BACKUP DATA REPORT 

NIOSH Method No. 6002 

 

NIOSH Manual of Analytical Methods (NMAM) 5th Edition 

Title: Phosphine 

Analyte: Phosphine 

Author/developer: Developed under contract #210-76-0123

Date: March 17, 1978 

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NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

 

 

Backup Data Report 6002 

March 17, 1978 

Substance: Phosphine 

OSHA Standard: 0.3 ppm (0.4 mg/m3

) 

Chemical Used: Phosphine in nitrogen, 306 and 350 μg/L, Matheson Gas Company 

General Considerations 

The method for phosphine has been tested in accordance with the various criteria for validation described in 

Reference 1 and in conformity with the statistical analysis described in Reference 2. The statistical criteria 

established for this program are related to the present suggested standard for air monitoring accuracy, i.e., the 

absolute total error (sampling and analysis) should be less than 25% in at last 95% of the samples analyzed at the 

level of the OSHA standard. In order to satisfy the statistical criteria, a measure of accuracy and precision was 

established, i.e., overall recovery must be 100 ± 10% and the pooled CVT of an unbiased method must be less 

than or equal to 0.105. The fine points of the statistical basis for this program are discussed in Reference 2. 

The protocol for the validation of a method for phosphine included the following experimental studies: 

• Analysis of a total of eighteen analytical samples (six samples at each of the three test levels-0.5, 1, and 

2X the OSHA standard) spiked with the appropriate amount of phosphine to represent a sample volume 

equal to sixteen liters; 

• Analysis of a total of eighteen samples collected from dynamically generated test atmospheres (six 

samples at each of the three test levels-0.5, 1, and 2X the OSHA standard) for the same sample volume 

as above; 

• Determination of the breakthrough capacity of mercuric cyanide coated silica gel tubes at high relative 

humidity at two test levels (1.07 and 2.39X the OSHA standard); 

• Testing of the storage stability of collected samples; 

• Assessment of the precision and accuracy of the method. 

The details with respect to each of these items are discussed in the following appropriate sections. The method 

tested experimentally and documented in this report has passed all the requirements of this program. 

Preliminary Experiments 

The colorimetric analysis of phosphate by extraction of the phosphomolybdate complex into a mixture of isobutanol and benzene and subsequent reduction using stannous chloride was chosen as the analytical method 

because of its increased sensitivity and lesser interferences over other colorimetric phosphate methods. The 

utility of the method over the range of 1-20 μg of phosphine was shown by preparation of a standard curve 

(using KH2PO4) over this range with a sensitivity of 0.0467 absorbance units per μg of PH3 and a regression 

coefficient of 0.9993. The effect of mercuric cyanide on the method was checked by adding various amounts to 

a standard amount of phosphate. The results given below indicate that low levels of mercuric cyanide do not 

interfere with the analysis of phosphate. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 6002-1. Effect of added Hg(CN)2 

Hg(CN)2 added (mg) Phosphorus added (μg PH3) Phosphorus found (μg PH3) 

0 7.00 6.94 

10.0 7.00 6.94 

21.2 7.00 7.04 

Experiments were performed to test the suitability of mercuric cyanide coated Chromosorb-P tubes for 

collection of phosphine. As received Chromosorb-P (Johns-Manville, acid washed) had a high and variable 

phosphate blank (2.01, 3.71 and 8.87 μg PH3/200 mg). Repeated acid washing of this material (1 N H2SO4 at 

50°C) reduced the phosphate blank to 0.63±0.1 μg PH3 /200 mg (average of three determinations). This material 

was coated to a 2% loading of Hg(CN)2 using a procedure similar to that described in NIOSH Method 6002 

(Reference 3). 

Spiked phosphine samples on the Hg(CN)2 /Chromosorb-P sorbent were prepared by adding various amounts of 

the gas in nitrogen (350 μg/L) using a 50-cc syringe to 200 mg of the solid sorbent at a rate of 0.42 mL/min. The 

spiked samples were extracted for one hour at room temperature using 10 mL of 0.01 KMnO4 in 0.4N H2SO4 

solution and the extracts analyzed as described in NIOSH 6002 (Reference 3). The data obtained (shown below) 

indicate erratic recoveries. 

Table 6002-2. Recovery of Phosphine from Hg(CN)2 /Chromosorb-P 

Volume Added (mL) PH3 added (μg) PH3 found (μg) Recovery 

20 7.00 6.94 0.991 

20 7.00 6.78 0.968 

20 7.00 6.03 0.861 

20 7.00 5.70 0.814 

40 14.00 9.38 0.670 

Samples which were similarly spiked but stored for 8 days at room temperature before analysis similarly showed 

low and erratic recoveries. These data are given below. 

