Why do extracted samples and quality controls have lower signal compared to neat standards?

For research use only. Not for use in diagnostic procedures.

Answer

When a sample or a spiked quality control is extracted, the signal is usually lower than that of the corresponding standard made in pure solvents. There are two reasons behind the loss of signal in extracted samples:

1. Extraction efficiency and loss of analyte due to extraction: During sample preparation and extraction steps, such as SPE and evaporation, some of the analyte is lost, resulting in lower signal.

2. Matrix effect: The presence of matrix will suppress ionization of analyte and result in lower signal.

Understanding the differences between these two causes of signal loss and quantifying them is very important when troubleshooting an analytical method. Also see:
https://sciex.com/support/knowledge-base-articles/what-is-matrix-effect-how-to-quantify-it_en_us