Chm510 - Spe

1.0 INTRODUCTION High levels of pesticides are used every year in the production and post-production treatments of agricultural commodities. Chlorpyrifos (CPF) is one of the most frequently used organophosphorus pesticides (OPPs) in agriculture and in households. OPPs are mostly sprayed over crops or applied to soils, leading to their direct transfer from drainage of agricultural lands to other parts of surrounding environments, including ground and surface waters. Therefore, there is an increasing concern regarding the determination of these compound. Chlorpyrifos is moderately toxic and classified in Toxicity Category II for all exposure routes. According to the United States Environmental Protection Agency, exposure to CPF could result in neurotoxicity in animals and humans, decreased birth weight of babies and increased risk of lung cancer. The maximum permissible level for CPF in fresh water is 0.041 µg/L, according to the USEPA water quality criteria. Solid-phase extraction (SPE) is an extraction method that uses solid and liquid phase to isolate analyte from solution. It is a rapid and selective sample preparation. The purpose of using the SPE is to purify, trace enrichment, solvent exchange and derivatization. The advantages of the SPE are high recovery of analyte, concentration of analyte, ease of automation and reduction of organic solvent consumption. The general procedure of SPE is the loading of solution through SPE phase, wash away undesired components, and lastly wash off the desired analytes with other solvent into the collection tube. Steps of SPE are from column solvation and equilibration, sample loading, interference elution and lastly, the analyte elution. The objectives of this experiment are to calculate the amount of chlorpyrifos in each waste water sample and the percentage of recovery.

2.0 METHODOLOGY Condition C18 SPE cartridge by passing 10 ml of methanol. The cartridge was rinsed by passing 6 ml of deionized water without applying vacuum. The filtered water sample (50 ml) were passed through the preconditioned column using a vacuum manifold at 6 ml per min (48 drops/min). the column should not be allowed to dry during this sample enrichment step. The column was dried by vacuum for 15 minutes. The interference was removed by eluting the column with 10 ml of deionized water and the cartridge was vacuum dried again for 10 minutes. The pesticide was eluted using 5 ml of hexane. Concentrate to 1 ml by blowing down using gentle nitrogen and the sample ready for GC analysis. The instrument was set-upped, temperature’s injector was 280°C, detector temperature was 300°C, flow rate of carrier gas was 20.0 ml/min (nitrogen) and column temperature was 165°C for 3 minutes initial temperature, then increased to 260°C at 3°C/min with a final time for 2 minutes. For the quantitative analysis of chlorpyrifos, 1µL of sample was injected onto the column. The injection was repeated to get reproducible peak areas. 1 µL of standard chlorpyrifos was injected. The injection was repeated to get reproducible peak area. The concentration of chlorpyrifos in the sample was calculated by using the data from the standard solution.

3.0 RESULT AND DISCUSSION

A. Comparison in retention time of standard and samples Retention time of standard

Average

(min)

retention time

Sample

of sample

Injection 1

Injection 2

1

6.724

6.725

6.7245

2

6.717

6.721

6.719

3

6.720

6.721

6.7205

(min)

6.711

Retention time of sample

(min)

B. Calculation of response factor for standard compound 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 𝑓𝑎𝑐𝑡𝑜𝑟, (𝑅𝐹) = =

𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑐ℎ𝑙𝑜𝑝𝑦𝑟𝑖𝑓𝑜𝑠 𝑝𝑒𝑎𝑘 𝑎𝑟𝑒𝑎 30 𝑝𝑝𝑚 1.11956 𝑋 106 𝐻𝑧𝑠

= 2.6796 𝑋 10−5 𝑝𝑝𝑚/𝐻𝑧𝑠

C. Amount of chlorpyrifos in sample Area (Hz*s) Sample

Amount of chlorpyrifos

Injection 1

Injection 2

(Hz*s)

1

537482

546153

541817.5

14.52

2

110798

113080

111939.0

3.00

3

241467

244626

243046.5

6.51

Average amount of chlorpyrifos =

Average area

14.52+3.00+6.51 3

= 8.01 ppm

(ppm)

D. Percentage of recovery sample amount of chlopyrifos in sample

% recovery = amount of chlophyrifos in standard x 100 Amount of chlopyrifos in standard = 300 ppm

Sample

= 26.70 %

Percentage recovery (%)

14.52

48.40

2

3.00

10.00

3

6.51

21.70

48.40+10.00+21.70 3

in sample (ppm)

1

Average % recovery =

Amount of chlorpyrifos

4.0 DISCUSSION In this experiment, the chlorpyrifos was analysed in water by using solid-phase extraction (SPE) and gas chromatography-electron capture detector (GCECD). Based on the result, each sample was injected for two times. For sample 1 the retention time that has a nice peak is at 6.724 minutes and 6.725 minutes. For the sample 2, the nice peak was observed at retention time 6.717 minutes and 6.721 minutes. Lastly, the sample 3 has nice peak at retention time 6.720 minutes and 6.721 minutes for each injection respectively. The retention time become longer from sample 1 to sample 3. The response factor was calculated for this sample. The response factor is 2.6796 𝑋 10−5 𝑝𝑝𝑚/𝐻𝑧𝑠. This response factor was calculated with formula the sample amount over the peak area for the standard solution. The sample amount for the standard that was used is 30 ppm. Then, by using the value of response factor, the amount of chlorpyrifos in the sample can be calculated by multiplied the response factor that calculated before with the peak area of each sample, sample 1, sample 2 and sample 3. The amount of chlorpyrifos in the sample 1 is 14.52 ppm. While in the sample 2 the amount is 3.00 ppm and last in sample 3 is 6.51 ppm. Then, the percentage recovery also was calculated by divide the amount of chlorpyrifos in sample with the amount of chlorpyrifos in standard then multiplied it with 100. The percentage recovery for sample 1 is 48.40 %, sample 2 is 10.00 % and lastly sample 3 is 21.70 %.

5.0 CONCLUSION

Based on the experiment, the amount of chlorpyrifos in each waste water sample are 14.52 ppm for sample 1, 3.00 ppm for sample two and 6.51 ppm for sample 3 while the percentage of recovery for sample 1,2 and 3 are 48.40 %, 10.00 % and 21.70 % respectively.

6.0 REFERENCES Nor’ashikin S., Ruziyati T., Mardiana S. (2012), Analytical Separation Methods Laboratory Guide (2nd edition)

Studia Universitatis Babes-Bolyai Chemia. (2014), Determination of chlorpyrifos in

surface

water

using

SPE-DI-SPME/GC-ECD.

Retrieved

from

https://www.researchgate.net/publication/287299453_Determination_of_chlorpyrifo s_in_surface_water_using_SPE-DI-SPMEGC-ECD

Azhar. A., (2014), Analysis Of Chlorpyrifos In Water By Solid-Phase Extraction (SPE) And Gas Chromatography-Electron Capture Detector (GC-ECD). Retrieved from

https://www.vbook.pub.com/doc/249342246/ANALYSIS-OF-CHLORPYRIFOS-

IN-WATER-BY-SOLID-PHASE-EXTRACTION-SPE-AND-GASCHROMATOGRAPHY-ELECTRON-CAPTURE-DETECTOR-GC-ECD