In this experiment, inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was used to determine the content of 30 elements in rice from six places of production and to explore the relationship between the multielement content in rice and the producing area. The contents of Ca, P, S, Zn, Cu, Fe, Mn, K, Mg, Na, Ge, Sb, Ba, Ti, V, Se, As, Sr, Mo, Ni, Co, Cr, Al, Li, Cs, Pb, Cd, B, In, and Sn in rice were determined by ICP-MS/MS in the SQ and MS/MS mode. By passing H2, O2, He, and NH3/He reaction gas into the ICP-MS/MS, respectively, the interference was eliminated by means of in situ mass spectrometry and mass transfer. The detection limit of each element was 0.0000662–0.144 mg/kg, and the limit of quantification was in the range of 0.000221–0.479 mg/kg, the linear correlation coefficient was greater or equal to 0.9987 (
Rice is the main staple food of our country, which contains sugar, protein, fat and dietary fiber, and other main nutrition elements and also contains a lot of necessary trace elements, such as Ca, Fe, Zn, Se, and other mineral elements [
At present, the origin traceability indexes in food mainly include stable isotope [
In this paper, ICP-MS/MS was first used to determine the 30 elements’ contents in rice from six rice-production areas in Anhui, Guangxi, Guangdong, Jilin, Heilongjiang, and Inner Mongolia. Under SQ and MS/MS models [
Li, Na, Mg, Al, B, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Se, Sr, Mo, Cd, In, Sn, Sb, Cs, Ba, Pb, Sc, Bi, Rh, and Y element standard solution (1000
The samples were collected from six rice-producing areas in Anhui Province, Guangxi Province, Guangdong Province, Jilin Province, Heilongjiang Province, and Inner Mongolia. We purchased common local rice samples with large planting areas in each rice market, a total of 18 batches. Three independent packages were purchased for each batch, and mixed samples were taken to ensure uniformity. The rice samples of each batch were hulled, ground, crushed, and stored in a sealed, low-temperature, and dark place.
In a PTFE digestion tank, each rice sample which weighs 0.3–0.5 g (accurate to 0.001 g) was added to 4 mL HNO3 and 1 mL 30% H2O2 and soaked for 3–4 h or overnight, the upper cap was screwed, and it was digested with the microwave digestion instrument (CEM MARS6, CEM, Matthews, USA). The conditions of the microwave digestion instrument are shown in Table
The condition of microwave digestion.
Step | Climbing time (min) | Hold time (min) | Temperature (°C) | Power (W) |
---|---|---|---|---|
1 | 06 : 00 | 03 : 00 | 120 | 1500 |
2 | 08 : 00 | 06 : 00 | 155 | 1500 |
3 | 08 : 00 | 15 : 00 | 180 | 1500 |
This experiment was carried out by tandem mass spectrometry. The concentration of 30 isotopes (7Li, 23Na, 24Mg, 27Al, 11B, 31P, 32S, 39K, 44Ca, 47Ti, 51V, 52Cr, 55Mn, 56Fe, 59Co, 60Ni, 63Cu, 66Zn, 72Ge, 75As, 78Se, 88Sr, 95Mo, 111Cd, 115In, 118Sn, 121Sb, 133Cs, 137Ba, and 208Pb) in rice was determined by inductively coupled plasma tandem mass spectrometry (Agilent 8900 Series, Agilent, USA). 1
Instrument parameters of ICP-MS/MS.
Instrument conditions | No-gas mode | H2 mode | He mode | O2 mode | NH3/He mode |
---|---|---|---|---|---|
−3.0 | 1.0 | −3.0 | 1.0 | 1.0 | |
−3.0 | −18.0 | −15.0 | −10.0 | −12.0 | |
Collision pool gas | — | H2 | He | O2 | NH3/He |
Gas flow rate of collision pool (L·min−1) | — | 7.0 | 5.0 | 4.5 | 4.5/1.0 |
Deflection voltage of eight-stage pole (V) | −8.0 | −18.0 | −18.0 | −3.0 | −5.0 |
For the selection of element determination mode and reagent gas, this method involves two modes: the SQ (single quadrupole) standard mode and MS/MS tandem mode. There are He and no-gas reagent gas modes in the SQ mode and He, NH3/He, H2, O2, and no-gas reagent gas modes in the MS/MS mode. The elements are measured in all modes, and the mode with the lowest detection limit of each element is determined as the best measurement mode.
