Determination of Methyl‑mercury by Microwave Assisted Extraction‑Solid Phase Membrane Extraction in Water Sediments

doi:10.19894/j.issn.1000-0518.210300

Chinese Journal of Applied Chemistry ›› 2022, Vol. 39 ›› Issue (9): 1360-1370.DOI: 10.19894/j.issn.1000-0518.210300

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Determination of Methyl‑mercury by Microwave Assisted Extraction‑Solid Phase Membrane Extraction in Water Sediments

Xin ZHAO¹, He LIU¹, Zhong-Bo WU¹, He WANG¹, Zi-Ming WANG²()

^1.Ecology and Environmental Monitoring Center of Jilin Province，Changchun 130011，China
^2.College of Chemistry，Jilin University，Changchun 130012，China

Received:2021-06-19 Accepted:2021-12-11 Published:2022-09-01 Online:2022-09-08
Contact: Zi-Ming WANG
About author:wangziming@jlu.edu.cn

Abstract

Abstract:

A novel and simple method of microwave assisted extraction combined with solid phase membrane extraction enrichment and purification with high performance liquid chromatography-atomic fluorescence spectrometer （LC-AFS） for determination of methyl-mercury in water sediments is developed. The key of this method is the extraction process of the sample， in the extraction process， it is necessary to ensure that the original form of methyl mercury in the sample is not damaged and transformed， and it is fully extracted from the sample to achieve stable and reliable recovery. The methyl-mercury in water sediment is extracted to the solution by microwave-assisted extraction technology. The C18 solid phase extraction membrane is modified by 0.01% diethyldithiocarbamate， and the methyl-mercury is enriched and purified at the same time. The eluent is determined by LC-AFS. Some experimental conditions such as the effects of mobile phase， microwave extraction conditions and solid phase membrane extraction conditions on methyl-mercury are investigated. Under the optimal experimental conditions， the actual sediment samples and the spiked samples are analyzed， and the results obtained show that the detection limit of methyl-mercury is 0.20 μg/kg ^{in the sediment， and the relative standard deviation is 2.0%～6.36%. The spiked recovery is 71.3%～87.6%， and the experimental results are satisfactory. This method has the advantages of fast extraction speed， less solvent consumption and high extraction efficiency， which can simultaneously process multiple samples and save energy consumption. It is the development trend of modern monitoring and analysis and is suitable for the analysis and determination of methyl-mercury in water sediments.}

Key words: Microwave-assisted extraction, Solid phase membrane extraction, Water sediments, Methyl mercury

CLC Number:

O652.6

Xin ZHAO, He LIU, Zhong-Bo WU, He WANG, Zi-Ming WANG. Determination of Methyl‑mercury by Microwave Assisted Extraction‑Solid Phase Membrane Extraction in Water Sediments[J]. Chinese Journal of Applied Chemistry, 2022, 39(9): 1360-1370.

Figures/Tables 13

Fig.1 Effects of different L-cysteine on methyl mercury

Fig.2 The Chromatogram of mercury speciation separated by different organic solvents

Fig.3 Effect of different mass fractions of ammonium acetate on chromatogram peak

Fig.4 Types of extraction solventsa.10% HCl+1% thiourea+0.15% KCl； b.10% HCl+0.5%L-cysteine+0.15% KCl； c.5% KOH+10% acetonitrile；d.5% KOH+10% methanol； e.5% KCl-methanol

Fig.5 Effect of extracting temperature

Fig.6 Effect of extracting time

Fig.7 Effect of modified solution

Fig.8 Concentration of modified solution

Table 1 The detection limit of methyl?mercury

目标物

Analyte

样品测定次数

Test number

平均值

x ˉ

标准偏差 SD

检出限 MDL

测定下限 LOQ

实际样品中甲基汞的浓度

c（MeHg）/（μg·kg^-1）

Table 1 The detection limit of methyl?mercury

目标物

Analyte

样品测定次数

Test number

平均值

x ˉ

标准偏差 SD

检出限 MDL

测定下限 LOQ

实际样品中甲基汞的浓度

c（MeHg）/（μg·kg^-1）

0.79

0.84

0.79

0.89

0.86

0.75

0.71

0.80

0.063

3.143

0.20

0.80

Table 2 The intra?day precision and inter?day precision and recovery of methyl?mercury