Table 6002-3. Recovery of Phosphine from Hg(CN)2 /Chromosorb-P after 8 days of storage 

Volume Added (mL) PH3 added (μg) PH3 found (μg) Recovery 

19.3 6.75 5.59 0.828 

19.3 6.75 5.29 0.784 

19.3 6.75 5.00 0.741 

These data suggested that the erratic results may be partly due to the poor spiking method and low capacity of 

the sorbent for phosphine. Experiments were thus performed to determine the capacity of the sorbent. These 

experiments were performed using a silver nitrate coated on silica gel (2% loading) indicator tube which gave a 

detectable stain in the presence of 0.4 μg of phosphine (sampling of a 0.7 μg/L PH3 atmosphere for three 

minutes at 0.2 liter per minute) to determine when breakthrough occurred. For 200 mg of sorbent sampled at 

0.2 liter per minute from an atmosphere of 0.7 mg/m3 of phosphine in dry air, a detectable stain was observed 

after 32 ± 2 minutes of sampling (average of 3 tubes). The capacity of this sorbent is calculated to be less than 

4.48 μg PH3 under these conditions. These data confirm the previous expectation and accounts for the erratic 

results obtained in the spiking experiments. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

Principle of the Method 

The procedure for collection and analysis of air samples of phosphine is described in NIOSH Method 6002 

(Reference 3). This method is based upon collection of phosphine on mercuric cyanide coated silica gel, 

extraction and oxidation of the phosphorus to phosphate using a hot acidic permanganate solution and 

colorimetric analysis of the phosphate using the stannous chloride reduction of a phosphomolybdate complex 

after extraction into a mixture of isobutanol and toluene. A sample volume of 16 liters is recommended. 

Analytical Method 

A detailed description of the procedure for analysis is given in NIOSH Method 6002. The reliability of the 

colorimetric method of analysis for phosphate (for acidic silica gel extracts) was established by checking the 

effects of the following:· 

a. Stability of the absorbance with time. 

b. Effect of mercuric cyanide. 

c. Linearity of the calibration curve over the working range. 

The results are discussed below. 

The absorbance readings obtained in the analyses of three levels of phosphine (corresponding to those that 

would be obtained from collection at 0.5, 1, and 2X the OSHA standard) obtained from spiked mercuric cyanide 

coated silica gel tubes as a function of time are shown in Table 6002-3. These data indicate that the 

absorbances decrease as a function of time at rates which depend on the initial phosphorus concentration. The 

rate of decrease is slow, being about 1% per minute. Thus, in all absorbance measurements, readings were 

made 30 seconds after the addition of the stannous chloride reducing agent. 

The lack of effect of mercuric cyanide on the analysis of standard amounts of phosphate was shown in the 

previous section. 

A calibration curve was constructed according to the prescribed procedure using standards prepared from 

KH2PO4. The linear calibration curve fitted to the data by the method of least squares linear regression had a 

correlation coefficient of 0.9995 over the working range of 1.58-15.8 μg PH3. The sensitivity of the method as 

given by the slope of the calibration curve is 0.0524 absorbance units per μg PH3. The observed absorbances 

cover the range of 0.088-0.829 absorbance units. 

All of the work described in this backup data report was done using isobutanol/benzene mixture in the 

extraction step of the colorimetric analysis. However, due to the OSHA standard limiting employee exposure 

to 1 ppm of benzene, the recommended analysis involves substitution of toluene for benzene in the extraction 

step. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

Table 6002-3. Stability of the reduced Phosphomolybdate complex 

Added Phosphorus (μg PH3) Absorbance (time) % loss 

4.1 0.200 (30 sec) 0 

4.1 0.199 (60 sec) 0.5 

4.1 0.198 (90 sec) 1.0 

4.1 0.197 (120 sec) 1.5 

7.6 0.363 (30 sec) 0 

7.6 0.360 (60 sec) 0.8 

7.6 0.357 (90 sec) 1.7 

7.6 0.353 (120 sec) 2.8 

13.4 0.699 (30 sec) 0 

13.4 0.689 (60 sec) 1.4 

13.4 0.683 (90 sec) 2.3 

13.4 0.677 (120 sec) 3.1 

The suitability of isobutanol/toluene solvent system for extraction of the phosphomolybdate complex was 

shown by preparation of a standard curve over the range of 0.693-13.86 μg PH3 (added as KH2PO4) which had a 

sensitivity of 0.0501 absorbance units per μg PH3 and a correlation coefficient of 0.9993. 

