主题:【第十三届原创】Determination of methane, ethane, ethylene and propane in the Water by GC 水质 甲烷、乙烷、乙烯和丙烷的测定 气相色谱法

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菜鸟分析队发表于:2020/09/14 15:44:37 楼主 管理 分享 倒序浏览 只看楼主 回复 私聊
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Determinationof methane, ethane, ethylene and propane in the Water by GC

水质甲烷、乙烷、乙烯和丙烷的测定气相色谱法


1.      Scopeand application范围和应用

This method is forthe analysis of methane, ethane, ethylene and propane in water samples. The informationof target compounds is listed in Table1.

本方法适用于水中甲烷,乙烷,乙烯和丙烷的检测。目标化合物见表1

2.      Principle原理

Watersamples are analyzed by GC headspace technique using a flame ionization detector (FID).The target compounds are characterized by the relative retention time andmeasured by peak area quantitatively.

水样利用顶空-GC/FID测定。目标化合物通过保留时间定性、峰面积定量。

3.      Interferences干扰

Methane is a verycommon contaminant and occurs naturally in the atmosphere. Automobile exhaustcontains high levels of the target compounds so care must be exercised toprevent contamination in transport. Care must be also exercised in the sampleanalyses. Moisture interferes with the low level analyses. A procedure tominimize the injection of moisture into the GC is advisable.

甲烷是自然界大气中常见、自然发生的污染物。汽车尾气中含有较高的目标化合物,因此必须小心防止运输过程中带来的污染。样品分析过程中也需注意防止污染。水汽会干扰低含量化合物的分析,因此在进样过程中应尽量减少水汽进入GC的量。

4.      Equipmentsand apparatus仪器和设备

4.1 Gaschromatography: Agilent 7890A GC/FID with Agilent Chemstation software. 

气相色谱:安捷伦7890A GC/FID配备安捷伦化学工作站。

4.2 Column: Agilent PLOT-Q, 30 m × 0.53 mm ×40 μm, or equivalent.

色谱柱:安捷伦PLOT-Q, 30 m × 0.53 mm × 40 μm,或等同色谱柱

4.3 Autosampler: Agilent 7697 Headspace Autosampler.

自动进样器:安捷伦7697顶空自动进样器。

4.4 20 mL vial with crimp top septa lids, or equivalent.

样品瓶:20mL安捷伦透明顶空瓶,或同等型号样品瓶。

4.5 Syringes: 25 μL to 500 μL.

微量注射器:25 μL 500 μL.

5.      Standardsand reagents标样和试剂

5.1 Stock standards标准气体


Shanghai WeichuangInc., GBW(E) gases 1-3 mixed in % moles: Methane (4.95×10-3%),Ethane (4.97×10-3%) , Ethylene (4.96×10-3%) and propane(4.98×10-3%) balanced with nitrogen.

Shanghai WeichuangInc., GBW(E) gas 4 mixed in % moles: Propane (50.0 ×10-6%) balanced withnitrogen.

上海伟创GBW(E)混合气%(摩尔百分比/氮气):甲烷 (4.95×10-3%), 乙烷 (4.97×10-3%),乙烯 (4.96×10-3%) 和丙烷(4.98×10-3%)

5.2 Working standard solutions工作曲线

The concentration of standard gas sources is expressedas a mole fraction. In order to convert the amount of the standard expressed inmoles to a concentration, the practical ambient temperature and atmosphericpressure should be recorded every time and involved in the calculation.

标准储备气浓度以摩尔分数计。每次配标时应记录实际环境温度和压力参数,并代入计算,以便将标准储备气的摩尔浓度单位换算为以浓度为单位。

Ifnecessary, additional standards may be added to extent the calibration curve.