目标物 Analyte	加标浓度 Spiked concentration/（μg·kg^-1）	日内精密度 Intra?day		日间精密度 Inter?day
目标物 Analyte	加标浓度 Spiked concentration/（μg·kg^-1）	Recovery/%	RSD/%	Recovery/%	RSD/%
甲基汞 MeHg	1	77.5	5.60	67.2	17.8
	2	79.6	5.34	71.3	15.4
	4	83.5	3.45	73.6	13.1

Table 3 Effects of storage conditions on the stability of methylmercury in samples with different concentrations

储存时间 Storage time/d				加样浓度 Spiked concentration/（μg·kg^-1）
	1	2	4	1	2	4	1	2	4
	室温下回收率 Recovery（RT）/%			4 ℃回收率 Recovery（4 ℃）/%			-15 ℃回收率 Recovery（-15 ℃）/%
1	79.0	82.5	84.3	79	82.5	84.3	79.0	82.5	84.3
2	75.0	79.5	80.3	75	79.5	80.3	78.0	81.0	83.5
3	71.0	73.5	75.3	70	75.5	77.8	73.0	80.0	82.5
4	62.0	65.5	68.0	67	72.5	75.5	71.0	80.0	81.3
5	49.0	55.5	60.3	64	67.5	71.3	69.0	78.5	79.8
10	—	—	—	—	—	—	59.0	71.0	75.3
12	—	—	—	—	—	—	58.0	70.0	73.3
15	—	—	—	—	—	—	56.0	67.4	71.3

Table 4 The analysis of actual and spiked samples

平行样品编号 Sample number		样品1 Sample 1	样品1加标 Spiked sample 1			样品2 Sample 2	样品2加标 Spiked sample 2			样品3 Sample 3	样品3加标 Spiked sample 3
甲基汞浓度 c（MeHg）/（μg·kg^-1）	1	0.79	1.61	2.38	4.21	1.31	2.10	2.92	4.27	0.93	1.69	2.59	4.39
	2	0.84	1.45	2.56	4.26	1.39	2.06	2.65	4.31	0.95	1.62	2.51	4.08
	3	0.79	1.59	2.46	4.31	1.35	1.95	2.86	4.56	0.89	1.52	2.38	4.29
	4	0.89	1.64	2.65	4.45	1.27	1.91	3.05	4.30	0.92	1.66	2.18	4.02
	5	0.86	1.39	2.34	4.32	1.36	2.14	2.76	4.62	0.93	1.75	2.54	4.16
	6	0.75	1.52	2.31	4.39	1.24	2.24	2.81	4.34	0.95	1.62	2.31	4.59
平均值 $x ˉ$		0.82	1.53	2.45	4.32	1.32	2.07	2.84	4.40	0.93	1.64	2.42	4.26
标准偏差 SD		0.052	0.098	0.133	0.087	0.057	0.122	0.137	0.151	0.022	0.078	0.157	0.213
相对标准偏差 RSD/%		6.36	6.40	5.44	2.00	4.34	5.90	4.83	3.44	2.40	4.72	6.48	5.00
加标浓度 Spiked concentration/（μg·kg^-1）		—	1	2	4	—	1	2	4	—	1	2	4
加标回收率 Spiked recovery/%		—	71.3	81.5	87.6	—	74.7	76.1	77.0	—	71.3	74.4	83.1

