Author
Kenneth Ong

PerkinElmer Life and Analytical Sciences 710 Bridgeport Avenue Shelton, CT 06484 USA

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FIAS-ICPOES and Continue Hydride-ICPOES – Improve lab efficiency on hydride analysis

In our last issue of Inorganic Newsletter we have discussed hydride analysis using FIAS coupled with AAS, in this issue we will look at some work with FIAS-ICPOES and continue hydride-ICPOES analysis.

Arsenic and Mercury in potable water causes bladder, lung and skin cancer, and may cause kidney and liver cancer. It is found that arsenic harms the central and peripheral nervous systems, as well as heart and blood vessels, and causes serious skin problems. It also may cause birth defects and problems related to reproductive system. Most arsenic and Mercury enters water supply either from natural deposits in the earth or from industrial and agricultural pollution.

The concentration of such toxic elements varies from ppm to ppb levels. Analysis of Hg and As up to ppb level is possible using ICP-OES with Flow Injection Analysis (FIAS); where we can enhance the detection levels to sub ppb levels.

To do this, the PerkinElmer Dual view ICP spectrometer with shear gas and chiller was used in combination with FIAS 100/400 flow injection system as shown in the figure.

Figure 1. FIAS 400 & Optima™ 7300 DV ICP-OES

Figure 2. Optima™ 7300 DV ICP-OES

Figure 3. FIAS 400

The FIAS 400 provides extensive flexibility.

Standard and sample preparation

Sample and standards are first reduced by adding 5% of KI and 5% of Ascorbic acid and then diluted with 10% HCl solution.

The graph below shows the best linearity and very good reproducibility along with low RSD for every replicate of the readings even at such low level concentrations.

From the observed results metal ion such as Mercury and Arsenic which are very toxic in nature for environment as well as human health can be detected in very low ppb level with the help of FIAS and ICP-OES. PerkinElmer Optima ICP spectrometer with FIAS 100/400 is the best available solution in the market for variety of inorganic analysis in different matrices.

The plasma conditions and nebulizer flow conditions were optimized for the calibration of the instrument. Since Optima ICP Spectrometer is having very high speed of analysis; we could also include other elements as well.

In a continuous flow system, the acidified sample, blank or standard is continuously pumped and mixed with a pumped stream of reductant, usually sodium borohydride, to produce the gaseous hydrides. This allows unlimited number of metal hydride/wavelength for analysis. A flow of argon is added to this mixture and the hydrides are "stripped" into the gas phase. A gas/liquid separator allows the gaseous, hydride-containing phase to enter the ICP for analysis, and allows the remaining liquids to be pumped to waste.

Standard preparation for continue hydride analysis

Pre-Reduction Step is still needed for As and Sb.

For the pre-reduction of Sb and As, 20 mL of sample was placed in a 50 mL polypropylene autosampler tube. To this, 2 mL of a 5% solution of KI and ascorbic acid was added. Six mL of concentrated HCl was also added, and the mixture was allowed to sit for at least 20 minutes. The tube was brought to the 50 mL mark with deionized water and the sample was ready to run.

For analysis of Sn, the standard was doped with 1% of L-Cysteine in 3%HCl. The L-Cysteine is able to remove the interference from transition metal which otherwise interfered in the analysis of metal hydride.

Mercury standards are prepared in 3% HCl.

Reducing agents

The table shows a typical concentration of NaBH4/NaOH use for FIAS-MHS.

For continue flow injection hydride analysis, in order to determine metals halides and Hg in a single analysis run, 0.2% of NaBH4 was prepared in 0.05% of NaOH solution.

The graph below shows the best linearity and very good reproducibility along with low RSD for every replicate of the readings even at such low level concentrations.

Conclusion

ICPOES is capable of multielements analysis, laboratory efficiency could be improved with most other hydride being analyzed in a single run. The number of analytes and wavelength that can be analyzed with FIAS-ICPOES is only limited by the sample loop and the sample read time set at ICPOES method.

References