The lack of effect of any silica extracted from the silica gel on the analysis using the isobutanol/toluene mixture 

was also confirmed by preparing a standard curve using an acidic permanganate which had been used to extract 

blank mercuric cyanide coated silica gel (10 mL extract of 300 mg silica gel). The standard curve was prepared to 

cover the range 0.693-13.86 μg PH3 (added as KH2PO4) and had a sensitivity of 0.0508 absorbance units per μg 

PH3 and a correlation coefficient of 0.9987. The good correlation coefficients and the agreement between the 

sensitivity of the method using benzene and that using toluene indicate that toluene is an acceptable substitute 

for benzene in the analytical method. Toluene is thus recommended in the sampling and analytical method but 

all the values given in this report were obtained using isobutanol/benzene in the extraction step. 

Detection Limit 

The detection limit for the determination of phosphorus using the phosphomolybdate/isobutanolbenzene/stannous chloride method was taken to be twice the standard deviations obtained for the absorbance 

of a set of six determinations of blank mercuric cyanide coated silica gel samples (300 mg). The data are given 

below: 

Table 6002-4. Absorbance data for blank Hg(CN)2/SiO2 

Sample Absorbance 

1 0.010 

2 0.008 

3 0.011 

4 0.014 

5 0.005 

6 0.019 

Avg=0.011; std dev=0.005 

The detection limit corresponds to 0.010 absorbance units or 0.19 μg of PH3. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

 

 

Analysis 

The reliability of the analytical method was based upon the analysis of 18 analytical samples. These samples 

were prepared by spiking 300 mg of mercuric cyanide coated silica gel with 11.0, 22.0 and 41.78 mL of 

phosphine gas in nitrogen (350 μg/L) representing the equivalent of a 16 liter sample at 0.5, 1 and 2X the OSHA 

standard. The procedure and apparatus used to prepare the spiked samples are described in Attachment A. 

The data for the full set of analytical samples are shown in Table 6002-5. 

Table 6002-5. Analysis of spiked Phosphine samples 

Level μg added μg found Recovery 

0.5S 3.85 3.74 0.971 

3.85 3.85 1.000 

3.85 3.72 0.966 

3.85 3.75 0.974 

3.85 4.01 1.042 

3.85 4.12 1.070 

1S 7.70 7.37 0.957 

7.70 7.45 0.979 

7.70 7.64 0.992 

7.70 7.85 1.019 

7.70 7.59 0.986 

7.70 7.00 0.909 

2S 14.62 14.47 0.990 

14.62 13.75 0.940 

14.62 14.52 0.993 

14.62 14.69 1.005 

14.62 14.58 0.997 

14.62 14.52 0.993 

Sampling and Analysis 

Test atmospheres of phosphine were generated using the basic system described in Attachments B and C. A 

steady stream of phosphine in nitrogen (306 μg/L-see section on Independent Method for Verifying Generator 

Concentration) was delivered from a gas cylinder via a rotameter at a flow rate of 309 mL/min or 94.6 

μg/minute of phosphine to a dry stream of air flowing at 0.1129 m3

/min. 

The three sample lines were maintained at measured dilution ratios of 0.233:0.501:1.000 to produce test levels 

0.5, 1 and 2X the OSHA standard. The delivery rate of the phosphine gas mixture was determined by calibration 

using a soap-bubble flow meter. The data are presented in the section on Independent Method of Verifying 

Generator Concentration. 

Twenty-four samples were collected simultaneously at 0.2 liter per minute for 80 minutes (16 liters) in tubes 

containing a front section of 300 mg and a backup section containing 150 mg of treated silica gel. Eighteen 

samples, six each at the three test levels, were analyzed after one day as described in NIOSH Method 6002. The 

six remaining were stored and analyzed after seven days. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

The data obtained for the eighteen samples analyzed after one day are shown in Table 6002-6. The average 

recovery was 100.3%. 

Table 6002-6. Phosphine Generated Samples Analysis (n=6) 

Test Level μg found Liters found mg/m3 found mg/m3 taken Recovery 

0.5S 3.53 18.08 0.1952 0.1950 1.001 

3.14 15.36 0.2044 0.1950 1.048 

2.64 14.08 0.1875 0.1950 0.962 

3.88 20.88 0.1858 0.1950 0.953 

3.27 18.48 0.1769 0.1950 0.907 

3.64 16.64 0.2188 0.1950 1.122 

1S 6.49 16.08 0.404 0.420 0.962 

5.50 14.08 0.391 0.420 0.931 

5.94 15.04 0.395 0.420 0.940 

8.03 20.48 0.392 0.420 0.933 

5.89 15.28 0.385 0.420 0.917 

7.21 16.48 0.438 0.420 1.043 

2S 12.95 16.08 0.805 0.838 0.961 

16.55 17.44 0.949 0.838 1.132 

12.51 15.76 0.794 0.838 0.947 

12.73 15.60 0.813 0.838 0.970 

17.41 17.92 0.972 0.838 1.160 

16.64 18.00 0.924 0.838 1.103 

Storage Stability 

Studies were done to assess the stability of phosphine samples upon storage for seven days at ambient 

