The National Chromium and Boron Occurrence Survey
(NCBOS) specifically addressed the following questions:
What are the analytical method challenges and sensitivities for reliable low-level
detection of chrome species and boron in drinking water supplies;
What are the national occurrence patterns for chromium species and boron in
drinking water sources; and,
What is the fate of these compounds through drinking water facilities and
distribution systems? This project investigated analytical challenges for both chromium and boron analysis.
The investigation focused on interferences, preservation techniques, and digestion methods for
accurate and repeatable recovery performance. Laboratory experiments were first used to
investigate the analytical challenges. Preliminary field sampling based on knowledge gained
from the laboratory experiments validated the analytical methods used for the regular survey.
Interferences in boron analysis were found with aluminum and iron for at least one
spectrum evaluated when background concentrations approached 100 mg/L as either Fe or Al.
Therefore at least two spectra were used to confirm all boron analyses. Boron was found to be
otherwise unaffected by sample handling and processing methods as long as base preservation
methods were employed (pH > 8).
Sampling for chromium necessitated consideration of both total chromium and
hexavalent chromium analyses. Previous field sampling experiences had resulted in total
chromium concentrations less than corresponding hexavalent chromium concentrations (Eaton et
al. 2001). A series of lab experiments were conducted to determine the best approach for
chromium analysis to correctly quantify both hexavalent and total chromium.
Using in-bottle acid digestion procedures that follow Method 3500-Fe B (Standard
Methods 1998) - the hydroxylamine digestion for iron solublization - was found to perform best
in achieving complete recovery of total chromium. Base preservation for hexavalent chromium
was found to be adequate when the sample pH was raised above pH 8.
The final survey sample kit preservation, digestion procedures, and sample analysis
procedures were developed based on results from the investigation of both chromium and boron
analytical challenges. Includes 4 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 350 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 11/15/2004 |
