Materials & Methods

Gas chromatography

Agilent model 5890 gas chromatograph equipped with Agilent model 5971A mass-selective detector operating in electron impact mode (70 eV)

Column used:  30 m × 0.25 mm × 0.25 µm HP1-MS column

Split/Splitless injector: Split injector

Injector temperature: 250°C

Oven temperature:  Programmed from 50°C to 110°C (At 2°C /min.)

Mobile phase used: Helium

Materials

Moth repellent balls

Toluene (used as the extracting solvent) from Fisher Scientific

Standards of naphthalene from UCB

Cotton cloth

Vials

Cabinet (109cm X 90cm X 34cm)

Reagent preparation

1) Standard preparation

- Prepared by using the known standard solution of naphthalene.

2) Sample preparation

The exposure period for all cloth strips was 120 h.

- During the experiments, the room temperature was kept constant at 22 °C during morning and afternoon hours, but was allowed to drop to 18 °C at night.

- The room was kept closed during the exposure to keep the conditions constant.

- Each cloth was analyzed separately after the exposure period.

Direct transfer of moth repellent to clothing

Downward migration of the repellent agent

1) A moth repellent ball was placed directly on ten layers of cotton cloth (4 × 4 cm) (cotton is the most often used type of fabric.)

2) Pieces measuring 4 × 4 cm were analyzed using ultrasonic extraction followed by GC–MS analysis.

Ultrasonic bath

3) The cloth pieces were placed in vials containing 5 ml of toluene and extracted in an ultrasonic bath for 15 min prior to gas chromatographic analysis.

4)  All experiments were repeated three times and mean values were calculated.

5) Analyte concentrations in the extracts were calculated from external calibration graphs determined using 1:10 split injection.

Horizontal migration of the repellent agent

1) A moth repellent ball on a strip of cloth (4 × 60 cm), which was cut after the exposure into seven sections (4 cm in length, centered at 2, 6, 14, 28, 36, 44 and 55 cm.)

2) These strips were analyzed using ultrasonic extraction followed by GC–MS analysis

3) The cloth pieces were placed in vials containing 5 ml of toluene and extracted in an ultrasonic bath for 15 min prior to gas chromatographic analysis.

4) All experiments were repeated three times and mean values were calculated.

5) Analyte concentrations in the extracts were calculated from external calibration graphs determined using 1:10 split injection.

2) Indirect transfer of moth repellents to clothing

1) Pieces of cloth were placed on all three shelves in the cabinet-109 cm in height, 90 cm in length and 34 cm in width. (lower, middle and upper).  

2) Mothball repellent tablet was placed on the middle shelf.

3) One piece of cloth, placed on the shelf with mothball, was exposed to air for one-hour prior to extraction and analysis. The other pieces were extracted and analyzed immediately after exposure.

3) The cloth pieces were placed in vials containing 5 ml of toluene and extracted in an ultrasonic bath for 15 min prior to gas chromatographic analysis.

4) All experiments were repeated three times and mean values were calculated.

5) Analyte concentrations in the extracts were calculated from external calibration graphs determined using 1:10 split injection.