Public Lab Research note


Chemical/Analytical Methods Used When Testing for Lead

by read_holman | December 12, 2018 06:05 | 349 views | 6 comments | #17875 | 349 views | 6 comments | #17875 12 Dec 06:05

Read more: publiclab.org/n/17875


Summary

This page contains methods of detecting lead in a medium, be it in paint, water, dust, soil, or other surfaces. This page is devoted primarily to presenting information on the ~methods~ for detection; the chemical or scientific approaches behind various commercial products, laboratory-based services, and DIY methods.

There are very few DIY methods that allow for the testing of lead. Because of this, testing for lead -- be it in paint, soil, dust, water, or other mediums -- involves using commercial products. Therefore, this page contains links to commercial products. Their mention here does not equal endorsement.

On this page:

Laboratory-based testing methods (most expensive, most reliable)

  • These methods are 'advanced'; they require an understanding of chemistry and some training on how to operate expensive equipment.
  • A number of consumer-facing lead testing "products" are mail-in services. Those services -- in which you collect a sample yourself and then mail that sample to a lab for analysis -- will leverage one or more of these methods.

Professional At-the-source testing Methods (moderately expensive, moderately reliable)

  • These methods are typically used by professionals remotely (aka: not in a lab). Though this limitation is due primarily to their costs, not necessarily the technical skill needed to use them.
  • These are less expensive than the lab-based methods, but much more expensive than the consumer-facing screening methods.

Consumer-facing At-the-source screening methods (least expensive, less reliable)

  • These methods are less advanced; they exist to provide results faster and at a lower cost than those provided by a lab or portable-XRF. They are also less scientific; typically the accuracy, precision, and sensitivity are in question. Still, there are occasions in which these types of screenings may be useful.

Exploratory methods still in research phase

  • These methods are provided for the curious. Most of these methods have been documented only by a University-based researcher or by a company that claims to have a new way of doing things.
  • At the time of writing, there is no commercial product available for any of these.
  • Some of these methods are expensive, replacing the advanced machinery; other methods are cheaper and provide a more DIY opportunity.

This page is devoted to the science of detecting lead, the methods and approaches used.

For information on how to test for lead, including using a profession service, using a mail-in testing service, and for specific products that can be purchased online, visit the following page: How to Test for Lead in Your Environment


Laboratory-based testing methods (most expensive, most reliable)

The following is a list of the most relevant *laboratory-based* methods, techniques, and technologies for testing samples for lead.

These require professional training and expensive machinery which means these are not available to the average person. These exist within most colleges and universities (particularly their chemistry departments), city/county-based chemical analysis labs, as well as within private, professional laboratories. Advancement of these methods and explorations of deviations of these methods is generally beyond the scope of the Public Lab community's work. However, I am posting here for reference.

ICP-MS (Inductively Coupled Plasma - Mass Spectrometry)

ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy)

FAA (Flame Atomic Absorption)


Professional At-the-source testing Methods (moderately expensive, moderately reliable)

XRF Analysis (X-Ray Fluorescence)

  • This is documented as EPA Method 6200 (PDF):
  • Wikipedia article...
  • Detection limit: "This method is a screening method to be used with confirmatory analysis using other techniques" (from the above EPA Method file)
  • XRF Analyzers can be portable and are often used by professional home inspectors
  • Cost = ~$7,000+ used (ebay link)

Voltammetry: Ion Selective Electrode (ISE) (Water only)

  • This method involves applying a potential to a system of electrodes and measuring the resulting current created from the interaction with select ions. These are handheld devices which can be used multiple times.
  • Detection limit: 2 ppb, some down to 1 ppb
  • Cons: These products tend to be more expensive.

Commercial products that leverage this method: Hanna HI98191: Professional Waterproof Portable pH/ORP/ISE Meter ($595) + lead-specific ISE (additional $890) | SA1100 Scanning Analyzer by Palintest

Biosensors (e.g. DNA-based methods, Enzyme reaction mechanisms)

  • This method leverages microorganisms, enzymes, microspheres, and nanomaterials that have been developed to detect heavy metal.
  • Detection limit: 2 ppb
  • Cons: Due to its complexity and use of biomaterial, this method typically requires a professional lab setting to develop. Products are in their early stages of commercialization.

Commercial products that leverage this method: Andalyze (No pricing shown.)