Through the measured experimental conditions and methods, the elements Sc, Y, Rh, and Bi were used as the internal standard elements. Analyzing the experimental data can get a linear fitting standard curve with the
Linear range and detection limit of isotopes.
Calibration ( | Internal standard | LOD (mg/kg) | LOQ (mg/kg) | ||
---|---|---|---|---|---|
7Li | 0∼100 | 0.9998 | Sc | 0.000659 | 0.0220 |
23Na | 0∼1000 | 0.9999 | Sc | 0.144 | 0.479 |
24Mg | 0∼1000 | 0.9999 | Sc | 0.00372 | 0.0124 |
27Al | 0∼100 | 0.9987 | Sc | 0.0907 | 0.302 |
11B | 0∼100 | 0.9995 | Sc | 0.0375 | 0.125 |
31P | 0∼1000 | 0.9994 | Sc | 0.0204 | 0.0679 |
32S | 0∼1000 | 0.9997 | ScO | 0.0614 | 0.205 |
39K | 0∼1000 | 1.0000 | Sc | 0.0291 | 0.0970 |
44Ca | 0∼1000 | 1.0000 | Sc | 0.105 | 0.351 |
47Ti | 0∼100 | 0.9999 | ScO | 0.00219 | 0.00731 |
51V | 0∼100 | 0.9999 | ScO | 0.000946 | 0.00315 |
52Cr | 0∼100 | 0.9997 | ScO | 0.00521 | 0.0174 |
55Mn | 0∼1000 | 1.0000 | Sc | 0.00148 | 0.00495 |
56Fe | 0∼1000 | 1.0000 | Sc(NH3)2 | 0.0170 | 0.0567 |
59Co | 0∼100 | 1.0000 | Sc(NH3)2 | 0.000510 | 0.00170 |
60Ni | 0∼100 | 1.0000 | Sc(NH3)2 | 0.00133 | 0.00444 |
63Cu | 0∼1000 | 1.0000 | Sc | 0.00474 | 0.0158 |
66Zn | 0∼1000 | 1.0000 | Sc | 0.0115 | 0.0383 |
72Ge | 0∼100 | 1.0000 | Y | 0.000206 | 0.000686 |
75As | 0∼100 | 1.0000 | YO | 0.00250 | 0.00832 |
78Se | 0∼100 | 1.0000 | Y | 0.00152 | 0.00507 |
88Sr | 0∼100 | 1.0000 | Y | 0.000929 | 0.00310 |
95Mo | 0∼100 | 0.9999 | YNH3 | 0.000605 | 0.00202 |
111Cd | 0∼100 | 1.0000 | Rh | 0.0000662 | 0.000221 |
115In | 0∼100 | 0.9998 | Rh | 0.00123 | 0.00410 |
118Sn | 0∼100 | 1.0000 | Rh | 0.00176 | 0.000588 |
121Sb | 0∼100 | 1.0000 | Rh | 0.000196 | 0.000653 |
133Cs | 0∼100 | 1.0000 | Rh | 0.000227 | 0.000756 |
137Ba | 0∼100 | 1.0000 | Rh | 0.00158 | 0.00525 |
208Pb | 0∼100 | 1.0000 | Bi | 0.000949 | 0.00317 |
At the same time, the content of each element in rice reference materials (GBW10043, GBW10044, and GBW10045) was determined, the standard value was compared, and the recovery rate was calculated to prove the accuracy and reliability of the method, and the recovery experiment was conducted.
All analyses were conducted in triplicate. The results reported were the average of these three replicates. Each sample was considered as an assembly of 30 variables represented by the data of chemical information. The analysis data and the fitted linear regression curve were analyzed by Agilent Mass Hunter software (Agilent Inc., USA). A normal distribution test of multielements, principal component analysis, and clustering analysis were performed with SPSS 25.0 software (SPSS, IBM Corp., USA).
In this experiment, the SQ (single quadrupole) standard mode and MS/MS tandem mode were used to simultaneously determine the concentration of multielement. The elements were measured in different modes and different reaction gas modes, and the element detection limit was used as the criterion to determine the best measurement mode for each element. The results are shown in Table
Isotope mass spectrometry.
