1. General Discussion
1.1 Background
1.1.1 History
This wipe sampling method was developed to provide a uniform and practical means of
taking wipe samples for 1,6-hexamethylene diisocyanate (HDI). The sampling of HDI on
surfaces was performed using Ghost Wipes (Environmental Express). The Ghost Wipe was
chosen for its durability and its use in surface sampling of other analytes. The samples are
analyzed following the procedure in OSHA Method 421, using high performance liquid
chromatography (HPLC). Glass plates were used as the ideal surface to check the surface
sampler removal efficiency. The use of a surface that approximates an ideal surface
(extremely smooth and non-porous) minimizes the effect of the surface on the evaluation of
the media. No interactions between the glass plate and HDI were found. In this evaluation,
the media are pre-wetted with a solution of 50:50 isopropanol:water. After sampling, the
samples were immediately placed in vials containing 5 mL of a derivatizing reagent solution
of 50:50 dimethyl sulfoxide (DMSO):ethyl acetate and 0.025 M 1-(2-pyridyl) piperazine (1-
2PP). The derivatizing reagent (1-2PP) reacts with HDI by attaching a chromaphore to the
molecule. This improves the analytical sensitivity of the method. Also, without the
derivatizing reagent, the HDI will begin to hydrolyze or polymerize and the HDI on the sample
will be lost. A derivatizing reagent solution of 0.025 M 1-2PP in acetonitrile was initially
used. However, other isocyanates that were to be evaluated did not go into solution in this
reagent. To make this method as uniform and practical as possible for other isocyanate
sampling methods, the derivatizing reagent with DMSO and ethyl acetate as solvent was
used. A study was conducted to investigate the reaction of HDI with the alcohol and the
water in the wetting solution prior to being derivatized. It was determined that the time
interval, from beginning collection of the sample, until the sample is placed in contact with
the derivatizing reagent should not exceed three minutes. (Section 4.9)
1.1.2 Toxic effects (This section is for information only and should not be taken as the basis of
OSHA policy.)
Many dermal exposure studies on animals describe the ability of HDI to cause contact
sensitization or direct irritation to the skin of laboratory animals.2 Respiratory
hypersensitivity has been induced by exposure of diisocyanates to the skin of laboratory
animals.3, 4, 5, 6
Human skin exposure to diisocyanates has resulted in erythema,
eczematous dermatitis, contact eczema characterized by follicular papules and dermal
sensitization.7 A procedures for conducting urinalysis for 1,6-hexamethylene diamine as an
indicator of the biological metabolite of HDI has been published.9
1.1.3 Workplace exposure
Occupations with the greatest potential for exposure to HDI are painters and paint spraying
machine operators, aircraft engine mechanics, and aircraft machinists. Other occupations
with potential for exposure to HDI include construction laborers, chemical technicians,
mixing and blending machine operators in the chemical industry, plumbers, pipe fitters,
steam fitters, metal plating machine operators, miscellaneous machine operators in the
aircraft equipment industry, and production workers and supervisors in the fabricated
structural metal industry.8
1.1.4 Physical properties and descriptive information10
|
CAS number: |
822-06-0 |
vapor pressure (mmHg): |
0.05 |
|
IMIS number: |
137711 |
molecular weight: |
168.20 |
|
flash point (OC): |
135ºC |
boiling point: |
255ºC |
|
melting point: |
-67ºC |
odor: |
pungent |
|
appearance: |
Pale yellow liquid |
synonyms: |
1,6-diisocyanatohexane, HDI |
|
molecular formula: |
OCN-(CH2)6-NCO |
solubility: |
poorly soluble in water, |
|
specific gravity: |
1.04 g/mL |
|
reacts slowly with water |
|
LD50, rabbit, dermal: |
570 µg/kg12
|
|
|
|
SD50 (sensitization dose) mouse, dermal: 0.088 mg/kg |
|
LOAEL (Lowest observable adverse effects level), guinea pig, dermal: 0.1 mg |
This method was evaluated according to the OSHA SLTC "Evaluation Guidelines for Surface Sampling
Methods".13 The Guidelines define analytical parameters, specify required laboratory tests, statistical
calculations and acceptance criteria. The analyte surface concentrations throughout this method are based
on the evaluated sampling area and analytical concentration parameters.
1.2 Limit defining parameters
1.2.1 Detection limit of the overall procedure
The detection limit of the overall procedure is 0.29 µg per sample. This is the smallest
amount of HDI spiked on the wipe sampler that will give a detector response that is
significantly different from the response of the wipe sampler blank. (Section 4.1 )
1.2.2 Reliable quantitation limit
The reliable quantitation limit is 0.96 µg per sample. This is the amount of HDI spiked on
the wipe sampler that will give a detector response that is considered the lower limit for a
precise quantitative measurement. (Section 4.1)
1.2.3 Recovery effects of storage
The recovery of HDI from spiked samples used in a 15-day storage test remained above
88.6% when the samples were stored at 22 °C. (Section 4.2)
1.2.4 Surface sampler removal efficiency
The removal efficiency of Ghost Wipe moistened with 0.5 mL of wetting reagent for HDI
spiked at the target concentration of 340.0 µg/100cm2 is 68.3%. This was the percentage
of HDI that was removed from a glass plate surface, spiked at the target concentration.