Consumer-facing At-home (DIY) screening methods (least expensive, less reliable)

Colorimetry

At-home / DIY testing methods tend to use colorimetry as its analytical method. This methodology requires a user to compare the change of color in a tested sample -- a strip ("dipstick") you put in water or swab you wipe on a surface -- with a reference. If the color change in your tested strip or swab is darker than the reference, this is supposed to indicate the presence of lead.

Products you find online and in department stores use this method. Their generally reliability is a constant conversation. This methodology lends itself towards two problems:

  • The sensitivity is typically set to a "regulatory" level, which is higher than the amount health professionals say we should have (zero). Thus these are not good at detecting low-levels of lead.
  • These are often hard to read generally
  • They are known to have rates of high-false positive.

The EPA has a program to evaluate these types of testing kits (see EPA Lead Testing Kit website). However, only two products have been evaluated, whereas many more are available for purchase. Neither of them passed the full evaluation criteria; they both a "EPA verified" but only for negative findings. Both are also only for paint.


Exploratory methods still in research phase

The following are methods that have been communicated through peer-reviewed articles or other methods sufficiently verifiable. These are in the research phase of their development.

...for single use detection

Smartphone Nanocolorimetry from researchers at the University of Houston (source): A single-step sedimentation approach by mixing a controlled quantity of chromate ion (CrO42--) to react with Pb2+ containing solutions to form highly insoluble lead chromate (PbCrO4) nanoparticles as vivid yellow precipitates. This is followed by microscopic color detection and intensity quantitation at nanoscale level using dark-field smartphone microscopy.

DNA-based method: Microfluidic chip + Smartphone from researchers at Hong Kong Baptist University (source): A plastic microfluidic chip pre-loaded with reagents and probes. The smartphone app compares the signal from the user's sample with that from the pre-loaded control sample

Biosensors (modified bacteria) from the company FredSense (source): utilizes a tunable bacteria that can provide ultra-sensitive measurements of trace chemicals in a water. Currently have arsenic, iron, and manganese.

Arduino processor + carbon nanotubes from an 11-year old in a science competition. She calls her product Tethys (source)

...for continuous water monitoring

Sensors that can live within water systems, either within pipes or at the tap, that continuously monitor water quality and report that data to a central repository is an exciting and emerging area of research. The particular methods deployed may include the above. The below details a few different research activities that I'm aware of.

  • Example from researchers at the University of Michigan: Platinum electrodes for the detection of heavy metal contamination (source)

  • Example from researchers at the University of Wisconsin, Milwaukee (UWM): Graphene-based nanomaterial (source)

  • Example from researchers at Widener University: voltammetry / ISE + 24-bit analog digital converter and miniaturized open-source potentiostat. (source)


This page is devoted to the science of detecting lead, the methods and approaches used.

For information on how to test for lead, including using a profession service, using a mail-in testing service, and for specific products that can be purchased online, visit the following page: How to Test for Lead in Your Environment



6 Comments

Hi @read_holman -- I did find this XRF tool for soil testing: https://www.bruker.com/products/x-ray-diffraction-and-elemental-analysis/handheld-xrf/lead-testing-gun.html -- I assume it's pretty cost-inaccessible but just since you asked!

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Wow, interesting; these "SprayView" kits have a great illustration of colorimetric detection:

https://www.chemsee.com/residential/detection-kits-for-lead/

Before-and-After-Small.png

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Also the UMASS Amerst Soil Lab offers a $20 test for lead, although I don't know much more about it. It is a "mail-in" test though so perhaps outside the scope of this list, but maybe useful until we do find some soil tests that aren't lab-dependent:

http://ag.umass.edu/services/soil-plant-nutrient-testing-laboratory/ordering-information-forms

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And the same page above lists Alternate EPA 3050B and 6010 methods for lead at $55.

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Not really relevant. I was on the PublicLab Open Hour call and I asked a question but can't remember the answer. I asked about finding lead on twitter and you said something about element 82 because any search on lead wouldn't turn up the element.

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There are several manufacturers of handheld XRF analyzers. And yes, they are usually cost limited. The cost can be reduced somewhat by renting, instead of buying.

The handhelds still have to be optimized for the element. Some use radioactive sources instead of xray tubes, and will be more sensitive to different elements because of this.

Often, the handhelds use beryllium windows. Beryllium is a nasty and expensive element. Something to watch out for when renting.

Regards

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