GD Air Testing, Inc

Application Note by Using Nutech Preconcentrator System for PAMS Compounds in Lab Analysis

gdair — Fri, 16 Oct 2020 08:12:11 +0000

Abstract

Using a three-stage cryogenic system + GC/MS technology (Full Scan and/or SIM) 57 PAMS target VOC compounds (PAMS Mix by Linde) in air will be analyzed in a single run performance test. The results show that in 0.5-10.0ppb range the calibration, precision, accuracy, blank etc. all meet EPA TO-15 and PAMS requirements. The MDL may reach 0.02ppb or lower. It is within specifications for PAMS target VOCs in ambient air.

Introduction

“Using Summa or silica coated canister to take ambient air samples to the lab and using three stage cryogenic preconcentration system + GC/MS to analyze air VOCs is an approved reliable technology. US EPA published EPA TO-15 method on 1999 and has been continuously used in USA labs from then on. The major target compounds are the listed 65 VOCs. According to USA EPA experience China published HJ759-2015 in 2015 and the technology is similar with US EPA. In USA TO-15 method is also used for Photochemical Air Monitoring System (PAMS) which includes 57 hydrocarbon compounds. This application is focused on the PAMS 57 compounds analyzed in the labs. The application presents the method and conditions for using Nutech preconcentrator with a GC/MS system to achieve the above purpose.

Usually using the preconcentrator with a GC/FID can achieve this PAMS analysis. This is also used the Nutech preconcentrator system. Here we give the lab another approach by using the preconcentrator system with GC/MS. By doing this the lab may combined TO-15 and PAMS together and save their resources and cost for the analysis. Our results show that in a relative wide concentration range (0.5-10.0ppb), the analysis precision, accuracy, blank, initial calibration, continue calibration verification etc. all meet the QA/QC control requirements in EPA TO-15 and PAMS targets.

1 Experiment

1.1 Configuration of Used Instruments

Preconcentration System Nutech 8910/3610 Preconcentrator/autosampler, Nutech 2203 Static Dilutor, Nutech 2104 Canister Clean System and 6 L Summa or Silica coated Canisters.

GC/FID/MS：Agilent 8890/5977B（Optional Deans Switch with FID, but not used in this application) As shown in the following flow path.：

1.2 Standard Gases

The standard gases are all from Linde. ：

1.2.1 VOC Standards

57 Compounds PAMS Standard Concentration: 1.00ppm；

65 Compounds TO-15 Standard Concentration: 1.00ppm (as additional)

13 Compounds TO-11A Aldehyde Standard Concentration: 1.00 ppm (as additional)

1.2.2 Internal Standard/Surrogate Standard

Bromochloromethane, 1,4-Difluorobenzene, Deuterichlorobenzene, 4- Bromofluorobenzene

1.3 Making Working Standard

Connect 3 high concentration standard and certified clean 6-liter Summa canister to Nutech 2203 and set up 5 ppb as working standard to make the working standard. Do same as internal/Surrogate standard but concentration as 30ppb. The canisters were humidified with 50% humidity.

1.4 Instruments Parameters

1.4.1 8910 Method Set:

Trap 1: -160℃，Trap 2: -40℃，Transfer from Trap 1 to Trap to 20°C, Trap 2 desorption: 230℃. Focuser: -160°C，Focuser Injection impulse: 80℃，Transfer line: 40℃。

1.4.2 8890GC Set

Injection：250℃

Split Split/Splitless

Column Restek Rtx-1，60m×0.32mm×3.0μm

Buffer Column for Dean Switch：2.5m×0.18mm×0μm （May not use it if no Dean Switch not apply）

Temperature program：-40℃（ 5 min）- 10℃/min – 220℃（18min）

Carrier Gas Constant flow at: 1.8 ml/m

1.4.3 5977B MS

Ion Source：320 ℃

Connect temperature：250 ℃

Scan Full Scan/SIM

Scan range Full Scan: 25-300 amu

SIM: 26,27,29,30,31,39,40,41,42,43,95,128,130,114,117 amu

1.5 Initial Calibration

“8910/3610 loading 30ml, 60 ml, 120 ml, 240 ml, 300 ml, 600 ml Basic volume is 300 ml.

Using 5 ppb working standard gas the related concentration will be: 0.5 ppb, 1.0 ppb, 2.0 ppb, 4.0 ppb, 5.0 ppb, 10.0ppb.，The curve will be concentration ppb vs. Responses (Peak area). The internal/surrogate standard is loaded 20ml and the concentration is 6.67 ppb.

