Food

Elemental Analysis Manual: Section 4.4A Inductively Coupled Plasma-Atomic Emission Spectrometric Determination of Elements in Food Using Microwave Assisted Digestion

Appendix A - Supplemental Information on In-house Method Validation

Version 1 (June 2008)
Authors: William R. Mindak
Stephen G. Capar

GLOSSARY


Validation experiments of EAM 4.4 were perform using a CEM Corporation model MDS 2000 microwave digestion system with TFM Teflon lined Heavy Duty Vessels and an Applied Research Laboratories (ARL) Model 3580 inductively coupled plasma atomic emission spectrometer. Both a pneumatic nebulizer (ARL Maximum Dissolved Solids Nebulizer) and an ultrasonic nebulizer (CETAC U-5000 AT) were used. In-house validation results have been published1.

4.4A.1 ANALYTICAL LIMITS

Analytical limits were estimated by the analysis of method blanks and the results are summarized in 4.4A Table 1.

Note: When the method validation was conducted, the protocol at the time required ASQL and LOQ be calculated based on 10 times the standard deviation of the blank. The values reported in this appendix thus reflect "10×σ" values rather than the current protocol of "30×σ".

4.4A Table 1. Estimated Analytical Limits

    Pneumatic Nebulizer Ultrasonic Nebulizer
Element Symbol ASDL
(mg/L)
LODa
(mg/kg)
LOQa
(mg/kg)
ASDL
(mg/L)
LODa
(mg/kg)
LOQa
(mg/kg)
Aluminum Al 0.054 0.8 2 0.0074 0.1 0.3
Arsenic As 0.086 2 4 0.0022 0.03 0.08
Barium Ba 0.0033 0.05 0.2 0.011 0.2 0.4
Boron B 0.021 0.3 0.8 0.0040 0.05 0.2
Cadmium Cd 0.023 0.3 0.9 0.00039 0.005 0.02
Calcium Ca 0.63 8 30 1.1 20 40
Chromium Cr 0.13 2 5 0.0035 0.05 0.2
Cobalt Co 0.021 0.3 0.8 0.00037 0.005 0.02
Copper Cu 0.0079 0.1 0.3 0.00071 0.009 0.03
Iron Fe 0.0083 0.2 0.3 0.0038 0.05 0.2
Lead Pb 0.17 3 6 0.0032 0.04 0.2
Magnesium Mg 0.16 2 6 0.52 7 20
Manganese Mn 0.0099 0.2 0.4 0.000079 0.001 0.003
Molybdenum Mo 0.027 0.4 1 0.00081 0.02 0.03
Nickel Ni 0.066 0.9 3 0.0015 0.02 0.06
Phosphorus P 0.16 2 6 0.0048 0.06 0.2
Potassium K 1.1 20 40 0.053 0.7 2
Selenium Se 0.24 3 9 0.0086 0.2 0.4
Sodium Na 0.12 2 5 0.87 20 40
Strontium Sr 0.0019 0.03 0.07 0.027 0.4 1
Thallium Tl 0.16 2 6 0.0031 0.04 0.2
Vanadium V 0.014 0.2 0.5 0.00043 0.006 0.02
Zinc Zn 0.023 0.3 0.8 0.0013 0.02 0.05

a Based on 10×σ of method blanks, 4 g analytical portion, and 50 mL analytical solution.

4.4A.2 REFERENCE MATERIAL RESULTS

Reference Material Results

The results of replicate analyses of RMs (0.5 g to 1 g analytical portions) were used to assess accuracy and precision. Pneumatic and ultrasonic nebulization were assessed using independently prepared sets of RMs. RM recoveries were calculated based on available certified, informational, or consensus values for analytical results above LOQ.

Pneumatic nebulization

Results for 9 RMs analyzed using pneumatic nebulization are listed in 4.4A Table 2. At least one RM recovery was attainable for each element except chromium, cobalt, molybdenum, nickel, selenium, and thallium. RM recoveries were acceptable (80-120%) for arsenic, boron, cadmium, calcium, copper, lead, magnesium, manganese, phosphorus, potassium, vanadium, and zinc. As expected, aluminum RM recoveries were low especially materials containing appreciable levels of silicon. Low recovery of aluminum appears to be associated with incomplete dissolution of samples containing silica and requires the use of hydrofluoric acid to obtain complete recovery especially for plant materials2-3. Aluminum RM recoveries for 3 of 4 RMs were low (about 68%) and two of these were plant materials and the other, oyster tissue, has about 0.11% silicon4. Aluminum recovery from the fourth RM (dogfish liver; DOLT-2) was acceptable. Barium RM recoveries for 2 of 4 RMs were low. The barium recovery from oyster tissue (79%) is based on a consensus value (n = 4) with a relative standard deviation of about 14% but this variability does not fully account for the somewhat low recovery. The barium recovery from non-fat milk powder (42%) is also based on a consensus value (n=2) without an estimate of variability. Iron RM recovery for 1 (non-fat milk powder) of 9 RMs was high (121%). The iron concentration was near the LOQ (2 mg/kg) and, as expected had a high RSD (12%). Sodium RM recovery for 1 (orchard leaves) of 7 RMs was low (70%). The sodium level of this RM (58 mg/kg) was much lower than the other RMs and was somewhat near the LOQ (20 mg/kg) but the RSD of measurements was good (2%). This low recovery may indicate a MBK correction problem. Strontium RM recovery for 1 (non-fat milk powder) of 5 RMs was high (121%). This strontium recovery is based on a consensus value (n=2) without an estimate of variability. Molybdenum could not be measured above the LOQ in any RM but was measurable at "trace" level in one RM (rice flour). RSD for this level was good (8%) and the mean level is in close agreement with the reference value. Nickel also could not be measured above LOQ in any RM but was measurable at "trace" levels in two RMs (spinach and lobster). The RSD for nickel measured in spinach RM was good (4%) and the mean level is in close agreement with the reference value. However, the RSD measured in lobster RM was poor (41%) as expected for this "trace" level near the LOD and the mean level was not in agreement with the reference value. Arsenic could only be measured above the LOQ in one RM. However, arsenic was found in 5 other RMs at "trace" levels and all these concentrations were in fairly good agreement to the reference values which may indicate a high estimate of the arsenic LOQ. Precision of replicate analysis (measured as RSD) was 15% or less for all element concentration measurements above LOQ. The somewhat poor precision for aluminum in dogfish muscle is probably due to non-homogeneity. In general, the RM recoveries using microwave digestion and pneumatic nebulization are good except for aluminum and no assessment can be made for chromium, cobalt, molybdenum, nickel, selenium, and thallium due to lack of data.

