Self test 10.4

1. An analyst has developed a LC/MS method for determining pesticides in tomatoes. One important aspect for your method is that each analyte is analyzed in a fixed time window.

Therefore it is important to verify if the method is robust enough from the retention times point of view (i.e. if the retention times are stable enough). Analyst uses isocratic elution with eluent composition 30% (v/v) of 1 mM acetic acid buffer with pH 4.5 and 70% (v/v) of acetonitrile. Analyst wants to study the effect of buffer concentration (0.9 mM to 1.1 mM)|pH (4.0 to 5.0) and organic modifier content (68% to 72%). Please indicate which experiments need to be carried out to evaluate the robustness with full factorial design.

3. The analyst is evaluating robustness with full factorial design. Most of all she is concerned about limit of detection. From previous knowledge she knows that LoD in case of her method is mostly influenced by ionization source parameters. Therefore she determined LoD dependence on nebulizer gas pressure and drying gas temperature (data given below).

Calculate how large is the effect of the nebulizer gas pressure, on the drying gas temperature and on the interaction of drying gas temperature* nebulizer gas pressure on the LoD!

Please use dots (.) instead of commas (,) for separating the decimals and present the answer with 2 decimals.

The effect of the factor A (nebulizer gas pressure) on LOD is   µg/L.

The effect of the factor B (drying gas temperature) on LOD is   µg/L.

The effect of the interaction of factors A and B (drying gas temperature*nebulizer gas pressure) on LOD is   µg/L.

Create an order of significants of effects and interactions from most impactful (top) to least impactful (bottom).

I (most impactful) factor A (nebulizer gas pressure)interaction of factors A and B (drying gas temperature*nebulizer gas pressure)factor B (drying gas temperature)

II factor B (drying gas temperature)factor A (nebulizer gas pressure)interaction of factors A and B (drying gas temperature*nebulizer gas pressure)

III (least impactful) factor A (nebulizer gas pressure)factor B (drying gas temperature)interaction of factors A and B (drying gas temperature*nebulizer gas pressure)