Question

What detector(s) could be used to measure chloroacetaldehyde using GC? How would the detector(s) measure the separated analyte?

Answer 1

Air samples are collected by drawing known volumes of air through 6-mm i.d. glass sampling tubes, each containing 520 mg of silica gel adsorbent in the front section and 260 mg in the backup section. The samples are desorbed with acetonitrile and analyzed by GC using an electron capture detector.

How would the detector(s) measure the separated analyte? ( For more information iam giving the full data)

Analytical Procedure

3.1. Apparatus

3.1.1. A GC equipped with an electron capture detector (ECD). A Hewlett-Packard 5890 Gas Chromatograph equipped with a 7673A Autosampler and an ECD was used in this evaluation.

3.1.2. A GC column capable of separating chloroacetaldehyde from potential interferences. A 30-m ×0.32-mm i.d. fused-silica capillary column coated with SP-2250 (0.20-µm film thickness) was obtained from Supelco, Inc. for use in this evaluation.

3.1.3. An electronic integrator or other suitable means of measuring detector response. AHewlett-Packard 5895A GC ChemStation was used in this evaluation.

Analytical conditions

GC conditions
temperatures:	40°C (column) 250°C (injector) 300°C (detector)
temperature program:	hold initial temp 5.0 min, increase temp at15°C/min to 230°C and hold until all peaks have eluted
column head pressure:	31 kPa (hydrogen)
column flow rate:	1.7 mL/min (hydrogen)
septum purge flow rate:	4.8 mL/min (hydrogen)
split vent flow rate:	15.7 mL/min (hydrogen)
detector make-up flow rate:	70 mL/min (nitrogen)
injection volume:	1.0 µL
split ratio:	1 to 10
column:	A 30-m × 0.32-mm i.d. fused-silicacapillary column coated with SP-2250(0.20-µm film thickness)
chromatogram:	Section 4.11

3.5.2. Measure detector response using a suitable method such as electronic integration.

3.5.3. Use an internal standard procedure to prepare a calibration curve using several freshly prepared standards over a range of concentrations. Bracket the samples with analytical standards.3.6. Interferences (analytical)

3.6.1. Any compound having a similar retention time as chloroacetaldehyde or the internal standard is a potential interference. Generally, chromatographic conditions can be altered to separate an interference.

3.6.2. Retention time on a single column is not proof of chemical identity. Confirmation by GC/MS is a useful means of identification.

3.7. Calculations3.7.1. Prepare calibration curves from analytical standards by plotting detector response for chloroacetaldehyde versus the analytical standard concentrations (in terms of micrograms chloroacetaldehyde per milliliter). Determine the best-fit line through the data points.

3.7.2 Determine the concentration, in micrograms of chloroacetaldehyde per milliliter, of a sample by comparing its detector response to the calibration curve. Perform blank corrections for each section before adding the results together. If any chloroacetaldehyde is found on the backup section, add that amount to the amount found on the front section.

3.7.3. The air concentration of chloroacetaldehyde can be expressed in mg/m³ by using the following equation:mg/m³  = [(A)(B)] / [(C)(D)]

where	A =	µg/mL of chloroacetaldehyde from Section 3.7.2.
	B =	desorption volume (3.0 mL)
	C =	liters of air sampled
	D =	desorption efficiency decimal form (0.910)

3.7.4. Convert chloroacetaldehyde results in mg/m³ to ppm using the following equation:ppm = (mg/m³)(24.46) / (78.50)

where	mg/m3  =	results from Section 3.7.3.
	24.46 =	molar volume at 760 mm Hg and 25°C
	78.50 =	molecular weight of chloroacetaldehyde

3.8. Safety precautions (analytical)

3.8.1. Avoid skin contact and inhalation of all chemicals.

3.8.2. Restrict the use of all chemicals to a fume hood.

3.8.3. Wear safety glasses in all laboratory areas.