二维离子排斥-离子交换色谱配合阀切换技术测定G2级磷酸中的痕量阴离子

doi:10.3724/SP.J.1123.2024.04010

摘要/Abstract

摘要：

本研究建立了在超净环境下基于二维离子排斥-离子交换色谱配合阀切换技术测定G2级磷酸中痕量阴离子含量的方法。通过比较确定了第一维超纯水流经离子排斥柱的最佳柱流速为0.5 mL/min,并确定阀切换窗口,以尽可能降低PO₄^3-在阴离子富集柱上的富集水平,减小了磷酸基体的干扰;采用抑制器外接水模式,降低了基线噪声;优化了第二维的淋洗程序,实现了痕量目标阴离子的良好分离,避免了硝酸根的假阳性风险。结果表明:Cl^-、Br^-、NO₃^-和SO₄^2- 4种阴离子在0.5~20 μg/kg含量范围内呈现良好的线性关系,相关系数>0.999;检出限和定量限分别为0.09~0.29 μg/kg和0.29~0.97 μg/kg。在4个添加水平下,各阴离子的加标回收率为91.7%~103.6%,RSD为0.1%~4.9%。本方法具有重复进样稳定性好、检出限低的优势,方法的精密度和准确度高,能满足G2级磷酸中痕量阴离子的检测需求。此外,通过单一标准物质保留时间定性,本研究在G2级磷酸中发现除常规阴离子外,可能还存在以亚磷酸根(HPO₃^-)和六偏磷酸根(PO₃^-)₆为代表的其他磷系阴离子和阴离子簇。这一发现对于今后更高纯度磷酸的纯化工艺开发具有一定的理论和应用意义。

关键词: 电子级磷酸, 痕量阴离子, 阀切换, 二维离子色谱

Abstract:

This study established a method for determining trace anions in G2-grade phosphoric acid under ultra-clean conditions that used two-dimensional ion-exclusion-ion-exchange chromatography coupled with valve-switching technology. The optimal flow rate of ultrapure water through the ion-exclusion column in the first dimension was determined to be 0.5 mL/min through comparative experiments. The valve-switching window was optimized to minimize enriching PO₄^3- on the anion-enrichment column and reduce interference from the phosphoric-acid matrix. The use of external water mode for the suppressor led to lower baseline noise, and optimizing the elution program of the second dimension enabled target trace anions to be well separated, thereby avoiding the risk of a false positive for NO^3-. The anions of Cl^-, Br^-, NO^3-, and SO₄^2- exhibited good linearities within the 0.5-20 μg/kg, with correlation coefficients ≥0.999. The limits of detection (LODs) and quantification (LOQs) were 0.09-0.29 μg/kg and 0.29-0.97 μg/kg, respectively. The spiked recoveries of each anion at four spiked levels ranged from 91.7% to 103.6%, with RSDs of 0.1%-4.9%. The developed method demonstrated excellent stability through repeated injections, and low detection limits; it is highly precise and accurate, and meets the detection requirements for trace anions in G2-grade phosphoric acid. Additionally, retention-time comparisons with single standard substances led to the discovery of other phosphorus-related anions and anion clusters, such as hypophosphite (HPO₃^-) and hexametaphosphate (PO₃^-)₆, in G2-grade phosphoric acid, in addition to conventional anions. This finding is theoretically and practically significant for the future development of purification processes for higher-purity phosphoric acid.

Key words: electronic grade phosphoric acid, trace anions, valve switching, two-dimensional ion chromatography (2D-IC)

中图分类号:

O658

王佳鼎, 唐高, 鹿燕, 卢珩俊, 叶涛. 二维离子排斥-离子交换色谱配合阀切换技术测定G2级磷酸中的痕量阴离子[J]. 色谱, 2025, 43(3): 237-244.

WANG Jiading, TANG Gao, LU Yan, LU Hengjun, YE Tao. Determination of trace anions in G2-grade phosphoric acid using two-dimensional ion-exclusion-ion-exchange chromatography with valve-switching technology[J]. Chinese Journal of Chromatography, 2025, 43(3): 237-244.

图/表 9

图1 2D-IC阀切换系统结构示意图

Fig. 1 Structure diagram of 2D-IC valve-switching system Solid line indicates the load state, dashed line indicates the inject state.

