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Liquefied Petroleum Gas (LPG) in Insecticide Aerosol

Liquefied Petroleum Gas (LPG) in Insecticide Aerosol. Nur Zahidah Syahirah Marzuki (4154655) CHEM 4101: Intermediate Instrumental Analysis December 9, 2011. Overview 1, 2. LPG is a mixture of hydrocarbons primarily propane , butane , and isobutane in a liquid state.

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Liquefied Petroleum Gas (LPG) in Insecticide Aerosol

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  1. Liquefied Petroleum Gas (LPG) in Insecticide Aerosol NurZahidahSyahirahMarzuki (4154655) CHEM 4101: Intermediate Instrumental Analysis December 9, 2011

  2. Overview1, 2 • LPG is a mixture of hydrocarbons primarily propane, butane, and isobutane in a liquid state. • Uses: fuel in heating appliances and vehicles, and increasingly replacing CFCs as an aerosol propellant and refrigerant. • Produced either as a by-product of petroleum, or a by-product of direct production of oil and gas. • LPG is very volatile at room temperature. • Its odorless, colorless, heavier than air, highly flammable, and have potential health effect.2 Images obtained from http://www.chemistry.about.com

  3. Problem In Malaysia, insecticide aerosol is used in a household almost everyday and sometimes many times a day. Too much inhalation of insecticide aerosol containing LPG may cause respiratory tract irritation. Therefore, it is crucial to know how much of LPG are exposed to when using the insecticide aerosol. How much of LPG is contained in an insecticide aerosol? How much of LPG is released per spray of an insecticide aerosol with different durations of spraying? What are the limitations (no. spray per use, duration of spraying) when using the particular insecticide aerosol? Hypothesis The use of insecticide aerosol that contains LPG as propellant is harmful to health when sprayed for more than a second with more than one spray per use.

  4. Analytes2 • Propane: CH3CH2CH3 • Molecular weight: 44.09 g/mol • Boiling point: -42.1°C • Threshold limit value: 1000 ppm (1800 mg/m3) • Butane: CH3CH(CH3)2 • Molecular weight: 58.12 g/mol • Boiling point: -0.5°C • Threshold limit value: 800 ppm (1900 mg/m3) • Isobutane: CH3CH2CH2CH3 • Molecular weight: 58.12 g/mol • Boiling point: -12°C • Threshold limit value: 800 ppm (1900 mg/m3) Images obtained from http://www.chemistry.about.com

  5. Analytical Procedures3, 4, 6

  6. Preferred Analytical Procedure • GC equiped with FID • HP5890A gas chromatography with FID and HP7673A autosampler. • Supelco capillary column: • 60m long x 0.32 mm inner diameter with 1.0 µm film • Reagents: • Purified GC grade nitrogen, hydrogen, and air • Desoprtion solution: 250 µL of p-Cymene mixed with 1L of carbon disulfide Image obtained from http://www.google.com/

  7. Sampling Procedure2 • Carbosieve S-III tubes (matrix: air) • High sensitivity • High recovery • Reuseable • Two Carbosieve S-III tubes are connected in series and the ends are opened. • Sample gas from insecticide aerosol are sprayed directly into the tubes. • Tubes are selaed with PTFE-line caps. • Volume of sample is recorded. • Both samples and standards are prepared. Image obtained from http://www.skcinc.com/prod/226-356.asp

  8. Experiment2, 4 • Samples obtained are desorbed with 1.0 ml of desorbing solution in vials and sealed with PTFE-lined septa. • Desorption is allowed for 30 minutes with occasional shaking. • 1µL of sample are injected into the GC instrument. • GC is run for 20 mins. • Conditions of GC: • Temp: hold initial temp. 50°C for 5 min, increase temp. at 10°C/min to 170°C, hold final temp. For 1.5 mins. • Detector gas flow: hydrogen- 30 mL/min, air flow- 240 mL/min, nitrogen- 30 mL/min • Head pressure: 8.5 psi • Limit of detection: 0.79 ppm (1.88 mg/m3)

  9. Experiment Flow of sample in the instrument. Image obtained from http://en.wikipedia.org/wiki/Gas_chromatography

  10. Data Analysis • The spectrum of the samples are compared to the spectrum of standards to identify the analytes in the samples. • A calibration curve for the standards is plotted with area counts versus concentration. • The amount of analytes present in the samples are calculated. Sample spectrum obtained from http://www.cdc.gov/niosh/

  11. Conclusion • GC is the best method to quantitatively identify the main molecues in LPG, propane, butane, and isobutane. • FID is suitable for detection of hydrocarbons and it is a mass-sensitive. • By identifying the amount of LPG in the insecticide aerosol, we can produce a guideline on the proper way to use the insecticide aerosol as in the number of spray per use and the duration of spraying per spray. • It could also help to determine the optimum use of insecticide in different surrounding condition so that insects are killed without affecting human health.

  12. References • http://swissloanspetrol.com/index.php?option=com_content&view=article&id=100&Itemid=175 (Accessed Nov 11, 2011) • http://www.cdc.gov/niosh/ (Accessed on Dec 3 2011) • Laitinen T., Martín S. H., Parshintsev J., Hyötyläinen T., Hartonen K., Riekkola M., et al. Determination of Organic Compounds from Wood Combustion Aerosol Nanoparticles by Different Gas Chromatographic Systems and by Aerosol Mass Spectrometry. J. of Chromatography A. 2010, 1217(1), 151-159 • www.unodc.org/pdf/technical_series_1997-01-01_1.pdf • www.arb.ca.gov/testmeth/cptm/sas05.pdf • Skoog , D, et al. Principles of Instrumental Analysis, 6th ed.; Brooks/Cole: Belmont, CA, 2007

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