4.4A Table 2. Reference Material Results Using Pneumatic Nebulizationa (1 of 3)

  Oyster Tissue
(NIST 1566)
  Rice Flour
(NIST 1568)
  Trace Elements inSpinach
(NIST 1570)
Element Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
Aluminum 255b 172 4 67   2.8b <3 - -   870 593 0.3 68
Arsenic 13.4 (13.5) 13 -   0.41 <5 - -   0.15 <5 - -
Barium 4.9b 3.9 3 79   0.3b (0.19) 3 -   14.6b 14.7 3 101
Boron 8.0b 7.4 4 93   0.64b <1 - -   28.0b 26 1 93
Cadmium 3.5 (3.79) 4 -   0.029 <2 - -   1.39b <2 - -
Calcium 1500 1340 3 89   140 148 4 90   13500 12500 2 93
Chromium 0.69 <7 - -   0.06b <7 - -   4.6 <7 - -
Cobalt 0.35b <1 - -   0.02 <1 - -   1.49b <1 - -
Copper 63 64.7 2 103   2.2 2.16 4 98   12 12.2 1 102
Iron 195 194 3 99   8.7 9.08 3 104   550 513 1 93
Lead 0.48 <9 - -   0.045 <9 - -   1.2 <9 - -
Magnesium 1280 1230 3 96   474b 479 2 101   8500b 7980 1 94
Manganese 17.5 16.5 4 94   20.1 20.1 0.3 100   165 160 1 97
Molybdenum 0.20b <2 - -   1.62b (1.72) 8 -   0.31b <2 - -
Nickel 1.03 <4 - -   0.14b <4 - -   5.6b (6.2) 4 -
Phosphorus 7600b 7300 6 96   1620b 1580 3 98   5500 4970 1 90
Potassium 9690 9600 1 99   1120 1140 3 102   35600 33000 1 93
Selenium 2.1 <20 - -   0.4 <20 - -   0.043b <20 - -
Sodium 5100 5400 1 106   6 (19.1) 24 -   13900b 14500 1 104
Strontium 10.36 10.1 2 98   0.19b (0.22) 11 -   87 86.3 2 99
Thallium ≤ 0.005c <8 - -   <0.002b <8 - -   0.03c <8 - -
Vanadium 2.6b 2.33 3 90   0.006b <0.7 - -   1.2b (1.3) 5 -
Zinc 852 764 7 90   19.4 19.5 5 100   50 45 3 90

4.4A Table 2. Reference Material Results Using Pneumatic Nebulizationa (2 of 3)

  Orchard Leaves
(NIST 1571)
  Non-Fat Milk Powder
(NIST 1549)
  Dogfish Muscle (NRCC
DORM-1)
Element Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
Aluminum 330b 224 4 68   2c <3 - -   nv 14.9 16 -
Arsenic 10 -12.3 5 -   0.00193b <5 - -   17.7 (17.8) 9 -
Barium 43b 44.4 1 103   2.2b 0.93 1 42   nv (0.27) 36 -
Boron 33 30 1 91   1.98b -2.1 6 -   nv <1 - -
Cadmium 0.11 <2 - -   0.0005 2 - -   0.086 <2 - -
Calcium 20900 17100 4 82   13000 12300 0.1 95   nv 1300 5 -
Chromium 2.6 <7 - -   0.0026 <7 - -   3.6 <7 - -
Cobalt 0.16b <1 - -   0.0041c <1 - -   0.049 <1 - -
Copper 12 12.8 3 107   0.7 -0.86 2 -   5.22 5.23 5 100
Iron 300 257 2 86   1.78 2.15 12 121   63.6 66.3 3 104
Lead 45 40.8 6 91   0.019 <9 - -   0.4 <9 - -
Magnesium 6200 5260 3 85   1200 1200 0.2 100   1210 1190 4 98
Manganese 91 79.9 2 88   0.26 <0.5 - -   1.32 (1.52) 8 -
Molybdenum 0.3 <2 - -   0.34c <2 - -   nv <2 - -
Nickel 1.3 <4 - -   0.10b <4 - -   1.2 <4 - -
Phosphorus 2100 1790 3 85   10600 11000 0.3 104   nv 10100 3 -
Potassium 14700 13800 2 94   16900 17000 0.4 101   15900 15200 5 96
Selenium 0.08 <20 - -   0.11 <20 - -   1.62 <20 - -
Sodium 82 58 2 70   4970 5540 0.5 111   8000 8140 5 102
Strontium 36b 34.9 1 97   3.1b 3.7 0.2 121   nv 8.5 8 -
Thallium 0.041b <8 - -   0.00052b <8 - -   nv <8 - -
Vanadium 0.51b <0.7 - -   0.005b <0.7 - -   nv <0.7 - -
Zinc 25 24 2 96   46.1 44.8 1 97   21.3 18.1 4 85

4.4A Table 2. Reference Material Results Using Pneumatic Nebulizationa (3 of 3)

  Dogfish Liver
(NRCC DOLT-1)
  Dogfish Liver
(NRCC DOLT-2)
  Lobster Hepatopancreas
(NRCC TORT-1)
Element Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
Aluminum nv (5) 16 -   25.2 25.4 6 101   nv 35.5 8 -
Arsenic 10.1 (11.5) 8 -   16.6 (14.1) 7 -   24.6 28.2 3 114
Barium nv (0.19) 14 -   nv 0.6 10 -   nv 3.98 3 -
Boron nv <2 - -   nv <2 - -   nv 5.45 11 -
Cadmium 4.18 4.66 2 111   20.8 19.4 1 93   26.3 25.4 3 96
Calcium nv 483 4 -   nv 521 2 -   8950 7930 5 89
Chromium 0.4 <8 - -   0.37 <8 - -   2.4 <8 - -
Cobalt 0.157 <2 - -   0.24 <2 - -   0.42 <2 - -
Copper 20.8 20.1 1 97   25.8 27.7 1 107   439 429 1 98
Iron 712 693 1 97   1103 1010 0.4 91   186 191 4 103
Lead 1.36 <10 - -   0.22 <10 - -   10.4 (9.3) 20 -
Magnesium 1100 1020 2 93   nv 784 1 -   2250 2380 3 106
Manganese 8.72 8.45 1 97   6.88 5.91 0.2 86   23.4 22.2 3 95
Molybdenum nv <2 - -   nv <2 - -   1.5 <2 - -
Nickel 0.26 <4 - -   0.2 <4 - -   2.3 (4.7) 41 -
Phosphorus nv 9820 3 -   nv 8330 0.3 -   8790 8820 5 100
Potassium 10100 9200 1 91   nv 8380 0.3 -   10410 10700 3 103
Selenium 7.34 <20 - -   6.06 <20 - -   6.88 <20 - -
Sodium 7260 7240 0.3 100   nv 7630 0.3 -   36700 36300 2 99
Strontium nv 4.7 4 -   nv 4.53 2 -   113 113 2 100
Thallium nv <9 - -   nv <9 - -   nv <10 - -
Vanadium nv <0.8 - -   nv <0.8 - -   1.4 (1.42) 9 -
Zinc 92.5 82.5 4 89   85.8 77.6 0.3 90   177 154 5 87

a Mean result based on 3 analyses except 5 analyses for Oyster Tissue, Dogfish Muscle (DORM-1), and Lobster Hepatopancreas. NIST=National Institute of Standards and Technology, NRCC=National Research Council of Canada, nv=no value available. Mean results in ( ) are "trace" levels and mean results below the LOD are listed as < LOD.
b Reference value not certified; consensus value7.
c Reference value not certified; informational value provided by certifying organization.