表1 分析系统淋洗液梯度及阀切换工作程序表

Table 1 Analytical system eluent gradient and valve-switching operation procedure table

Time/min	c(OH^-)/(mmol/L)	Valve 1	Event of 1D system	Valve 2	Event of IC system
-9.0	8.0	inject	/	inject	analyzing system balance
-2.0	8.0	inject	matrix separation window start	load	target anion enrichment
0	8.0	inject	matrix separation window end	inject	target ion analysis
5.0	8.0	load	preparing a new sample for injection	inject	target ion analysis
10.0	8.0	load	equilibrium exclusion column	inject	target ion analysis
60.0	60.0	load	equilibrium exclusion column	inject	target ion analysis
63.0	60.0	load	equilibrium exclusion column	inject	target ion analysis
63.1	8.0	load	equilibrium exclusion column	inject	target ion analysis

图2 不同流速下阴离子混合溶液和磷酸溶液在离子排斥柱上的洗脱情况

Fig. 2 Elution profiles of anionic mixed solution and phosphoric acid solution at different flow rates on the ion exclusion column Detector connected after ion exclusion column.

图3 不同流速下阴离子磷酸混合溶液的第一维色谱图

Fig. 3 Chromatograms of anionic phosphoric acid mixed solution at different flow rates in the first dimension a. 0.3 mL/min (10.5-16.5 min in Fig. 2a); b. 0.4 mL/min (8-12.5 min in Fig. 2b); c. 0.5 mL/min (7-10 min in Fig. 2c); d. 1 mL/min (3.5-5.5 min in Fig. 2d). Elution gradient: 0-8 min, 8 mmol/L KOH, 8-30 min, 8-60 mmol/L; sample: 100 μg/kg anionic mixed standard solution in 33% (v/v) phosphoric acid solution.

图4 两种阀切换窗口下连续分析33%(体积分数)磷酸溶液的色谱图

Fig. 4 Chromatograms of continuous analysis of 33% (v/v) phosphoric acid solution under two valve switching windows a. valve switching window of 7-10 min, first injection; b. valve switching window of 7-10 min, second injection; c. valve switching window of 7-9 min, first injection; d. valve switching window of 7-9 min, fifth injection. Elution gradient: 0-8 min, 8 mmol/L KOH, 8-30 min, 8-35 mmol/L KOH; suppressor curren: 87 mA; sample: 33% (v/v) phosphoric acid solution.

图5 未知离子(可能是亚磷酸根)引起的NO3-假阳性干扰

Fig. 5 False positive interference of NO3- caused by unknown ion (possibly HPO3-) a. 20 μg/kg anionic mixed standard solution in 1% (v/v) phosphoric acid solution; b. 1% (v/v) phosphoric acid solution; c. 20 μg/kg anionic mixed standard solution in pure water matrix. Elution gradient: 0-8 min, 8 mmol/L KOH, 8-35 min, 8-60 mmol/L KOH, 35-38 min, 60 mmol/L KOH.

图6 最终的淋洗梯度及样品加标测试图

Fig. 6 Final elution gradient and sample spiked test plot a. 1% (w/w) phosphoric acid solution; b. 20 μg/kg anionic mixed standard solution in 1% (w/w) phosphoric acid solution.

表2 4种阴离子的线性方程、线性范围、相关系数、检出限和定量限

Table 2 Linear equations, linear ranges, correlation coefficients (r), limits of detection (LODs) and limits of quantification (LOQs) for the four anions

Anion	Linear equation	Linear range/ (μg/kg)	r	LODs/(μg/kg)		LOQ/(μg/kg)
Anion	Linear equation	Linear range/ (μg/kg)	r	This study	Literature	LOQ/(μg/kg)
Cl^-	y=0.005x-0.0003	0.5-20	0.99974	0.09	3^[5], 60^[14], 12^[15], 7^[19]	0.29
Br^-	y=0.0024x-0.0003	0.5-20	0.99978	0.29	/	0.97
N	y=0.0031x+0.0004	0.5-20	0.99978	0.15	4^[5], 40^[14], 19^[15], 3^[19]	0.50
S	y=0.0043x+0.0148	0.5-20	0.99978	0.16	90^[5], 680^[14], 30^[15], 3^[19]	0.54

表3 磷酸样品中阴离子在4个水平下的加标回收率(n=5)

Table 3 Spiked recoveries of anions in phosphoric acid samples at four levels (n=5)

Anion	Background/ (μg/kg)	Spiked/ (μg/kg)	Recovery/ %	RSD/ %
Cl^-	0	0.52	91.7	4.9
	0	4.07	99.6	1.1
	0	10.18	100.0	0.4
	0	16.33	99.3	0.1
Br^-	0	0.52	93.3	2.3
	0	4.13	93.2	2.0
	0	10.34	95.6	0.4
	0	16.59	99.3	0.2
N	0	0.52	94.0	2.8
	0	4.10	103.6	2.3
	0	10.28	101.2	0.4
	0	16.48	99.4	0.3
S	3.19	0.48	98.1	4.3
	3.12	3.76	96.2	1.3
	3.17	9.42	97.2	0.3
	3.17	15.11	98.9	0.2

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