Overview of the Nature, Extent, Health Risks, and Treatment of Metal-affected Drinking Water in Bangladesh

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Table 3. The percent recoveries of independent standards and sample matrix spikes analyzed by the ICDDR,B laboratory (Results are reported as means ± standard deviations). ^a

Analyte	Independent Standard Recovery	Sample Matrix Spike Recovery
Arsenic (As)	83%	89 ± 11%
Ferrous iron (Fe²⁺)	93 ± 10%	34 ± 23% without dilution 96 ± 13% with 1 to 10 dilution
Total iron (Fe)	95%	120 ± 12% with 1 to 10 dilution
Sulfate (SO₄^2-)	106%	106 ± 20%
Chloride (Cl^-)	114%	90 ± 15%
Phosphate (PO₄^3-)	88%	84 ± 2%

^a These results are from our 1997 field program.

In contrast to these other laboratories, ICDDR,B had an effective quality control program and performed exceptionally well. Our team used ICDDR,B for all locally provided laboratory results.
The recoveries from the blind analysis of all independently prepared standards and sample matrix spikes for arsenic, sulfate, chloride, and phosphate were within the 100 ± 25% range considered acceptable for routine analytical laboratories.
However, the matrix spike recovery from the determination of ferrous iron in undiluted groundwater by the 1,10-phenanthroline method (34 ± 23%) was suppressed by an analytical interference. This interference was defeated by diluting all ferrous iron samples 10 times with distilled water before color development.
Similarly, all samples submitted for total iron analysis by the 1,10-phenanthroline method were diluted 10 times with distilled water to defeat this interference; despite this precaution, 24 of 89 samples (27%) failed to develop proper color or generated a whitish colloidal precipitate upon the addition of 1,10-phenanthroline.

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Table 3. The percent recoveries of independent standards and sample matrix spikes analyzed by the ICDDR,B laboratory (Results are reported as means ± standard deviations). a

Table 3. The percent recoveries of independent standards and sample matrix spikes analyzed by the ICDDR,B laboratory (Results are reported as means ± standard deviations). ^a