Ultrasonic nebulization

Results for 9 RMs analyzed using ultrasonic nebulization are listed in 4.4A Table 3 (only oyster tissue and dogfish muscle were not the same analytical solutions analyzed using pneumatic nebulization). At least one RM recovery is attainable for each element except thallium. RM recoveries were acceptable (80-120%) for arsenic, barium, boron, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, molybdenum, phosphorus, potassium, sodium strontium, vanadium and zinc. Aluminum RM recoveries for 2 of the 8 RMs were poor. The aluminum recovery from oyster tissue was low (65%) probably for the reasons discussed above. The aluminum recovery from bovine liver was very high (344%) and cannot be readily explained but could be due to the reference value (1.7 mg/kg) and the level found (5.8 mg/kg) being near the LOQ (2 mg/kg) or a contamination problem. A low (68%) nickel RM recovery for 1 (dogfish muscle) of 4 RMs cannot be readily explained. Selenium RM recoveries of all 4 RMs were high (mean 156%). All these RMs have an LOQ of 2 mg/kg and have reference values between 2 and 3 mg/kg, which may indicate that the estimated LOQ is too low or there is not sufficient correction of spectral background emission. Replicate analysis precision (measured as RSD) was 15% or less for all element concentration measurements above LOQ except for chromium in mussel (85%) and soy powdered infant formula (52%), and selenium in whole egg powder (22%). Extremely high variability was observed for chromium and many divergent results were excluded from performance assessment. The cause of this variability was not thoroughly investigated but environmental contamination or spectral interference is suspected. Chromium reference values for all RMs except dogfish muscle were below LOQ. The somewhat high selenium variability for whole egg powder is probably due a low estimated LOQ. Boron was not detected (<0.3 mg/kg) in soy powdered infant formula having a reference value of 0.60 mg/kg. Although the reference value is below the LOQ (1 mg/kg) trace levels should have been detected which may indicate that the estimated LOD may be too low. The trace vanadium result for total diet RM is a factor of 10 lower than a consensus value (n=1) without an estimate of variability indicating the low creditability of the value. A more recent publication by one of the same authors whose work provided the consensus value reported a vanadium concentration for the Total Diet RM of 0.037 mg/kg (mean of 2 analyses)5 which more closely agrees with the trace result. Cobalt was not detected (<0.03 mg/kg) in dogfish muscle having a reference value of 0.049 mg/kg. Although the reference value is below the LOQ (0.07 mg/kg) trace levels should have been detected which may indicate that the estimated LOD may be too low.

4.4A Table 3. Reference Material Results Using Ultrasonic Nebulizationa (1 of 3)

  Oyster Tissue
(NIST 1566)
  Bovine Liver
(NIST 1577a)
  Rice Flour
(NIST 1568a)
Element Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
Aluminum 255b 166 5 65   1.7b 5.8 15 344   4.4 5.3 6 120
Arsenic 13.4 14 2 105   0.047 <0.2 - -   0.29 (0.36) 21 -
Barium 4.9b 3.9 1 80   0.08b <0.9 - -   nv <0.7 - -
Boron 8.0b 7.2 6 90   0.84b <0.4 - -   0.54c (0.44) 11 -
Cadmium 3.5 3.65 3 104   0.44 0.454 6 103   0.022 (0.044) 44 -
Calcium 1500 1430 2 95   120 (153) 5 -   118 (151) 14 -
Chromium 0.69 <0.4e - -   0.2b (0.79) 21 -   nv <0.3e - -
Cobalt 0.35b 0.317 5 91   0.21 0.205 7 98   0.018d <0.03e - -
Copper 63 63 2 100   158 149 3 94   2.4 2.5 1 105
Iron 195 184 3 94   194 175 3 90   7.4 7.6 1 103
Lead 0.48 (0.54) 10 -   0.135 <0.3e - -   <0.010d <0.2 - -
Magnesium 1280 1150 2 90   600 554 3 92   560 483 1 86
Manganese 17.5 16.8 3 96   9.9 9.45 4 95   20 20.3 2 102
Molybdenum 0.20b (0.16) 2 -   3.5 3.69 3 105   1.46 1.62 1 111
Nickel 1.03 0.91 5 88   0.71b (0.30)e 21 -   nv (0.31) 24 -
Phosphorus 7600b 8170 3 108   11100 11600 4 105   1530 1750 3 114
Potassium 9690 8830 3 91   9960 8600 3 86   1280 1220 3 95
Selenium 2.1 2.8 7 134   0.71 (0.99) 44 -   0.38 <0.6 - -
Sodium 5100 5140 2 101   2430 2370 2 98   6.6 <60 - -
Strontium 10.36 10.7 2 103   0.138 <3 - -   nv <2 - -
Thallium ≤0.005d <0.2 - -   0.003d <0.3 - -   nv <0.2 - -
Vanadium 2.6b 2.44 3 94   0.099 (0.068) 25 -   0.007d <0.03 - -
Zinc 852 788 4 92   123 115 4 93   19.4 19.3 4 99

4.4A Table 3. Reference Material Results Using Ultrasonic Nebulizationa (2 of 3)

  Total Diet
(NIST 1548)
  Whole Egg Powder
(NIST 8415)
  Dogfish Muscle
(NRCC DORM-1)
Element Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
Aluminum 33d 39 2 119   540 604 6 112   nv 11.4 7 -
Arsenic 0.104b <0.2 - -   0.01d <0.2 - -   17.7 18.6 3 105
Barium nv (1.3) 1 -   3d 3.6 5 119   nv <0.7 - -
Boron 2.61c 2.23 7 86   0.41 <0.4 - -   nv 0.87 5 -
Cadmium 0.028 (0.041) 32 -   0.005d <0.04 - -   0.086 0.103 5 120
Calcium 1740 1680 2 97   2480 2580 4 104   nv 1390 3 -
Chromium 0.5b <0.4 - -   0.37 (0.78) 34 -   3.6 4.3e 10 119
Cobalt nv (0.043) 12 -   0.012 (0.044)e 96 -   0.049 <0.03e - -
Copper 2.6 2.68 2 103   2.7 2.86 5 106   5.22 5.21 11 100
Iron 32.6 30.6 3 94   112 104 3 93   63.6 59 1 93
Lead 0.05d <0.3 - -   0.061 <0.3 - -   0.4 (0.43) 17 -
Magnesium 556 494 2 89   305 295 4 97   1210 1070 4 88
Manganese 5.2 4.88 2 94   1.78 1.75 4 99   1.32 1.17 3 88
Molybdenum 0.27d 0.3 8 110   0.247 0.26 9 105   nv (0.18) 2 -
Nickel 0.43b (0.27) 32 -   nv <0.2 - -   1.2 0.81 13 68
Phosphorus 3240 3590 2 111   10010 10600 4 106   nv 11 3 -
Potassium 6060 5950 2 98   3190 3140 14 98   15900 13700 2 86
Selenium 0.245 <0.7 - -   1.39 2.2 22 162   1.62 2.84 9 175
Sodium 6250 6560 2 105   3770 3900 8 103   8000 7930 2 99
Strontium nv (3.8) 5 -   5.63 (6.8) 6 -   nv 9.1 1 -
Thallium nv <0.3 - -   nv <0.3 - -   nv <0.2 - -
Vanadium 0.49b (0.048) 17 -   0.459 0.536 12 117   nv (0.044) 17 -
Zinc 30.8 29.9 3 97   67.5 66.6 5 99   21.3 18 5 84

