DIY Spectrometers, or "Want a chem analysis lab at home?"

 A spectrometer is a device which identifies chemical substances based on their spectrum, e.g. what wavelengths of energy they output or respond to when driven by a stimulus. The stimulus can be naturally occurring or produced by the experimenter.

WIRED science blogs ran a very basic story on DIY spectrometers in July 2012 for looking at illuminating objects (light bulb, sun) which should give a general idea of what spectroscopy is about, for those unfamiliar.

Emission and Absorption Spectrometer:

For self illuminated, simple sources like the sun or a CFL, it is easy to make this at home using a prism, diffraction grating, darkening medium such as cardboard, and either a sensor such as a webcam or your naked eye. For an easy 30 minute project demonstrating this, check out this entry on Instructables

This supports both emission lines (e.g. a flourescent bulb) and absorption / drop out lines (e.g. from the sun).

Flourescence Spectrometer:

Public labs has created a kickstarter which uses a $35 kit and free software, plus their own database, to identify samples after they have been suspended in a known oil, by illuminating the sample with a known light source and then diffracting it. 

http://publiclab.org/wiki/spectrometer

Ramen Spectrometer: 

Uses a laser to excite a sample and measure the way monochromatic light scatters off of a sample. The scattered light is affected by vibration mode, rotational mode, and angular momentum of the molecules. The scattered light is picked up by a CMOS sensor like you find in digital camera, filtered, and then put into the frequency domain using Fourier transform. The spectral signature is then looked up against a database and the chemical composition of the sample (likely statistical model) is displayed to the user.

There are multiple parties working on this including Ben Krasnow. This is a completely open project. Structural parts are 3d-printable, software is open source and the acquirable parts are provided in a Bill of Materials (BOM).

https://hackaday.io/project/1279-ramanpi-raman-spectrometer
http://benkrasnow.blogspot.com/2013/05/intro-to-diy-raman-spectroscopy.html

Ion-mobility Spectrometer: 

Works on vapor samples. The sample is ionized using a radiation source such as Americium or Francium. The spectrometer then uses a drift tube to determine the length of time it takes for the ions to flow through a buffer gas in the tube. This is a common method used in airport screening "sniffers" such as those made by Smith's Detection, Implant Sciences Corportation.  May not be suitable for home production due to the difficulty of the ionization process (can one person buy enough smoke detectors to get an ionization source?)

Mass Spectrometer:

Measures the mass of individual molecules by some means. The traditional mass spectrometers are expensive, bench top laboratory equipment based on time of flights. Micro-electro-mechanical (MEMS) devices which vibrate at a resonant frequency are being developed, to act like tiny tuning forks. When a molecule of substance touches these tiny tuning forks, it will change the resonant frequency in a measurable way. This is similar to the MEMS accelerometers, gyroscopes, and microphones which are already common in cell phones today, so a DIY or low cost mass spectrometer may not be far out.

How might you use a spectrometer in your home or small lab? For instance, would this be useful for identifying chemical contaminants such as lead? Leave a comment below.