(Section 4.3)
1.2.5 Sampling reproducibility and analytical reproducibility
Six glass plate surfaces were spiked at the target concentration. Chemists, other than the
one developing the method, conducted sampling on the glass plate surfaces as described
in Section 2. The test was repeated with a second chemist performing the sampling. The
first chemist was able to achieve a removal efficiency of 60.7%. The second chemist was
able to achieve a removal efficiency of 55.5%. (Section 4.5.1)
Six samples spiked at the target concentration by liquid injection were submitted for
analysis by the OSHA Salt Lake Technical Center. The samples were analyzed according
to a draft copy of this procedure after 22 days of storage at 22 °C. The average analytical
result was 111% of theoretical. (Section 4.5.2)
2. Sampling Procedure
All safety practices that apply to the work area being sampled should be followed. The sampling should
be conducted in such a manner that it will not interfere with work performance or safety. The derivatizing
reagent solution contains DMSO. DMSO is readily absorbed by the skin and is an excellent vehicle to
transfer contaminants dissolved in it through the skin barrier. Skin contact with the derivatizing solution
containing DMSO should be avoided.
2.1 Apparatus
2.1.1 Chemical resistant gloves; samples are collected using firm hand pressure to wipe the
sampling medium across a surface. Wear a clean pair of gloves for each sample. The
gloves selected are to be resistant to penetration of the chemical being sampled and any
other chemicals expected to be present. Nitrile gloves were used for sampling
1,6-hexamethylene diisocyanate based on a review of glove manufacturer's chemical
resistivity and degradation information.
2.1.2 Labeled 20-mL scintillation vials with PTFE lined caps, one for each sample, each
containing 5 mL of derivatizing reagent solution.
2.1.3 Ghost Wipes, dry, catalog number SC4050, Environmental Express, Mt. Pleasant, S.C.
2.1.4 Disposable pipette and bulb, capable of delivering 0.5 mL. Non-sterile graduated pipette,
catalog no. 13-711-9A, Fisher Scientific, Fair Lawn, NJ.
2.1.5 Optional steel or plastic measuring tape or disposable Sampling Template 10 × 10 cm,
catalog number 1010, Environmental Express, Mt. Pleasant, S.C.
2.2 Reagents
2.2.1 Water, HPLC grade. A Millipore Milli-Q system was used to prepare the deionized water (DI
water) for this evaluation.
2.2.2 Isopropanol, HPLC grade, Lot No. 001456, Fisher Scientific, Fair Lawn, NJ.
2.2.3 Ethyl acetate, HPLC grade, Lot No. 924366, Fisher Scientific, Fair Lawn, NJ.
2.2.4 Dimethyl sulfoxide (DMSO), HPLC grade, Lot No. BB965, Baxter, Muskegon, MI.
2.2.5 1-(2-Pyridyl) piperazine (1-2PP), Lot No. 09914JU, Aldrich, Milwaukee, WI.
2.2.6 Wetting reagent, 50:50 isopropanol:deionized water (DI) water.
2.2.7 Derivatizing solution, 50:50 ethyl acetate:DMSO with 0.025 M
1-2PP.
2.3 Shipping media and reagents to the sampling site and reagent preparation
The media are received from the supplier in packages containing 100 wipes per package. Wear clean
gloves and remove a sufficient number of wipes to perform the sampling. Remember to include extra
wipes to serve as blanks. Place the wipes in a 5 × 7 in. recloseable polyethylene zipper bag. Place
the remaining wipes in a large recloseable polyethylene zipper bag. The selected wipes can now be
shipped or taken to the workplace for sampling.
Place a disposable pipette and bulb, capable of delivering 0.5 mL in a small recloseable polyethylene
zipper bag and ship with the wipe media.
Prepare the 50:50 isopropanol:DI water wetting reagent that is needed to moisten the wipe prior to
sampling. Place 50.0 mL of the wetting reagent in a labeled bottle and cap securely.
Prepare the derivatizing solution that is combined with the wipe sample after sampling. The
derivatizing solution consists of 50:50 ethyl acetate:DMSO with 0.025 M 1-2PP.
Place 5.0 mL of derivatizing solution in each scintillation vial, one for each sample. Cap the vials
securely.
Following current Department of Transportation (DOT) regulations. Pack the bottle containing the
wetting reagent and the vials containing the derivatizing solution in a shipping container and label it.
2.4 Sampling technique
Label a sufficient number of vials containing the derivatizing solution with a unique number, for the
projected sampling needs. Wear clean unpowered gloves when handling the media.
Prepare a diagram of the area or rooms to be wipe sampled along with the locations of key surfaces.