4.4A Table 3. Reference Material Results Using Ultrasonic Nebulizationa (3 of 3)

  Mussel
(NIES No.6)
  Cocoa Powder
(FDA CP)
  Soy Powder Infant Formula
(FDA SPIF)
Element Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
  Ref.
Value
(mg/kg)
Mean
Result
(mg/kg)
RSD
(%)
RM
Rec
(%)
Aluminum 220d 218 5 99   50.1 45.2 6 90   12.5 12.6 8 101
Arsenic 9.2 9.6 1 105   nv <0.2 - -   nv <0.2 - -
Barium nv <0.8 - -   nv 14.7 5 -   nv <0.9 - -
Boron 12.9c 12.2 1 95   28.6 28.4 9 99   0.6 <0.3 - -
Cadmium 0.82 0.849 1 104   0.39 0.366 12 94   nv (0.081) 74 -
Calcium 1300 1260 2 97   1710 1520 13 89   6200 5640 7 91
Chromium 0.63 (0.88)e 85 -   0.92 <0.4 - -   nv (0.91) 52 -
Cobalt 0.37d 0.307 6 83   1.164 1.06 13 91   nv <0.03 - -
Copper 4.9 5.31 12 108   41.7 43.6 5 104   9.3 8.77 7 94
Iron 158 147 4 93   131 113 10 86   100d 95.8 6 96
Lead 0.91 0.83 11 91   0.117d <0.3 - -   nv <0.3 - -
Magnesium 2100 1750 2 83   5990 5950 10 99   485 438 4 90
Manganese 16.3 15 3 92   54.2 46.7 11 86   2.67 2.28 7 85
Molybdenum nv 0.84 3 -   nv 0.35 3 -   nv 0.29 13 -
Nickel 0.93 0.87 13 94   12.4d 10.4 12 84   nv (0.26)e 4 -
Phosphorus 7700d 8220 2 107   8070 8220 11 102   3900d 4310 4 111
Potassium 5400 5270 3 98   18750 18300 8 98   5660 5690 2 101
Selenium 1.5d 2.3 9 152   nv <0.6; - -   nv <0.7 - -
Sodium 10000 9640 3 96   19 <60 - -   2350 2400 4 102
Strontium 17d 18.5 3 109   18.3d 20 5 107   nv (3.2) 16 -
Thallium nv <0.2 - -   nv <0.3 - -   nv <0.3 - -
Vanadium nv 0.562 3 -   0.096 (0.079) 11 -   0.161 0.172 12 107
Zinc 106 100 2 95   79.2 70.7 15 89   60d 52.7 7 88

a Mean result based on 3 analyses except 4 analyses for Rice Flour, Whole Egg Powder, and Mussel. NIST=National Institute of Standards and Technology, NRCC=National Research Council of Canada, NIES=National Institute for Environmental Studies of Japan, FDA=Food and Drug Administration, nv=no value available. Cocoa Powder and Soy Powdered Infant Formula are FDA in-house reference materials. Mean results in ( ) are "trace" levels and mean results below the LOD are listed as < LOD.
b Reference value not certified; consensus value7.
c Reference value not certified; value based on prompt gamma-ray activation analysis8-9.
d Reference value not certified; informational value provided by certifying organization.
e Excluded one highly divergent analytical result due to spectral interference or environmental contamination.

4.4A.3 FOOD RESULTS

The results of replicate FAP analyses of foods were used to assess analyte recovery and matrix induced interference. Foods were analyzed using ultrasonic nebulization. All foods were portions of FDA Total Diet Study market basket 1994-4 prepared and analyzed for 14 elements under FDA's Total Diet Study program6 enabling comparison of analytical results for some elements.

FAP recovery

Results for 20 foods analyzed using ultrasonic nebulization are listed in 4.4A Table 4. FAPs were analyzed for all elements except calcium, magnesium, phosphorus, potassium and sodium. FAP recoveries for all foods were acceptable (80-120%) for arsenic, barium, cadmium, chromium, copper, iron, manganese, molybdenum, nickel, strontium thallium, and vanadium. Aluminum FAP recovery was low for 3 foods: peanut butter (44%), pancakes (62%), and broccoli (73%). Low FAP recoveries for pancakes and broccoli are attributed to fortification at less than 1 times the native level. Low FAP recovery for peanut butter cannot be explained with confidence but appears to be contamination or an instrument anomaly that caused the result of the unfortified analytical portion to be high (12.0 mg/kg). An aluminum concentration of 6.61 mg/kg for this peanut butter was determined by neutron activation analysis. Using this result for the unfortified analytical portion produces a 95% FAP recovery for the ICP-AES aluminum fortification result. This acceptable FAP recovery suggests that the unfortified aluminum results for peanut butter are erroneously high. Boron FAP recovery was high for 1 food: prune juice (123%). This high recovery may be attributed to fortification at less than 1 times the native level. Cobalt FAP recovery was low for 1 food: corn (67%). This low recovery cannot be explained. Lead FAP recovery was slightly low for 2 foods: pork bacon (74%) and broccoli (79%). These low recoveries cannot be readily explained. The high sodium concentration of the pork bacon may have hindered the ultrasonic nebulization but the other analyte FAP recoveries are acceptable. For broccoli, other analyte FAP recoveries are on the low end of the acceptable range (except selenium), which may indicate an inaccurate fortification. Selenium FAP recoveries are slightly high for 2 foods: spaghetti (122%) and haddock (121%). These high recoveries cannot be readily explained. A high bias on RM selenium results was also observed as mentioned above. In addition, most selenium FAP recoveries were on the high end of the acceptable range (average of acceptable FAP recoveries was 112%). These results indicate that insufficient correction of spectral background emission may be the cause of the slightly high bias on selenium results. Zinc FAP recovery was low for 1 food: fruit flavored cereal (69%). This low recovery may be attributed to fortification at less than 1 times the native level.

