# Elements by ICP (Microwave Digestion) (7302)

​‌ MW: Table 1
CAS: Table 2
RTECS: Table 2
METHOD: 7302, Issue 1
EVALUATION: FULL
Issue 1: 21 July 2014
OSHA: Table 2 ​ NIOSH: Table 2 Other OELs: [1,2]*
PROPERTIES:
Table 1
cadmium lead phosphorus strontium yttrium ELEMENTS: aluminum
antimony calcium lithium platinum tellurium zinc
SAMPLING SAMPLER:
FILTER (mixed cellulose ester membrane (MCE), 37-mm diameter, 0.8-µm pore size)
FLOW RATE: 1 to 4 L/min VOL-MIN: -MAX:
Table 1
SHIPMENT: Routine SAMPLE STABILITY: Stable BLANKS:
2 to 10 field blanks per set ACCURACY
MEASUREMENT TECHNIQUE:
INDUCTIVELY COUPLED ARGON PLASMA, ATOMIC EMISSION SPECTROSCOPY (ICP-AES)
ANALYTE:
Elements listed above
REAGENTS:
10.0 mL of 1:1 nitric (HNO3) and ASTM Type II water
FINAL SOLUTION:
20% HNO3, 25 mL
WAVELENGTH:
Depends upon element (see Table 3)
BACKGROUND CORRECTION:
Spectral wavelength shift
RANGE STUDIED:
See Table 4
CALIBRATION:
Elements in 20% HNO3
ACCURACY:
See Table 4
RANGE:
See Table 4
BIAS:
See Table 4
ESTIMATED LOD: Table 3
OVERALL ˆ PRECISION ( S
rT
See Table 4
PRECISION ( Sr ) : Table 3
APPLICABILITY: This method is for the analysis of metal and nonmetal dust collected on MCE filters in the workplace. The working range varies from element to element. The method entails simultaneous elemental analysis using a microwave digestion approach to simplify and expedite the analysis. INTERFERENCES: Spectral interferences are the primary interferences encountered in ICP-AES analysis. These are minimized by judicious wavelength selection, inter-element correction factors and background correction [3]. OTHER METHODS: This method complements NIOSH hotplate digestion methods 7300 and 7301 for trace elements. Flame atomic absorption spectroscopy (e.g., Methods 7013 through 7082) is an alternative analytical technique for many of these elements [4]. Graphite furnace AAS (e.g., 7102 for Be, 7105 for Pb) is usually more sensitive [4]. NMAM 7301 and 7303 contain alternative extraction procedures.
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 2 of 9
REAGENTS:
EQUIPMENT:
1. Nitric acid, conc., trace metal grade* 2. Calibration stock solutions, 1000 µg/mL and 10,000 µg/mL commercially available, or prepared per instrument manufacturer’s recommendation (see step10) 3. Digestion acid*. 1:1 water, ASTM type II, and nitric acid*, trace metal grade 4. Argon, liquid 5. De-ionized Water, ASTM Type ll [5] 6. Dilution acid*, 20% nitric acid in ASTM Type II water
1. Sampler: mixed cellulose ester membrane (MCE) filter, 0.8-µm pore size, 37-mm diameter; in 2-piece cassette filter holder 2. Personal sampling pump, 1 to 4 L/min, with flexible connecting tubing 3. Inductively coupled plasma-atomic emission spectrometer, equipped as specified by the manufacturer for analysis of elements of interest 4. Regulator, two-stage for argon 5. Microwave, programmable power, active temperature control, minimum of 574 W, corrosion resistant ventilated oven and turntable 6. Microwave digestion vessels, high pressure, closed PTFE, 100-mL capacity 7. Volumetric flasks, 25 mL** 8. Assorted volumetric pipettes as needed**
SPECIAL PRECAUTIONS: Wear gloves, lab coat, and safety glasses while handling all chemicals. All work should be performed with adequate ventilation to personnel and equipment. Because this method involves the use of capped digestion containers, avoid the use of other acids such as perchloric acid in combination with nitric acid that could cause a violent reaction [6,7]. In the preparation of the digestion and dilution acids, it is imperative that acid be added to water in order to avoid a violent exothermic reaction. SAMPLING 1. Calibrate each personal sampling pump with a representative sampler connected to the pump (in line). 2. Sample at an accurately known flow rate between 1 and 4 L/min. For estimated sampling volumes see Table 1. For TWA measurements see Table 2. Do not exceed a filter loading of approximately 2 mg total dust. NOTE: Filter overloading can be assessed by periodic visual checks. See NMAM Chapter O,   “Factors Affecting Aerosol Sampling,” for additional discussion on filter capacity.
