An Improved Method for Determination of Trace Silver in Geochemical Exploration Samples by Graphite Furnace Atomic Absorption Spectrometry
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摘要: 应用石墨炉原子吸收光谱法测定地球化学样品中的痕量银,一般采用盐酸-硝酸-氢氟酸-高氯酸电加热溶样,铱、铂为基体改进剂,以硫脲作为介质可能会导致大量铜与硫脲发生沉淀,干扰测量结果,分析流程繁琐、成本高。本文采用50%的王水水浴溶样,以湿加方式加入50 g/L硫脲基体改进剂,避免了铜在溶液中与硫脲络合,消除了干扰。方法检出限为0.01 μg/g,准确度和精密度好,内外检合格率符合地质矿产行业标准。该方法简化了样品处理步骤,提高了工作效率,分析成本降低,适合批量样品的分析,且溶解样品的溶液还可继续用于氢化物发生法测定砷、汞、铋、锑等元素。
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关键词:
- 化探样品 /
- 痕量银 /
- 王水 /
- 硫脲 /
- 石墨炉原子吸收光谱法
Abstract: The chemical procedure of the HCl-HNO3-HF-HClO4 acids system on the electric heating plate is usually used to determine trace Ag in geochemical exploration samples using the Graphite Furnace Atomic Absorption Spectrometry (GFASS) method. Ir and Pt are usually used as the matrix modifiers. However, the thiourea serving as the medium probably leads to a large amount of precipitation with Cu, which interferes with the measurement results. Also, this dissolution method is time consuming during the analysis process and costly. In this paper it is reported that sample in water bath is dissolved by 50% aqua regia. The 50 g/L thiourea matrix modifier was added as the solution, avoiding the precipitation with Cu. The detection limit was 0.01 μg/g with good accuracy and precision. The qualified rates of internal and external examination were in agreement with the standard values. This new method simplifies the processing steps, saving time and cost, and is suitable for batch samples analyses. Furthermore, the dissolved solution of the samples was applied to determine As, Hg, Bi, Sb and other elements by the hydride generation method. -
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表 1 仪器工作条件
Table 1. Working parameters of the instrument
工作参数 条件 波长 328.1 nm 狭缝 0.5 nm 灯电流 7.5 mA 积分方式 峰高 背景扣除 Zeeman 进样体积 20 μL 基体改进剂体积 5 μL 辅助气流速 0.2 L/min 重复次数 1 积分时间 2 s 表 2 石墨炉升温程序
Table 2. Temperature program of graphite furnace
步骤 温度θ/℃ 时间t/s 斜坡/(℃·s-1) 气体流量
ν/(L·min-1)干燥 90 30.0 0 0.2 干燥 130 15.0 5 0.2 灰化 750 10.0 0 0.2 原子化 2100 1.5 0 0 除残 2500 3.0 0 0.2 表 3 准确度和精密度试验
Table 3. Accuracy and precision tests of the method
标准物质编号 w(Ag)/(μg·g-1) 准确度 精密度RSD/% 本法分次测定值 平均值 标准值 ΔlgC RE/% GWB 07448 0.058 0.051 0.041 0.047 0.050 0.046 0.049 0.050 0.000 0.0 10 0.050 0.054 0.051 0.052 0.057 0.050 GWB 07447 0.079 0.070 0.071 0.067 0.064 0.071 0.072 0.066 0.038 9.1 7 0.071 0.076 0.078 0.076 0.079 0.068 GWB 07456 0.158 0.166 0.157 0.150 0.147 0.159 0.155 0.140 0.044 10.7 5 0.164 0.147 0.163 0.156 0.138 0.162 GWB 07402 0.057 0.058 0.067 0.049 0.057 0.062 0.056 0.054 0.016 3.7 11 0.063 0.047 0.054 0.050 0.057 0.052 GWB 07406 0.216 0.204 0.208 0.213 0.194 0.189 0.218 0.200 0.037 9.0 12 0.193 0.201 0.243 0.248 0.257 0.246 GWB 07455 0.055 0.065 0.063 0.067 0.061 0.076 0.071 0.070 0.006 1.4 10 0.066 0.075 0.085 0.071 0.074 0.075 GWB 07305 0.358 0.368 0.340 0.333 0.345 0.334 0.341 0.36 -0.024 -5.3 4 0.328 0.356 0.332 0.329 0.336 0.338 GWB 07305a 0.697 0.644 0.681 0.671 0.587 0.643 0.650 0.630 0.014 3.2 8 0.558 0.656 0.700 0.620 0.615 0.756 GWB 07307a 1.200 1.120 1.280 1.100 1.380 1.020 1.240 1.200 0.014 3.3 12 1.070 1.200 1.390 1.470 1.250 1.410 GWB 07308a 0.121 0.112 0.114 0.113 0.146 0.121 0.122 0.120 0.007 1.6 9 0.116 0.113 0.132 0.123 0.135 0.121 GWB 07312 1.170 1.170 1.120 1.150 1.380 1.110 1.150 1.150 0.000 0.0 8 1.170 1.080 1.060 1.050 1.140 1.190 GWB 07107 0.042 0.045 0.047 0.049 0.045 0.040 0.043 0.047 -0.039 -8.5 9 0.038 0.044 0.040 0.035 0.041 0.045 -
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