Mode | Reaction gas | Mass number | Eliminate interference | |
---|---|---|---|---|
7Li | MS/MS | NH3/He | In situ mass spectrometry | |
23Na | MS/MS | H2 | In situ mass spectrometry | |
24Mg | MS/MS | NH3/He | In situ mass spectrometry | |
27Al | MS/MS | H2 | In situ mass spectrometry | |
11B | MS/MS | NH3/He | Mass transfer | |
31P | MS/MS | O2 | Mass transfer | |
32S | MS/MS | O2 | Mass transfer | |
39K | MS/MS | O2 | In situ mass spectrometry | |
44Ca | MS/MS | NH3/He | In situ mass spectrometry | |
47Ti | MS/MS | O2 | Mass transfer | |
51V | MS/MS | O2 | Mass transfer | |
52Cr | MS/MS | O2 | Mass transfer | |
55Mn | MS/MS | H2 | In situ mass spectrometry | |
56Fe | MS/MS | NH3/He | Mass transfer | |
59Co | MS/MS | NH3/He | Mass transfer | |
60Ni | MS/MS | NH3/He | In situ mass spectrometry | |
63Cu | SQ | He | — | |
66Zn | MS/MS | H2 | In situ mass spectrometry | |
72Ge | MS/MS | H2 | In situ mass spectrometry | |
75As | MS/MS | O2 | Mass transfer | |
78Se | MS/MS | H2 | In situ mass spectrometry | |
88Sr | MS/MS | H2 | In situ mass spectrometry | |
95Mo | MS/MS | NH3/He | In situ mass spectrometry | |
111Cd | SQ | No gas | — | |
115In | MS/MS | H2 | In situ mass spectrometry | |
118Sn | SQ | He | — | |
121Sb | SQ | No gas | — | |
133Cs | MS/MS | O2 | In situ mass spectrometry | |
137Ba | MS/MS | NH3/He | In situ mass spectrometry | |
208Pb | SQ | No gas | — |
The interference was eliminated by making full use of the collision mode between the element and the reaction gas. In the SQ mode, the mass ions of 63Cu, 111Cd, 118Sn, 121Sb, and 208Pb had the characteristics of high abundance value and less interference. The corresponding
In the MS/MS mode, the NH3/He mixture gas collided with 7Li, 24Mg, 44Ca, 60Ni, 95Mo, and 137Ba ions in the reaction cell, H2 collided with 23Na, 27Al, 55Mn, 66Zn, 72Ge, 78Se, 88Sr, and 115In ions, and O2 collided with 39K and 133Cs ions, respectively. The interference was eliminated by in situ mass spectrometry, which means the elements only collide with the reaction gas and do not combine with each other. Therefore, the mass number of the front and after tetrodes to be set remains unchanged (
Interference cancellation model of the MS/MS mode. The ions collided with gas in the ORC.
Multielement determination was performed on the standard materials GBW10043, GBW10044, and GBW10045, and the results are shown in Table
Recovery rate of reference materials.
Recovery (%) | As | B | Ba | Ca | Cd | Co | Cr | Cs | Cu | Fe | Ge | K | Li | Mg | Mn | Mo | Na | Ni | P | Pb | S | Sb | Se | Sr | Sn | Ti | V | Al | Zn | In |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
GBW10043 | 92.6 | 91.6 | 92.6 | 95.2 | 109 | 89.4 | 91.7 | 103 | 92.2 | 104 | 106 | 96.5 | 92.8 | 105 | 96.5 | 88.6 | 95.3 | 90.6 | 102 | 89.5 | 95.3 | 106 | 105 | 95.6 | ND | 94.8 | 105 | 92.6 | 95.6 | ND |
GBW10044 | 95.1 | 93.8 | 104 | 105 | 108 | 90.2 | 93.5 | 107 | 85.6 | 108 | 109 | 94.8 | 107 | 103 | 91.5 | 85.7 | 92.1 | 105 | 106 | 115 | 90.7 | 108 | 109 | 96.1 | ND | 93.8 | 109 | 90.2 | 94.1 | ND |
GBW10045 | 96.3 | 103 | 105 | 93.8 | 102 | 96.5 | 107 | 87.5 | 93.8 | 95.6 | 112 | 95.9 | 111 | 96.5 | 90.3 | 82.9 | 94.8 | 92.8 | 103 | 106 | 93.1 | 110 | 103 | 92.8 | ND | 91.1 | 113 | 93.5 | 103 | ND |
∗ND means not detected.