conditions. For these studies six samples collected at the OSHA standard level were stored for seven days and 

analyzed. These results were compared with the data for six samples collected simultaneously and analyzed 

after one day. The data for these samples are shown in Table 6002-7. The results indicate that the samples are 

stable over a seven-day period. The average recovery was 95.5% for the one-day-old samples vs. 101.7% for the 

seven-day-old samples. 

Table 6002-7. Storage stability of collected samples (1S level) 

Days Stored mg found Liters found mg/m3 found mg/m3 taken* Recovery 

1 6.49 16.08 0.404 0.420 0.962 

1 5.50 14.08 0.391 0.420 0.931 

1 5.94 15.04 0.395 0.420 0.940 

1 8.03 20.48 0.392 0.420 0.933 

1 5.89 15.28 0.385 0.420 0.917 

1 7.21 16.48 0.438 0.420 1.043 

7 6.43 15.28 0.421 0.420 1.002 

7 6.70 15.68 0.427 0.420 1.017 

7 7.32 15.60 0.469 0.420 1.117 

7 5.83 15.28 0.382 0.420 0.910 

7 7.13 15.20 0.469 0.420 1.117 

7 8.03 20.32 0.395 0.420 0.940 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

Breakthrough Tests 

Breakthrough tests were done in an atmosphere where the relative humidity was 90%. Breakthrough is defined 

as the time at which the effluent concentration from the collection tube (containing 300 mg of mercuric 

chloride-treated silica gel) is 5% of the concentration in the test gas mixture. The criterion for acceptance is that 

the volume of air that has passed through the tube at the time of breakthrough must be greater than 1.5 times 

the volume of air that would be passed through the tube during collection of a field sample, when the substance 

of interest in the test atmosphere is at the 2X OSHA standard level. 

A description of the equipment used is included in Attachment B under the section on Breakthrough Studies. 

These tests were conducted at two test levels (1.1X and 2.4X the OSHA standard) by taking samples after various 

sampling times (1 to 4 hours) and analyzing both the front and backup sections of the tube. The sampling rate 

was 0.2 liter per minute. The results obtained for the experiments are presented in Table 6002-8. The data for 

the 2.4X the OSHA standard level are plotted in Figure 6002-1 and indicate a 5% breakthrough volume of 20.75 

liters at this level. This indicates a maximum sampling volume of 16.5 liters at the 2S level. The capacity of the 

tube is 19.9 μg PH3. Based on this data, a sampling volume of 16 liters is recommended for phosphine (80 

minutes at 0.2 liter per minute). 

Table 6002-8. Breakthrough data 

Level mg/m3 Volume sampled L Front found μg Backup found μg Total found μg %breakthrough 

0.446 10.14 4.18 0.30 4.48 6.70 

0.446 15.84 6.44 0.30 6.74 4.45 

0.446 21.12 8.53 0.25 8.78 2.85 

0.446 30.8 12.98 0.30 13.28 2.26 

0.446 36.5 15.40 0.31 15.71 1.97 

0.446 49.2 20.70 0.50 21.20 2.36 

0.928 10.14 9.24 0.10 9.34 1.07 

0.928 15.84 13.74 0.53 14.27 3.71 

0.928 23.40 22.53 1.30 23.83 5.45 

0.928 26.40 24.42 2.00 26.42 7.57 

0.928 29.53 26.62 3.40 30.0 11.33 

0.928 34.2 26.84 4.12 31.0 13.29 

Avg recovery 0.446 level=0.962; avg recovery 0.928 level=0.976 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
Figure 6002-1. Breakthrough curve for phosphine collected on Hg(N)2/SiO2 tubes 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

Independent Method of Verifying Generator Concentration 

Attempts to determine the generated phosphine concentration by collection in a series of impingers filled with 

10 mL of 0.01 N KMnO4 in 0.2 N H2HSO4 at 0.2 liter per minute indicated a collection efficiency of only about 

50% (see data below). This low collection efficiency precluded the use of this method as an independent 

method. 

Table 6002-9. Collection efficiency of impingers 

Volume collected (L) PH3 found front (μg) PH3 found back (μg) %Collection efficiency* 

21.24 4.20 2.20 47.6 

27.12 4.05 2.00 50.4 

26.64 4.40 1.95 55.7 

*The collection efficiency has been determined using the equation μg found (2nd impinger)/μg found (1st 

impinger)=1-(collection efficiency). This equation assumes that the collection efficiency is independent of the 

phosphine level for the two impingers. 