Precision

The precision of replicate analysis of unfortified portions (measured as RSD; 4.4A Table 4) was 15% or less for all element concentration measurements above LOQ except for cadmium in spaghetti (19%), calcium in haddock (30%), copper in cheddar cheese (16%), iron in cheddar cheese (19%) and mayonnaise (17%), nickel in prune juice (16%), potassium in mayonnaise (17%), and selenium in haddock (20%). Imprecision due to concentration measurements being near the LOQ and unknown sample homogeneity may explain the results for cadmium in spaghetti (LOQ 0.02 mg/kg), copper in cheddar cheese (LOQ 0.2), iron in mayonnaise (LOQ 2 mg/kg), and selenium in haddock (LOQ 0.8 mg/kg). Imprecision of calcium in haddock may be explained by non-homogeneity caused by haddock bone fragments and the relatively low level of calcium (LOQ 90 mg/kg). Imprecision due to levels being near the LOQ could not explain the slightly poor precision of iron in cheddar cheese (LOQ 0.7 mg/kg), nickel in prune juice (LOQ 0.05 mg/kg) or potassium in mayonnaise (LOQ 20 mg/kg). Non-homogeneity may be the cause of the imprecision for iron in cheddar cheese. An extremely divergent aluminum result was obtained for 1 of the 3 replicates of unfortified pork bacon, beef, and haddock. These results ranged from a factor of about 2 to 5 higher than the other replicates and were excluded from the calculations. The cause of this variability was not thoroughly investigated but environmental contamination is suspected. Extremely divergent chromium results were obtained for 1 of 3 replicates of unfortified pork bacon, 1 of 3 replicates of fortified pork bacon, and 2 of 3 replicates of fortified tuna. Most of these results were negative values indicating spectral interference that may have affected background correction. An extremely divergent lead result was obtained for 1 of 3 replicates of unfortified pork bacon, tuna, and corn. These results ranged from a factor of about 70 to 300 higher than the other replicates and were excluded from the calculations. The cause of this variability was not thoroughly investigated but environmental contamination is suspected.

Comparison to Total Diet Study

FDA Total Diet Study results for market basket 1994-4 were available for comparison for all elements except barium, boron, chromium, molybdenum, strontium, and thallium. The Total Diet Study uses (1) a nitric-perchloric-sulfuric acid digestion and inductively coupled plasma atomic emission spectrometry to measure calcium, copper, iron, magnesium, manganese, phosphorus, potassium sodium and zinc, (2) the same digestion and hydride generation atomic absorption spectrometry to measure arsenic and selenium and (3) a dry ash mineralization and graphite furnace atomic absorption spectrometry to measure cadmium, lead, and nickel. Aluminum, cobalt, and vanadium results were only available for 3 foods (determined by instrumental neutron activation analysis as part of Total Diet Study independent quality assurance activity) and nickel was not available for 1 food. A majority of the results were in agreement with Total Diet Study results (4.4A Table 4). Direct comparisons were made when both results were above LOQ and results were considered in agreement if within ±20% of Total Diet Study result. No cobalt, lead, selenium or vanadium comparisons were available. Two of 3 aluminum results are in agreement and the high result for peanut butter discussed above is probably due to environmental contamination. The 2 arsenic comparisons and 1 cadmium comparison were in agreement. Fourteen of the 15 calcium comparisons agreed. The slightly low and imprecise calcium result for haddock is probably due to non-homogeneity and the relatively low concentration (LOQ 90 mg/kg). All 4 copper comparisons agreed. Eleven of 13 iron comparisons agreed. The iron results for prune juice and broccoli were about 25% lower than the Total Diet Study result. Both Total Diet Study results are near the LOQ (2 and 3 mg/kg, respectively), which may account for the discrepancy. Iron fortification recoveries for these foods were good. Seventeen of 18 magnesium comparisons agreed. The magnesium result for prune juice was about 25% lower than the Total Diet Study result. No reasonable explanation for this discrepancy was found. All 8 manganese comparisons agreed. Only 3 of 6 nickel comparisons agreed. Nickel results for peanut butter, pancakes, and fruit flavored cereal were 25% to 50% higher than Total Diet Study results. No reasonable explanation for this discrepancy was found. Nickel fortification recoveries for these foods were good. Eighteen of 19 phosphorus comparisons agreed. The phosphorus result for peanut butter was about 25% higher than the Total Diet Study result. No reasonable explanation for this discrepancy was found. Twelve of 20 potassium comparisons agreed. Potassium results for prune juice, broccoli, sweat potato, spaghetti, beer, beef and haddock were 21% to 27% lower than Total Diet Study results. No reasonable explanation for this discrepancy was found. Potassium result for mayonnaise was about 85% higher than the Total Diet Study result. The potassium level in mayonnaise was relatively low compared to other foods and measurement precision was at the high end of the acceptable range indicating that the LOQ for mayonnaise (20 mg/kg) may be under estimated. In addition, the Total Diet Study potassium result was near the estimated LOQ (40 mg/kg). All 19 sodium comparisons agreed. Fifteen of 16 zinc comparisons agreed. The zinc result for prune juice was about 30% lower than the Total Diet Study result. The Total Diet Study zinc result was near the LOQ (1 mg/kg), which may explain the disagreement.

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (1 of 7)

  Evaporated milk (8)   Cheddar cheese (12)   Pork bacon (20)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum <0.2 - 2.6 88 -   (0.6) 28 7.3 95 -   (1.3)e 5 11 92 -
Arsenic <0.05 - 5.3 97 <0.01   <0.2 - 15 93 <0.02   <0.2 - 23 87 <0.02
Barium <0.3 - 1.1 103 -   (1) 18 2.9 93 -   <1 - 4.5 101 -
Boron 0.71 8 5.3 90 -   (0.47) 20 15 96 -   (0.69) 42 23 95 -
Cadmium <0.009 - 0.53 98 <0.002   <0.03 - 1.5 94 <0.003   <0.04 - 2.3 91 (0.004)
Calcium 1770 5 - - 2040   6220 5 - - 7480   (120) 13 - - 84
Chromium <0.2 - 2.6 91 -   <0.3 - 7.3 97 -   <0.5e - 11 92e -
Cobalt <0.009 - 1.1 88 -   <0.03 - 2.9 90 -   <0.04 - 4.5 88 -
Copper <0.02 - 2.6 89 <0.25   0.35 16 7.3 92 (0.401)   0.96 1 11 93 (0.886)
Iron 0.45 6 26 85 (0.713)   1.51 19 73 87 (2.53)   8.03 0.3 113 86 8.74
Lead <0.07 - 5.3 95 <0.007   <0.2 - 15 85 <0.014   <0.3e - 23 74 (0.014)
Magnesium 157 8 - - 194   238 7 - - 283   (182) 10 - - 181
Manganese 0.024 12 5.3 86 <0.3   0.182 8 15 89 <0.4   0.122 6 23 87 <0.4
Molybdenum <0.02 - 1.1 92 -   (0.13) 23 2.9 92 -   <0.07 - 4.5 92 -
Nickel <0.04 - 2.6 90 <0.025   <0.09 - 7.3 91 <0.05   <0.2 - 11 87 <0.05
Phosphorus 1900 6 - - 1700   4890 3 - - 4840   3420 3 - - 3390
Potassium 2440 5 - - 2860   733 9 - - 736   3260 6 - - 2940
Selenium <0.2 - 11 114 0.04   <0.5 - 29 113 0.217   <0.8 - 45 102 0.295
Sodium 702 10 - - 786   5340 7 - - 6240   17400 6 - - 17500
Strontium (1.6) 20 2.6 95 -   6.2 11 7.3 98 -   <3 - 11 100 -
Thallium <0.07 - 11 87 -   <0.2 - 29 88 -   <0.3 - 45 85 -
Vanadium <0.01 - 0.53 85 -   <0.03 - 1.5 93 -   <0.04 - 2.3 92 -
Zinc 6.34 1 11 91 6.9   32.3 9 29 86 36   19.8 6 45 83 22.3