The recoveries of analytes were evaluated by adding the standard solutions with three different concentration levels to the known amounts of samples. The data of recovery and precision are given in Table
The spike recovery and reproducibility of the spiked sample (
Element | Background (mg/kg) | Added (mg/kg) | Recovery (%) | RSD (%) |
---|---|---|---|---|
As | 0.127 | 10 | 105.3 | 3.5 |
1 | 108.1 | 3.2 | ||
0.1 | 104.6 | 1.1 | ||
B | 0.506 | 10 | 98.6 | 0.6 |
1 | 86.1 | 2.8 | ||
0.1 | 105.8 | 1.6 | ||
Ba | 0.351 | 10 | 94.3 | 2.8 |
1 | 95.2 | 2.6 | ||
0.1 | 82.8 | 8.9 | ||
Ca | 41.6 | 100 | 93.6 | 0.9 |
50 | 95.4 | 2.2 | ||
10 | 102.5 | 1.6 | ||
Cd | 0.0272 | 10 | 107.6 | 5.8 |
1 | 92.5 | 0.9 | ||
0.1 | 108.6 | 3.5 | ||
Co | 0.00675 | 10 | 91.6 | 4.5 |
1 | 95.3 | 4.1 | ||
0.1 | 106.8 | 0.9 | ||
Cr | 0.0138 | 10 | 84.3 | 5.0 |
1 | 93.5 | 1.5 | ||
0.1 | 89.6 | 1.1 | ||
Cs | 0.00152 | 10 | 110.5 | 0.6 |
1 | 92.3 | 2.8 | ||
0.1 | 94.2 | 2.3 | ||
Cu | 2.06 | 10 | 95.1 | 0.5 |
1 | 96.7 | 4.1 | ||
0.1 | 97.6 | 4.8 | ||
Fe | 2.45 | 10 | 105.6 | 2.3 |
1 | 103.9 | 6.8 | ||
0.1 | 107.5 | 0.5 | ||
Ge | 0.00261 | 10 | 85.3 | 2.4 |
1 | 96.4 | 2.9 | ||
0.1 | 95.8 | 6.3 | ||
K | 510 | 100 | 84.3 | 2.5 |
50 | 82.2 | 2.7 | ||
10 | 93.6 | 4.1 | ||
Li | 0.00365 | 10 | 109.5 | 0.9 |
1 | 106.4 | 2.2 | ||
0.1 | 93.6 | 5.4 | ||
Mg | 105 | 100 | 104.3 | 3.6 |
50 | 106.4 | 1.1 | ||
10 | 83.2 | 1.8 | ||
Mn | 7.46 | 10 | 92.6 | 2.0 |
1 | 91.1 | 1.5 | ||
0.1 | 93.7 | 2.9 | ||
Mo | 0.496 | 10 | 94.5 | 0.4 |
1 | 105.6 | 7.1 | ||
0.1 | 93.2 | 3.8 | ||
Na | 1.97 | 10 | 108.9 | 4.5 |
1 | 103.7 | 4.8 | ||
0.1 | 82.6 | 1.5 | ||
Ni | 0.168 | 10 | 91.6 | 0.5 |
1 | 106.3 | 0.8 | ||
0.1 | 87.5 | 1.6 | ||
P | 448 | 100 | 101.2 | 1.3 |
50 | 104.5 | 2.9 | ||
10 | 93.4 | 3.5 | ||
Pb | 0.00152 | 10 | 89.9 | 6.6 |
1 | 104.2 | 1.7 | ||
0.1 | 106.6 | 0.9 | ||
S | 552 | 100 | 80.6 | 1.1 |
50 | 85.9 | 0.7 | ||
10 | 93.8 | 2.5 | ||
Sb | 0.000154 | 10 | 106.4 | 3.9 |
1 | 95.3 | 3.3 | ||
0.1 | 92.8 | 0.6 | ||
Se | 0.0274 | 10 | 94.7 | 2.5 |
1 | 95.9 | 2.1 | ||
0.1 | 84.6 | 0.8 | ||
Sr | 0.163 | 10 | 106.4 | 0.7 |
1 | 108.5 | 0.9 | ||
0.1 | 84.9 | 5.3 | ||
Sn | ND | 10 | 104.3 | 1.4 |
1 | 96.1 | 5.6 | ||
0.1 | 95.6 | 2.0 | ||
Ti | 0.0865 | 10 | 85.3 | 1.7 |
1 | 91.8 | 0.8 | ||
0.1 | 85.9 | 7.6 | ||
V | 0.00594 | 10 | 92.7 | 1.6 |
