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Access Agilent eNewsletter August 2016

PerkinElmer FAAS with Agilent consumables: Accurate determination of nutrients and mineral elements in water samples

Ankit Shah, Agilent Spectroscopy Consumables Support Specialist

Everyone wants a safe environment, and accurate monitoring of minerals and contaminants in drinking, waste, surface, and ground water is essential to ensure good water quality. Contamination from inorganic elements may occur by natural deposition or by discharge from industrial, agricultural, and household wastes. If you use a PerkinElmer instrument for elemental analysis, now you can get high-quality results with Agilent spectroscopy supplies.

Although more advanced instrumental techniques such as ICP-OES and ICP-MS are applied to elemental analysis of waters, flame atomic absorption spectrometry (FAAS) is preferred due to its simplicity, low operating cost, and comparatively fast analysis for major analytes like Ca, Cu, Fe, Mg, K, Na, and Zn. The FAAS technique also requires minimal sample preparation, and it detects the expected analyte concentrations typically found in environmental water samples.

Excellent recoveries demonstrate suitability of Agilent supplies

For a recent study, we used a PerkinElmer AAnalyst 800 FAAS to analyze a number of municipal and bottled water samples for Ca, Cu, Fe, Mg, K, Na, and Zn. Only Agilent consumables and supplies were used with the PerkinElmer FAAS instrument.

All samples were pretreated by acidification with 1% nitric acid (HNO3). The final solution included 0.1% lanthanum chloride (LaCl3), used as a releasing agent for analysis of Ca and Mg, and as an ionization suppressant for analysis of Na and K. Agilent Application Note 5991-7046EN gives the instrument parameters and standard concentrations used for calibration.

Two independent standards were analyzed to validate the results for the water samples. We used an Agilent initial calibration verification (ICV) standard for ICP, AA or GFAA to confirm the accuracy of the calibration, and a High-Purity Standards Trace Metals in Drinking Water certified reference material (CRM-TMDW) to validate the measured results for the water samples. We achieved excellent recoveries for a 100-fold dilution of the Agilent ICV standard and the High-Purity Standards CRM-TMDW (Table 1 and Table 2), which confirmed the accuracy and suitability of the method.

Analyte Measured result (mg/L) Analyte concentration with 100-fold dilution (mg/L) Recovery (%)
Ca 4.85 5.00 97
Cu 0.25 0.25 100
Fe 1.05 1.00 105
Mg 4.86 5.00 97
K 4.86 5.00 97
Na 5.35 5.00 107
Zn 0.21 0.20 105

Table 1. Excellent recoveries for the elements determined in the Agilent ICV standard.

Analyte Measured result (mg/L) Certified concentration (mg/L) Recovery (%)
Ca 36.6 35.0 105
Cu 0.019 0.020 95
Fe 0.102 0.100 102
Mg 8.43 9.00 94
K 2.33 2.50 93
Na 5.90 6.00 98
Zn 0.071 0.070 101

Table 2. Good recoveries for the elements determined in the High-Purity Standards Trace Metals in Drinking Water certified reference material (CRM-TMDW).

Accurate measurement of both low- and high-concentration elements

With the same calibration, samples of drinking water, recycled water from a municipal water treatment facility, and bottled water were measured. Table 3 shows the results.

Analyte Municipal (drinking) water 1 (mg/L) Municipal (recycled) water 2 (mg/L) Municipal (drinking) water 3 (mg/L) Bottled mineral water (mg/L)
Ca 3.85 13.92 4.88 1.17
Cu 0.12 0.03 0.13 <DL
Fe 0.05 < Detection limit (DL) 0.03 <DL
Mg 1.86 7.87 1.14 1.82
K 0.59 20.56 0.61 0.53
Na 4.10 Over range 4.17 7.76
Zn 0.04 2.47 0.14 <DL

Table 3. Measured results for the three municipal water and drinking water samples.

Waters 1 and 3 are drinking waters that were sampled from different localities, but the supply originates from the same reservoir. The differences in the elemental concentrations are probably due to the condition of the pipework, the distance from the reservoir, and the holding time for the water in the pipework prior to sampling. Water 2 is a Class A recycled water, which is unfit for human consumption, but does meet the local Environmental Protection Authority [1] and Department of Health guidelines.

Analyte Detection limit (mg/L)
Cu 0.003
Fe 0.007
Zn 0.004

Table 4. Sensitive analysis: low detection limits achieved using the PerkinElmer AAnalyst 800 FAAS with Agilent consumables and supplies.

The bottled water was free of Cu, Fe, and Zn, which confirmed that these elements had been removed during purification prior to bottling. The Mg and K concentrations were remarkably similar to those measured in the drinking waters 1 and 3.

Detection limits were calculated for Cu, Fe, and Zn (Table 4). The other elements were present at higher concentrations and had been measured using low-sensitivity conditions, so the detection limits were not determined.

Reliable performance with Agilent supplies for PerkinElmer FAAS

This method is ideal for rapid, direct, and simple measurement of the nutrients and mineral elements in both municipal water supplies and bottled water samples. By measuring Ca, K, Mg, and Na (all present at high concentration) with reduced-sensitivity conditions, it was possible to analyze both high- and low-concentration elements in the same samples.

The performance and dynamic range were demonstrated by the excellent recoveries obtained for both the low- and high-concentration elements determined in the Agilent ICV standard and High-Purity Standards Trace Metals in Drinking Water CRM. To learn more, download Agilent publication 5991-7046EN. Then explore the full portfolio of Agilent supplies for the PerkinElmer AA, ICP-OES, and ICP-MS instruments.

Reference

  1. Environment Protection Authority Victoria, “Guidelines for Environmental Management—Dual Pipe Water Recycling Schemes– Health and Environmental Risk Management,” (Publication 1015.1) Feb., 2015.