可根据需要增加工作曲线浓度范围。


Level

Methane Concentration

 

甲烷浓度(μg/L)

 

@ 25.0 C

Methane Concentration

 

乙烷浓度(μg/L)

@ 25.0 C

Methane Concentration

 

乙烯浓度(μg/L)

 

@ 25.0 C

Methane Concentration

 

丙烷浓度 (μg/L)

 

@ 25.0 C

Dilution
 
稀释

1

5

8.2

7.7

7.7

15 μL / 10 mL

2

10

19

15

24

31 μL / 10 mL

3

20

37

31

36

62 μL / 10 mL

4

50

93

77

48

154 uL / 10 mL

5

100

186

155

120

309 μL / 10 mL


6.      Procedures步骤

6.1 Sample collection and storage 样品采集和保存


Add 2 drops of 1:1hydrochloric acid (HCl) to the vial and add the sample by gently pouring thesample down the side of the vial without agitation. Cap quickly so there are nobubbles and prepare 2-3 vials. Ship the samples on ice at 4°C (±2°C) to the laboratory.

滴两滴盐酸(1:1 v/v)到40ml棕色采样瓶,然后沿着瓶子的侧壁轻轻添加样品(无震荡),迅速的盖上瓶盖压紧(无空隙无气泡),准备2-3瓶。在4°C (±2°C)使用冰袋条件下运输。

Samples are storedat 4°C (±2°C) prior to analysis. The sample container must notbe opened prior to analysis. The sample must be analyzed within 14 days fromsampling.

样品分析前保存在4°C (±2°C)条件下,样品分析前不得打开瓶盖,且必须在采样14天内完成测试。

6.2 Analytical Procedures分析过程

6.2.1 Headspace AutosamplerOperating Conditions顶空自动进样器操作条件
Parameters参数Descriptions条件

Oven炉温
50 °C
Loop60 °C
Loop Fill Time环填充时间0.2 min
Loop EQ Time环平衡时间0.02 min
Transfer Line传输线70 °C

Vial EQ. Time样品平衡时间
30 min
Pressure Time加压时间1 min
Injector Time进样时间1 min
Sample volume:进样体积:1 mL

6.2.2 GC Operating Conditions气相操作条件

Parameters参数Descriptions条件
Injector temperature进样口温度:70 °C
Detector temperature: 检测器温度:250 °C
Column: 色谱柱:Agilent PLOT-Q, 30 m × 0.53 mm × 40 μm
Initial column temperature and hold time: 初始温度和平衡时间:60 °C for 2 min;
Column temperature program: 程序升温:60-200 °C at 20 °C/min.
Column flow: 柱流速:5.0 mL/min
Carrier gas: 载气:Nitrogen
Sample injection:进样模式Split, split ratio 5:1

6.2.3 Initialcalibration初始校准

Establishautosampler and GC operation conditions according to section 6.2.1 and 6.2.2. Aset of at least 5 working standards is necessary. Calculate the mean responsefactor and the relative standard deviation (RSD) of the response factors foreach target compound. The RSD should be less than or equal to 15%.

根据6.2.16.2.2设定仪器条件,至少建立5个标准曲线点。计算每个目标化合物的平均响应因子和相对标准偏差(RSD),相对标准偏差在15%以内。

6.2.4 Continuing calibration check (CCC) 连续校准核查

The mediumcalibration standard is used to check initial calibration every 20 samples. Continuingcalibration must be repeated if the recovery is greater than 25%.

20个样品用标线中间浓度点进行连续校准核查,若连续校准的回收率大于25%则必须进行或者维护仪器重新配置标准曲线。

6.2.5 Sample preparation样品的制备

Obtain watersamples from refrigerator. Fill labeled 20 mL vials with 10 mL of sample. Usinga crimp top tool, secure tightly septa lids on each vial preventing gas loss.Allow samples to come to room temperature. Load sequence onto instrument andplace vials in corresponding spaces on autosampler.

  从冰箱中拿出样品,用5mL 微量注射器移取10 mL样品到干净顶空瓶中,用压平器压上顶空盖,压紧不漏气。取样过程要迅速,无暴曝,无震荡。排样上机。

6.2.6 Sample analysis 样品分析

Samples areanalyzed according to section 6.2.1 and 6.2.2. If result exceeds the limits ofthe initial calibration range, a dilution of the sample must be analyzed.

根据6.2.16.2.2部分分析样品,若样品浓度超过标准曲线则根据需要稀释样品。

6.2.7 Calculation 计算

For water sample,if dilutions were performed, the appropriate factors must be applied to samplevalues.