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (2 of 7)

  Tuna (canned in oil) (32)   Eggs (boiled) (37)   Peanut butter (47)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum (0.9) 2 5.6 91 -   (0.38) 23 3 95 -   12 8 11 44 6.61g
Arsenic 0.86 8 11 101 0.966   <0.07 - 6 98 <0.01   <0.2 - 21 102 (0.021)
Barium <0.6 - 2.2 100 -   (0.64) 4 1.2 100 -   3.6 2 4.2 95 -
Boron (0.6) 16 11 90 -   (0.2) 51 6 95 -   16.2 0.1 21 93 -
Cadmium (0.028) 20 1.1 105 0.022   <0.02 - 0.6 105 <0.002   (0.099) 4 2.1 105 0.067
Calcium (100) 15 - - 78   523 2 - - 506   592 4 - - 499
Chromium <0.3 - 5.6 118f -   (0.25) 29 3 102 -   <0.5 - 11 97 -
Cobalt <0.02 - 2.2 97 -   <0.02 - 1.2 97 -   <0.04 - 4.2 81 0.031g
Copper 0.45 1 5.6 90 (0.403)   0.58 1 3 95 (0.55)   4.66 1 11 92 4.48
Iron 7.93 3 56 92 8.38   16.6 1 30 94 16.9   19.9 1 106 95 19.5
Lead <0.2e - 11 86 (0.011)   <0.1 - 6 95 <0.007   <0.3 - 21 106 <0.014
Magnesium 242 3 - - 251   114 2 - - 109   1650 1 - - 1580
Manganese 0.265 4 11 94 <0.3   0.272 1 6 95 <0.3   13.9 1 21 94 13
Molybdenum <0.05 - 2.2 99 -   0.084 6 6 95 -   1.3 2 4.2 98 -
Nickel (0.08) 23 5.6 96 (0.041)   <0.05 - 3 98 <0.025   1.24 7 11 98 0.931
Phosphorus 1610 4 - - 1490   2080 2 - - 1870   3980 5 - - 3230
Potassium 1930 2 - - 2070   1180 2 - - 1170   5490 2 - - 5500
Selenium (0.88) 2 22 114 0.613   (0.48) 9 12 110 0.375   <0.8 - 42 116 0.118
Sodium 3200 3 - - 3530   1200 2 - - 1180   4260 3 - - 4160
Strontium <2 - 5.6 111 -   (0.86) 6 3 103 -   (5.5) 3 11 101 -
Thallium <0.2 - 22 94 -   <0.1 - 12 95 -   <0.3 - 42 96 -
Vanadium <0.03 - 1.1 97 -   <0.02 - 0.6 100 -   <0.04 - 2.1 98 <0.12g
Zinc 4.45 9 22 94 4.4   12.2 2 12 91 12   26 1 42 87 25.2

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (3 of 7)

  Corn (54)   White bread (58)   Pancakes (68)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum (0.21) 6 1.8 91 <0.052g   2.3 2 4.2 101 2.32g   61.3 4 3.7 62 -
Arsenic <0.04 - 3.7 95 <0.01   <0.1 - 8.5 100 <0.02   <0.09 - 7.3 100 <0.01
Barium <0.2 - 0.73 101 -   (1.2) 2 1.7 103 -   (0.65) 5 1.5 99 -
Boron 0.61 3 3.7 93 -   (0.47) 12 8.5 99 -   1.4 4 7.3 98 -
Cadmium (0.009) 24 0.37 102 (0.004)   (0.041) 6 0.85 103 0.021   <0.02 - 0.73 102 0.011
Calcium (32) 8 - - 23   577 2 - - 578   1380 2 - - 1330
Chromium <0.1 - 1.8 93 -   <0.3 - 4.2 107 -   <0.2 - 3.7 103 -
Cobalt <0.007 - 0.73 67 0.0011g   <0.02 - 1.7 110 0.0073g   <0.02 - 1.5 92 -
Copper 0.28 0.4 1.8 91 <0.25   1.07 3 4.2 96 (1.07)   0.9 3 3.7 95 (0.746)
Iron 2.4 6 18 90 (2.93)   29.5 2 42 91 31.5   14.2 2 37 90 14.1
Lead <0.06e - 3.7 90 <0.007   <0.2 - 8.5 93 <0.01   <0.2 - 7.3 85 (0.012)
Magnesium 189 2 - - 183   212 2 - - 206   316 2 - - 292
Manganese 0.884 2 3.7 92 (0.855)   4.36 2 8.5 94 4.46   3.06 1 7.3 90 2.8
Molybdenum (0.031) 2 0.73 95 -   0.16 3 1.7 98 -   0.3 3 1.5 94 -
Nickel (0.044) 33 1.8 93 <0.025   (0.17) 7 4.2 95 0.124   0.29 5 3.7 91 0.191
Phosphorus 683 2 - - 613   1170 1 - - 1040   4140 2 - - 3540
Potassium 1600 1 - - 1730   1150 1 - - 1160   2340 1 - - 2150
Selenium <0.2 - 7.3 110 <0.01   <0.4 - 17 115 0.146   <0.4 - 15 116 0.123
Sodium <20 - - - <7   4900 1 - - 5180   4620 1 - - 4470
Strontium <0.5 - 1.8 110 -   (2.5) 8 4.2 104 -   (1.3) 6 3.7 102 -
Thallium <0.06 - 7.3 91 -   <0.2 - 17 94 -   <0.2 - 15 90 -
Vanadium <0.008 - 0.37 96 <0.0047g   <0.02 - 0.85 101 <0.12g   (0.021) 28 0.73 96 -
Zinc 3.5 1 7.3 87 3.92   5.56 2 17 93 5.83   6.99 4 15 86 6.79

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (4 of 7)