SAMPLE PREPARATION NOTE: If total weights are desired, weighing should be done at this step. Follow NIOSH method 0500 for gravimetric analysis [11]. 3. Open the cassette filter holders and transfer the samples, blanks, and Quality Control (QC) filters to clean PTFE digestion vessels. Wipe the internal cassette surfaces with a 37-mm MCE filter, polyvinyl alcohol wipe or cellulosic wipe wetted with deionized water, and add to the digestion vessel to transfer non-filter aerosol deposits into the digestion vessels. 4. Add digestion acid up to 10 mL, and cap the vessels.
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 3 of 9
NOTE: In order to avoid a violent exothermic reaction, do not add water to concentrated nitric acid. Acid should be added after the water has been placed in the vessel. 5. Place digestion vessels in microwave, and run the preprogrammed digestion procedure for 12vessel digestion: 1200 W power, ramp to 150 °C over 20 min, hold for 10 min at 215 °C followed by at least a 5 min cool down (power will be adjusted lower for fewer vessels). 6. Allow the samples to cool to room temperature. 7. Remove vessel lids and rinse contents into 25-ml volumetric flasks with ASTM Type ll water. 8. Dilute to the mark with ASTM Type ll water and mix. 9. Submit extracted and diluted samples for analysis. CALIBRATION AND QUALITY CONTROL 10. Calibrate the spectrometer according to the manufacturer recommendations. NOTE: Typically an acid blank and multi-element working standards are used. The following multi element combinations are chemically compatible in 20% HNO3. a. Al, As, Ba, Be, Ca, Co, Cr, Cu, Fe, Li, Mg, Mn, Mo, Na, Ni, Pb, Se, Sr, Ti, V, Y, Zn, Zr; b. B, K, P, Sn, Te, Tl; c. Ag, Cd, Sb; d. Pt. 11. Analyze all applicable standards at least once every twenty (20) analyses (minimum frequency 5%). 12. Check recoveries with at least one media blank and two spiked media blanks per twenty samples. Use a spike level that is within the range of 10 to 20 times the LOQ. NOTE: Whenever possible, QA/QC samples should be prepared from certified reference materials in a matrix similar to the bulk material sampled. Liquid spiked filters are only surrogates for real world samples and QC data based upon certified samples are preferred. MEASUREMENT 13. Set ICP-AES spectrometer to conditions specified by manufacturer. 14. Analyze standards and samples at applicable wavelengths for each element (target analytes are in Table 3). NOTE: If the values for the samples are above the linear range of the instrument, dilute the    solutions with dilution acid, reanalyze, and apply the appropriate dilution factor in    calculations.
