Gaschromatograph

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About: DIY Bio, DIY Chemistry, Development of Lab equipment, Citizen Science Education: University of Education Heidelberg (Chemistry, Biology) since 2017 (University of Applied Science Mannheim) to study bi...

Gas chromatography is an analytical method to separate and detect a mixture of substances in a column. The separation is based on different levels of interaction between the column and the analytes.
Professional GC are very expensive (5000$) and not affordable for schools or the private basement lab.
With this GC-Column it is possible to separate and analyse LPG or other low molecular weight alkanes (C1-C5) which can be found in lighter gas.
The packend column of this GC is made of an PVC 1,5m infusionssystem filled with Silika gel.

Step 1: General Structure of GC

A typical gaschromatograph consists of different components.

1. Temperaturen-controlled oven containing the column.
2. The column in where the sample is separated on the stationary phase.
3. A carrier Gas (Helium, Hydrogen, Nitrogen) that transports the sample through the column.
4. A detektor to dedicate the different components of the sample. Mostly are flame Ionisation or thermal conductivity detektors are used.
5. Interface or integrator to translate data into a chromatogram.
6. Injektionunit for injecting the sample onto the column.

The sample (for example a mixture of Butane and Propane) is injectet into the column. The two components stays different long in the column and can be determined qualitatively over the retention time.
The Area below the peak is proportional to the concentration of the analyts.

Step 2: Hardware

•5V diaphragm pump
•silicon tubing
•clamp for the pump
•Switch
•CARESITE® Positive Displacement Needleless Connectors
•Arduino UNO
•TGS-813 Gassensor
•push button to reset program
•three way valve
•breadboard
•10k Resistor
•Jumper wires




https://m.youtube.com/watch?v=nDdQ6vMInPI


Step 3: Arduino Gas Detection Unit

Sketch is from another sensorprogram, some parts arent´t nessesary for the GC, but it works verry well.

To plot the chromatogram in excel you have to download PLX DAQ, its a plotting macro for MS excel.

It is also possible to use the serial plotter


Sketch:

float vp = 1.7;
float r1 = 100000;
float r2 = 10000;
float ts = 0;

void setup() {

Serial.begin(9600);
Serial.println("CLEARDATA");
Serial.println("LABEL");
Serial.println("RESETTIMER");

Serial.println((int) (vp / (r2 / (r1 + r2))));

delay(1000);
}
void loop() {
float v = (analogRead (0) * vp) / 1024.0;
float v2 = ((v / (r2 / (r1 + r2))*10)+1); // here you can calibrate the sensor
if (v2 <2) {
v2 = 0.00;

}
Serial.print("DATA,TIME,TIMER,");
Serial.println(v2);
delay (1000);
}

Step 4: How to Fill the Column

To pack the column you need silica gel 60 for column chromatography grain size 0,03-0.2mm. Bigger Grain size is also possible, but not bigger than 0,5mm.

For one column you need:
•10g Silica gel 60 (Carl Roth Sigma Aldrich)
•30ml Petroleum Ether 40-60 pharmazeutical purity (buy in your local Pharmacie)
•1g high-viscosity paraffin pharmazeutical purity
•200ml beaker
•glasrod
•oven
•1,5m infusion system with Luer-Lock joint. (Intrafix Braun)
•Balance


Solve the paraffin in petrolether and add the Silica Gel. Leave it by good ventilation until solvent is evaporated.
Dry the silica gel by 120°C (30 minutes) and fill it in the infusionsystem.
connect to the pump an rinse the column until you get a constant baseline.

Your column is now ready to use.



Step 5: Connection Between Column and Sensor

The distance between column and sensor have to be as small as possible so that the flow velocity does not change. Big distance leads in wide peaks and tailing.
For the fitting you can use a syringe.

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    14 Discussions

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    marlin_maker

    Question 4 months ago

    That's a nice project. If I'm not mistaken, the TGS-813 only detects pro bu and methan. Could you try a sample with less of those and post the result?
    Did you try breath?

    4 answers
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    valtecmarlin_maker

    Reply 4 months ago

    The detektor is always very sensitive for ethers, esters, Alkohols and ketones, in an project for my university I will test the detector unit in an usual GC.

    Problem of this GC is the column temperature and length for sepearation of liquid samples.

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    marlin_makervaltec

    Reply 4 months ago

    I would love to see the results. Will you post them here?
    Regarding the problems you highlight:
    -temp shoud be no problem. If you are too lazy to prgramm it yourself, there are done pcbs where you have to attach a heater, a sensor and 12V for 3$. (https://www.banggood.com/DC-12V-50-to-110-Temperat...
    -length: why? Is your pump limiting?

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    valtecmarlin_maker

    Reply 4 months ago

    Heating is not the problem but for a packed Column you will get long time if the different samples will leaves the column. But if you are interested in the results i will post them or send you a pm. But you have to wait unit i get the results.

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    SHOE0007

    4 months ago

    Well very cool! Have you tested it with gases to percison test it? We had an HPLC and gas chromography even one with GS-Mass spec in Biotech at Algonquin College. I am amazed that with Audrino and gas sensor you could build this!

    5 replies
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    valtecSHOE0007

    Reply 4 months ago

    the Problem is, that the pure gases for a calibration standard are very expensive (60$ Per L) and my university doesent store them for reasearch.
    But if your have the possibility at university or faculty to calibrate the column for alkanes, I would be very happy if you had any useful results.

    Kind Regards

    0
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    SHOE0007valtec

    Reply 4 months ago

    Well, that Seems like the logical choice. Did you know drugs like codeine, Morphine, etc are detected by Gas chromography? Poisoning from Strychnine and Tetramethylenedisulfotetramine! Tetramethylenedisulfotetramine is 100 times as Lethal as Potassium cyanide it inhibits GABA receptors. GC-MS for that one and Morphine and Codeine addiction monitering mangement.

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    valtecSHOE0007

    Reply 4 months ago

    If you can vaporize without destroying the samples it is maybe possible but this GC with this column is just for gases by room temperature.

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    SHOE0007valtec

    Reply 4 months ago

    Sadly I don't have any leads I left College 4 years ago but do home science stuff. Wow 60 dollars a L of gasses no wonder GC is expensive!

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    valtecSHOE0007

    Reply 4 months ago

    Maybe I will get information about the composition of the Lighter gas by the company.

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    kymyst

    4 months ago

    Could you please describe the operating conditions for the Zippo Lighter chromatogram
    ( carrier gas, flow rate, oven temperature, etc ).
    How do you control the column temperature ? What is its maximum temperature ?

    1 reply
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    valteckymyst

    Reply 4 months ago

    Hi,

    the maximum Temperatur for the column is 120°C, but you need Metal tubing or PTFE.
    This GC is for room Temperature only, but i think ist is possible to add a simple heating element.

    Conditions for the lighter gas chromatogram

    Carrier Gas: air from the pump
    Flow Rate: i have no idea but the max pressure of the pump is 600mbar.

    I hope this information will help you

    kind regards

    valtec


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    seamster

    4 months ago

    Very interesting, this is something I don't think I've ever heard of before. Thanks!