2 The Results

2.1 57 Compounds (with mixed 65 TO-15 compound and 13 aldehydes)

2.2 Ical

Using 0.5 ppb, 1.0 ppb, 2.0 ppb, 4.0 ppb, 5.0 ppb, 10.0ppbto set up an initial calibration the linear range is 1:20. By using Bromochloromethane and Duterochlorobenzene as internal standard (IS), Difluorobenzene and bromofluorobenzene as surrogate standard (SS), The calibration data shown as follows:

2.3 CCV

Using 5ppb working standard loading 120 ml concentration is 2.0pp. The CCV results are shown in the flowing table:

2.4 Blank Spike Recovery %（Accuracy %）

Spike 5.0 ppb into a canister as blank spike evaluation standard to Performed by the instrument the recovery as shown as follows: (10ppb is due to some compounds are replicate in standard. ）

2.5 Replicates

The duplicated samples are selected 0.5ppb and 2.0ppb with 7 points the data shows that the RSD% of most compounds are less than 10%.

2.5.1 Replicate Data, 0.5 ppb Level

2.6 The MDL Study

The data shows that the MDL of all 117 compounds are ＜0.1 ppb, and some compounds may go as low as ＜0.05 ppb,

MDL is based on 600mL Loading Volume with 7 replicate Run

Number	Compound	Spike Conc. (ppbv)	Avg. Conc. (ppbv)	% RSD	MDL
1	Bromochloromethane (ISTD)	5	5.00
2	Ethylene	0.5	0.41	14.67	0.09
3	Acetylene	0.5	0.53	11.46	0.10
4	Ethane	0.5	0.55	16.44	0.14
5	Propene	0.5	0.51	7.20	0.06
6	Propane	0.5	0.53	6.20	0.05
7	Isobutane	0.5	0.50	5.82	0.05
8	1-Butene	0.5	0.52	8.62	0.07
9	n-Butane	0.5	0.52	8.32	0.07
10	trans-2-Butene	0.5	0.53	8.51	0.07
11	cis-2-Butene	0.5	0.52	10.11	0.08
12	Isopentane (2-Methylbutane)	0.5	0.53	7.44	0.06
13	1-Pentene	0.5	0.52	8.50	0.07
14	n-Pentane	0.5	0.52	4.97	0.04
15	Isoprene	0.5	0.52	6.87	0.06
16	trans-2-Pentene	0.5	0.49	5.43	0.04
17	cis-2-Pentene	0.5	0.49	5.43	0.04
18	2,2-Dimethylbutane	0.5	0.50	7.70	0.06
19	2,3-Dimethylbutane	0.5	0.50	8.04	0.06
20	2-Methylpentane	0.5	0.52	10.20	0.08
21	Cyclopentene	0.5	0.58	17.41	0.16
22	3-Methylpentane	0.5	0.50	9.55	0.07
23	1-Hexene	0.5	0.53	7.24	0.06
24	Hexane	0.5	0.51	8.05	0.06
25	2,4-Dimethylpentane	0.5	0.52	8.01	0.07
26	Methylcyclopentane	0.5	0.52	8.28	0.07
27	Benzene	0.5	0.52	7.89	0.06
28	2-Methylhexane	0.5	0.51	7.46	0.06
29	1,4-Difluorobenzene (Circuit)	5	5.01	0.87	0.07
30	Cyclohexane	0.5	0.52	9.06	0.07
31	2,3-Dimethylpentane	0.5	0.54	9.86	0.08
32	3-Methylhexane	0.5	0.54	9.86	0.08
33	n-Heptane	0.5	0.50	8.51	0.07
34	2,2,4-Trimethylpentane	0.5	0.51	8.25	0.07
35	Methylcyclohexane	0.5	0.51	8.17	0.07
36	2,3,4-Trimethylpentane	0.5	0.05	8.84	0.01
37	2-Methylheptane	0.5	0.51	6.29	0.05
38	Toluene	0.5	0.51	7.74	0.06
39	n-Octane	0.5	0.50	8.73	0.07
40	3-Methylheptane	0.5	0.51	8.23	0.07
41	Chlorobenzene-d5 (ISTD)	5	5.00
42	Ethylbenzene	0.5	0.51	7.67	0.06
43	m-Xylenes	0.5	0.52	8.04	0.07
44	p-Xylenes	0.5	0.52	7.44	0.06
45	Nonane	0.5	0.52	8.86	0.07
46	Styrene	0.5	0.52	8.02	0.07
47	o-Xylene	0.5	0.51	7.64	0.06
48	Bromofluorobenzene (circuit)	5	5.04	0.49	0.04
49	isopropylbenzene (Cumene)	0.5	0.52	8.41	0.07
50	n-propylbenzene	0.5	0.52	8.08	0.07
51	1,3,5-Trimethylbenzene	0.5	0.52	7.15	0.06
52	m-ethyltoluene	0.5	0.52	8.97	0.07
53	p-ethyltoluene	0.5	0.52	8.97	0.07
54	n-Decane	0.5	0.52	8.14	0.07
55	o-ethyltoluene	0.5	0.52	7.80	0.06
56	1,2,4-Trimethylbenzene	0.5	0.53	8.21	0.07
57	1,2,3-Trimethylbenzene	0.5	0.52	8.15	0.07
58	m-Diethylbenzene	0.5	0.54	9.34	0.08
59	p-Diethylbenzene	0.5	0.52	8.44	0.07
60	n-Undecan	0.5	0.56	10.56	0.09
61	Dodecane	0.5	0.66	15.70	0.16

