Laboratory Products Focus
5749:2006 sets the standards for drinking water quality and GB 3838: 2002 is the environmental quality standard for surface water standard limits. The Indian regulations are governed by the Bureau of Indian Standards (BIS) under BIS 10500:1991 specifying the drinking water requirements, IS: 13428:1998 for packaged natural mineral water and IS: 14543:2004 for packaged drinking water.
To achieve regulatory compliance, water suppliers and bottled water manufacturers need a highly accurate technique for the dependable analysis of toxic elements in water.
ICP-OES
Inductively coupled plasma optical emission spectrometry is an elemental analysis technique that offers a dynamic linear range and measures all elements in a sample down to levels of 1ppb and lower. The method is capable of screening up to 60 elements in a single sample run within less than one minute.
The samples can be analysed in a wide range of aqueous or organic matrices. ICP-OES utilises a high temperature plasma source, which atomises the sample and excites the atoms. This causes an emission of photons, with each element in the sample emitting different and specific wavelengths.
The technique measures the intensity of these individual wavelengths and the quantity of each element present in the sample is then calculated from the observed intensity. The measurements can be made sequentially or simultaneously.
Latest advancements in ICP-OES have seen the introduction of pre-loaded, analysis-ready hardware parameters and software environmental method templates.
Environmental method templates provide a simple, rapid and cost- effective tool for routine analysis of toxic elements in tap and bottled water samples. Regulatory compliance is facilitated with no requirement for method development.
A variety of tap and bottled waters were analysed for toxic elements using a new ICP-OES method to demonstrate the technique’s superior capabilities for this type of analysis.
Figure 1. iTEVA method templates for the iCAP 6200
Sample and Standard Preparation
A selection of Chinese tap and bottled drinking waters were chosen for the analysis. A European bottled water which imports into China was also tested for compliance.
A total of five samples were selected, including a tap water sample from Dingpu river area, Shanghai; a tap water sample from Jinqiao lake area, Shanghai; Waterman packaged drinking water; Nestle natural mineral water and Evian natural mineral water.
The samples did not require any pre-treatment and after preservation
in 0.5% HNO3, they were analysed directly. Calibration standards were
prepared in 0.5% HNO3 at concentrations of 0, 50 and 100 ppb. A QC check solution was used at 10 ppb to test the recovery and stability of the method.
Method Development
The environmental method template, containing all of the required method parameters and standard concentrations required for this experiment, was opened in the software.
A standard sample handling kit was used for the analysis as per the recommendations in the method. The method parameters are shown in Table 1.
Table 2. Averaged results and method detection limits (MDL) in ppb
Figure 2. Flexible sequence automation options in iTEVA
Results and Discussion
The samples were analysed repeatedly in batches of 10 (two of each of the five samples), followed by a QC check. As the matrix was very clean and deionised water was used to make up the calibration standards, the typical detection limits for the instrument were employed as the method detection limits. Table 2 demonstrates the averaged results of samples over the four hours and the method detection limits. All of the results were well below the requirements of both the Chinese and Indian regulations with all of the method detection limits shown to be suitable for the analyses. The only exception was mercury in relation to the GB 3838: 2002 regulation, which is too low to quantify when aspirated directly.
Experimental
A dual view compact Thermo Scientific iCAP 6200 ICP-OES instrument was used for the analysis. The instrument is powered by Thermo Scientific iTEVA ICP software suite, which incorporates a pre-loaded analysis-ready environmental method template (Figure 1) to simplify method development and enable ‘out-of-the- box’ analysis with little or no requirement for method development.
Table 1. Method parameters
The samples were repeatedly analysed in a single automated run over a period of four hours. Using the software’s sequence automation and check tables, a QC check was analysed after every 10 samples and a calibration was performed after every 25 samples. Figure 2 shows how the Continuing Actions were set up.
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