1 | 108.5 | 1.5 | ||
0.1 | 106.9 | 0.8 | ||
Al | ND | 10 | 94.5 | 2.6 |
1 | 93.7 | 2.1 | ||
0.1 | 105.2 | 1.0 | ||
Zn | 10.9 | 100 | 92.3 | 6.8 |
50 | 82.8 | 4.6 | ||
10 | 94.6 | 3.7 | ||
In | ND | 10 | 91.5 | 2.5 |
1 | 85.4 | 8.9 | ||
0.1 | 96.3 | 1.9 |
∗ND means not detected.
There are obvious differences in the content of Ba, Ge, Co, Cu, Cr, Ti, S, Ca, Mg, Na, Li, and other elements in rice from different producing areas in north and south China. In southern China, there are differences in the content of Na, Mg, K, Ca, V, Ge, Cs, Ba, and other elements in rice produced in Anhui Province, Guangxi Province, and Guangdong Province. However, in northern China, there are obvious differences in the content of B, Na, Ca, P, Cr, Mn, Ni, Co, Zn, Sr, Mo, Cs, and other elements in batches of rice in Jilin Province, Heilongjiang Province, and Inner Mongolia (Table
Element content of rice.
Li | B | Na | Mo | Al | As | Ca | P | S | Ti | V | Cr | Mn | Ni | Cu | Fe | Sb | Pb | Ge | In | Sr | K | Sn | Cd | Se | Mg | Co | Cs | Ba | Zn | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A-1 | 3.47 | 0 | 1.91 | 0.546 | 0 | 0.124 | 41.5 | 436 | 569 | 77.6 | 5.17 | 13.6 | 7.05 | 0.122 | 2.11 | 2.37 | 0.135 | 0 | 2.62 | 0 | 0.148 | 513 | 0 | 26.8 | 21.5 | 96.6 | 6.68 | 1.57 | 0.316 | 10.9 |
A-2 | 0 | 0 | 1.35 | 0.484 | 0 | 0.106 | 40.5 | 466 | 581 | 75.3 | 3.68 | 19.7 | 7.60 | 0.114 | 2.55 | 1.95 | 0.0227 | 0 | 2.64 | 0 | 0.120 | 517 | 0 | 52.0 | 34.3 | 98.2 | 7.53 | 1.13 | 0.297 | 12.4 |
A-3 | 1.90 | 0 | 1.73 | 0.546 | 0 | 0.117 | 40.2 | 494 | 605 | 72.6 | 4.85 | 11.8 | 9.94 | 0.130 | 2.39 | 2.15 | 0.0625 | 0.368 | 2.75 | 0 | 0.139 | 524 | 0 | 201 | 28.2 | 89.9 | 7.49 | 1.20 | 0.304 | 12.3 |
X-1 | 9.56 | 0.506 | 4.80 | 0.502 | 0 | 0.134 | 48.3 | 540 | 630 | 45.6 | 8.33 | 5.22 | 8.43 | 0.130 | 2.31 | 2.79 | 0.350 | 16.6 | 1.91 | 0 | 0.121 | 701 | 0 | 5.59 | 38.9 | 172 | 5.94 | 1.79 | 0.187 | 11.8 |
X-2 | 4.84 | 0.333 | 4.44 | 0.485 | 0 | 0.112 | 49.3 | 528 | 624 | 51.7 | 7.81 | 0 | 9.54 | 0.129 | 3.15 | 2.32 | 0.245 | 2.76 | 2.44 | 0 | 0.132 | 739 | 0 | 28.9 | 27.9 | 200 | 6.29 | 1.91 | 0.190 | 11.9 |
X-3 | 1.39 | 0 | 3.63 | 0.474 | 0 | 0.115 | 48.1 | 499 | 611 | 82.2 | 7.98 | 7.99 | 9.45 | 0.117 | 3.04 | 2.53 | 0.116 | 1.15 | 2.31 | 0 | 0.128 | 716 | 0 | 150 | 26.8 | 167 | 6.35 | 1.24 | 0.178 | 11.6 |
