A PRETREATMENT PROCESS FOR DETERMINATION OF MULTIPLE ELEMENTS IN PLANT SAMPLES BASED ON ICP-OES
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摘要:
在农业生态环境地球化学调查与评价中，植物的化学组成是重要的直接指标，因此对植物样品元素含量进行准确测定具有重要意义.本研究的主要目的是开发一种利用电感耦合等离子体发射光谱（ICP-OES）测定植物样品中多元素的分析方法，同时不需要在光谱测定之前进行费力而繁琐的样品前处理.采用微波消解、电热板消解及超声消解3种方法处理植物样品，利用ICP-OES分别测定植物样品中Ca、Cr、Cu、Fe、Mg、Mn、Ni、Pb、Sr、Zn等10种元素的含量，并对3种方法的消解效果进行比较.结果表明：3种方法的检出限分别为0.042×10-6~0.239×10-6、0.046×10-6~0.237×10-6、0.026×10-6~0.232×10-6；测定待测元素的相对标准偏差均低于10%；相对误差分别为-11%~+13.8%，-22.1%~+8.7%，-13.3%~+8.9%.其中超声消解表现出更低的检出限和较好的准确度，满足DD2005-03《生态地球化学评价样品分析技术要求（试行）》.同时验证了超声消解在实际工作中的可行性.实验证明，王水溶样超声辅助消解是一种简单、快速、准确的样品制备方法，能够满足植物样品分析测试要求.
Abstract:The chemical composition of plants is as an important direct indicator in the geochemical survey and evaluation of agroecological environment. It is of great significance to accurately determine the element content of plant samples. The main purpose of this study is to develop an analytical process for the determination of multiple elements in plant samples using inductively coupled plasma optical emission spectrometry (ICP-OES) without the need for tedious sample pretreatment prior to spectroscopic determination. The plant samples are treated by three methods including microwave digestion, electrothermal plate digestion and ultrasonic digestion. The contents of Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr and Zn in plant samples are determined respectively by ICP-OES, with comparison of digestion effects of the three methods. The results reveal that the detection limits of three methods are 0.042×10-6-0.239×10-6, 0.046×10-6 -0.237×10-6 and 0.026×10-6-0.232×10-6, respectively. The relative standard deviations of the elements to be measured are all lower than 10%, with the relative errors of -11% to +13.8%, -22.1% to +8.7%, and -13.3% to +8.9%, respectively. Ultrasonic digestion shows a lower detection limit and better accuracy, which meets the requirements of DD2005-03 Technical Requirements for Sample Analysis of Eco-geochemical Evaluation (Trial), and its feasibility in practice is verified. The test proves that dissolving samples in aquaregia with the assisted ultrasonic digestion is a simple, quick and accurate sample preparation method, which can meet the requirements of plant sample analysis.
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表 1 分析元素的ICP-OES测量条件
Table 1. Test conditions of ICP-OES for analyzed elements
参数 指标 泵速 50 rpm 雾化器气流量 0.6 L/min 辅助气流量 0.5 L/min 载气流量 15 L/min 射频功率 1150 W 积分时间 15 s UV/10 s Vis 元素波长 Ca: 317.933 nm, Cr: 205.560 nm, Cu: 324.752 nm,
Fe: 238.204 nm, Mg: 285.213 nm, Mn: 259.372 nm,