Table 4 The analysis of actual and spiked samples

平行样品编号 Sample number		样品1 Sample 1	样品1加标 Spiked sample 1			样品2 Sample 2	样品2加标 Spiked sample 2			样品3 Sample 3	样品3加标 Spiked sample 3
甲基汞浓度 c（MeHg）/（μg·kg^-1）	1	0.79	1.61	2.38	4.21	1.31	2.10	2.92	4.27	0.93	1.69	2.59	4.39
	2	0.84	1.45	2.56	4.26	1.39	2.06	2.65	4.31	0.95	1.62	2.51	4.08
	3	0.79	1.59	2.46	4.31	1.35	1.95	2.86	4.56	0.89	1.52	2.38	4.29
	4	0.89	1.64	2.65	4.45	1.27	1.91	3.05	4.30	0.92	1.66	2.18	4.02
	5	0.86	1.39	2.34	4.32	1.36	2.14	2.76	4.62	0.93	1.75	2.54	4.16
	6	0.75	1.52	2.31	4.39	1.24	2.24	2.81	4.34	0.95	1.62	2.31	4.59
平均值 $x ˉ$		0.82	1.53	2.45	4.32	1.32	2.07	2.84	4.40	0.93	1.64	2.42	4.26
标准偏差 SD		0.052	0.098	0.133	0.087	0.057	0.122	0.137	0.151	0.022	0.078	0.157	0.213
相对标准偏差 RSD/%		6.36	6.40	5.44	2.00	4.34	5.90	4.83	3.44	2.40	4.72	6.48	5.00
加标浓度 Spiked concentration/（μg·kg^-1）		—	1	2	4	—	1	2	4	—	1	2	4
加标回收率 Spiked recovery/%		—	71.3	81.5	87.6	—	74.7	76.1	77.0	—	71.3	74.4	83.1

Table 5 Comparison with literature methods

目标物 Analyte	基质 Matrix	检测方法 Monitoring method	前处理方式 Pretreatment	耗时 Time	有毒有害试剂Toxic reagents	试剂毒性大小/量 Toxicity	操作难易度 Operation	检出限 MDL	文献 Ref.
MeHg	Sediment	GC?ECD	Enrichment of thiol cotton	6~8 h	Benzene	High toxicity	tedious	0.02 μg/kg	GB/T 17132?1997
MeHg	Sediment	GC?AFS	Acid leaching	3~4 h	CH₂Cl₂	High toxicity	difficult	——	［7］
MeHg	Soil	PT?GC?AFS	Acid leaching	5 h	CH₂Cl₂	High toxicity	difficult	0.8 μg/kg	［8］
MeHg	Biological Samples	ICP?MS	Ultrasonic assisted Solvent extraction	1 h	CH₂Cl₂	Large number	difficult	0.01 ng/mL	［5］
MeHg	Sediment	HPLC?CVAFS	Microwave assisted extraction	30 min	2? Mercaptoethanol	High toxicity	easy	0.58 μg/kg	［9］
MeHg	Soil、Sediment	CV?AFS	Ultrasonic assisted extraction	4 h	CH₂Cl₂	Large number	difficult	0.10 μg/kg	［10］
Alkyl mercury	Soil， Sediment	PT?GC?AFS	Alkaline digestion	4 h	Sodium tetraphenyl boron，methanol	Low toxicity	easy	0.02 μg/kg	［11］
MeHg	Soil	HPLC	Alkaline digestion	2.5 h	Tetrabutylammonium bromide	Low toxicity	difficult	10 μg/kg	［12］
MeHg	Soil， Sediment	GC?CVAFS	Acid leaching	2 h	CH₂Cl₂，tetraethyl borate	High toxicity	difficult	0.6 μg/kg	［13］
Hg²⁺ and MeHg	Water， Sediment	HPLC?ICP?MS	Solvent extraction	2 h	n?Butanol	Non? toxicity	difficult	0. 5 μg/L	［14］
Mercury species	Water， Sediment， Fish	CVAFS	Solvent extraction	——	Methanol	Non?toxicity	difficult	——	［15］
Mercury species	Sediment	HPLC?DBD plasma?CVG?AFS	Solvent extraction	12 h	CH₂Cl₂	High toxicity	difficult	0.42 μg/L	［16］
Alkyl mercury	Drinking water	PT?GC?AFS	——	30 min	Sodium tetraphenyl boron，methanol	Low toxicity	easy	0.0055 ng/L	［19］
Alkyl mercury	Food	HPLC?AFS	——	1 h	——	Non?toxicity	easy	0.2 μg/kg	［20］
Mercury species	Fish	UV?CVG?H PLC?ICP?MS	Alkaline digestion	5 h	Methanol	Low toxicity	difficult	0.0093 g/L	［21］
MeHg	Sediment	HPLC?AFS	Microwave assisted extraction?solid phase membrane extraction	30 min	——	Non?toxicity	easy	0.2 μg/kg	This work