D-1 | 1.52 | 0 | 1.04 | 0.459 | 0 | 0.126 | 37.1 | 456 | 599 | 42.6 | 5.17 | 11.5 | 8.63 | 0.136 | 2.06 | 1.77 | 0.159 | 0 | 1.13 | 0 | 0.137 | 593 | 0 | 39.7 | 59.4 | 52.6 | 6.94 | 9.94 | 0.194 | 11.6 |
D-2 | 1.57 | 0 | 1.03 | 0.317 | 0 | 0.0618 | 37.8 | 450 | 581 | 43.3 | 5.35 | 13.7 | 10.9 | 0.113 | 2.96 | 1.81 | 0.177 | 0 | 1.71 | 0 | 0.180 | 578 | 0 | 175 | 23.0 | 54.1 | 6.95 | 10.9 | 0.205 | 11.7 |
D-3 | 1.46 | 0 | 0.563 | 0.514 | 0 | 0.112 | 38.6 | 463 | 606 | 79.4 | 4.15 | 9.15 | 9.10 | 0.116 | 2.10 | 1.73 | 0.125 | 0.216 | 1.59 | 0 | 0.116 | 685 | 0 | 169 | 61.3 | 69.6 | 6.94 | 12.6 | 0.224 | 11.0 |
J-1 | 5.46 | 0.283 | 21.3 | 0.270 | 0 | 0.0930 | 50.0 | 409 | 448 | 21.8 | 7.34 | 34.5 | 10.1 | 0.0611 | 1.26 | 1.74 | 0.150 | 5.97 | 0.529 | 0 | 0.137 | 537 | 0 | 9.17 | 24.5 | 120 | 2.78 | 0.734 | 0.0479 | 10.4 |
J-2 | 6.45 | 0.233 | 19.5 | 0.201 | 0 | 0.0858 | 52.4 | 413 | 436 | 38.4 | 6.74 | 34.8 | 10.1 | 0.0508 | 1.12 | 2.91 | 0.136 | 0 | 0.630 | 0 | 0.156 | 514 | 0 | 3.49 | 14.3 | 124 | 2.84 | 0.695 | 0.0486 | 9.27 |
J-3 | 7.10 | 0.245 | 16.6 | 0.254 | 0 | 0.111 | 54.1 | 454 | 467 | 36.6 | 9.47 | 41.9 | 10.6 | 0.0597 | 1.15 | 2.22 | 0.984 | 0 | 0.520 | 0 | 0.131 | 526 | 0 | 3.10 | 34.1 | 128 | 2.64 | 0.624 | 0.0508 | 10.5 |
H-1 | 2.64 | 0.0219 | 5.66 | 0.470 | 0 | 0.106 | 47.9 | 448 | 514 | 36.2 | 7.68 | 55.2 | 10.4 | 0.126 | 1.72 | 2.34 | 0 | 8.65 | 0.969 | 0 | 0.103 | 549 | 0 | 5.73 | 24.7 | 124 | 4.84 | 1.05 | 0.0357 | 13.6 |
H-2 | 2.63 | 0 | 6.63 | 0.406 | 0 | 0.166 | 47.1 | 450 | 481 | 36.3 | 6.95 | 59.4 | 10.4 | 0.106 | 1.60 | 2.05 | 0.105 | 0 | 0.911 | 0 | 0.0802 | 516 | 0 | 15.5 | 53.0 | 114 | 4.95 | 1.56 | 0.0375 | 12.6 |
H-3 | 3.10 | 0.0311 | 4.05 | 0.414 | 0 | 0.0646 | 45.8 | 428 | 495 | 56.5 | 6.03 | 61.9 | 9.83 | 0.106 | 1.32 | 2.44 | 0.209 | 0 | 0.949 | 0 | 0.102 | 472 | 0 | 4.26 | 16.0 | 105 | 4.39 | 1.19 | 0.0343 | 12.8 |
N-1 | 5.97 | 0 | 13.0 | 0.363 | 0 | 0.110 | 41.0 | 499 | 525 | 19.9 | 5.22 | 65.8 | 7.12 | 0.0515 | 1.43 | 2.99 | 0.089 | 0 | 0.972 | 0 | 0.182 | 616 | 0 | 4.69 | 25.8 | 127 | 3.90 | 0.833 | 0.0247 | 11.2 |
N-2 | 5.19 | 0.0377 | 10.9 | 0.376 | 0 | 0.0900 | 45.1 | 519 | 537 | 23.1 | 5.72 | 61.4 | 7.25 | 0.0515 | 1.51 | 2.93 | 0.104 | 1.20 | 0.948 | 0 | 0.191 | 582 | 0 | 3.87 | 21.4 | 125 | 4.45 | 0.741 | 0.0292 | 10.4 |
