Fluorimeter (From Household Scraps): Video Demo

In this video, my associate Victor will demonstrate how the instrument works and how we put the pieces together.

1 Arduino Mega

2 Paper Towel Rolls

1 Prism

1 Plastic Dental Cup

1 UV LED

1 Photoresistor

1 Converging Lens

Aluminum Tape

Electrical Tape

Soda Can

1 Mirror

1 220 Ohms Resistor

1 10,000 Ohms Resistor

1 Flashlight Ellipsoidal Mirror

10 Connecting Wires

Tonic Water

This homemade fluorimeter is made of basically scraps that we found lying around Victor's house. This can be used to detect fluorescent emission from tonic water. The compound that makes this phenomenon possible is something called Quinine, which has one emission wavelength. Because of this, the instrument does not need an analyzer. If there is only one wavelength there is no reason to split the wavelengths.

The total cost of this only comes down to the Prism, the Arduino mega, and the tonic water. The rest of the materials we found from neighbors and lying around our homes.

Tonic Water= $2.38

Arduino = $25.00

Prism= $13.27

The rest of the supplies are listed with the Video Demo.

The set up of the Arduino circuitry was actually the easiest part. As you can see from the pictures, the board is set up like any other photoresistor with a UV LED light. There was no need for any extra bells and whistles because the experiment is pretty straight forward. I would orient the board so that the connections for the UV LED are near one side of the board and the connections for the photoresistor are as well. This will cut down on your clutter.

This is the part where the rubber meets the road. There are quite a few small details that need attention to get the best data. The inside of every inch of the paper towel rolls is covered with aluminum tape, to increase the source light throughout the system. The prism also needs to fit into the paper towel roll very securely. This can be done by cutting the paper towel roll as we did in the picture above. We also placed the converging lens from an old camera inside of a soda can. It may look fancy but that is actually only there as a way to keep the lens in place. The most important part is the 90-degree angle between the light coming into the sample and the fluorescence coming out. To get as much source light out of the system there is a slit, in the sample compartment, to allow the light to shine through. This is how fluorescence is measured. If the light was shown right through to the detector, the photoresistor, there would be nothing but source light getting through to the resistor. This would be UV/Vis Spectroscopy, not fluorescence. So, in summary, make 100% sure, out of all this instruction and pictures, that you make a 90-degree angle at the location.

This is also an extraordinarily easy step. We will provide you the code to put in the Arduino application. If you copy and paste this exact code and set up all the connections exactly like the pictures from step 3, everything from a coding standpoint will work perfect.

//photometer circuit
//dx.doi.org/10.1021/ed4006216 | J. Chem. Educ. 2014, 91, 1458−1463

//Connect analog out (spec 20) to A0 and ground (spec 20) to ground

// 1v = 100%T

const int transmitPin = A0; //analog signal is proportional to %transmittance

void setup()

{

Serial.begin(9600); //sets baud rate

}

void loop()

{

float voltage, getVoltage, absorbValue; //declare variables as floating point values.

getVoltage = analogRead(transmitPin);

voltage = getVoltage; // This is the transmittance.

absorbValue = -log(voltage)/2.303; //calculates absorbance. "log" is really "ln". The 2.303 converts to log base 10.

Serial.println(absorbValue);

delay(2*1000);

}

Okay, so down to the main event, the moment everyone has been waiting for, actually using the instrument. This instrument is extremely easy to use. From the picture above, you can see the sample compartment in the lower left-hand corner, the one with the cool blue light coming off. We collected the data and put it into an excel spreadsheet, the picture can be seen above.. From the excel, you can see how consistent or data collection was, how sensitive the instrument is, and how pretty we can make a calibration curve.

Limit of Detection was determined to be 1.67 ± 0.02 mL of Tonic Water

Limit of Quantitation was determined to be 8.24 ± 0.02 mL of Tonic Water

https://www.perkinelmer.com/lab-solutions/resources/docs/APP_Quinine_in_Tonic_Water_014133_01.pdf