3. Standard addition is one possibility to account for matrix effect. However it assumes that matrix effect is a proportional effect independent of the analyte concentration. In order to control this assumption analyst prepared both standards and post-extraction spiked samples at analyte concentration of 10 and 2.5 mg/kg.

Following results were observed:

**Standard 10 mg/kg** |
**Sample 10 mg/kg** |
**Standard 2.5 mg/kg** |
**Sample 2.5 mg/kg** |

7832180 |
6964080 |
2406174 |
827948 |

7718368 |
6722779 |
2434535 |
854663 |

7822817 |
7387993 |
2586852 |
764868 |

**Question 1: **Estimate matrix effect for 10 mg/kg and 2.5 mg/kg from the measured signals.

Please give the answer in percents with one decimal place and please use dot as decimals separator (i.e. please give 91.7% and not 0.917; 91,7% or 91.765%).

Matrix effect (10 mg/kg)

Matrix effect (2.5 mg/kg)

**Question 2: **Can standard addition be used in this case in order to account for matrix effect?