Wear a new pair of clean gloves for each sample to prevent contamination of future samples as well
as oneself. The gloves selected are to be resistant to penetration of the chemical being sampled and
any other chemicals expected to be present. Nitrile gloves are recommended for sampling
1,6-hexamethylene diisocyanate based on a review of glove manufacturer's chemical resistivity and
degradation information.
Record the sample vial number and the location where the sample is taken. Withdraw a Ghost Wipe
from the zipper bag with your gloved fingers or clean tweezers. Use the disposable pipette to moisten
the medium with 0.5 mL of the wetting reagent.
Depending on the purpose of the sample, it may be useful to determine the surface loading of the
contamination (e.g., in micrograms of analyte per area). For these samples, it is necessary to
determine the area of the surface wiped (e.g., 100 cm2). To make this measurement, hold the
measuring tape above the surface (without touching) or place the disposable sampling template on
the surface before sampling. This would not be necessary for samples taken to simply show the
presence of the contaminant.
The amount of time, from beginning to collect the sample, until the sample is placed in the vial
containing the derivatizing reagent, should not exceed three minutes. (Section 4.9)
Firm pressure should be applied when wiping. Start at the outside edge and progress toward the
center making concentric squares of decreasing size. Fold the medium with the contaminant side
inward and repeat.
Without allowing the medium to come into contact with any other surface, fold the medium with the
exposed side inward. Place the medium in a sample vial containing the derivatizing solution, cap and
shake vigorously for one minute. Place a number corresponding the sample to the location on the
diagram. Include notes with the sketch giving any further description that may prove useful when
evaluating the sample results (e.g., a description of the surface sampled, such as: pencil, doorknob,
safety glasses, lunch table, inside respirator, employee's names, etc.).
Submit at least one blank wipe medium, treated in the same fashion as the wipe samples, but
without wiping.
Record sample location, employees names, surface area (if pertinent), work description, PPE, and
any other necessary information, along with any potential interferences on the OSHA-91A form.
Submit the samples to the OSHA Salt Lake Technical Center together with OSHA-91A forms as
soon as possible after sampling. Ship any bulk samples separate from the surface samples. Package, label, and ship samples according to current DOT regulations.
2.5 Extraction efficiency (Section 4.4)
It is the responsibility of each analytical laboratory to determine the surface sample extraction
efficiency because the wipe sampling media, reagents and laboratory techniques may be different
than the those listed in this evaluation and influence the results.
2.5.1 The mean extraction efficiency for 1,6-hexamethylene diisocyanate from Ghost Wipes over
the range of RQL to 10 times the target concentration (0.99 to 3400
µg per sample) was
96.8%.
2.5.2 Extracted samples remain stable for at least 24 h.
2.6 Interferences, sampling
Suspected interferences should be reported to the laboratory with submitted samples.
Blank wipe sampling media was moistened with the wetting reagent, placed in vials and analyzed.
Additional samples were prepared by wiping glass plates with wipe sampling media moistened with
the wetting reagent. The surfaces were not spiked with HDI. The samples were analyzed. No
significant interferences were found. (Section 4.6)
3. Analytical Procedure
Adhere to the rules set down in your Chemical Hygiene Plan14. Avoid skin contact and inhalation of all
chemicals and review all appropriate MSDSs before beginning the analytical procedure.
This analysis closely follows the analytical procedure in OSHA Method 42.15
3.1 Apparatus
3.1.1 A high performance liquid chromatograph (HPLC) equipped with fluorescence (FL) and
ultraviolet (UV) detectors, liquid chromatograph pump, manual or automatic injector, and
chart recorder. A Hewlett-Packard Series 1050 HPLC equipped with a UV detctor and a
Kratos Spectroflow 980 FL detector was used in this evaluation.
3.1.2 LC column capable of separating diisocyanate derivatives. A 25-cm × 4.6-mm i.d. Alltech
Econosphere CN (5-µm) column was used during this evaluation.
3.1.3 An electronic integrator, or some other suitable method of measuring detector response.
A Waters Corporation Millennium32 (version 3.20) data system was used in this evaluation.
3.1.4 Vials, 2-mL with PTFE-lined caps.
3.1.5 Volumetric flasks, pipets, and syringes.
3.1.6 Micro-analytical balance used to weigh standard preparations.
3.1.7 Centrifuge.
3.2 Reagents
3.2.1 Acetonitrile (ACN), HPLC grade, Lot No. 012683, Fisher Scientific, Fair Lawn, NJ.
3.2.2 Water, HPLC grade. A Millipore Milli-Q system was used to prepare the water for this
evaluation.
3.2.3 Ethyl acetate, HPLC grade, Lot No. 924366, Fisher Scientific, Fair Lawn, NJ.
3.2.4 Dimethyl sulfoxide (DMSO), HPLC grade, Lot No. BB965, Baxter, Muskegon, MI.
3.2.5 1,6-Hexamethyl diisocyanate (HDI), Lot No. 01104EU, Aldrich, Milwaukee, WI.