CALCULATIONS 15. Obtain the solution concentrations for the sample, Cs (µg/mL), and the average media blank, Cb (µg/ mL), from the instrument. 16. Using the solution volume of sample, Vs (mL), and media blank, Vb (mL), calculate the concentration for the sample, C (mg/m3), of each element in the air volume sampled, V (L), as follows:
C=
(Cs Vs )-(Cb Vb ) V
, mg/m3
NOTE: µg/Liter air is equivalent to mg/m3. EVALUATION OF METHOD Method 7302 was evaluated using multi-element filter spikes at six spiking levels, based on the estimated LOQ for each element [8]. Using microwave digestion is less time consuming and more NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 4 of 9
convenient than using the traditional mixed acid hot plate approach. The elimination of perchloric acid in the sample digestion procedure helps to improve the safety of the method. [7] Summary data are presented in Table 3 for levels 3X LOQ (lower level in Table 3) and 300X LOQ (higher level in Table 3) and for the ranges of loadings given in Table 4. Samples were subjected to microwave digestion using a CEM MDS-2100 device according to the conditions specified in the “sample preparation” section above (see Note of step #5). The values in Tables 3 and 4 were determined using several different ICP-AES instruments which were operated according to manufacturer’s instructions. The precision and recovery data, instrumental detection limits, sensitivity, and analytical wavelengths are listed in Table 3 and Table 4. All of the precision data were evaluated for homogeneity for all six concentration levels tested using the Bartlett’s test and the results are listed in the method backup data report [8] and summarized in Tables 3 and 4. A statistical analysis found that the data were poolable and all elements had calculated method precision accuracies of less than 25%. This overall precision (ŜrT ) and accuracy as given in Table 4 is an upper limit predictor of precision. Accuracy data (Table 4) demonstrate the utility of the method for all of the elements listed. A discussion of metals and metalloid analysis by ICP-AES is presented in an international voluntary consensus standard [3] and the microwave digestion procedure has been evaluated against other digestion procedures through an interlaboratory trial [10]. REFERENCES [1] ACGIH [2013]. TLVs and BEIs based on the documentation of the Threshold Limit Values for chemical substances and physical agents and Biological Exposure Indices. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists. [www.acgih.org]. [Data accessed April 2014.] [2] Institut fur Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung [2013]. GESTIS database on hazardous substances (German Social Accident Insurance). Sankt Augustin, FRG: [http://www. dguv.de/ifa/Gefahrstoffdatenbanken/GESTIS-Stoffdatenbank/index-2.jsp]. [Data accessed April 2014.] [3] ASTM [2010]. ASTM D7035-10, Standard test method for the determination of metals and metalloids in airborne particulate matter by inductively coupled plasma atomic emission spectrometry. West Conshohocken, PA: ASTM International [www.astm.org]. [4] NIOSH [1994] NIOSH Manual of analytical methods (NMAM). 4th ed. Schlecht PC, O’Connor PF, eds. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113 [www.cdc.gov/niosh/nmam/]. [5] ASTM International [2011]. ASTM D1193-77, Standard specification for reagent water. West Conshohocken, PA: ASTM International [www.astm.org]. [6] NIOSH [2005]. NIOSH Pocket guide to chemical hazards. Barsan ME, ed. Cincinnati, OH: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2005-149. [7] Furr AK, ed. [1995]. CRC Handbook of laboratory safety, 4th ed. Boca Raton, FL: CRC Press. [8] Stone LC, Perkins JB, Rogers DM [2003]. Elements by ICP using microwave digestion, NMAM 7302, Issue 1, Backup data report. Cincinnati OH: Datachem Laboratory developed under contract CDC200-2001-08000. Unpublished. [9] Lide DR, ed. [1994] Handbook of chemistry and physics. 74th ed. Baca Raton, FL.: CRC Press. [10] Butler OT, Howe AM [1999]. Development of an international standard for the determination of metals and metalloids in workplace air using ICP-AES: Evaluation of sample dissolution procedures through an interlaboratory trial. J. Environ. Monit. 1: 23-32.