2.7 The Blank

After analyzed 600ml 10 ppb standard gas immediately load 300ml nitrogen blank and there is no compound tested above MDL. The blank chromatography shows the following.

3 Conclusion

3.1 Using Nutech 8910 preconcentrator system with GC/MS full Scan and/or SIM the 57 PAMS target compounds can be tested at one time performance. All QA/QC meets EPA PAMS requirements. ，

3.2 The method and instrument configuration needs is just GC/MS and no Deans Switch with FID is necessary. That give the lab to using existing instruments a good example of a successful application. The analysis cost can be saved by combined PAMS and TO-15 target compounds together.

3.3 The results also show that the linear range can be from 0.5ppb to 10ppb and is better than similar application (1.25-10ppb). The performance is stable and no carry over is another advantage.

Application Note by Using Nutech Preconcentrator System for TX 85 Target Compounds in Lab Analysis

gdair — Fri, 16 Oct 2020 08:10:04 +0000

Abstract

By Using three stage cryogenic preconcentration system + GC/MS technology (Full Scan and/or SIM) 85 TX (TCEQ) target VOC compounds (PAMS+TO-15 Mix by Linde and diluted by our lab) in air will be analyzed in a single run. The results show that in 0.5-10.0ppb range the calibration, precision, accuracy, blank etc. all meet EPA TO-15 requirements. The MDL may reach 0.02ppb or lower. It is good for the TX (TCEQ) 85 targeted VOCs in ambient air.

Introduction

Using Summa or silica coated canister to take ambient air samples to the lab and using three stage cryogenic preconcentration system + GC/MS to analyze air VOCs is an approved good technology. The US EPA published EPA TO-15 method which includes 65 target compounds in 1999 and has been continuously used in USA labs from then. In USA, TO-15 method is also used for Photochemical Air Monitoring System (PAMS) which includes 56 hydrocarbon compounds. The Texas (TECQ) requires 85 target compounds to be analyzed and reported to the State of Texas. Scientific research and new instrument development is focusing on combining all the targeted compounds together and analyzed them by using the same method and/or technology. This application note is trying to develop a method to cover 85 VOC compounds listed by TX (TCEQ) in a single sample run. Nutech team in both the USA and China’s applications air Lab and instrument R&D department in USA tried by using Nutech preconcentration system with GC/MS to achieve this goal. This application note is their recent results.

1 Experiment

1-1 Configuration of Used Instruments

Preconcentration System Nutech 8910/3610 Preconcentrator with autosampler, Nutech 2203 Static Dilutor, Nutech 2104 Canister Clean System and 6 L Summa or Silica coated Canisters.

GC/FID/MS：Agilent 8890/5977B（Optional Deans Switch with FID but not used in this application)

As Shown as flowing：

1.2 Standard Gases

The standard gases are all from Linde. ：

1.2.1 VOC Standards

57 Compounds PAMS Standard (Linde) ，Concentration: 1.00ppm；

65 Compounds TO-15 Standard Linde) ，Concentration: 1.00ppm；

8 Compounds TCEQ Special (By Liquid), Concentration: 1.00ppm,

1.2.2 Internal Standard/Surrogate Standard

Bromochloromethane, 1,4-Difluorobenzene, Deuterichlorobenzene, 4- Bromofluorobenzene，IS/SS Standard (Linde) Concentration: 1.00ppm

1.3 Making Working Standard

Connect 3 high concentration standard and certified clean 6-liter Summa canister to Nutech 2203 and set up 5 ppb as working standard to make working standard. Do same as internal/Surrogate standard but concentration as 10.0 ppb. The canisters were humidified with 50% humidity.