The generator concentration of phosphine was established by experimentally determining the concentration of 

the stock phosphine in nitrogen mixture and the delivery rate of the mixture (in mL/min) into a measured 

dilution air flow (in m3/min). The concentration of the 25 line was calculated using these values (in mg/m3). The 

concentration of the 0.58 and 18 lines can be calculated by measuring the dilution ratios of these lines relative to 

the 25 line (main). 

The concentration of the stock phosphine gas in nitrogen was determined by injection of a 20-cc or 40-cc sample 

of the gas into an evacuated gas sampling bottle containing 10 mL of an acidic permanganate solution (0.01 N 

KMnO4 in 0.2 N H2SO4). The gas sampling bottle was shaken mechanically for 30 minutes. The phosphate 

content of the acidic solution was determined colorimetrically using the same procedure described in NI0SH 

Method 6002. No difference in phosphine level was observed for samples shaken for 30 minutes or 2 hours. The 

data obtained for the two stock samples of PH3 in N2 used in this study are given in Table 6002-10. 

Table 6002-10. Phosphine concentrations in stock samples 

Sample* Volume Analyzed μg PH3 

found 

Level (μg/L) Avg (μg/L) Std dev CV 

1 20.04 6.59 329 

1 40.08 14.87 371 

1 20.24 7.27 359 

1 40.48 14.45 357 

1 20.22 6.83 338 

1 20.22 7.00 346 350 15.31 0.0437 

2 20.04 5.69 284 

2 20.24 6.47 320 

2 20.34 6.27 308 

2 20.24 6.60 326 

2 20.34 6.21 305 

2 20.22 5.89 291 306 16.18 0.053 

*Sample 1 used in analytical set and other experiments; sample 2 used in generated set. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

The delivery rate of the stock phosphine gas into the generation system was determined by calibration of the 

flow using a soap-bubble meter. The data obtained for the delivery rate in mL/min at 21.5°C and 761.8 mm Hg 

are shown below: 

Flow mL/min. 

310 

309 

309 

310 

307 

310 

Average: 309 mL/min or 94.6 μg PH3/min; Std Dev=1.17; CV= 0.0038 

The corrected main line flow was found to be 0.1129 m3

/min at the respective atmospheric temperature and 

pressure conditions given above. The dilution ratios used to produce the test levels at 0.5, 1 and 2X the OSHA 

standard were 0.233; 0.501; 1.000. Based on these data, the "taken" generator concentration at the 0.5, 1 and 

28 lines are, respectively; 0.195; 0.420; 0.838 mg/m3

. 

Confirmation of the Absence of Particulate Phosphate in the Generation of Phosphine at High Humidity 

Atmospheres 

Experiments were made to determine if any particulate phosphoric compounds were formed in the 

breakthrough experiments where phosphine was generated in a high-humidity atmosphere. In these 

experiments, samples of the phosphine were collected on six treated silica gel tubes (both front and backup 

sections) and the results compared to three samples which were passed through 1.0 μm polytetrafluoroethylene 

filters (PTFE) prior to collection in the tubes. The results are presented in Table 6002-11 and indicate that little 

particulate phosphorus is present and little adsorption of PH3 occurs on the filter. 

Table 6002-11. Comparison of filtered and unfiltered phosphine samples 

Sample Type Volume sampled (L) Total μg PH3 found* Level (mg/m3) 

Unfiltered 10.14 9.34 0.921 

Unfiltered 15.84 14.27 0.901 

Unfiltered 23.40 24.13 1.031 

Unfiltered 26.40 26.42 1.001 

Unfiltered 29.53 30.00 1.016 

Unfiltered 34.20 31.00 0.906 

Filter through PTFE filter 24.24 24.55 1.013 

Filter through PTFE filter 23.64 20.94 0.886 

Filter through PTFE filter 22.80 20.85 0.914 

*Sum of front and backup sections. 

Precision and Accuracy 

The precision of the method was determined by using the statistical procedures described in Reference 2 and 

the data in Tables 6002-5 and 6002-6. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

 

Bartlett's test for homogeneity of variances was applied to the coefficients of variation at 0.5, 1, and 2X the 

OSHA standard for generated samples. The data (Table 6002-6) gave a chi squared value of 2.39, indicating that 

the hypothesis of equal variance is satisfied at p (probability) less than 0.01. Thus, CV

͞T is calculated based on the 

pooled data. 