Ni: 221.648 nm, Pb: 220.353 nm, Sr: 407.771 nm,
Zn: 206.200 nm
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表 2 三种消解方式下ICP-OES测定的方法检出限
Table 2. Detection limits of ICP-OES by three digestion methods
元素 微波消解/10-6 电热板消解/10-6 超声消解/10-6 Ca 0.191 0.326 0.186 Cr 0.094 0.177 0.097 Cu 0.077 0.098 0.041 Fe 0.157 0.366 0.151 Mg 0.239 0.247 0.232 Mn 0.103 0.139 0.036 Ni 0.045 0.058 0.029 Pb 0.138 0.171 0.143 Sr 0.042 0.046 0.026 Zn 0.131 0.150 0.137
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表 3 三种方法测定的准确度和精密度
Table 3. Accuracy and precision of three digestion methods
标样 元素 标准值 微波消解 电热板消解 超声消解 平均值 RE/% RSD/% 平均值 RE/% RSD/% 平均值 RE/% RSD/% GBW10010a
（大米）Ca 0.007 0.0067 -4.3 6.8 0.0064 -8.6 4.9 0.0074 5.7 3.1 Cr 0.08 — — — — — — — — — Cu 3.0 3.20 6.7 4.0 2.71 -9.7 4.2 2.93 -2.3 3.0 Fe 4.0 3.82 -4.5 3.8 3.27 -13.9 2.9 3.74 -6.5 2.6 Mg 0.013 0.0124 -4.6 5.5 0.0117 -10.0 4.2 0.0136 4.6 2.0 Mn 11.1 11.28 1.6 4.7 11.62 4.7 3.7 10.38 -6.5 5.0 Ni 0.21 0.187 -11.0 4.7 0.191 -9.0 6.1 0.205 -2.4 4.9 Pb 0.10 — — — — — — — — — Sr 0.15 0.156 4.0 3.6 0.163 8.7 9.7 0.159 6.0 5.4 Zn 13.3 13.68 2.9 5.3 12.14 -8.7 5.6 14.21 6.8 3.6 GBW10011a
（小麦）Ca 0.03 0.031 3.3 4.3 0.028 -6.7 10.1 0.027 -10.0 2.9 Cr 0.09 — — — — — — — — — Cu 3.0 2.85 -5.0 4.1 2.75 -8.3 7.4 2.91 -3.0 6.2 Fe 25 26.1 4.4 6.8 21.6 -13.6 9.6 23.8 -4.8 2.3 Mg 0.062 0.061 -1.6 5.5 0.066 6.5 6.8 0.060 -3.2 7.0 Mn 10.0 9.32 -6.8 5.3 9.56 -4.4 4.4 9.27 -7.3 4.8 Ni 0.08 0.073 -8.8 2.9 0.073 -8.8 3.6 0.070 -12.5 4.5 Pb 0.09 — — — — — — — — — Sr 2.6 2.45 -5.8 4.7 2.41 -7.3 4.4 2.52 -3.1 4.2 Zn 12.3 12.77 3.8 5.0 13.15 6.9 6.6 11.82 -3.9 4.1 GBW10013
（黄豆）Ca 0.153 0.151 -1.3 5.7 0.148 -3.3 5.4 0.156 2.0 3.2 Cr 0.28 0.262 -6.4 3.6 0.267 -4.6 4.7 0.264 -5.7 5.5 Cu 10.2 9.73 -4.6 4.5 10.30 1.0 5.7 10.48 2.7 2.4 Fe 139 142.5 2.5 3.1 116.2 -16.4 8.3 120.5 -13.3 2.6 Mg 0.230 0.214 -7.0 7.3 0.208 -9.6 4.1 0.211 -8.3 3.9 Mn 28 29.37 4.9 5.2 29.91 6.8 6.6 28.39 1.4 6.7 Ni 4.0 3.87 -3.3 6.6 3.74 -6.5 3.3 3.83 -4.3 5.6 Pb 0.07 — — — — — — — — — Sr 9.9 10.06 1.6 6.1 9.27 -6.4 5.7 9.55 -3.5 8.0 Zn 38 36.14 -4.9 4.7 37.28 -2.0 4.4 34.21 8.4 4.8 GBW10048
（芹菜）Ca 1.66 1.654 -0.4 8.4 1.617 -2.6 9.1 1.632 -1.7 7.8 Cr 1.35 1.42 5.2 7.3 1.30 -3.7 5.6 1.47 8.9 3.9 Cu 8.2 8.41 2.6 6.9 8.88 8.3 5.8 8.53 4.0 5.5 Fe 597 563 -5.7 6.4 465.1 -22.1 4.0 577 -3.4 5.9 Mg 0.53 0.522 -1.5 3.4 0.546 3.0 8.7 0.528 -0.4 3.4 Mn 45 47.82 6.3 7.2 37.15 -17.4 2.5 39.37 -12.5 6.9 Ni 1.8 1.66 -7.8 6.3 1.54 -14.4 6.1 1.74 -3.3 6.3 Pb 2.7 2.57 -4.8 5.7 2.51 -7.0 7.4 2.90 7.4 4.6 Sr 213 211.7 -0.6 5.4 200.5 -5.8 6.3 199.2 -6.5 3.6 Zn 26 29.6 13.8 4.8 27.4 5.4 3.0 24.1 -7.3 5.0 含量单位: Ca、Mg为10-2, 其他为10-6. -表示低于检出限.