Table 5 Comparison with literature methods

目标物 Analyte	基质 Matrix	检测方法 Monitoring method	前处理方式 Pretreatment	耗时 Time	有毒有害试剂Toxic reagents	试剂毒性大小/量 Toxicity	操作难易度 Operation	检出限 MDL	文献 Ref.
MeHg	Sediment	GC?ECD	Enrichment of thiol cotton	6~8 h	Benzene	High toxicity	tedious	0.02 μg/kg	GB/T 17132?1997
MeHg	Sediment	GC?AFS	Acid leaching	3~4 h	CH₂Cl₂	High toxicity	difficult	——	［7］
MeHg	Soil	PT?GC?AFS	Acid leaching	5 h	CH₂Cl₂	High toxicity	difficult	0.8 μg/kg	［8］
MeHg	Biological Samples	ICP?MS	Ultrasonic assisted Solvent extraction	1 h	CH₂Cl₂	Large number	difficult	0.01 ng/mL	［5］
MeHg	Sediment	HPLC?CVAFS	Microwave assisted extraction	30 min	2? Mercaptoethanol	High toxicity	easy	0.58 μg/kg	［9］
MeHg	Soil、Sediment	CV?AFS	Ultrasonic assisted extraction	4 h	CH₂Cl₂	Large number	difficult	0.10 μg/kg	［10］
Alkyl mercury	Soil， Sediment	PT?GC?AFS	Alkaline digestion	4 h	Sodium tetraphenyl boron，methanol	Low toxicity	easy	0.02 μg/kg	［11］
MeHg	Soil	HPLC	Alkaline digestion	2.5 h	Tetrabutylammonium bromide	Low toxicity	difficult	10 μg/kg	［12］
MeHg	Soil， Sediment	GC?CVAFS	Acid leaching	2 h	CH₂Cl₂，tetraethyl borate	High toxicity	difficult	0.6 μg/kg	［13］
Hg²⁺ and MeHg	Water， Sediment	HPLC?ICP?MS	Solvent extraction	2 h	n?Butanol	Non? toxicity	difficult	0. 5 μg/L	［14］
Mercury species	Water， Sediment， Fish	CVAFS	Solvent extraction	——	Methanol	Non?toxicity	difficult	——	［15］
Mercury species	Sediment	HPLC?DBD plasma?CVG?AFS	Solvent extraction	12 h	CH₂Cl₂	High toxicity	difficult	0.42 μg/L	［16］
Alkyl mercury	Drinking water	PT?GC?AFS	——	30 min	Sodium tetraphenyl boron，methanol	Low toxicity	easy	0.0055 ng/L	［19］
Alkyl mercury	Food	HPLC?AFS	——	1 h	——	Non?toxicity	easy	0.2 μg/kg	［20］
Mercury species	Fish	UV?CVG?H PLC?ICP?MS	Alkaline digestion	5 h	Methanol	Low toxicity	difficult	0.0093 g/L	［21］
MeHg	Sediment	HPLC?AFS	Microwave assisted extraction?solid phase membrane extraction	30 min	——	Non?toxicity	easy	0.2 μg/kg	This work

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Determination of Methyl‑mercury by Microwave Assisted Extraction‑Solid Phase Membrane Extraction in Water Sediments

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