1.4 Instruments Parameters

1.4.1 8910 Method Set:

Trap 1: -170℃，Trap 2: -40℃，Transfer from Trap 1 to Trap to: 20°C, Trap 2 Desorption: 230℃. Focuser: -170°C，Focuser Injection impulse: 80℃，Transfer line: 40℃。

1.4.2 8890GC Set

Injection：250℃

Split Split/Splitless

Column Restek Rtx-1，60m×0.32mm×3.0μm

Buffer Column for Deans Switch：2.5m×0.18mm×0μm （Not use as no Deans Switch was needed）

Temperature program：-50℃（ 5 min）- 10℃/min – 220℃（18min）

Carrier Gas Constant flow at: 1.8 ml/m

1.4.3 5977B MS

Ion Source：320 ℃

Connect temperature：250 ℃

Scan Full Scan/SIM

Scan range Full Scan: 25-300 amu

SIM: 26, 27,41,42,43, 95,128,130,114,117 amu

1.5 Initial Calibration

“8910/3610 loading 30ml, 60 ml, 120 ml, 240 ml, 300 ml, 600 ml Basic volume is 300 ml.

Using 5 ppb working standard gas the related concentration will be: 0.5 ppb, 1.0 ppb, 2.0 ppb, 4.0 ppb, 5.0 ppb, 10.0ppb，the curve will be concentration ppb vs. Responses (Peak area). The internal/surrogate standard is loaded 30ml and the concentration is 1.00 ppb.

2 The Results

2.1 85 Compounds Chromatography (with mixed 65 TO-15 compound and 13 aldehydes)

2.2 Ical

2.3 CCV

Using 5ppb working standard loading 120 ml concentration is 2.0pp. The CCV results is shown in the flowing table:

2.4 BD/BSD %（Accuracy %）

Spike 5.0 ppb into a canister as a blank spike evaluation standard to performed by the instrument the recovery as shown as follows: (10ppb is due to some compounds are replicate in standard. ):

2.5 Replicates

The replicates are selected 0.5ppb and 2.0ppb with 7 points The data shows that the RSD% of most compounds are less than 10%.

2.5.1 Replicate Data, 0.5 ppb Level

2.6 The MDL Study

The data shows that the MDL of all 117compounds are ＜0.1 ppb, and some compounds may go as low as ＜0.01 ppb,

2.7 The Blank

After analyzed 600ml 10 ppb standard gas immediately load 300ml nitrogen blank and there is no compound tested above MDL. The blank chromatography shows as following.

3 Conclution

3.1 Using Nutech 8910 preconcentrator system with GC/MS full Scan and/or SIM the 85 TX (TCEQ) target compounds can be tested at one run performance. All QA/QC meets EPA TO-15 and TECQ requirements. ，

3.2 The method and instrument configuration needs are just GC/MS and no Deans Switch with FID is necessary. That give the lab to using existing instruments a good example of this application. The analysis cost can be saved by not using necessary gases supply for FID operation.

3.3 The results also show that the linear range can be from 0.5ppb to 10ppb and is better than similar application (1.25-10ppb). The performance is stable and no carry over is another advantage.

Application Note by Using Nutech 2104 Canister Clean System for Sample Train Clean and Certification

gdair — Fri, 16 Oct 2020 08:08:22 +0000

Abstract

By Using Nutech 2104 Canister Clean System, users may do the sample train clean and certification at professional way. The 2104 supplies a pure gas fill and vacuum cycles to clean the sample train automatically, and fill the blank gas, as well as standard gas to certify the sample train. This gives the lab a more professional way to clean and certify the sample train. This application note gives you a way to do sample train clean and certification according to EPA TO-15A step by step.

Introduction

The newly published US EPA TO-15A method requires you to clean and certify the sample train, to verify it with a blank and recovery. The sample train should include all the sampling parts such as sampling inlet, filters, valve and time controllers, tubes, flow controllers etc.The best way is to clean and certify all of those together. Nutech 2104 system can do all those steps automatically with a computer controlled program. This application will show you how to do this step by step professionally.

1 Experiment

1.1 Configuration of Used Instruments

Nutech 2104 Canister Clean System with humidify unit and 8 position manifold，Sample train to be cleaned and certified. This experience used Nutech 2703 sampling train, which includes the sample inlet with sample filter, MFC controlled flow controller, pressure sensor, start/stop control timer, all the tubes, and fittings. The system assembly as follows:

1.2 Distilled water and or Supper clean water

1.3 Ultra pure Nitrogen from a liquid nitrogen tank.

2 The Steps to clean the sample train

2.1 Connect sample train (2703 sampler or other sample train devices as you need) and canister to the manifold as shown as below:

2.2 Turn on the sample train path valve to make the highest flow rate for the flow path. (As Shown below)

2.3 In the parameter Setting, set the cycle number, vacuum parameters and pressurized pressure parameters as below:

Once everything is set, click Auto to start the automatically clean program.

