Portable scanning analyser for measuring lead contamination found to be more precise than instruments costing over seven times as much in US government trials
US government tests have found Palintest's portable SA-5000 scanning analyser for measuring lead contamination to be more precise than instruments costing over seven times as much, and it performed exceptionally well in other performance criteria. Palintest is a UK company and is a world leading manufacturer of environmental testing products.
As part of the US Environmental Protection Agency's Environmental Technology Verification (ETV) programme the company's analyser was tested in the presence of Oak Ridge National Laboratory staff at a field site in Hartford, Connecticut.
The ETV programme evaluated field portable instruments that detect and measure lead in dust wipes. The results confirmed that the Palintest sensor technology, in addition to being 'very precise', was relatively simple to operate, matched extremely well with a reference laboratory sample and often demonstrated superior performance than other, more expensive, portable instruments.
The test consisted of the blind analysis of 160 dust wipe samples containing known amounts of lead ranging in concentration from <2mg to 1500mg per wipe. The experimental design was built around three clearance levels, 40mg/ft2 (0.43mg/m2) for floors, 250mg/ft2 (2.7mg/m2) for window sills and 400mg/ft2 (4.3mg/m2) for window troughs (window wells). The Palintest SA-5000 gave excellent correlation with the certified lead concentration up to 800mg/wipe and importantly covered the three levels for clearance testing.
The results were comparable to the conventional laboratory methodology results, often much better than the more expensive field instruments' results, and demonstrated the applicability of the SA-5000 as a field portable method for lead in dust analysis.
The ETV programme exists to provide high-quality and credible performance data through third party organisations to those involved in the USA in the approval, selection, purchase and use of innovative environmental technologies.
The goal is to accelerate the use of innovative technologies in the field, to help speed the identification and clean up of lead-laden dust in homes.
All the test reports can be found on the Environmental Protection Agency's website at www.epa.gov/etv The SA-5000 uses anodic stripping voltammetry analysis, and can analyse surface dust, airborne particulates, water, paint and soil.
Particulate samples are firstly prepared as a solution by agitating the sample with dilute nitric acid.
A disposable mercury-film electrode is then immersed in the sample and the elements present are electroplated on to the electrode.
These are then anodically scanned, reoxidised and stripped out of the electrode, and the resulting current generated can be used to provide a concentration measurement for each element present.
One of the other instruments tested was also an anodic stripping analyser.
The other three were energy dispersive x-ray fluorescence spectrometers that use radioisotope sources to excite characteristic x-rays of a test sample's constituent elements.
The rate at which x-rays of a given energy are counted provides a determination of quantity of each particular element present.
The laboratory method used was similar, using hot plate/nitric acid digestion, followed by inductively coupled plasma-atomic emission spectrometry analysis.
The verification of performance was assessed in terms of precision, accuracy, comparability and completeness.
False positive and negative results, sample throughput and ease of use were also assessed. The SA-5000 performed extremely well.
It displayed the highest level of precision of all the instruments.
In terms of accuracy it was the only instrument to report all of one set of detectable samples within the acceptance range, and was also found to have acceptable amounts of bias.
It also showed a strong linear relationship with the conventional laboratory analysis.
While some other instruments also showed a strong linear relationship, their slopes displayed more bias than that of the SA-5000. Completeness is the percentage of measurements that are judged to be useable.
The SA-5000 generated results for all 160 dust wipe samples, for a completeness of 100%.
For detectable blanks, the SA-5000 reported all blank samples as less than its reporting limits.
It reported no false positive results but did, along with one of the other instruments and the laboratory, record a high number of false negatives.
This was due to a slight negative bias, but the overall evaluation found that the negative bias of the instrument was of an acceptable amount.
Sample throughput was found to be similar for all the instruments, and the SA-5000 the lowest cost instrument in the trial.