3.2.6 1-(2-pyridyl) piperazine (1-2PP), Lot No. 09914JU, Aldrich, Milwaukee, WI.
3.2.7 Ammonium acetate, Lot No. 897484, Fisher Scientific, Fair Lawn, NJ.
3.2.8 Phosphoric acid, Lot No. 025821, Baker, Phillipsburg, NJ.
3.2.9 N,N'-1,6-hexanediylbis[4-(2-pyridinyl)-1-piperazinecarboxyamide], (1-(2-pyridyl)piperazine
derivative of HDI), U. S. Department of Labor OSHA Technical Center Salt Lake City, UT.
(An external source is: Product number 48146, Supelco, Bellefonte, PA.)
3.3 Standard preparation
3.3.1 All applicable Quality Assurance procedures and accreditation requirements should be
observed.
3.3.2 A stock standard solution is prepared by dissolving derivatized HDI in DMSO. The
derivatized HDI may be purchased or prepared following Section 3.3.1 of OSHA Method
4216. The ratio of the molecular weights of HDI to the HDI derivative is 0.340. Use this factor
to express the mass of HDI derivative as the mass of HDI. All dilutions of the stock
solutions are made with 90:10 ACN:DMSO to arrive at the working range.
3.3.3 Bracket sample concentrations with standard concentrations. If, upon analysis, sample
concentrations fall outside the range of prepared standards, prepare and analyze additional
standards to confirm instrument response, or dilute high samples with the 90:10 ACN:DMSO
dilution solution.
3.4 Sample preparation
3.4.1 The surface samples are received in 20-mL vials containing the wipe media and 5.0 mL of
derivatizing reagent solution. The vials are placed in a centrifuge that has been set at 2500
rpm for 4 min.
3.4.2 Remove an aliquot of approximately 1 mL and place into an appropriate autosampler vial
and seal with a PTFE-lined cap. 3.5 Analysis
3.5.1 HPLC conditions
|
column: |
25-cm × 4.6-mm i.d. Alltech Econosphere CN (5 µm). |
 |
|
mobile phase: |
40:60 ACN:water, 0.02 M ammonium acetate adjusted to
pH 5.9 with phosphoric acid. |
|
flow rate: |
1.0 mL/min for 15 min |
|
FL detector: |
240 nm excitation, 370 nm emission |
|
UV detector: |
254 nm |
|
injection size: |
10 µL |
Figure 3.5.1. Chromatogram
obtained from the samples spiked at the target
concentration and diluted 1/50. (1- excess 1-2PP (derivatizing
reagent); 2-HDI. |
|
retention time: |
9 min |
|
chromatogram: |
Figure 3.5.1 |
 |
| Figure 3.5.2. Calibration curve of HDI.
(Y=813X - 6.30) |
3.5.2 An external standard (ESTD)
calibration procedure is used to
prepare a calibration curve using at
least 2 stock standards from which
dilutions are made. The calibration
curve is prepared daily. The samples
are bracketed with analytical
standards.
3.6 Interferences (analytical)
3.6.1 Any compound that produces a
fluorescence or UV detector response
and has a similar retention time as
HDI is a potential interference. If any
potential interferences were reported,
they should be considered before samples are extracted. Generally, chromatographic
conditions can be altered to separate an interference from the analyte. Material Safety Data Sheets
(MSDS) identify solvents prevalent in spray painting operations. Three solvents
commonly found were separately added to individual media that had been placed in vials,
moistened with the wetting reagent and spiked with HDI at the target level. The samples
were prepared and analyzed. Benzaldehyde and 2,4-toluene diisocyanate were also tested
as potential interferences in the same manner. Neither the solvents or the chemicals
caused a discernable interference. (Section 4.6)
3.6.2 When necessary, the identity of an analyte peak may be confirmed with additional analytical
data. An absorbance response ratio of UV detector response to fluorescence detector
response is determined. The response ratio of samples and standards of similar
concentration are compared. (Section 4.8) 3.7 Calculations
The amount of HDI per sampler is obtained from the appropriate calibration curve in terms of
micrograms per mL, uncorrected for extraction efficiency. This amount is then adjusted by
subtracting the amount (if any) found on the blank and corrected for extraction efficiency. Correct for
the 5.0 mL of derivatizing solution that was present in the samples when they were received and any
dilutions performed. Perform the calculation using the following formula.
 |
where |
MS
is the mass of HDI recovered from the sampled surface (µg) |
|
V
is the volume of the derivatizing solution and any dilutions (mL) |
|
M
is micrograms per mL from the sample derivatizing solution |
|
MB
is micrograms per mL from the blank derivatizing solution |
|
EE
is the extraction efficiency |
The amount may be expressed as micrograms HDI per 100 cm2 if the surface area that was sampled
was provided, by using the following formula.
 |
where |
MS
is the mass on the sampled surface (µg) |
|
CS
is the mass (in µg) of HDI per 100 cm2 |
|
S
is the surface area sampled (cm2) |
|
100
is 100 cm2 |
The surface that was sampled may be less ideal (more porous, less smooth) than the surface that
was used to evaluate the removal efficiency of the sampling media. In this circumstance, the media
will remove the surface contaminant less effectively. There may be significant amounts of
contaminant remaining on the surface after sampling. Nevertheless, the amount found in the sample
indicates that at least this amount of HDI was present on the surface.