The system will fill the pure gas from each connected sample train into the canisters to achieve the flush clean with the positive pressure and then vent the system. After vented the system, the vacuum pump continues pumping the system so that the whole sample train will continue to be cleaned, under vacuum condition with a revised direction. Once the system has reached the vacuum setting point the first clean cycle is done and system will start second clean cycle by starting the second filling. The automatic clean will continue until the set clean cycle is finished.

3 Certify the sample train

3.1 Wait until the clean step finished, and the system and canister reach the necessary vacuum.

3.2 Reset the sample train (Nutech 2703) flow according to the required flow rate and start/stop time as follows:

3.3 Reset the Nutech 2104 clean filling pressure in the computer interface.

3.4 If it is for a blank certificate, just leave the gas supplly line as clean.

3.5 If it is to spike the standard gas to the canister through the sample train, connect the supplly gas to a standard gas supplly with the certified concentration standard gas.

3.6 Start the manual filling procedure to take the certified (Blank or standard gas) into canisters until they reach the set pressure.

3.7 Finished the fill and take the canisters for certificate analysis.

4 Conclusion

Using Nutech 2104 Canister clean system to clean and certify the sample train is a professional practise for EPA TO-15A. This is an excellent tool for automatically clean the sample train as well as certify them. The clean cycles include filling positive pressure flow clean and the back flush flow under some vacuum. This procedure can make the sample train clean faster, better, and automatically. This also gives the sample train certification for both blank and standard process in a same setting to save the time. 8 or more position cleaner makes a group of devises clean and certified at the same time. This method and procedure can be widely used in all the labs which perform EPA TO-15 and TO-15A analysis.

Application Note by Using Nutech 2203 Dilutor for Canister Humidification

gdair — Fri, 16 Oct 2020 08:02:13 +0000

Abstract

By using Nutech 2203 Dilutor Liquid Injection function you may do the canister humidification quantitatively and easily. The humidification process will be controlled by computer program and a proprietary adapter is used to make sure the humidification process is going correctly.

Introduction

USEPA TO-15A and TO-15 method need to humidify the canisters before they are used for standard making or sampling. Humidifying the canisters is an especially important procedure to make sure the standard is correctly made, and the canisters are TO-15 or TO-15A compliant. By Using Nutech 2203 Dilutor Liquid Injection function you may do the canister humidification accurately. The humidification process will be controlled by computer program and a proprietary adapter is used to make sure the humidification process is quantifiable as well.

1 Experiment

1.1 Configuration of Used Instruments

Nutech 2203 Dilution System or 2202A Dilution System, Liquid Adopter, and dilution gases. Cleaned Canister, 3L, 6 L or other size Summa or Silica coated Canisters, Ultra-pure water, or distilled water.

Photos to show configuration and assembly of 2203, Liquid adapter, Syringe as above. A special syringe VICI adaptor with leading guide ferrule and septum to introduce the pure water from the syringe to the canister. To make sure the water is entering into canister as vapor but not liquid drops the 1/8” leading tube is bent or packing with some glass beads. The injected water firstly on the tube wall or the surface of glass beads to form a water film and then it is changed to vapor by the slow flow of the carrier gases (dilution gases). This may take 5-15 minutes, but it makes the humidification process identical each time and makes sure there is no water stuck somewhere in the path. Comparison with all other humidification methods this is more reliably and repeatable. Using a heated strip (Optional, 2203 provided and controlled) to heat the adapter to 120°C may make sure the water is evaporated.

2 The Steps to humidify the canister

2.1 Use the follow table to find out the water volume you will need to humidify your canisters.

2.2 Connect canister to 2203 as shown as below:

Make sure the adapter is correctly connected and it is leakage free.

2.3 Turn on in computer application interface as below:

In liquid injection section set the time to about 3 minutes, that is the time for you to add pure water. Set the final pressure as 3 psi (5‘’ Hg), that is your finished pressure of humidification.

Click Liquid to start flashing and then inject water from the adapter as show as below:

When finished you may wait 30 minutes or one hour then start your standard preparation or take the canister away for any other use.

3 Conclusion

Using liquid injection function of Nutech 2203 dilution system you may make your canister humidification is quantitative and easily. You may also combine the humidification and dilution together to make the calibration standard as one simple set up and one time. The water will be entering into the canister by a constant flow without losing water on the wall of the tube or other surface. The humidification process will be based on the controlled SOP and will be more reliable.