  Fruit flavored cereal (72)   Prune juice (103)   Lemonade (105)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum 2 5 7.2 102 -   0.44 10 1.3 97 -   (0.09) 11 0.76 100 -
Arsenic <0.2 - 14 101 <0.01   <0.03 - 2.6 103 <0.01   <0.02 - 1.5 100 <0.01
Barium <0.7 - 2.9 101 -   (0.28) 12 0.52 99 -   <0.08 - 0.3 110 -
Boron <0.3 - 14 97 -   4.8 8 2.6 123 -   0.32 8 1.5 97 -
Cadmium (0.057) 7 1.4 107 0.018   <0.005 - 0.26 109 <0.001   <0.003 - 0.15 105 <0.001
Calcium 703 4 - - 645   83 11 - - 98   32 1 - - 28.8
Chromium (0.38) 68 7.2 107 -   (0.17) 123 1.3 93 -   <0.04 - 0.76 109 -
Cobalt (0.068) 9 2.9 99 -   <0.005 - 0.52 100 -   <0.003 - 0.3 100 -
Copper 1.01 5 7.2 98 0.96   0.17 8 1.3 96 (0.213)   0.06 1 0.76 97 <0.2
Iron 214 5 72 81 201   2.31 9 13 98 3.2   0.27 2 7.6 96 <0.5
Lead <0.2 - 14 102 (0.01)   <0.04 - 2.6 96 <0.005   <0.03 - 1.5 97 <0.004
Magnesium 273 5 - - 249   94 11 - - 126   17 4 - - 17.2
Manganese 6.91 3 14 95 6.56   0.66 9 2.6 100 (0.862)   0.041 1 1.5 97 <0.2
Molybdenum 0.23 3 2.9 100 -   (0.01) 24 0.52 99 -   <0.006 - 0.3 101 -
Nickel 0.55 4 7.2 98 0.441   0.1 16 1.3 101 0.113   <0.01 - 0.76 100 <0.014
Phosphorus 1370 3 - - 1160   188 13 - - 192   26 3 - - (22.5)
Potassium 1160 3 - - 1090   1760 9 - - 2350   229 4 - - 262
Selenium <0.6 - 29 110 0.055   <0.1 - 5.2 115 <0.01   <0.06 - 3 103 <0.01
Sodium 5140 3 - - 5300   (16) 11 - - (16.9)   (14) 0.1 - - (12.9)
Strontium <2 - 7.2 119 -   (0.7) 11 1.3 104 -   (0.25) 3 0.76 104 -
Thallium <0.2 - 29 98 -   <0.04 - 5.2 97 -   <0.02 - 3 98 -
Vanadium 0.093 6 1.4 101 -   (0.008) 84 0.26 99 -   <0.003 - 0.15 104 -
Zinc 159 5 29 69 157   0.94 9 5.2 99 1.3   0.11 13 3 93 <0.2

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (5 of 7)

  Broccoli (113)   Sweet potato (140)   Spaghetti and meatballs (142)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum 1.3 4 0.6 73 -   (0.4) 10 2.4 100 -   6.46 2 2 88 -
Arsenic <0.02 - 1.2 90 <0.01   <0.06 - 4.8 94 (0.011)   <0.04 - 3.9 95 <0.01
Barium 0.34 4 0.24 83 -   2.2 3 0.97 97 -   (0.44) 2 0.78 96 -
Boron 1.7 3 1.2 91 -   1.5 2 4.8 93 -   0.84 4 3.9 97 -
Cadmium 0.013 10 0.12 88 0.014   (0.013) 39 0.48 100 0.01   0.024 19 0.39 97 0.019
Calcium 280 4 - - 331   264 1 - - 275   307 5 - - 332
Chromium <0.03 - 0.6 91 -   <0.2 - 2.4 106 -   <0.09 - 2 102 -
Cobalt 0.017 2 0.24 83 -   (0.025) 10 0.97 94 -   <0.007 - 0.78 91 -
Copper 0.28 1 0.6 86 (0.295)   1.26 2 2.4 95 1.27   1.01 0.3 2 90 0.961
Iron 3.67 4 6 81 4.69   3.55 3 24 91 3.93   10.6 0.5 20 86 11.2
Lead <0.02 - 1.2 79 <0.007   <0.08 - 4.8 91 <0.007   <0.06 - 3.9 88 <0.007
Magnesium 92 2 - - 107   179 2 - - 199   146 5 - - 168
Manganese 1.34 5 1.2 86 1.6   8.4 2 4.8 92 8.85   1.65 5 3.9 87 1.8
Molybdenum 0.023 1 0.24 85 -   (0.046) 8 0.97 96 -   0.098 7 0.78 93 -
Nickel 0.17 2 0.6 84 0.167   0.19 6 2.4 94 0.127   0.11 9 2 91 (0.078)
Phosphorus 439 1 - - 441   599 1 - - 558   779 4 - - 724
Potassium 858 3 - - 1170   3470 4 - - 4450   1600 4 - - 2090
Selenium <0.05 - 2.4 117 <0.01   <0.2 - 9.7 109 <0.01   <0.2 - 7.8 122 0.094
Sodium 124 2 - - 116   235 0.1 - - 237   2020 3 - - 2190
Strontium 2.4 1 0.6 85 -   2.8 4 2.4 100 -   (1.6) 2 2 98 -
Thallium <0.02 - 2.4 81 -   <0.08 - 9.7 92 -   <0.06 - 7.8 87 -
Vanadium (0.004) 34 0.12 89 -   <0.01 - 0.48 99 -   <0.008 - 0.39 97 -
Zinc 1.52 5 2.4 80 1.79   2.52 3 9.7 90 2.73   8.38 4 7.8 84 9.01

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (6 of 7)