4. Backup Data
General background information about the determination of detection limits and reproducibility of the overall
procedure is found in the "Evaluation Guidelines for Surface Sampling Methods".17
4.1 Detection limit of the overall procedure (DLOP) and reliable quantitation limit
(RQL)
Table 4.1
Detection Limit of the Overall Procedure |
|
mass per sample
(µg) |
response
(mV) |
|
| 0 |
35 |
| 0.66 |
102 |
| 1.32 |
193 |
| 1.98 |
304 |
| 2.64 |
400 |
| 3.30 |
506 |
|
The DLOP is measured as mass per sample. Five
samplers were moistened with 0.5 mL wetting solution
and spiked with equal descending increments of analyte,
such that the highest sampler loading was 3.30
g/sample. 5.0 mL of derivatizing reagent was added to
these spiked samplers, and also a sample blank. The
samplers were analyzed with the recommended
analytical parameters, and the data obtained used to
calculate the required parameters (standard error of
estimate and the slope) for the calculation of the DLOP.
The data is presented in Table 4.1. Values of 145.5 and
14.0 were obtained for the slope and standard error of
estimate, respectively. The DLOP was calculated to be 0.29 µg/sample.
The RQL is considered the lower limit for precise quantitative measurements. It is determined from
the regression line parameters obtained for the calculation of the DLOP, providing 75% to 125% of
the analyte is recovered. The RQL is 0.962 µg/sample. Average recovery at this level is 90.5%.
 |
 |
| Figure 4.1.1. Plot of data to determine the DLOP/RQL.
(Y=146X + 16.7) |
Figure 4.1.2. Chromatogram of the RQL. (1)-
derivatizing reagent; (2) -HDI. |
4.2 Storage tests
Storage samples were prepared by spiking Ghost Wipes, that had been moistened with the wetting
solution, with HDI at the target concentration. Samples were immediately placed in vials containing
the derivatizing reagent. Twenty-one storage samples were prepared. Three samples were analyzed
on the day prepared. Nine of the samples were stored at reduced temperature (4
°C) and the other
nine were stored in a closed drawer at ambient temperature (about 22
°C). At about 5-day intervals,
three samples were selected from each of the two storage sets and analyzed. Sample results were
not corrected for extraction efficiency.
Table 4.2
Storage Test for HDI |
|
time
(days) |
ambient storage
recovery (%) |
refrigerated storage
recovery (%) |
|
| 0 |
93.1 |
69.7 |
92.4 |
93.1 |
96.7 |
92.4 |
| 5 |
92.3 |
91.1 |
92.9 |
94.3 |
92.7 |
93.9 |
| 11 |
85.1 |
85.9 |
87.4 |
87.4 |
91.5 |
89.4 |
| 15 |
90.6 |
90.9 |
90.7 |
90.7 |
92.3 |
89.4 |
|
 |
 |
| Figure 4.2.1. Ambient storage test for HDI. |
Figure 4.2.2. Refrigerated Storage test for HDI. |
4.3 Sampler removal efficiency
Table 4.3
Sampler Removal Efficiency
Data for HDI on Ghost Wipes |
|
theoretical
(µg/surface) |
recovered
(µg/sample) |
recovery
(%) |
|
| 340 |
220 |
64.7 |
| 340 |
246 |
72.3 |
| 340 |
244 |
71.7 |
| 340 |
219 |
64.4 |
| 340 |
228 |
67.1 |
| 340 |
236 |
69.3 |
|
Six glass surfaces were spiked at the target concentration of
HDI, 340 µg /100 cm2. Samples were collected from each
surface using the technique described in Section 2.4 and
analyzed. Sample results were corrected for extraction
efficiency. The results are shown in Table 4.3.
4.4 Extraction efficiency and stability of extracted samples
The extraction efficiency is dependent on the solvents used in
the derivatizing solution.
4.4.1 Extraction efficiency
The extraction efficiencies of HDI were determined by liquid-spiking Ghost Wipes with the
HDI at concentrations ranging from the RQL to 10 times the target concentration. The
sample media was placed in vials and moistened with the wetting solution. Each sampler
was then spiked and the derivatizing reagent solution was added. Four samplers at each
concentration were prepared. The samples were placed on a rotator for an hour. These
samples were stored overnight at ambient temperature and then analyzed. The mean
extraction efficiency over the working range of the RQL to 10 times the target concentration
is 96.8%. Note that extraction efficiency also accounts for the additional volume of the
wetting reagent.
