Using the Laboratory Information and Management System (LIMS), isocyanate results are converted to µmol/L, and Phenol results are converted to mmol/L and both results divided by the creatinine result (mol/L) to compensate for fluctuations in excreted human urine volume and concentration.

Jaffe-Kinetic Creatinine assays are performed using a Beckman AU480 Chemical Analyser. The limit of detection is 0.06 mmol/L, and the associated uncertainty is ± 0.03 mmol/L.

Isocyanate determination is performed by an accredited in-house methodology using High Performance Liquid Chromatography – Tandem Quadrupole Mass Spectrometer. The limit of Quantitation for 4,4-MDA is 0.50 µg/L (0.10 µmol/mol creatinine), 2,4-TDA is 0.50 µg/L (0.15 µmol/mol creatinine), 2,6-TDA is 0.50 µg/L (0.15 µmol/mol creatinine) and for 1,6-HDA is 0.5 µg/L (0.16 µmol/mol creatinine).

Phenol determination is performed by an accredited in-house methodology using a Gas Chromatography – Single Quadrupole Mass Spectrometer. Limit of Quantitation for Phenol is 1.0 mg/L.

Measurement of uncertainty is a parameter associated with a result of measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand. The measurement of uncertainty for Isocyanates, Creatinine and Phenols is estimated using the Eurochem CITAC guide Quantifying Uncertainty in Analytical Measurement and is a full estimate based on the in-house validation data using precision studies as well quality control data.

Associated Measurement of Uncertainty of the Analytes

The laboratory actively participates in an international external proficiency testing program, G-EQUAS (German External Quality Assessment Scheme) to ensure the highest level of accuracy and precision are maintained for the results produced.