  Mayonnaise (166)   Beer (198)   Beef (baby food) (205)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum (1.3) 8 12 96 -   (0.17) 2 0.76 84 -   (0.41)e 4 2.4 93 -
Arsenic <0.3 - 24 100 <0.02   <0.02 - 1.5 94 <0.01   <0.05 - 4.8 93 <0.01
Barium <2 - 4.8 106 -   <0.09 - 0.31 103 -   <0.3 - 0.96 101 -
Boron (1.1) 9 24 96 -   0.33 4 1.5 93 -   (0.28) 33 4.8 93 -
Cadmium <0.05 - 2.4 107 <0.007   <0.003 - 0.15 101 <0.001   <0.009 - 0.48 104 <0.002
Calcium <200 - - - 83.7   45 2 - - 52.8   -52 9 - - 40.6
Chromium <0.7 - 12 110 -   <0.04 - 0.76 108 -   <0.2 - 2.4 106 -
Cobalt <0.05 - 4.8 100 -   <0.003 - 0.31 92 -   <0.009 - 0.96 96 -
Copper (0.1) 19 12 97 <0.34   (0.018) 5 0.76 88 <0.17   0.42 2 2.4 92 (0.428)
Iron 2.26 17 121 96 (2.61)   (0.06) 13 7.6 88 <0.5   14.4 1 24 91 15
Lead <0.4 - 24 97 <0.035   <0.03 - 1.5 87 <0.004   <0.08 - 4.8 94 <0.007
Magnesium <70 - - - (13.3)   50 1 - - 62.9   124 1 - - 141
Manganese 0.072 4 24 98 <0.4   0.088 1 1.5 90 <0.2   0.052 2 4.8 93 <0.3
Molybdenum <0.1 - 4.8 103 -   0.024 7 0.31 93 -   <0.02 - 0.96 97 -
Nickel <0.2 - 12 100 -   <0.02 - 0.76 94 <0.014   <0.04 - 2.4 97 (0.06)
Phosphorus 261 2 - - 276   159 1 - - 159   1230 0.05 - - 1170
Potassium 183 17 - - 98.3   205 1 - - 281   1670 1 - - 2200
Selenium <1 - 48 115 (0.029)   <0.07 - 3.1 115 <0.01   <0.2 - 9.6 115 (0.03)
Sodium 5190 2 - - 4930   35 1 - - 41.6   393 1 - - 427
Strontium <4 - 12 110 -   (0.2) 3 0.76 95 -   <0.7 - 2.4 104 -
Thallium <0.4 - 48 98 -   <0.03 - 3.1 90 -   <0.07 - 9.6 94 -
Vanadium <0.06 - 2.4 103 -   0.03 2 0.15 95 -   <0.01 - 0.48 98 -
Zinc 1.49 1 48 93 (1.98)   <0.01 - 3.1 84 <0.2   32.4 2 9.6 83 32.2

4.4A Table 4. Food Fortification Results Using Ultrasonic Nebulizationa (7 of 7)

  Haddock (243)   Pears (canned) (255)
Element Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
  Unfort.
Resultb
(mg/kg)
 
RSD
(%)
Fort.
Level
(mg/kg)
Fort.
Recc
(%)
TDS
Resultd
(mg/kg)
Aluminum 0.85e 7 3.3 87 -   (0.19) 5 1.1 97 -
Arsenic 5.91 2 6.7 95 6.59   <0.03 - 2.2 94 <0.01
Barium <0.4 - 1.3 102 -   0.34 4 0.44 101 -
Boron 0.79 8 6.7 96 -   1.9 2 2.2 91 -
Cadmium <0.02 - 0.67 101 <0.002   <0.004 - 0.22 103 <0.002
Calcium 204 30 - - 269   46 3 - - 45.2
Chromium <0.2 - 3.3 105 -   (0.06) 59 1.1 105 -
Cobalt <0.02 - 1.3 95 -   <0.004 - 0.44 98 -
Copper 0.25 9 3.3 94 <0.29   0.38 2 1.1 96 (0.413)
Iron 1.54 2 33 91 (1.64)   6.52 2 11 92 6.39
Lead <0.1 - 6.7 90 <0.01   (0.041) 12 2.2 92 0.032
Magnesium 345 6 - - 400   38 2 - - 40
Manganese 0.34 10 6.7 92 (0.41)   0.979 2 2.2 94 1.03
Molybdenum <0.03 - 1.3 97 -   <0.008 - 0.44 98 -
Nickel (0.06) 28 3.3 93 <0.036   (0.044) 11 1.1 96 (0.042)
Phosphorus 2500 2 - - 2300   67 3 - - 68.4
Potassium 3060 6 - - 3860   533 1 - - 650
Selenium (0.82) 20 13 121 0.503   <0.09 - 4.4 107 <0.01
Sodium 1440 1 - - 1460   45 2 - - 41.3
Strontium (1.7) 40 3.3 102 -   (0.36) 9 1.1 103 -
Thallium <0.09 - 13 93 -   <0.04 - 4.4 96 -
Vanadium (0.034) 62 0.67 97 -   <0.005 - 0.22 101 -
Zinc 4.24 2 13 86 4.58   0.4 3 4.4 92 (0.447)

a Foods from FDA Total Diet Study market basket 1994-4 with food number in ( ) next to food name.
b Mean result based on 3 analyses (6 analyses for calcium, magnesium, phosphorus, potassium, and sodium) except 2 analyses (5 analyses for calcium, magnesium, phosphorus, potassium, and sodium) for evaporated milk or as indicated. Mean results in ( ) are "trace" levels and mean results below the LOD are listed as <LOD.
c Mean result based on 3 analyses except 4 analyses for haddock or as indicated. Calcium, magnesium, phosphorus, potassium and sodium not fortified.
d FDA Total Diet Study market basket 1994-4 results6 (n=1) except nickel results from FDA Kansas City District laboratory validation report10 or other source as indicated. Results in ( ) are "trace" levels and results below LOD are listed as <LOD.
e Mean result based on 2 analyses.
f Result of 1 analysis.
g Result by neutron activation analysis11.

4.4A.4 CONCLUSION

The in-house validation results for analysis of foods using microwave decomposition and element detection using ICP-AES indicate the following elements can be reliably measured at concentrations above LOQ: arsenic, barium, boron, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, molybdenum, nickel, phosphorus, potassium, sodium, strontium, vanadium and zinc. Thallium appears to be reliably measured but accuracy assessment is hindered by the lack of appropriate reference materials. The following elements appear prone to laboratory environmental contamination and therefore require extensive assessment of contamination control: aluminum, chromium, and lead. Aluminum concentrations using the method do not account for aluminum bound to silicates. Selenium concentrations may have been biased high in this study. Use of ICP-AES for determination of selenium in foods requires a thorough assessment of that background correction was effective.


REFERENCES

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  2. Hoenig, M., Baeten, H., Vanhentenrijk, S., Vassileva, E., and Quevauviller, Ph. (1998) Critical Discussion on the Need for an Efficient Mineralization Procedure for the Analysis of Plant Material by Atomic Spectrometric Methods, Anal. Chim. Acta 358, 85-94. 
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  8. Anderson, D. L., Cunningham, W. C., and Mackey, E. A., (1990) Determination of Boron in Food and Biological Reference Materials by Neutron Capture Prompt-γ Activation, Fresenius' J. Anal. Chem. 338, 554-558. 
  9. Anderson, D. L., and Cunningham, W. C. (2000) Revalidation and Long-Term Stability of National Institute of Standards and Technology Standard Reference Materials 1566, 1567, 1568, and 1570, J. AOAC Int. 83, 1121-1134.
  10. U.S. Food and Drug Administration. Total Diet Study Method Validation-Analysis of Food Items for Nickel by Graphite Furnace Atomic Absorption Spectrometry (September 9, 1996); Kansas City District Laboratory, Lenexa, KS, USA. 
  11. U.S. Food and Drug Administration. Trace Element Quality Control Exchange Samples: Findings for TDS Market Basket K994 (January 12, 1998); Center for Food Safety and Applied Nutrition, Elemental Research Branch, Washington, DC, USA. 

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