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地表水中可溶性阳离子(Li+、Na+、NH4+、K+、Ca2+、Mg2+)是水环境监测的常规项目[1],实验室主要采用ICP-MS(电感耦合等离子体质谱仪)测定Li+,采用ICP-OES(全谱直读等离子体发射光谱仪)测定K+、Na+、Ca2+和Mg2+,采用紫外分光光度法或快速化学分析仪测定NH4+, 以上6种阳离子需要使用3种不同的方法分别测定,耗时长,易受干扰,因此建立6种阳离子高效快速的检测方法十分必要[2-3].
近年来关于一些学者采用离子色谱法测定水体阳性离子的报道,大多数是同时测定4种或是5种可溶性阳离子,如赵云[4]研究了离子色谱同时检测地表水中的Na+、K+、Mg2+、Ca2+等4种阳离子的快速测定方法,马丽萍和杨磊[5]以及王晓梅[6]建立了利用离子色谱法同时测定不同水体中K+、Na+、Ca2+、Mg2+、NH4+等5种可溶性阳离子,然而关于城市河道中6种可溶性阳离子Li+、NH4+、Na+、K+、Mg2+、Ca2+同时测定鲜有报道.
分析水体中不同阳性离子组分对了解区域内水体污染情况和生态环境状况具有重要的指导意义,本文对北京市不同区域河道水体中的阳离子变化进行了季节性监测,取样点多,检测工作量大,而利用离子色谱法最大的优点是可同时测定多种离子,节约人力成本及时间成本,同时具有样品预处理简便、检出限及检测限低、速度快、灵敏度高、无污染、稳定性好的优势,使其在地表水环境的监测中发挥了重要作用.
因此,本文为了全面、准确地监测北京市不同区域河道水体可溶性阳离子变化,建立了离子色谱法同时测定水体中Li+、Na+、NH4+、K+、Ca2+、Mg2+ 的6种阳离子的方法,分析北京市不同区域河道水体中可溶性阳离子随季节变化情况,掌握河道水体生态环境状况,有利于水体生态环境保护.
离子色谱法同时测定北京市不同区域水体6种阳离子
Ion chromatography for simultaneously determining six cations in water bodies of different areasof Beijing
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摘要: 建立离子色谱法测定不同区域水体Li+、Na+、NH4+、K+、Ca2+、Mg2+等6种阳离子的方法,以及验证方法在实际应用的可行性. 以 ICS1000型离子色谱仪配有DionexIonPac CG12A 阳离子保护柱(4 mm×50 mm)和CS 12A 阳离子分离柱(4 mm×250 mm),CSRS 300 型抑制器(4 mm),甲基磺酸为淋洗液,流量为1.0 mL·min−1,6种阳离子的质量浓度在0.01—0.50 mg·L−1到5.0—100.0mg·L−1范围内线性较好,相关系数>0.9995,方法检出限为0.002—0.020 mg·L−1,与有证标准溶液相对误差−2.50%—4.38%(n=6),不同环境水样加标回收率90.7%—107.5%. 利用以上色谱条件分析北京市不同区域地表水阳离子分布特征,结果显示城乡结合部、城区和郊区水体pH稳定,呈弱碱性;城乡结合部水体6种阳离子总浓度为150.05 mg·L−1,明显高于城区和郊区25.35%和63.54%,阳离子浓度均值大小为:Ca2+> Na+>Mg2+> K+>NH4+>Li+,其中Ca2+和 Na+是3个区域水体的优势离子,NH4+和Li+质量浓度最低;城乡结合部和城区水体阳离子浓度在夏季和秋季低于春季和冬季. 实验结果表明,离子色谱法样品处理简便,分析速度快,准确可靠,灵敏度高,重复性好,适用于地表水中6种水溶性阳离子的快速批量测定.Abstract: A method for determination of Li+, Na+, NH4+, K+, Ca2+ and Mg2+in different areas of water bodies by ion chromatography was established, and verify the feasibility of the method’s chromatographic conditions and characteristic indexes in the laboratory. The method precautions were also discussed for the reference of model ICS1000 chromatography with DionexIonPac CG12A cation protection column (4 mm × 50 mm) and CS 12A cation separation column (4 mm×250 mm), CSRS 300 suppressed conductivity detector (4 mm), methane sulfonic acid as eluent, and flow rate of 1.0 mL·min−1. The mass concentration of six cations had a good linear relationship with the chromatographic peak area in the range of 0.01—0.50 mg·L−1and 5.0—100.0 mg·L−1, correlation coefficient > 0.9995, and the detection limits of the method were 0.002—0.020 mg·L−1, the relative error of −2.50%—4.38%(n=6)with the certified standard solution, and the recovery rate of standard addition of water samples measured in different environments was 90.7%—107.5%. Six cations in different areas of water bodies in Beijing were analyzed according to the above-mentioned chromatography conditions, and the result reflects that water bodies were weakly alkaline and pH was stable, the total concentration of six cations (150.05 mg·L−1) in the urban and rural joint area was higher than the city proper and the suburbs (25.35% and 63.54%); Order of mean values of cation concentrations: Ca2+> Na+>Mg2+> K+>NH4+>Li+, Ca2+ and Na+ were the dominant ions, while NH4+ and Li+ had the lowest concentrations. The total concentration of six cations of the urban and rural joint area and city area in summer and autumn was lower than in spring and winter. The results showed that the method is simple sample preparation, rapid determination, high sensitivity and accuracy, good repeatability, which is suitable for rapid determination of cations in surface water.
