1
Fe 0 0.1 0.5 1
Hg 0 0.1 0.5 1
K 10 25.5 2.5 5
Li 0 0.1 0.5 1
Mg 1 50.1 5.5 11
Mn 0 0.1 0.5 1
Mo 0 0.1 0.5 1
Na 5 11.1 100.5 51
Ni 0 0.1 0.5 1
P 0 0.5 2.5 5
Pb 0 0.1 0.5 1
Sb 0 0.1 0.5 1
Se 0 0.1 0.5 1
Si 0 0.1 0.5 1
Sn 0 0.1 0.5 1
Sr 0 0.1 0.5 1
Tl 0 0.1 0.5 1
V 0 0.1 0.5 1
Zn 0 0.1 0.5 5

NIST standard reference material 1643e was used to perform the quality control of the method. All solutions were acidified with 1% HNO3, suprapure quality.

Results and Discussion

The selected wavelengths and the achieved Limits of Detection (LOD) are given in Table 3. The LODs were determined according to the following equation:

    LOD = 3 RSDb c/ 100 SBR

Where RSDb is relative standard deviation of 10 replicates of the blank (in %), c is the concentration of the standard, and SBR is signal to background ratio.

Table 3. Limits of Detection (LOD) for the selected lines

Element λ [nm] Viewing mode LOD (3σ) [μg/L]
Ag 328.068 radial 1.9
Al 167.078 axial 0.06
As 189.641 axial 0.95
B 249.773 axial 0.45
Ba 455.404 radial 0.15
Be 313.042 radial 0.08
Ca 396.847 radial 0.09
Cd 214.438 axial 0.06
Co 228.616 axial 0.18
Cr 267.716 axial 0.22
Cu 324.754 radial 1.3
Fe 259,941 Axial 0.12
K 766.896 radial 65
Li 670.784 radial 1.4
Mg 279.553 axial 0.005
Mn 257.611 axial 0.04
Mo 202.030 axial 0.14
Na 589.59 radial 6.8
Ni 231.604 axial 0.29
P 177.495 axial 0.72
Pb 220.353 axial 0.88
Sb 206.833 axial 1.3
Se 196.090 axial 1.5
Si 251.612 axial 0.87
Sn 189.991 axial 0.48
Sr 407.771 radial 0.08
Tl 190.864 axial 0.75
V 311.071 radial 1.4
Zn 213.856 axial 0.08

The accuracy of the technique was analyzed by examining the NIST standard reference material 1643e. As illustrated in Table 4, the certified values and the measured values are in excellent agreement for all the elements.

Table 4. Comparison of certified and measured concentrations for NIST1643e

Element Cert. Conc. [µg/L] Conf. Range +/- [µg/L] Meas Conc. [µg/L] Recovery [%]
Al 141.8 8.6 140.6 99.2
As 60.45 0.72 58.16 96.2
B 157.9 3.9 158.7 100.5
Ba 544.2 5.6 523.1 96.1
Be 13.98 0.17 13.19 94.3
Ca 32300 1100 31914 98.8
Cd 6.568 0.071 6.541 99.6
Co 27.06 0.32 25.9 95.7
Cr 20.40 0.24 18.98 93.0
Cu 22.76 0.31 23.70 104.1
Fe 98.1 1.4 96.28 98.1
K 2034 29 1949 95.8
Li 17.4 1.7 18.3 105.1
Mg 8037 98 7869 97.9
Mn 38.97 0.45 38.35 98.4
Mo 121.4 1.3 119.3 98.3
Na 20740 260 20285 97.8
Ni 62.4 0.69 60.36 96.7
Pb 19.63 0.21 21.01 107.0
Sb 58.30 0.61 55.96 95.9
Se 11.97 0.14 11.21 93.7
Sr 323.1 3.6 311.4 96.3
Tl 7.445 0.096 7.23 97.1
V 37.86 0.59 37.09 97.9
Zn 78.5 2.2 74.8 95.3

Conclusion

One of the major applications for ICP-OES is the multi-elemental analysis of aqueous solutions. The SPECTROBLUE with twin interface plasma observation provides a fast, simple, accurate, and cost efficient method for the analysis of waters and aqueous solutions.

Together with an autosampler, the SPECTROBLUE TI can be completely automated. Independent from the number of elements and lines, an analysis including pre-flush, three replicates and method rinse can be carried out in less than 4 min.

The SPECTROBLUE allows for precise determination of earth alkali elements using the radial mode and enables high sensitivity detection of trace elements using the axial mode. Excellent recoveries were found for the NIST standard reference material NIST 1643e.

This information has been sourced, reviewed and adapted from materials provided by SPECTRO Analytical Instruments GmbH.

For more information on this source, please visit SPECTRO Analytical Instruments GmbH.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    SPECTRO Analytical Instruments GmbH. (2019, January 02). Analysis of Aqueous Solutions and Waters by ICP-OES with Twin Interface Plasma Observation. AZoM. Retrieved on July 23, 2019 from https://www.azom.com/article.aspx?ArticleID=11147.

  • MLA

    SPECTRO Analytical Instruments GmbH. "Analysis of Aqueous Solutions and Waters by ICP-OES with Twin Interface Plasma Observation". AZoM. 23 July 2019. <https://www.azom.com/article.aspx?ArticleID=11147>.

  • Chicago

    SPECTRO Analytical Instruments GmbH. "Analysis of Aqueous Solutions and Waters by ICP-OES with Twin Interface Plasma Observation". AZoM. https://www.azom.com/article.aspx?ArticleID=11147. (accessed July 23, 2019).

  • Harvard

    SPECTRO Analytical Instruments GmbH. 2019. Analysis of Aqueous Solutions and Waters by ICP-OES with Twin Interface Plasma Observation. AZoM, viewed 23 July 2019, https://www.azom.com/article.aspx?ArticleID=11147.

Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Submit