The precision of the method is expressed in terms of the coefficients of variation for the analytical method, the 

sampling and analytical method, and the overall method which includes a pump error of 0.05. These values are 

shown below. 

The accuracy of the method was determined by comparison of the average value found by analysis of six 

samples at each of the three test levels with the Taken generator concentration discussed in the appropriate 

section. The data summarized below show good agreement (Found and Taken) with an average of 100.2%. 

Table 6002-12. Accuracy of method 

Test level mg/m3 taken mg/m3 found Agreement (found/taken) 

0.5S (generated set) 0.1950 0.1948 0.999 

1S (generated set) 0.420 0.401 0.955 

2S (generated set) 0.838 0.877 1.047 

1S (storage stability) 0.420 0.427 1.017 

1S (breakthrough) 0.446 0.429 0.962 

2S (breakthrough) 0.928 0.957 1.031 

Avg agreement=1.002 

The difference between the Taken and Found concentrations may not represent a bias in the sampling and 

analytical method, but rather a random variation from the experimentally determined "true" concentration. 

Further confidence in the accuracy of the tested method is established by the results of the desorption 

efficiency test and the storage stability test, described in the appropriate sections. 

References 

1. NIOSH [1976]. Statement of Work: Article 1. NIOSH contract no. 210-76-0123. U.S. Department of 

Health, Education and Welfare, Center for Disease Control, National Institute for Occupational 

Safety and Health. 

2. NIOSH [1977]. Documentation of NIOSH Validation Tests. Cincinnati, OH: U.S. Department of 

Health, Education and Welfare, Center for Disease Control, National Institute for Occupational 

Safety and Health. DHEW (NIOSH) Publication No. 77-185. 

3. NIOSH [1976]. Phosphine: NIOSH Method No. S332 (validation date 3/17/78). NIOSH Contract No. 

210-76-0123. U.S. Department of Health, Education and Welfare, Center for Disease Control, 

National Institute for Occupational Safety and Health. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ATTACHMENT A 

PROCEDURE AND APPARATUS USED TO PREPARE SPIKED PHOSPHINE SAMPLES 

The apparatus shown in Figure 6002-A-1 was used to prepare spiked samples of phosphine for the 

determination of the analytical method recovery. Spiking was performed according to the following procedure. 

Standard phosphine in nitrogen gas mixture was flushed through the sampling loop for 3 minutes at a rate of 50 

mL/min with the exit valve open to the atmosphere. The valve was closed and the system pressurized at 20 psi 

with the phosphine gas mixture. The four-way valve was turned to the open position to adjust the pressure in 

the loop to atmospheric. The four-way valve was rotated to introduce a nitrogen flow of 2.9 mL min through the 

loop. The exit valve was adjusted to let the gas flow through the sorbent tube at that rate. This process was 

continued for 20 minutes. Sampling loops of approximately 10 and 40 mL were used. The exact volume of gas 

spiked was determined using the procedure described below. In order to spike with approximately 20 mL of gas, 

the 10 mL sampling loop was used and the process done twice. 

The exact volume of phosphine spiked onto the sorbent tube was determined using the following procedure. A 

mercury manometer (made out of 1 mm I.D. tubing) was attached to the end of the exit valve. A fitting with a 

rubber septum was attached to the other side of the exit valve. The four way valve was turned to the closed 

position and the pressure in the sealed system was adjusted to atmospheric. Air was introduced into the system 

(1 mL or 5 mL increments) using a gas tight syringe through the rubber septum and the pressure in the system 

recorded after each incremental addition. The volume of this system (spiking volume+ manometer volume) was 

determined using the equation 

V (in mL) =intercept + slope 

Where the slope and intercept values are calculated from a plot of the equation: 

Where: p=total pressure (in mm Hg) 

ΔV= incremental volume added (mL) 

The manometer volume was determined using a similar procedure and this volume subtracted from the total to 

arrive at the spiking volume. The values for the volume spiked using the apparatus with the small and the large 

loops connected, respectively, were (average of three measurements) 10.99 ± 0.10 and 41.78 ± 0.30 mL. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
Figure 6002-A-1. Apparatus used to prepare spiked phosphine samples 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

ATTACHMENT B 

VAPOR DILUTION/SAMPLING SYSTEM 

The vapor generation/dilution system used for the validation studies of several vapors and gases, such as this 

analyte, is shown schematically in Figure 6002-B-1. The system basically consists of a main line air stream to 

which are added predetermined amounts of various liquids, gases or aerosols to generate the desired vapor 

concentrations. From the main line, three dilution arms branch off in which the desired multiples 0.5, 1.0 and 

2.0 times the OSHA Standard concentration level are established. Six sampling devices are connected in parallel 

to each of the three dilution lines and are connected via critical flow orifices (CFOs) to the three corresponding 

vacuum lines. 