N-3 | 4.65 | 0 | 11.9 | 0.340 | 0 | 0.0902 | 41.5 | 510 | 529 | 21.7 | 5.62 | 59.5 | 7.03 | 0.0791 | 1.60 | 2.52 | 0.100 | 0.302 | 0.808 | 0 | 0.189 | 591 | 0 | 3.00 | 26.6 | 119 | 4.50 | 0.637 | 0.0202 | 10.8 |
The data unit is mg(kg), among which the element data unit of Li, Ti, V, Cr, Co, Ge, Se, Cd, Sb, Cs, and Pb is
We conducted further statistical analysis on the abovementioned experimental data, by calculating the standard deviation of each element and judging the difference of each element in different regions according to the degree of dispersion of the value of each element. As shown in Figure
The degree of dispersion.
The Kolmogorov–Smirnov test was conducted on the content of 30 elements in rice from different origins. The asymptotic significance (bilateral) value was calculated. The content data of 24 elements obeyed normal distribution.
Principal component analysis (PCA) is a multivariate statistical analysis method that analyses a few variables which can reveal the internal structure sufficiently by studying the relationship between multiple original variables.
According to the rule that the characteristic value is greater than 1 and the cumulative variance contribution rate is greater than 80%, six principal component factors were obtained through rotation and extraction factors, and the total contribution rate was 87.878%, indicating that the experimental data can fully reflect the original information (Table
Results of principal component analysis.
Component | Initial eigenvalue | Rotate the sum of squares loading | ||||
---|---|---|---|---|---|---|
Total | Variance (%) | Accumulate (%) | Total | Variance (%) | Accumulate (%) | |
1 | 10.41 | 38.56 | 38.56 | 7.547 | 27.95 | 27.95 |
2 | 4.800 | 17.78 | 56.34 | 4.870 | 18.04 | 45.99 |
3 | 3.142 | 11.64 | 67.97 | 3.225 | 11.94 | 57.94 |
4 | 2.243 | 8.306 | 76.28 | 3.223 | 11.94 | 69.87 |
5 | 1.850 | 6.852 | 83.13 | 2.809 | 10.41 | 80.28 |
6 | 1.282 | 4.749 | 87.88 | 2.052 | 7.599 | 87.88 |
The first principal component is mainly composed of S, Ti, Ni, Cu, Co, Ge, Mo, Cd, Cs, Ba, Zn, and Se elements. The second principal component is mainly composed of Li, B, Mg, K, Ca, P, V, Pb, Fe, and As elements. The third principal component is mainly composed of Mn and Sb elements (Table
Contribution value of the element’s principal component.