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Key words:
- ion chromatography /
- cations /
- surface water /
- distribution characteristics.
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表 1 标准曲线溶液配制(mg·L−1)
Table 1. Preparation of calibration solution (mg·L−1)
离子
Cations标准溶液 Standard Solution 1 2 3 4 5 6 7 8 Li+ 0.01 0.05 0.10 0.20 0.50 1.00 2.00 5.00 Na+ 0.20 0.50 1.00 2.00 5.00 10.00 20.00 50.00 NH4+ 0.01 0.05 0.10 0.20 0.50 1.00 2.00 5.00 K+ 0.50 1.00 2.00 5.00 10.00 20.00 50.00 100.0 Mg2+ 0.50 1.00 2.00 5.00 10.00 20.00 50.00 100.0 Ca2+ 0.50 1.00 2.00 5.00 10.00 20.00 50.00 100.0 表 2 标准工作曲线的回归方程和相关系数
Table 2. Regression equations and correlation coefficientsofthestandard curve
出峰顺序
Peak occurrence sequence离子名称
Cations线性方程
Linear equations相关系数
Related coefficient1 Li+ Y=0.9249X+0.0026 0.9999 2 Na+ Y=0.3115X+0.0490 0.9999 3 NH4+ Y=−0.0185X2+0.3390X+0.0173 0.9997 4 K+ Y=0.1899X+0.0553 0.9996 5 Mg2+ Y=0.4900X+0.1890 0.9998 6 Ca2+ Y=0.3768X-0.0918 0.9998 表 3 方法的检出限、测定下限(mg·L−1)
Table 3. Method detection limit and the limit of quantitation(mg·L−1)
离子名称
Cations平均值
Average value标准偏差
Standard deviation方法检出限
Method detection limit测定下限
Limit of quantitationLi+ 0.0507 0.0005 0.002 0.008 Na+ 0.0530 0.0021 0.01 0.04 NH4+ 0.0576 0.0031 0.01 0.04 K+ 0.4830 0.0026 0.01 0.04 Mg2+ 0.5195 0.0048 0.01 0.04 Ca2+ 0.4848 0.0027 0.02 0.08 表 4 不同浓度标准溶液的测定平均值和相对标准偏差
Table 4. Measured meanconcentrations and relative standard deviations of standard solutions with different concentrations
离子
Cations低浓度/(mg·L−1)
Low concentration相对标准偏差/%
Relative standard
deviation中浓度/(mg·L−1)
Medium
concentration相对标准偏差/%
Relative standard
deviation高浓度/(mg·L−1)
High concentration相对标准偏差/%
Relative standard
deviationLi+ 0.05 1.45 0.53 0.40 1.08 0.46 Na+ 0.55 0.52 12.68 0.87 21.47 0.10 NH4+ 0.11 2.98 1.15 1.25 5.77 0.36 K+ 0.26 0.76 7.34 0.64 21.74 0.94 Mg2+ 0.22 1.29 5.64 0.77 22.67 0.19 Ca2+ 0.76 0.82 5.48 0.17 21.16 0.18 表 5 有证标准溶液阳离子浓度测定结果
Table 5. Results of determination of cationic concentration in certified standard solution
离子
Cations平均值/(mg·L−1)
Average value标准样品浓度/(mg·L−1)
Standard sample concentration相对标准偏差/%
Relative standard deviation相对误差/%
Relative errorLi+ 0.77 0.76±0.03 1.41 0.72 Na+ 12.35 11.90±0.60 0.19 3.82 NH4+ 0.63 0.65±0.03 1.73 −2.50 K+ 6.34 6.36±0.51 0.74 −0.29 Mg2+ 5.68 5.56±0.27 1.45 2.11 Ca2+ 21.29 20.4±2.0 0.33 4.38 表 6 阳离子的加标回收率