Air flow rates through the system are established by means of CFOs and flow restrictors. The primary air system 

derived from the house air compressor is maintained at 20.0 psig. The appropriate orifice diameters are chosen 

to maintain an air flow of approximately 0.1 m3

/min in the Main Line and an addition of 0.05 m3/min to each of 

the dilution lines. The main line is maintained at 8 cm H2O pressure by means of a needle valve. Appropriate 

flow restrictor diameters are chosen for the 0.5S, 1S and 2S dilution lines so as to give the desired final 

concentrations of vapor in air. 

The system was designed to generate either 4X or 2X the OSHA Standard concentration in the Main Line. When 

a 4X level is generated, 0.05 m3

/min of dilution air is added to each dilution line. Orifices are selected so that the 

0.5S, 1S and 2S lines have flows equal to approximately 0.007, 0.017 and 0.050 m3

/min respectively of the Main 

Line concentration added to the dilution air, thus giving the desired final concentrations. Where a Main Line 

concentration of 2X the OSHA Standard is generated, no dilution air is added to the 25 dilution line-0.017 

m3

/min is simply allowed to flow through this line and 0.050 m3/min of dilution air is added to the 0.050 m3/min 

and 0.017 m3

/min of Main Line mixture admitted to the 15 and 0.5S dilution lines, respectively. 

All materials which the vapor may contact before collection are 316 or 304 stainless steel. A glass heater is 

included where the liquids are added to the main line. Shutoff ball valves are placed in the dilution lines to allow 

their independent operation and the calibration of air flows. The Main Line has a 2.54-cm (1 in) O.D., and the 

dilution lines are 1.90-cm (0.75 in) O.D. Diameters were chosen to give turbulent flow with an approximate 

minimum Reynolds number of 3000. 

Air Supply 

Air from the house compressor is treated by passing it sequentially through a cotton filter, a silica gel bed, a 

charcoal bed and a high efficiency glass fiber filter for removal of water, hydrocarbons and particulate. This air is 

then connected to a manifold containing six takeoff ball valves. The pressure (20 psig) at the manifold is 

maintained with a Nullmatic Moore 40H50 regulator and monitored with an Ashcroft 0-60 psig test gauge. The 

air supply is used for each of the dilution system connections as well as for the flame ionization detector 

monitor flame and "zero" air. 

Sample Collection Manifold 

Sample flow through the sampling devices connected to the dilution lines is established by connecting each 

device by means of a short piece of flexible tubing to a CFO which is connected to a. 1.27 cm (1/2 in) O.D. 

vacuum manifold. Each dilution line has a separate manifold which derives its vacuum from a Model 0322 Gast 

vacuum pump. The orifices are jewel orifices pressed into a threaded Teflon rod. One end of the rod is screwed 

into a tee on the manifold, and the other has a hose tabulation fitting connected to it. The orifice is protected 

from plugging by means of a piece of 100 mesh stainless steel screen. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
Figure 6002-B-1. Vapor Generation/dilution/sampling system

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vent System 

All excess vapor-laden air is collected via a 3.81-cm (1.5 in) PVC manifolding system where it is passed through a 

0.3 x 0.3 x 0.6-M charcoal bed. Flow is established by means of a pressure blower on the exit side of the 

charcoal bed, and it is vented to the laboratory hood exhaust. 

Air Flows Calibration 

Main Line-The air flow delivered by the Main Line CFO was determined by measurement with a Singer 

Dry Test Meter. The meter had previously been calibrated with a spirometer primary standard. Using 

the 0.310-cm diameter orifice at 20 psig air pressure, the flow was found to be 0.1086 m3

/min corrected 

to 25°C and 760 nm Hg. 

Dilution Lines-The air flow through each of the dilution line CFOs and restrictor orifices was similarly 

measured with the Dry Test Meter to assure that they met design parameters, but these values did not 

provide the primary basis for determination of vapor concentration. 

Collection CFOs-Since the flow rate through the sample collection CFOs was lower (0.2 and 1.0 liter per 

minute) than appropriate for use with the Dry Test Meter, the flow rate of each of these orifices was 

measured using an SKC soap bubble meter which was independently calibrated by gravimetrically 

measuring water capacity. 

All volume measurements have been referenced to normal temperature and pressure of 25°C and 760 mm Hg. 

Dilution Ratios 

The concentration of vapor in the dilution lines is determined from the concentration calculated in the Main Line 

and the dilution ratio determined between the dilution lines and the main line. These dilution ratios were 

measured by adding a controlled amount of propane gas to the Main Line and then measuring the relative 

concentration in each of the lines using a Beckman Model 402 heated hydrocarbon analyzer. The procedure 

was repeated several times and is regularly checked during the program. 

