1.1 Background 

1.1.1 History of procedure 

The OSHA Laboratory recently received samples collected on silica gel requesting analysis for p-chloroaniline. Several analytical procedures were tried, including gas chromatography and liquid chromatography, but the sensitivity of the liquid chromatography method was greater, and therefore it was used. The liquid chromatograph had an ultraviolet detector set at 254 nm, a secondary wavelength of 280 nm can also be used. The samples were desorbed with methanol and the desorption efficiency was 100%.

1.1.2 Potential workplace exposure 

Workers are exposed to p-chloroaniline in many industries, with the majority of them in the chemical manufacturing industries. It is used in azoic coupling compounds and dye manufacturing (Ref. 5.1). 

1.1.3 Toxic Effects (This section is included for information only and should not be taken as a basis of OSHA policy.) 

Exposure to p-chloroaniline is irritating to skin, eyes, mucous membranes, and through oral ingestion and inhalation. Upon entering the bloodstream p-chloroaniline damages the blood cells. The lowest toxic concentration by inhalation in humans was 44 mg/m³(8.4 ppm). The lowest lethal dose through oral ingestion in rats was 300 mg/kg. The lowest lethal dose applied dermally in rabbits was 36 mg/kg (Ref. 5.2). 

1.1.4 Physical properties: (Ref. 5.3)

Molecular weight: 127.57

Melting point: 72.5°C

Boiling point: 232°C

Odor: aniline-like

Color: white to pale gray

Vapor pressure: 1 mm at 59.3°C

Molecular formula: ClC6H4NH2

Structure:

1.2 Limit defining parameters 

1.2.1 The detection limit of the analytical procedure is 6 ng/injection. This is the smallest amount that could be easily detected under normal analytical conditions. The injection size was 10 µL. 

1.2.2 The detection limit of the overall procedure is 6 ng/sample (0.02 ppm based on a 6-liter sample). This is the amount of analyte placed on a silica gel tube which corresponds to the detection limit of the analytical procedure. 

1.3 Advantages 

1.3.1 The sampling procedure is convenient. 

1.3.2 The analytical method is reproducible and 
sensitive. 

1.3.3 Re-analysis of samples is possible.

1.3.4 It may be possible to analyze other compounds 
at the same time. 

1.3.5 Interferences may be avoided by proper selection of column and parameters. 

1.4 Disadvantages 

1.4.1 Silica gel tubes adsorb water vapor from, the air, thereby possibly lowering the capacity of the tube for p-chloroaniline. 

2.1 Apparatus

2.1.1 A calibrated personal sampling pump, the flow 
of which can be determined within + 5% at the recommended flow. 

2.1.2 Silica gel tubes (20/40 mesh) containing 150-mg adsorbing section with a 75-mg backup section separated by a 2 mm portion of urethane foam, with a silane-treated glass wool plug before the adsorbing section and a 3-mm plug of urethane foam at the back of the backup section. The ends are flame sealed and the glass tube containing the adsorbent is 7-mm long, with a 6-mm O.D. and 4-mm I.D., SKC tubes or equivalent. 

2.2 Sampling technique

2.2.1 The ends of the silica gel tube are opened immediately before sampling. 

2.2.2 Connect the silica gel tube to the sampling pump with flexible tubing.

2.2.3 Tubes should be placed in a vertical position to minimize channeling, with the smaller section towards the pump. 

2.2.4 Air being sampled should not pass through any hose or tubing before entering the silica gel tube. 

2.2.5 Seal the silica gel tube with plastic caps immediately after sampling. Seal each sample lengthwise with OSHA Form-21 sealing tape. 

2.2.6 With each batch of samples, submit at least one 
blank tube from the same lot used for samples. This tube should be subjected to exactly the same handling as the samples (break ends, seal, & transport) except that no air is drawn through it. 

2.2.7 Transport the samples (and corresponding paperwork) to the lab for analysis. 

2.2.8 Bulks submitted for analysis must be shipped in a separate container from the samples. 

2.3 Desorption efficiency 

2.3.1 The desorption efficiency averaged 100% at the concentration of 149.2 µg loading on the tubes, or 4.77 ppm based on a 6 liter air sample (see Table 2.3.2). 

2.3.2 The desorption study was generated by spiking 298.3, 149.2, or 74.59 µg of p-chloroaniline onto six tubes at each level and storing overnight at room temperature. They were opened the next day, desorbed with 1-mL methanol, and analyzed by LC-UV.

Table 2.3.2
 

Level spiked (µg)	%Recovered
298.3	98.7
298.3	102
298.3	102
298.3	102
298.3	99.7
298.3	99.8
average	101
149.2	101
149.2	101
149.2	99.8
149.2	102
149.2	101
149.2	102
average	101
74.59	99.1
74.59	98.4
74.59	101
74.59	101
74.59	102
74.59	104
average	101
overall average	101
standard deviation	±1.44

2.4 Retention efficiency

2.4.1 The retention efficiency was performed by liquid spiking silica gel tubes with 149.2 µg p-chloroaniline and drawing a known volume of humid air (R.H. 86%) through the tubes. There was little loss of the p--chloroaniline (see Table 2.4.2).

