INDUSTRIAL & MANUFACTURING CHEMISTRY

 

ISO / EIC 17025 and CDFA Certifications

 

determination of product & reactant mass balances at each manufacturing stage


 

A.     Refrigerant Gas Analysis from Cargo Containers

From late 2011 through 2012, several deaths have occurred world-wide as a result of the explosion of refrigerant gas in temperature controlled cargo containers. The general consensus is that a counterfeit refrigerant gas was used in place of the genuine R134a (Norflurane or tetrafluoroethane). MAI was the first lab worldwide to have analyzed this dangerous counterfeit gas and remains today as one of only a very few worldwide to have done so.  We developed safe extraction methods for sampling in an oxygen free atmosphere that are now being used throughout the industry. Since then, a further consensus has developed that more than one type of counterfeit gas exists, athough the other types found to date are far less dangerous or even harmless in their use as compressor gases.

 

Description: Description: Description: Description: 1aDescription: Description: Description: Description: 2a

 

a)      MAI has the following expertise:

 

 

b)         Contamination Types

Up to present, R134a refrigerant gas contents fall into the following categories.

1)      Substantially uncontaminated R134a

2)       R134a that is contaminated with historical refrigerant gases, R12, R142b, R133a, and may be thought as contaminated with waste refrigerant gases.

3)      R134a that is contaminated with non-refrigerant chlorinated compounds, such as Dichlormethane (DCM or Methylene chloride), Chloromethane (CM) or Dichloropropane, which may be thought of as being contaminated with waste chlorinated solvents/gases.

4)      R134a that is contaminated with reactive gases such as Tetramethylsilane (TMS). Trimethylaluminum has been hypothesized but its presence has yet to be confirmed in published data. Reaction products Neopentane & methylbutane are present with TMS and it can be inferred from reaction stoichiometry that H2,g and CH4,g are also present. This is the only type of contamination that is known with certainty to be dangerous, but suspicions prevail about type 3 as well.

 

Actual real world sample reports follow:

 

  

Type 1:  R40 Detected

 

 

 

 

 

Type 2: R40 NOT Detected

 

 

 

 

c)          Note that these reports have a special quantitation style, as discussed next.

Conventional calibration curves are avoided because:

·         Absolute gas phase amount of R134a is not useful because it is dependent upon sample P-T

·         Target list changes as new contaminants are discovered

·         Custom made gas phase standards are expensive & have long manufacture times.

·         Some target compounds are likely unstable and thus have poor utility as analytical standards

·         High (±0.5%) accuarcy for R134a is very difficult to achieve using a calibration curve

MAI’s chosen quantitation basis is % Area, derived from target ion area times multiplier to yield TIC area, merits discussion:

·         % Area will always sum to 100% of user selected peaks, so that peaks unwanted for summation such as air (N2 & O2 resulting from valve rotation) or lab artifact peaks can be excluded. It provides needed accuracy & target list flexibility.

·         Target ion times multiplier reduces to a minimum errors arising from manual peak integration of poorly resolved peaks, and of very small peaks that sit on the tail of a larger peak. The following table demonstrates this point.


 

 

Comparison of Methods for determining Compound Areas from GC-MS Data: TIC Direct Integration vs. Target Ion * Fixed Multiplier

Sample ID

R134a

R12

R142b

WO 1201123

Area from target* multiplier

TIC Area, RTEINT.P

% calculated / TIC Integration

Reported % R134a of Total Area

Area from target* multiplier

TIC Area, RTEINT.P

Reported % R12 of Total Area

% calculated / TIC Integration

Area from target* multiplier

TIC Area, RTEINT.P

Reported % R142b of Total Area

% calculated / TIC Integration

-001A

1.48E+07

1.33E+07

112

99.18

1.23E+05

1.52E+05

0.82

81

 

-002A

1.93E+07

1.67E+07

115

99.76

4.61E+04

2.60E+05

0.24

18

 

-003A

1.92E+07

1.67E+07

115

99.98

4.16E+03

1.28E+04

0.02

32

 

-004A

1.49E+07

1.32E+07

113

99.20

1.21E+05

1.44E+05

0.80

84

 

-005A

2.28E+07

1.95E+07

117

97.87

4.69E+05

5.20E+05

2.01

90

2.63E+04

4.28E+04

0.11

61

-006A

1.89E+07

1.66E+07

114

99.39

1.05E+05

1.41E+05

0.55

74

1.20E+04

2.27E+04

0.06

53

-007A

1.70E+07

1.51E+07

113

99.90

1.44E+04

4.60E+04

0.08

31

2.55E+03

1.01E+04

0.01

25

-008A

1.67E+07

1.48E+07

113

99.99

9.86E+02

0.00E+00

<0.01

TIC not found

 

-009A

1.28E+07

1.16E+07

111

100.00

 

-010A

1.32E+07

1.19E+07

111

99.95

7.00E+03

2.34E+04

0.05

30

 

-011A

9.28E+06

8.43E+06

110

99.95

4.22E+03

2.18E+04

0.05

19

 

-012A

1.61E+07

1.42E+07

113

99.99

8.38E+02

0.00E+00

<0.01

TIC not found

 

-013A

1.71E+07

1.50E+07

114

100.00

 

 

-014A

1.78E+07

1.55E+07

115

100.00

 

 

-015A

1.63E+07

1.43E+07

114

100.00

 

 

-016A

1.81E+07

1.58E+07

115

100.00

 

-017A

1.53E+07

1.35E+07

113

100.00

 

Average=

113

 

 

 

·         The above table demonstrates that target ion area times fixed multiplier quite accurately reflects the R134a TIC area, averaging 113%. Also demonstrated is that this calculation is much more accurate than TIC areas for minor peaks (~<0.8%) are highly inaccurate relative to target ion based quantitation.

·         BFB target tuning (for example Agilent ChemStation) is recommended, as is using the same NIST 2008 “M reference” fixed multiplier that is used in the above example reports.

·         The largest peak on the chromatogram must be within the linear working range of the MS.

 

d)              Reactive contaminant gases are very easy to distinguish from R134a & easy to identify using GC-MS

 

 


 

Reactive gas sample peaks are identified in the following chromatogram.