In the case where 4X or 2X concentration level conditions were generated, the dilution ratios reported below 

were observed. 

Table 6002-B-1. Dilution ratios 

Case generated Main Line Relative Conc (2S) Relative Conc (1S) Relative Conc (0.5S) 

4X 1.000 0.510 0.256 0.131 

2X 1.000 1.000 0.499 0.227 

Each of these sets of values represents a different set of air flow and orifice selection conditions as previously 

discussed. Point to point comparison of the six sample ports on each manifold showed less than a 1% variation 

in concentration among them. 

Monitors 

To provide a ready check on operating conditions, several gauges or monitors have been included in the system. 

Dwyer Magnehelic gauges monitor the pressure on the Main Line and each of the dilution lines. A 0-10 

cm H2O gauge is used on the Main Line (Setpoint 8 cm) and 0-2 cm H2O gauges are used for the dilution lines. 

The purpose of these latter gauges is to provide a check against possible back pressure developing in these lines 

which would affect the dilution ratios. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

The flame ionization detector (FID) is used to determine the time at which the Main Line concentration has 

reached equilibrium and to monitor the concentration level during breakthrough studies and sample collection. 

Breakthrough Studies 

A. Low Relative Humidity (Dry Air) 

For the measurement of sorbent tube capacity for a given vapor (breakthrough) six sorbent tubes containing 

only the 100 mg "front half" section of sorbent are connected in parallel to the 25 dilution line and to a 0.635-

cm (1/4-in) O.D. stainless steel six-port manifold. Flow through the manifold is controlled by a CFO and is 

established using a Metal Bellows Corp. Model MB41 pump. Flow through the orifice was measured as 1.14 

liters per minute providing a 0.19-liter per minute flow to each of the tubes. (A separate set of orifice allows a 

similar determination at a flow rate of 1.0 liter per minute through each tube.) Equal flow through each of the 

tubes is insured by carefully selecting and/or adjusting packing in the tubes to have an equal pressure drop 

when precalibrated at a 0.2-liter per minute flow rate. 

Once a steady state vapor concentration is established, the 2S concentration level is used to set the 100% point 

on the hydrocarbon analyzer. Then the valve is switched, and the flow from the breakthrough manifold is 

passed through the hydrocarbon analyzer and monitored either until 5% of the 25 level is observed or for a 

period of four hours-whichever occurs first. 

B. High Relative Humidity 

For the generation of a high relative humidity atmosphere, at least 80% R.H., water vapor is delivered into the 

generator Main Line via one of the side arms as shown in Figure 6002-B-2. A peristaltic pump, Cole Parmer 

Masterflex, Model No. 7013, is used to deliver water into a heated copper coil (1/8 in x 10 feet) contained in a 

tube furnace; the furnace temperature is maintained above 110°C and monitored by a thermocouple and optical 

pyrometer. Water is delivered at the rate of 1.9 g per minute to blend with the analyte-containing dry air 

stream flowing at a rate of 1.100 m3

/min to produce an atmosphere of at least 80% R.H. at 25°C and 760 mm Hg. 

All other aspects of the breakthrough test procedure are as described above. 

Procedure 

The overall procedure for a given sample is as follows: 

1. Line air flow and dilution ratios are verified. 

2. Sample delivery rate is determined by appropriate calibration. 

3. Sample is fed into Main Line until vapor concentration equilibrium is established. 

4. The breakthrough experiment is performed and subsequent sample collection volumes adjusted 

if necessary. 

5. The four sets of six samples from the three concentration levels are collected simultaneously. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
Figure 6002-B-2. Generation of high humidity atmospheres 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition 
 

 

 

 

 

ATTACHMENT C 

GAS GENERATION 

Controlled Gas Injection 

When gaseous substances are to be tested, the desired concentration of vapor is generated by a controlled flow 

injection. When a cylinder of gas is used, the gas is fed into the dilution/sampling system through a calibrated 

gas rotameter. The delivery rate is calibrated by either a dry gas meter or bubble meter depending on the flow 

rate used. 

Calculation of Main Line Concentration 

The calibrated gas delivery rate in mL/min is converted by ideal gas law calculations to units of mg/min. The 

Main Line concentration is then determined by dividing the delivery rate in mg/min by the Main Line flow rate in 

m3

/min. This gives the concentration generated in units of mg/m3. 

If a gas mixture is used for generation, the exact content of the cylinder is determined by chemical analysis. A 

correction factor is then applied to the calibrated delivery rate and the Main Line concentration calculated as 

above. 

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition