Interference by acetaldehyde is
observed when the acetaldehyde concentration is higher than approximately 250
mg/L in the 0.05 mL sample using the TSO2 Manual Assay Procedure (see Table 1).
At acetaldehyde concentrations higher than 250 mg/L the total sulphite
reaction is slower than stated in the TSO2 Manual Assay Procedure but generates the expected absorbance change when the reaction is allowed to complete. At a concentration of 1250 mg/L acetaldehyde in the sample, the TSO2reaction takes ~ 15 minutes to complete (at 25°C).
TABLE 1. Acetaldehyde Interference in the TSO2 Manual Assay. Reactions were performed using the TSO2 Manual Assay Procedure in 1 cm path-length cuvettes at 25°C.
[Acetadehyde] (mg/L) | [SO2] mg/L |
|
A1 |
A2 |
ΔAtotal SO2 |
% error |
0 | 300 |
| 0.042 | 1.477 | 1.435 | 0.0 |
31 | 300 |
| 0.041 | 1.458 | 1.417 | 1.3 |
63 | 300 |
| 0.042 | 1.502 | 1.460 | -1.7 |
125 | 300 |
| 0.042 | 1.498 | 1.456 | -1.4 |
250 | 300 |
| 0.041 | 1.466 | 1.425 | 0.7 |
625 | 300 |
| 0.042 | 1.347 | 1.305 | 9.1 |
1250 | 300 |
| 0.045 | 0.279 | 0.234 | 83.7 |