Have questions? Need help?
513.229.7000|800.874.2004

phone-1

Tekmar Talk Blog

UCMR3: Plug-and-Play, with some GC/MS tweaks

Posted by Teledyne Tekmar on Sun, May 13, 2012 @ 04:09 PM

The Unregulated Contaminant Monitoring Program (UCMR3) recently announced a new rule that requires public drinking water facilities to collect data on roughly 30 contaminants from January 2013 through December 2015. For the VOC portion of this rule, seven (down from the original nine) were selected for analysis by US EPA Method 524.3, using selective ion monitoring (SIM) to reach MRLs as low as 0.03 µg/L.

To evaulate this low-level method, we applied our standard 524.3 purge and trap parameters (524.3 application note). Table one displays adequate calibration curves across the low part-per-trillion level. The real issues started when we ran MDLs that did not return consistent results. Since it was the first run of this application, we did not know if the purge and trap parameters needed to be adjusted or if the GC/MS needed optimized.

Table 1: First GC/MS with Standard 524.3 Conditions

Analyte

Q Ion

Confirming Ion

Quadratic Regression Factor (r2)

MDL (ppt)

%RSD of MDLS

Chlorodifluoromethane

51

67

0.9951

5.49

27.9

Chloromethane

50

52

0.9952

2.72

20.8

1,3-Butadiene

54

53

0.9964

3.13

13.2

Bromomethane

94

96

0.9973

3.17

10.8

1,1-Dichloromethane

63

65

0.9980

3.71

15.7

Bromochloromethane

128

130

0.9989

3.77

13.8

n-Propylbenzene

91

120

0.9955

3.27

11.6

1,2,3-Trichloropropane

110

112, 75

0.9994

1.37

4.22

sec-Butylbenzene

105

134

0.9963

2.13

7.44

 

 

 

 

 

 

 

In parallel to the above test, we were also evaluating an application for 1,2,3-trichloropropane using SIM scan, at the ppt level, to meet California regulations. This system was optimized for low level analysis and could be used for an UCMR3 application as well. We once again used 524.3 purge and trap parameters and got very reproducible results. The results are displayed in Table 2 and in the UCMR3 application note (UCMR3 application note).

Many of the problems we encountered running the first GC/MS system can be attributed to water. However, there may be some optimizations required to discover the right split ratio and mass spec settings (voltage, gain, etc.) for this application.

Table 2: Second GC/MS – Optimized to run low level samples

Analyte

Q Ion

Confirming Ion

Quadratic Regression Factor (r2)

MDL (ppt)

%RSD of MDLS

Chlorodifluoromethane

51

67

0.9998

1.26

5.2

Chloromethane

50

52

0.9996

0.92

2.9

1,3-Butadiene

54

53

1.0000

2.16

9.4

Bromomethane

94

96

0.9998

1.09

4.0

1,1-Dichloromethane

63

65

0.9998

1.08

3.4

Bromochloromethane

128

130

0.9996

1.69

5.5

n-Propylbenzene

91

120

0.9997

0.87

3.3

1,2,3-Trichloropropane

110

112, 75

0.9994

0.86

2.7

sec-Butylbenzene

105

134

1.0000

0.59

2.1

 

 

 

 

 

 

 

We can apply the lessons learned from running these evaluations to optimize all our GC systems to run this application. Even though we specialize in sample prep instrumentation, we also devote many hours to method development and optimizing the conditions of the analyzer. Our analysts have a wealth of experience in method development for GC/MS and we are happy to share this knowledge with our customers when they need it.

Tags: Unregulated Contaminant Monitoring Program, UCMR3, drinking water, VOC, US EPA Method 524.3, selective ion monitoring, SIM

Subscribe via E-mail

Latest Posts

Posts by category

Follow Me