Table 4.4.1
Extraction Efficiency of HDI from Ghost Wipe |
|
|
level |
sample number |
× target
concn |
µg per
sample |
1 |
2 |
3 |
4 |
mean |
|
| RQL |
0.99 |
90.2 |
88.2 |
92.0 |
91.5 |
90.5 |
| 0.1 |
34.0 |
100.1 |
100.9 |
98.8 |
94.8 |
98.7 |
| 1.0 |
340 |
98.6 |
98.7 |
97.9 |
97.5 |
98.1 |
| 10.0 |
3400 |
99.2 |
100.9 |
100.1 |
99.2 |
99.9 |
|
4.4.2 Stability of extracted samples
The stability of extracted samples was investigated by re-analyzing the four target
concentration samples 24 h after initial analysis. After the original analysis, two of the auto-
sampler vials were recapped with new septa, while the remaining two retained their
punctured septa. The samples were re-analyzed with fresh standards. The average percent
change was 1.1% for the samples that were resealed and 1.2% for those that were stored
with their septa punctured. The septum was punctured 3 times for each injection.
Table 4.4.2
Stability of Extracted Samples for HDI |
|
|
punctured septa replaced |
punctured septa retained |
initial
(%) |
after
one day
(%) |
difference
(%) |
initial
(%) |
after
one day
(%) |
difference
(%) |
|
| 98.6 |
100.4 |
1.8 |
97.9 |
98.7 |
0.8 |
| 98.7 |
98.3 |
0.4 |
97.5 |
99.1 |
1.6 |
|
4.5 Reproducibility
4.5.1 Six glass surfaces were spiked at the target level of 340
µg. Two chemists, other than the
one developing the method, conducted sampling on the glass surfaces as described in
Section 2. The test was repeated with a second chemist performing the sampling. Sample
results were corrected for extraction efficiency.
Table 4.5.1.1
Sampling Reproducibility
Data for HDI on Ghost Wipe,
1st Chemist |
|
Table 4.5.1.2
Sampling Reproducibility
Data for HDI on Ghost Wipe,
2nd Chemist |
|
|
|
theoretical
(µg/surface) |
recovered
(µg/sample) |
recovery
(%) |
|
theoretical
(µg/surface) |
recovered
(µg/sample) |
recovery
(%) |
|
|
|
| 340 |
176 |
51.9 |
|
340 |
200 |
58.8 |
| 340 |
212 |
62.3 |
|
340 |
176 |
51.7 |
| 340 |
209 |
61.4 |
|
340 |
212 |
62.4 |
| 340 |
208 |
61.2 |
|
340 |
177 |
52.0 |
| 340 |
222 |
65.4 |
|
340 |
176 |
517 |
| 340 |
212 |
62.2 |
|
340 |
191 |
56.1 |
|
|
|
Table 4.5.2
Analytical Reproducibility
Data for HDI on Ghost Wipes |
|
theoretical
(µg/surface) |
recovered
(µg/sample) |
recovery
(%) |
|
| 340 |
382 |
112 |
| 340 |
370 |
109 |
| 340 |
375 |
110 |
| 340 |
365 |
107 |
| 340 |
393 |
116 |
| 340 |
377 |
111 |
|
4.5.2 Six samples were prepared by spiking media in the same manner that was used in the preparation
of samples for the storage study. The samples were submitted to the OSHA SLTC for analysis. The samples were analyzed after being stored for
22 days at 22 °C. Sample results were corrected for extraction efficiency.
4.6 Interferences
4.6.1 Media
Tests were conducted to determine interference due to contamination of the prepared media. Two blank wipe sampling media were placed in vials, moistened with the recommended
solvent. The derivatizing reagent solution was added and the samples were processed and
analyzed.
Table 4.6.1
Interference to the Analysis of HDI
from the Media or Surface (µg found) |
|
| sample |
1 |
2 |
mean |
|
| blank |
0.00 |
0.29 |
0.14 |
| from surface |
0.00 |
0.00 |
0.00 |
|
Two additional samples were prepared by wiping the same type of surface that was used for the
removal efficiency test (glass plate) with media moistened with 50:50
isopropanol:DI water. The surfaces were not spiked with HDI. The samples
were placed in vials containing the derivatizing reagent solution, processed and analyzed. The
results are shown in Table 4.6.1.
4.6.2 Tests were conducted to determine the effects of potential interference from three
solvents that are commonly found in auto-body repair shops (toluene, 2-heptanone and petroleum
distillate) and also, two additional chemicals (benzaldehyde and 2,4-toluene
diisocyanate). Three samplers were prepared for each compound tested. The sample media was placed
in vials and moistened with 0.5 mL of the wetting solution. Each sampler was then spiked
with 340 µg HDI and 5.0 mL of the derivatizing reagent. A potential interfering compound
was then added. The samples were processed and analyzed. The amounts of interfering
compound added and the results are shown in Table 4.6.2. None of the compounds tested
caused a significant interference.
Table 4.6.2
Interference to the Analysis of HDI, with an interferant compound added.