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表 4 ICP-OES法测定实际样品中的元素含量
Table 4. Analysis result of element contents in samples detected by ICP-OES
样品 元素 微波消解法 超声消解法 F-test t-test 样品 元素 微波消解法 超声消解法 F-test t-test S1（黄花） Ca 0.352 0.345 1.27 1.19 S2（黄花） Ca 0.350 0.347 1.22 0.51 Cu 4.92 5.23 2.20 1.57 Cu 4.86 4.70 1.01 1.03 Fe 104.5 106.2 1.06 1.18 Fe 96.4 102.1 1.57 2.21 Mg 0.148 0.145 2.32 1.27 Mg 0.143 0.148 2.29 1.00 Mn 18.37 18.25 1.63 0.19 Mn 16.6 17.7 1.18 2.36 Ni 0.780 0.815 2.72 1.76 Ni 0.794 0.735 3.11 1.92 Sr 23.9 25.0 2.44 2.0 Sr 27.0 28.7 1.27 2.72 Zn 23.0 23.5 1.62 1.54 Zn 20.4 20.5 1.09 0.27 S3（水稻） Ca 0.0121 0.0116 1.38 2.20 S4（水稻） Ca 0.0116 0.0121 1.48 1.61 Cr 0.410 0.422 1.93 1.16 Cr 0.438 0.428 2.61 0.75 Cu 2.46 2.51 2.93 2.53 Cu 2.00 1.94 1.44 2.12 Fe 59.6 62.8 1.30 2.17 Fe 25.9 26.5 1.40 1.03 Mg 0.141 0.138 1.15 0.97 Mg 0.140 0.144 1.77 1.50 Mn 31.6 31.8 1.49 0.65 Mn 29.3 28.3 2.16 2.13 Ni 0.462 0.485 4.15 1.94 Ni 0.231 0.238 1.11 1.79 Sr 1.56 1.47 1.21 1.83 Sr 1.18 1.14 2.02 1.67 Zn 16.6 17.1 2.01 0.90 Zn 15.8 17.2 1.94 2.37 S5（高粱） Ca 0.0145 0.0144 1.10 0.21 S6（高粱） Ca 0.0130 0.0128 2.69 0.48 Cr 0.145 0.139 1.65 1.39 Cr 0.168 0.170 2.18 0.54 Cu 3.01 3.06 3.69 1.33 Cu 3.14 3.23 3.54 1.95 Fe 38.6 39.5 1.77 0.63 Fe 45.5 47.5 1.09 1.58 Mg 0.170 0.168 2.69 0.58 Mg 0.190 0.192 3.32 0.79 Mn 18.2 17.9 4.18 2.14 Mn 20.6 20.4 1.44 0.65 Sr 1.99 2.01 3.38 0.73 Sr 1.07 1.07 1.17 0.79 Zn 21.7 21.0 1.00 1.91 Zn 23.84 24.4 2.34 2.15 S7（玉米） Ca 0.0060 0.0059 3.30 0.28 S8（玉米） Ca 0.0049 0.0048 3.73 0.53 Cr 0.113 0.118 1.69 1.84 Cr 0.123 0.118 1.80 1.40 Cu 1.07 1.07 2.12 0.02 Cu 1.22 1.21 2.55 0.31 Fe 18.7 19.3 1.15 1.10 Fe 17.4 16.0 1.37 2.71 Mg 0.131 0.129 1.06 0.73 Mg 0.117 0.114 1.62 0.85 Mn 5.05 5.25 3.18 1.80 Mn 4.87 4.78 3.56 0.61 Sr 0.410 0.420 1.88 1.59 Sr 0.438 0.434 1.42 0.26 Zn 14.0 14.1 1.09 0.27 Zn 14.5 14.6 1.32 0.82 含量单位:Ca、 Mg为10-2,其他为10-6; n=7, P=0.95, F=4.28, t=2.45.
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