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 5 of 9
[11] Code of Federal Regulations, 29 CFR Part 1910.1000 (Table Z-1) [https://www.osha.gov/pls/ oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9992]. Website accessed on December 13, 2013. METHOD WRITTEN BY: David M. Rogers, Lee C. Stone, James B. Perkins, DataChem Laboratories, Salt Lake City, Utah.; Yvonne Gagnon, Ronnee Andrews, Ph.D., NIOSH/DART. Disclaimer: Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health. In addition, citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of these Web sites. All Web addresses referenced in this document were accessible at the time of publication.
referring to the following sources for updated limits and guidelines on the use of this compound.
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 6 of 9
TABLE 1. PROPERTIES AND SAMPLING VOLUMES Air Volume, L @ OSHA PEL [11]
Element (Symbol) Aluminum (Al) Antimony (Sb) Arsenic (As) Barium (Ba) Beryllium (Be) Boron (B)(1) Cadmium Calcium (Ca)(1)
Properties [9] Atomic Weight MP, °C 26.98 660 121.76 630 74.92 817 137.3 727 9.01 1278 10.81 2300 112.40 321 40.08 842
MIN 5 10(2) 5 5(2) 1250 5 12 5
MAX 100 2000(2) 2000 200(2) 2000 2000 2000 200
Chromium (Cr)
52.00
1890
5
1000
Cobalt (Co)
58.93
1495
25
2000
Copper (Cu)
63.54
1083
5
1000
Iron (Fe)
55.85
1535
5
100
Lead (Pb)
207.19
328
50
2000
Lithium (Li)(1)
6.94
179
100
2000
Magnesium (Mg)
24.31
651
5
67
Manganese (Mn)
54.94
1244
5
200
Molybdenum (Mo)
95.94
651
5
67
Nickel (Ni)
58.71
1453
5
1000
Phosphorus (P)
30.97
44
25
2000
Platinum (Pt)
195.09
1769
1250
2000
Potassium (K)(1)
39.10
63
5
2000
Selenium (Se) Silver (Ag)
78.96 107.87
217 961
13 250
2000 2000
Sodium (Na)(1)
22.99
98
13
2000
Strontium (Sr)(1)
87.62
769
5
2000
Tellurium (Te)
127.60
450
25
Tin (Sn) Thallium (Tl)
118.69 204.37
232 304
20
2000 2000(2)
(2)
25
2000
5 5
100 2000
Titanium (Ti) Vanadium (V)
47.90 50.94
1675 1890
Yttrium (Y) Zinc (Zn)
88.91 65.37
1495 419
5 5
1000 200
Zirconium (Zr)
91.22
1852
5
200
(1)
(2)
No PEL, REL, or STEL data found [1,6,11]. Air volumes estimated from TWAs and LOQs (see Tables 2, 3) [1].
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 7 of 9
TABLE 2. EXPOSURE LIMITS, CAS #, RTECS [1,6,11]
Element (Symbol)
CAS #
RTECS
Aluminum (Al)
7429-90-5
BD0330000
Arsenic (As) Arsenic (As)
7440-38-2 7440-38-2 7440-39-3
CG0525000 CG0525000
Beryllium (Be) Cadmium (Cd) Calcium (Ca)
7440-41-7 7440-43-9 7440-70-2
DS1750000 EU9800000
Chromium (II) (Cr)
Exposure Limits in mg/m3 (C = ceiling limit) OSHA NIOSH