(µg found, not corrected for extraction efficiency) |
|
|
potential interferant |
amount of
interferant
spiked (µg) |
amount of HDI spiked (µg) |
amount of HDI recovered |
| 1 |
2 |
3 |
mean |
|
|
toluene |
173400 |
340 |
319 |
320 |
315 |
318 |
|
2-heptanone |
164000 |
340 |
305 |
307 |
305 |
306 |
|
petroleum distillate |
145300 |
340 |
309 |
307 |
311 |
309 |
|
benzaldehyde |
650 |
340 |
297 |
318 |
313 |
309 |
|
2,4-TDI |
650 |
340 |
312 |
320 |
318 |
317 |
|
4.7 Analyte confirmation or qualitative analysis
Diisocyanate qualitative analysis confirmation is not performed by GC/MS because the derivatized
diisocyanate is not sufficiently volatile for gas chromatography. Diisocyanate may be confirmed by
a peak ratio technique. The analysis is conducted with fluorescence and UV detectors in series.
A ratio is established between fluorescence detector response and UV detector response of a
standard that is the approximate concentration of the sample. A similar ratio is established between
fluorescence detector response and UV detector response of the sample. The ratio of the sample is
compared to the ratio of the standard for diisocyanate confirmation. Any required laboratory
confirmation criteria must be met before the analyte confirmation is reported.
4.8 Derivatizing reagent storage test
Table 4.8
Derivatizing Reagent Storage Test (60 days) |
|
× target
concn |
ambient storage
recovery (%) |
refrigerated storage
recovery (%) |
|
| 0.1 |
93.4 |
88.4 |
| 1.0 |
96.4 |
97.4 |
| 10.0 |
99.2 |
99.6 |
|
Derivatizing reagent solution was prepared as in Section 2.3 and divided into two
portions. One portion was placed in a refrigerator. The other portion was placed in
a fire cabinet at ambient temperature. After sixty days fresh derivatizing reagent was
also prepared. Standards were prepared at 0.1, 1.0, and 10 times the target
concentration using fresh derivatizing reagent. Spiked samples were prepared at 0.1, 1.0, and 10 times the target concentration using the
ambient and refrigerated derivatizing reagent solutions. Excess derivatizing reagent peak was noted
on the chromatograms for all samples and standards. Samples prepared with the derivatizing reagent
solution that was stored at ambient temperatures for sixty days gave average results that were
93.4%, 96.4%, 99.2% of the 0.1, 1.0, and 10 times the target concentration, respectively. Samples
prepared with the derivatizing reagent solution that was stored at refrigerated temperatures for sixty
days gave average results that were 88.4%, 97.4%, 99.6% of the 0.1, 1.0, and 10 times the target
concentration, respectively. The results are shown in Table 4.8. The effect of light on the derivatizing
solution was not tested. The derivatizing reagent solution may be stored in a dark place with
adequate ventilation, at room temperature for at least two months. No refrigeration is required for
storage.
 |
| Figure 4.9. Average recovery of HDI at timed
reaction intervals with wetting solution. |
4.9 Reaction time study
Many texts and articles indicate that water and alcohols will react with
isocyanates. One published study determined that the reaction rate of water with isocyanates was at least 5
orders of magnitude (100,000) times slower than the reaction rate of the derivatizing
reagent, 1,2-pyridyl piperazine with isocyanates.18 The use of a wetting solution
consisting of 50:50 isopropanol:water in this method required a reaction rate test
to be performed. The test was to determine whether the water and isopropanol in the wetting
reagent reacts with HDI rapidly enough to be a concern, relative to the amount of time it takes
to collect a sample and deposit it into a vial containing the derivatizing reagent. Vials
containing 0.5 mL 50:50 isopropanol:water (wetting solution) were spiked with HDI at 1.0, 0.5 and 0.1
times the target concentration. Two vial at each concentration were prepared. Five milliliters of
derivatizing reagent was added as quickly as possible. The vials were capped and agitated to insure
mixing. The procedure was repeated three more times, except intervals of 3, 6 and 15 minutes were
allowed to pass before adding the derivatizing reagent. Standards bracketing the concentrations were
prepared with the same spiking solution in a similar manner, with no wetting solution, but in 5.5 mL
of derivatizing reagent. Analysis was conducted and the result are presented in Table 4.9. The
concentration of the spike did not appear to effect the recovery but the amount of time the spike was
allowed to remain in the wetting reagent before being derivatized did effect the recovery. The percent
recovery for all concentrations was averaged for each reaction time interval and plotted against time
in minutes (Figure 4.9). Using the equation of the line, the recovery can be predicted for a given
reaction time. The average recovery at 3.5 minutes is 90.6%. Based on this information, the amount
of time it takes to collect a sample is important. The time interval, from beginning to collect the
sample, until the sample is placed in the vial containing the derivatizing reagent, should not exceed
three minutes.