Table 6. Therecovery rates of spiked cations
离子
Cations原样浓度/(mg·L−1)
Original concentration加标量/(mg·L−1)
Added scalar quantity加标回收率/%
Recovery rateLi+ 0.0167 0.05 90.7 0.50 103.0 5.00 97.4 Na+ 109.8143 0.50 98.1 5.00 99.5 50.00 95.9 NH4+ ND 0.05 92.6 0.50 96.2 5.00 97.9 K+ 12.2641 1.00 93.0 20.00 107.5 50.00 103.7 Mg2+ 41.7051 1.00 92.8 20.00 106.7 50.00 104.5 Ca2+ 93.1263 1.00 98.1 20.00 105.8 50.00 99.3 表 7 3个区域水体水化学特征值
Table 7. Hydrochemical characteristic values of water bodies in thethreeareas
区域
Region项目
ItempH 离子/(mg·L−1)
CationsK+ Na+ Ca2+ Mg2+ NH4+ Li+ 城乡
结合部最大值 9.45 29.07 112.13 94.56 31.72 1.47 0.031 最小值 7.45 1.63 6.09 26.52 6.93 0.00 0.001 平均值 8.31 12.34 58.39 59.61 19.59 0.11 0.013 标准差 0.36 7.15 30.79 18.52 6.52 0.28 0.006 变异系数CV/% 4.33 57.94 52.73 31.07 33.28 254.6 46.15 城区 最大值 9.69 20.31 109.16 131.59 49.17 0.23 0.044 最小值 7.73 1.53 4.85 19.92 6.65 0.00 0.00 平均值 8.74 6.63 41.04 52.49 19.48 0.06 0.010 标准差 0.36 4.71 32.14 21.76 10.47 0.07 0.01 变异系数CV/% 4.12 71.04 78.31 41.46 53.75 116.7 100.0 郊区 最大值 8.49 18.19 35.48 64.82 11.71 0.20 0.004 最小值 6.94 2.30 9.59 36.04 7.06 0.00 0.001 平均值 7.55 3.69 23.84 54.90 9.27 0.05 0.003 标准差 0.35 2.75 6.80 7.55 1.53 0.06 0.001 变异系数CV/% 4.64 74.53 28.52 13.75 16.50 120.0 33.33 表 8 3个区域水体阳离子相关性矩阵
Table 8. Correlation matrices of cation concentrations of water bodies in the three areas
郊区 Suburb K+ Na+ Ca2+ Mg2+ NH4+ Li+ K+ 1 −0.042 0.089 0.076 −0.110 0.105 Na+ 1 −0.889*** −0.778*** −0.354 0.500* Ca2+ 1 0.932*** 0.160 −0.227 Mg2+ 1 −0.004 −0.110 NH4+ 1 −0.641*** Li+ 1 城乡结合部 Urban fringe area K+ Na+ Ca2+ Mg2+ NH4+ Li+ K+ 1 0.906*** 0.684*** 0.651*** −0.037 0.648*** Na+ 1 0.755*** 0.793*** −0.043 0.614*** Ca2+ 1 0.862*** −0.028 0.401 Mg2+ 1 −0.019 0.383 NH4+ 1 −0.044 Li+ 1 城区 Urban area K+ Na+ Ca2+ Mg2+ NH4+ Li+ K+ 1 0.841*** 0.478*** 0.551*** −0.146 0.658*** Na+ 1 0.470*** 0.834*** −0.202 0.797*** Ca2+ 1 0.639*** −0.208 0.289* Mg2+ 1 −0.214 0.663*** NH4+ 1 −0.172 Li+ 1 注:***表示在 0.001 置信度下显著相关,**表示在 0.01 置信度下显著相关,* 表示在 0.05 置信度下显著相关.
Note:*** indicated a significant correlation between the 0.001 confidence level,** indicated a significant correlation between the 0.01 confidence level, * indicated a significant correlation between the 0.05confidence level. -
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