2.4.2 Twelve samples were spiked with 149.2 µg p-chloroaniline. Six had 3 liters, and the other six samples had 6 liters of humid air drawn through them. There was 1.6% loss with 3 liters and 2.9% loss with 6 liters humid air drawn. 

Table 2.4.2
 

Tube #	Liters drawn	% recovered
1	3	98.0
2	3	98.8
3	3	99.7
4	3	99.3
5	3	96.4
6	3	96.4
average	3	98.4
7	6	98.2
8	6	96.0
9	6	98.2
10	6	98.1
11	6	95.0
12	6	lost in analysis
average	6	97.1

2.5. Storage

2.5.1 Storage study was performed over a 14-day period with little loss of p-chloroaniline (see Table 2.5.2). 

2.5.2 The tubes were spiked with 149.2 µg/tube. They were analyzed on days 1, 6, 11, and 14. The day I samples were used for the desorption study.

Table 2.5.2
 

Day	% Recovered
1	101
1	101
1	99.8
1	102
1	101
1	102
6	96.5
6	97.3
6	95.6
11	99.6
11	97.9
11	99.8
14	97.5
14	97.3
14	100

2.6.Air volume and sampling rate studied 

2.6.1 The air volume studied is 6 liters. 

2.6.2 The sampling rate studied is 0.1 liters per minute.

2.7 Interferences 

2.7.1 Water vapor may cause a decrease in the collection capacity of p-chloroaniline. 

2.7.2 Suspected interferences should be listed on sample data sheets.

2.8 Safety precautions 

2.8.1 Sampling equipment should be placed on an employee in a manner that does not interfere with work performance or safety. 

2.8.2 Safety glasses should be worn at all times. 

2.8.3 Follow all safety practices that apply to the workplace being sampled. 

3.1 Apparatus 

3.1.1 Liquid chromatograph equipped with an ultraviolet detector at 254 rim. 

3.1.2 LC column capable of separating the analyte from any interferences. An Alltech C18 column was used in this evaluation.

3.1.3 An electronic integrator or some other suitable method of measuring peak areas. 

3.1.4 Two milliliter vials with Teflon-lined caps. 

3.1.5 A 10-µL syringe or other convenient size for sample injection.

3.1.6 Pipets for dispensing the desorbing solvent. The Glenco 1-mL dispenser was used in this method. 

3.1.7 Volumetric flasks 10 mL and other convenient sizes for preparing standards. 

3.2 Reagents

3.2.1 Methanol HPLC grade. 

3.2.2 Millipore deionized, water.

3.3 Sample preparation 

3.3.1 Sample tubes are opened and the front and back section of each tube are placed in separate 2-mL vials. 

3.3.2 Each section is desorbed with 1 mL methanol.

3.3.3 The vials are sealed immediately and allowed to desorb for 30 minutes with occasional shaking. 

3.4 Standard preparation 

3.4.1 Standards are prepared by diluting a known quantity of p-chloroaniline with methanol.. 

3.4.2 At least two separate stock standards should be made. Dilutions of these stock standards are made. The range used in this method was from 1492 ug/mL to 0.6 ug/mL. 

3.5 Analysis 

3.5.1 Liquid chromatograph conditions
 

Solvent mixture:	65% methanol 35% water
Injection size:	10 µL
Elution time:	6.62 minutes
Wavelength:	254 nm
Flow rate:	1mL/min
Column:	Alltech C18
Chromatogram:	(See Figure 1)

3.5.2. Peak areas are measured by an integrator or other suitable means.

3.6. Interferences (analytical)

3.6.1. Any compound having the general retention time of the analyte is an interference. Possible interferences should be listed on the sample data sheet. LC parameters should be adjusted if necessary so these interferences will pose no problems.

3.6.2. Retention time data on a single column is not considered proof of chemical identity. Samples over the target concentration should be confirmed by GC/Mass Spec or other suitable means. 

3.7. Calculations 

3.7.1 To calculate the ppm of analyte in standards based on a 6 liter air sample, and a 1-mL desorbing solution: 
 

24.46	= Molar volume (liters/mole) at 25°C and 760 mmHg.
MW	= Molecular weight
p	= Density
1 mL	= Desorption rate
6 L	=  6 liter air sample
DE	= Desorption efficiency

3.7.2 This calculation is done for each section of the sampling tube and the results added together. 

3.8.Safety precautions 

3.8.1 All handling of solvents should be done in a hood. 

3.8.2 Avoid skin contact with all solvents. 

3.8.3 Wear safety glasses at all times. 

5.1 Mark, H.F., Othmer, D.F., Overberger, C.G., Seaborg, G.T., "Encyclopedia of Chemical Technology", Third Edition, John Wiley & Son, N.Y., 1978, Vol. 2, p. 318. 

5.2 Sax, N.I., "Dangerous Properties of Industrial materials", Fifth Edition, Van Nostrand Reinhold Co., N.Y., 1979, p.488. 

5.3 Windholz, M., "The Merck Index", Tenth Edition, Merck & Co., Rahway N.J., 1983, p.297.