Table 4.9
Percent Recovery of HDI After Timed Reaction Intervals With the
Wetting Solution |
|
| µg spiked |
"Immediate" |
3 minutes |
6 minutes |
15 minutes |
|
| 34.0 |
105.4 |
97.7 |
89.0 |
62.5 |
| 34.0 |
105.6 |
100.3 |
87.2 |
59.2 |
| 170.0 |
99.7 |
92.2 |
78.3 |
49.8 |
| 170.0 |
97.9 |
88.9 |
77.3 |
50.4 |
| 340.0 |
101.6 |
92.5 |
79.5 |
50.4 |
| 340.0 |
101.7 |
92.4 |
77.9 |
49.5 |
| Average |
101.9 |
94.0 |
81.5 |
53.7 |
|
References:
1. Diisocyanates, 1,6-Hexamethylene Diisocyanate (HDI), Tolune-2,6-Diisocyanate,
Tolune-2,4-Diisocyanate, Method 42, 1989; http://www.osha.gov/dts/sltc/methods/organic/org042/org042.html,
(accessed May 2000).
2. Toxicological Profile for Hexamethylene Diisocyanate, U.S. Department
of Health and Human Services, Public Health Service, Agency for Toxic Substances
and Disease Registry, Atlanta, GA, 1998, pp 59-67.
3. Rattray, N., et al. Induction of Respiratory Hypersensitivity to
Diphenylmethane-4-4' diisocyanate (MDI) in Guinea Pigs. Influence of Route
Exposure. Toxicology 1994, 88, pp 15-30.
4. Karol, M. H., et al. Dermal Contact with Tolune Diisocyanate (TDI) Procedures
Respiratory Tract Hypersensitivity in Guinea Pigs, Toxicology and Applied
Pharmacology 1981, 58, pp 221-230.
5. Kimber, I. The Role of the Skin in the Development of Chemical Respiratory
Hypersensitivity, Toxicology Letters 1996, 86, pp 89-92.
6. Bickis, U. Investigation of Dermally Induced Airway Hyperreactivity to Tolune
Diisocyanates in Guinea Pigs. Ph.D. thesis, Queen's University, Kingston,
Canada, 1994.
7. Criteria for a Recommended Standard... Occupational Exposure to
Diisocyanate; DHEW (NIOSH) Publ. No. 78-215; U.S. Department if Health,
Education and Welfare, Public Health Service, Center for Disease Control,
National Institute for Occupational Safety and Health, U.S. Government Printing
Office: Washington DC, 1978, pp 35-36.
8. Maitre A., et al. Urinary Hexane Diamine as an Indicator of Occupational
Exposure to Hexamethylene Diisocyanate, International Archives of Occupational
and Environmental Health
1996, 69, pp 65-68.
9. National Occupational Exposure Survey; U.S. Department of
Health, Education and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health, Cincinnati, OH,
1989.
10. Toxicological Profile for Hexamethylene Diisocyanate, U.S.
Department of Health and Human Services, Public Health Service, Agency for Toxic
Substances and Disease Registry, Atlanta, GA, 1998, pp 100-102.
11. Chemical Sampling Information, Hexamethylene Diisocyanate, http://www.osha.gov/dts/chemicalsampling/data/CH_245198.html,
(accessed May 2001).
12. RTECS 2000, 1,6-Diisocyanate Hexane, Registry of Toxic
Effects of Chemical Substances, U.S. Department of Health and Human Services,
National Institute for Occupational Safety and Health, Washington, DC, December
2000.
13. Lawrence, R. Evaluation Guidelines for Surface Sampling Methods; OSHA Salt
Lake Technical Center, U.S. Department of Labor: Salt Lake City , UT, 2001
(unpublished).
14. Occupational Exposure to Chemicals in Laboratories. Code of Federal Regulations, Part 1910.1450, Title 29, 1998;
http://www.osha.gov/OshaStd_data/1910_1450_APP_A.html, (accessed May 2000)
15. Diisocyanates, 1,6-Hexamethylene Diisocyanate (HDI),
Toluene-2.6-Diisocyanate, Toluene-2.4-Diisocyanate, Method 42, 1989;
http://www.osha.gov/dts/sltc/methods/organic/org042/org042.html, (accessed May 2000).
16. Diisocyanates, 1,6-Hexamethylene Diisocyanate (HDI),
Toluene-2.6-Diisocyanate, Toluene-2.4-Diisocyanate, Method 42, 1989;
http://www.osha.gov/dts/sltc/methods/organic/org042/org042.html, (accessed May 2000).
17. Lawrence, R. Evaluation Guidelines for Surface Sampling Methods; OSHA Salt
Lake Technical Center, U.S. Department of Labor: Salt Lake City , UT, 2000,
unpublished.
18. Wu, W., et al. Application of Tryptamine as a Derivatizing Agent for
Airborne Isocyanate Determination part 4. Evaluation of Major High-performance
Liquid Chromatographic Methods Regarding Airborne Isocyanate Determination With
Specific Investigation of the Competitive Rate of Derivatization, Analyst
1991, 119, p 24.
|
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