15 (total dust) 5 (respirable) 0.010 (inorganic) 0.010 (inorganic) 0.5 (Soluble compounds, as Ba) 0.002, C 0.005 0.005 No OELs
10 (total dust) 5 (respirable, fume) C 0.002(1) C 0.002(1) 0.5 (Soluble compounds, as Ba) C 0.0005(1) lowest feasible conc.(1) No OELs
22541-79-3 GB6260000
0.5
0.5
Chromium (III) (Cr)
16065-83-1 GB6261000
0.5
0.5
Chromium (VI) (Cr)
18540-29-9 GB6262000
0.005
0.0002
Cobalt (Co) Copper (Cu)
7440-48-4 7440-50-8
GF8750000 GL5325000
Iron (Fe)
1309-37-1
NO7400000
0.1 1(dust, mists) 0.1 (fume) 10 (fume) as oxide
0.05 (dust, fume) 1 (dust, mists) 0.1 (fume) 5 (dust, fume) as oxide
Lead (Pb)
7439-92-1
OF7525000
0.05
0.05
Magnesium (Mg)
1309-48-4
OM3850000
15 (dust) as oxide
Manganese (Mn)
7439-96-5
OO9275000
C5
1; STEL 3
Molybdenum (Mo)
7439-98-7
QA4680000
Nickel (Ni)
7440-02-0
QR5950000
5 (soluble) 15 (total insoluble) 1
0.015, Ca
Phosphorus (P)
7723-14-0
TH3500000
0.1
0.1
Platinum (Pt) Antimony (Sb)
7440-06-4 7440-36-0
TP2160000 CC4025000
0.002 (soluble) 0.5
1 (metal) 0.5
Selenium (Se)
7782-49-2
VS7700000
0.2
0.2
Silver (Ag) Tellurium (Te)
7440-22-4 VW3500000 0.01 (soluble, metal) 13494-80-9 WY2625000 0.1
0.01 (soluble, metal) 0.1
Tin (Sn)
7440-31-5
XP7320000
2
2
Titanium (Ti)
7440-32-6
XR1700000
15 (as TiO2)
lowest feasible(1)
Thallium (Tl)
7440-28-0
XG3425000
0.1 (soluble)
Uranium (U)
7440-61-1
YR3490000
Vanadium (V)
7440-62-2
YW240000
Yttrium (Y)
7440-65-5
ZG2980000
0.1 (soluble) 0.25 (insoluble) 0.05 (soluble) C 0.5 (respirable) as V2O5 C 0.1 (fume) asV2O5 1
Zinc (Zn)
1314-13-2
ZH4810000
Zirconium (Zr)
7440-67-7
ZH7070000
Barium (Ba)
5 (ZnO fume) 15 (ZnO dust) 5 (ZnO respirable) 5
0.2; STEL 0.6 (insoluble) C 0.05 1 5; STEL 10 (ZnO fume) 5; C 15 (ZnO dust) 5, STEL 10
(1) Carcinogen
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 8 of 9
TABLE 3. MEASUREMENT WAVELENGTHS AND RECOVERY DATA [8] Element(1) Wavelength LOD µg/sample (nm)[6] (µg/sample)
Ag Al As B Ba Be Ca Cd Co Cr(2) Cu Fe K Li Mg Mn Mo Na Ni P Pb Pt(2) Sb Se Sn(2) Sr Te(2) Ti Tl V Y(2) Zn(2) Zr
328.1 308.2 193.8 249.7 493.4 313.0 315.9 228.8 228.6 267.7 324.8 259.9 766.5 670.8 279.1 257.6 202.0 589.0 231.6 214.9 220.4 265.9 206.8 196.1 189.9 421.6 214.3 337.3 190.9 292.4 371.0 213.9 339.2
0.1 1 1 0.5 0.06 0.009 2 0.1 0.3 0.4 0.07 2 2 0.03 0.5 0.02 0.2 4 0.2 2 0.6 8 0.4 3 0.8 0.02 2 0.2 0.9 0.1 0.02 0.1 0.06
1.50 7.50 7.50 3.75 0.752 0.076 22.5 1.50 3.75 3.75 0.752 15.0 15.0 0.752 7.50 0.752 2.25 37.5 2.25 15.0 7.50 75.0 7.50 37.5 37.5 3.75 15.0 1.50 7.5 0.752 0.376 1.50 0.750