Element | Component | |||||
---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | |
Li | −0.697 | 0.551 | −0.164 | 0.167 | 0.154 | −0.115 |
B | −0.367 | 0.753 | 0.162 | 0.324 | 0.003 | −0.068 |
Na | −0.927 | −0.009 | −0.038 | 0.184 | −0.016 | −0.114 |
Mg | −0.318 | 0.846 | −0.124 | −0.167 | −0.185 | 0.045 |
K | 0.324 | 0.644 | −0.263 | 0.291 | 0.289 | 0.282 |
Ca | −0.684 | 0.515 | 0.360 | 0.011 | −0.278 | −0.083 |
P | 0.236 | 0.617 | −0.559 | −0.079 | 0.253 | 0.182 |
S | 0.855 | 0.381 | −0.277 | 0.102 | 0.108 | 0.094 |
Ti | 0.772 | 0.070 | 0.141 | 0.016 | −0.375 | −0.333 |
V | −0.512 | 0.660 | 0.405 | 0.087 | −0.092 | 0.132 |
Cr | −0.693 | −0.380 | −0.096 | −0.508 | 0.140 | 0.175 |
Mn | −0.091 | −0.002 | 0.794 | 0.261 | −0.281 | 0.353 |
Ni | 0.847 | 0.248 | 0.297 | −0.177 | −0.010 | 0.113 |
Cu | 0.809 | 0.346 | −0.112 | 0.180 | −0.213 | 0.212 |
Fe | −0.476 | 0.361 | −0.587 | −0.277 | −0.133 | −0.014 |
Co | 0.984 | 0.033 | −0.093 | −0.020 | −0.007 | 0.000 |
Zn | 0.472 | 0.092 | 0.364 | −0.633 | −0.052 | 0.401 |
Ge | 0.818 | 0.301 | −0.192 | −0.039 | −0.363 | −0.216 |
Se | 0.432 | −0.003 | 0.368 | 0.081 | 0.778 | −0.154 |
Sr | −0.221 | −0.212 | −0.822 | 0.384 | −0.008 | 0.107 |
As | 0.244 | 0.383 | 0.273 | −0.316 | 0.480 | −0.448 |
Mo | 0.822 | 0.277 | −0.040 | −0.395 | 0.056 | −0.117 |
Cd | 0.715 | −0.172 | 0.034 | 0.380 | −0.209 | 0.165 |
Sb | −0.368 | 0.308 | 0.329 | 0.438 | 0.062 | −0.237 |
Cs | 0.547 | −0.332 | 0.152 | 0.521 | 0.399 | 0.247 |
Ba | 0.860 | 0.097 | −0.044 | 0.198 | −0.203 | −0.350 |
Pb | −0.087 | 0.706 | 0.132 | −0.114 | 0.148 | 0.236 |
Score distribution of principal component analysis.
The contents of multielements in rice from different areas were analyzed by cluster analysis. The samples were successfully divided into two categories (the north and south of China) and six subcategories (six rice-producing areas) by the method of intergroup connection (Figure
Systematic clustering of element content. A- Anhui Province, X- Guangxi Province, D- Guangdong Province, J- Jilin Province, H- Heilongjiang Province, and N- Inner Mongolia.
In this experiment, the ICP-MS/MS method was developed to determine the content of 30 elements in rice from different production areas. The determination mode and reaction gas conditions were optimized, and the optimal determination conditions were selected for each element in five determination modes of no gas, H2, O2, He, and NH3/He. In addition, in situ mass spectrometry and mass transfer technology were used to eliminate the interference and reduce the detection limit. To achieve the determination of ultratrace elements, we established a complete detection method, which provided a method basis for rice origin traceability. Through the principal component analysis of the multielement content of 18 batches of samples from different origins, the distribution of the six principal components of the samples and the characteristic elements of each principal component were determined. Through cluster analysis, the samples were accurately classified according to the place of production based on the multielement content, which proved that there was a significant correlation between the content of multielement in rice and the place of production, providing technical support and research direction for the traceability of the origin of rice.
The data used to support the findings of this study are included within the article.
The authors declare no conflicts of interest regarding the publication of this article.
YZ, QL, and YW conceived and designed the study. YW and LNL performed the experiments. YW and XXY wrote the paper. YZ, QL, JMM, and SFF reviewed and edited the manuscript. All authors read and approved the manuscript.
This work was supported by the National Key Research and Development Program of China (Project no. 2018YFC1603400), State Administration for Market Regulation Special Technical Support Program (Project no. 2019YJ009), and Scientific Research Projects of Hebei Market Supervision and Administration Bureau (Project no. 2021ZC07).