C (μg/L) = Cinstrument reading (μg/L) x Dilution Factor

Report in μg/L, accurateto 0.1.

水样,如果有稀释稀释倍数必须参与计算

C (μg/L) = C 仪器读数(μg/L)x 稀释倍数

μg/L为单位报告,精确到0.1

7.      QualityAssurance and Quality Control 质量保证与质量控制

(1) The continuing calibration check is analyzedevery 20 samples. The recovery for each analyte must be within ± 25%.

20个样品做一个曲线中间点校准,所有目标化合物回收率必须在±25%以内。

(2) A method blankis analyzed every 20 samples. All analytes should below the limit of report.

20个样品做一个空白,所有目标化合物需低于检出限。

(3) Sample duplicates: The acceptance criterion forsample duplicates is less than 30% RPD.

20个样品做一个平行样,平行样的RPD小于30%

(4) LCS: 60 mL of the gas standard are spiked into the 10 mLnitrogen bubbled DI water (methane concentration, 20 mg/L) and immediately capped with crimp top septacap. The acceptance criteria are recoveries between 70% to 130%.

LCS:每20个样品做一个LCS,选择标线的中间浓度点且做法类似。LCS回收率在±30%以内。

(5) MS/MSD: 60 mL of the gas standard are spiked into the 10 mLsample (methane concentration, 20 mg/L) and immediately capped with crimp top septacap. The acceptance criteria are recoveries between 70% to 130% and agreementbetween the two spikes within 30% RPD.

MS/MSD:20个样品做一套MS/MSD,选择标线的中间浓度点且选择相应的样品做溶剂介质。MS/MSD回收率在±30%以内, MSMSDRPD30%以内。

8.      Methodperformance 方法性能

8.1 Table 2 lists the method precision and accuracy using laboratoryfortified blanks with target compounds at different concentrations.

2列出了目标化合物在不同浓度下的方法精密度和准确性。

8.2 Table 3 lists LOR of Methane, ethane, ethylene and propane in watersample.

3列出了水样中目标化合物甲烷,乙烷,乙烯和丙烷的检出限。

9.      References参考文献

9.1 USEPA RSKSOP-175, 2004. Standard operating procedure. Samplepreparation and calculations for dissolved gas analysis in water samples usinga GC headspace equilibration technique.

9.2 Technical Guidance for the Natural Attenuation Indicators: Methane,Ethane, and Ethene. USEPA, Region1, 2002.

      Table 1 Methane, ethane, ethylene andpropane detected by this method


Compounds化合物

Formula

CAS NO.

Methane甲烷

CH4

74-82-8

Ethane乙烷

C2H6

74-84-0

Ethylene乙烯

C2H4

74-85-1

Propane丙烷

C3H8

74-98-6


Table2 Accuracy and precision data for water samples (n=8)


 

Compounds

 

Approximate  Retention Time (min.)

 

Spike 10  μg/L

 

Spike 20  μg/L

Average

Recovery  (%)

RSD (%)

Average

Recovery  (%)

RSD (%)

 

Methane甲烷

1.651

9.64

96

3.66

18.4

92

2.53

 
 

Compounds

 

Approximate Retention Time (min.)

 

Spike 19 μg/L

 

Spike37  μg/L

 

Average

Recovery  (%)

RSD (%)

Average

Recovery  (%)

RSD (%)

 

Ethane 乙烷

2.791

17.4

92

3.51

34.7

94

2.15

 
 

Compounds

 

Approximate Retention Time (min.)

 

Spike 15 μg/L

 

Spike 31  μg/L

 

Average

Recovery  (%)

RSD (%)

Average

Recovery  (%)

RSD (%)

 

Ethylene乙烯

2.436

14.5

97

3.31

29.1

94

2.40

 
 

Compounds

 

Approximate Retention Time (min.)

 

Spike 24 μg/L

 

 

Average

Recovery  (%)

RSD (%)

 

Propane丙烷

5.137

24.7

103

9.46

 




Table 3 LOR ofMethane, ethane, ethylene and propane in Water


Compounds化合物

LOR (μg/L)

Methane 甲烷

5.0

Ethane乙烷

5.0

Ethylene 乙烯

5.0

Propane 丙烷

5.0


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