Lower Level Higher Level % Recovery % RSD µg/sample % Recovery % RSD N=6) (N=6)
95.5 92.7 101 112 104 95.8 107 98.8 99.7 103 98.8 112 98.3 92.4 89.3 86.2 96.8 100 98.3 100 98.9 98.3 94.4 104 105 92.6 90.1 101 103 93.7 107 106 93.1
1.01 0.981 2.22 2.96 3.09 2.36 2.87 3.46 1.72 7.87 3.47 2.43 5.70 2.98 3.52 2.38 5.41 0.823 5.21 5.67 3.94 0.282 3.21 3.21 5.04 2.36 21.8 1.70 4.14 4.74 4.44 13.1 5.35
150 750 750 375 75.2 7.60 2250 150 375 375 75.2 1500 1500 75.2 750 75.2 225 3750 225 1500 750 10000 750 3750 3750 375 1500 150 750 75.2 37.6 150 75.0
99.0 98.7 107 99.5 101 103 99.0 104 104 103 94.2 101 103 98.8 95.1 98.2 103 110 97.7 104 104 95.7 103 106 90.3 97.5 103 98.8 99.3 103 102 97.4 95.4
0.497 0.462 0.340 0.454 0.438 0.714 0.620 0.701 0.566 3.36 0.371 0.263 0.472 0.749 0.309 0.389 0.373 0.457 0.592 0.315 0.570 1.49 0.255 0.270 3.23 0.553 0.614 0.575 0.352 0.341 3.33 3.42 0.971
(1) Values reported were obtained with a Fisons ARL Accuris ICP-AES; performance may vary with instrument and should    be independently verified. (2) Values reported were obtained with a Perkin Elmer Optima 3000 DV ICP-AES. Sample concentration was based on Fisons    ICP LOD data.
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition ​ELEMENTS by ICP (Microwave Digestion): METHOD 7302, Issue 1, dated 21 July 2014 - Page 9 of 9
TABLE 4. PRECISION AND ACCURACY DATA BY ELEMENT [8] Element (µg/sample) Ag Al As Ba Be Ca Cd Co Cr Cu Fe K La Li Mg Mn Mo Ni P Pb Sb Se Sn Sr Te Ti Tl V Y Zn Zr
Range (µg/sample)
Bias
Ŝrt (%)
0.5 to 150 2.5 to 750 2.5 to 750 0.25 to 75.2 0.025 to 7.60 7.43 to 2250 0.50 to 150 1.24 to 375 1.24 to 375 0.248 to 75.2 5.00 to 1500 5.00 to 1500 12.6 to 50.1 0.25 to 75.2 2.5 to 750 0.25 to 75.2 0.75 to 225 0.75 to 225 5.0 to 1500 2.5 to 750 2.5 to 750 12.4 to 3750 12.4 to 3750 1.24 to 375 5.0 to 1500 0.5 to 150 2.5 to 750 0.25 to 75.2 0.12 to 37.6 0.5 to 150 0.25 to 75.0
-0.0175 0.0505 -0.2249 -0.0330 0.0297 -0.0081 -0.0082 -0.0161 -0.0204 0.0160 -0.0039 0.1487 -0.0136 0.2241 0.0180 -0.0348 0.0140 -0.0063 0.0669 -0.0246 0.0172 0.0538 0.0561 -0.0074 0.0161 0.0212 -0.0293 0.0175 -0.0179 0.0075 0.0314
0.668 1.455 0.554 0.920 0.863 0.836 0.729 0.574 0.655 0.984 1.637 1.665 0.920 1.209 0.844 0.865 1.469 0.672 1.212 0.544 0.722 0.758 0.936 0.710 0.892 1.043 0.602 1.223 1.115 1.343 0.980
Accuracy 2.85 7.41 23.40 4.82 4.39 2.18 2.02 2.56 3.12 3.21 3.30 17.61 2.87 24.40 3.19 4.91 3.82 1.73 8.69 3.36 2.91 6.63 7.15 1.90 3.08 3.84 3.92 3.76 3.62 3.02 4.76
NIOSH Manual of Analytical Methods (NMAM), Fifth Edition