Why are there differences in Points Across Peak between Analyst® software and SCIEX OS software?

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

Answer

Why are there differences in Points Across Peak between Analyst® software and SCIEX OS software?

The primary reason for the difference lies in the sMRM dwell time calculation algorithm. SCIEX OS software introduces enhancements to better match the actual cycle time with the targeted cycle time, resulting in more efficient data acquisition.

Target Cycle Time:
This parameter allows users to control the overall cycle time, regardless of the number of experiments or MRM transitions in one cycle. The number of data points across a peak is determined by the LC peak width. For example:
- Cycle Time = 1 sec
- Peak Width = 20 sec
- Data Points Across Peak = 20

Factors Affecting Cycle Time:
Target cycle time may not always be met due to:
- High concurrency (many overlapping RT windows), leading to longer actual cycle times.
- Low concurrency (few overlapping RT windows), leading to shorter actual cycle times.
- Methods containing looped experiments or IDA experiments.

---

Enhancements in SCIEX OS software:

SCIEX OS improves dwell time calculation by considering looped sMRM methods and complex sMRM-IDA methods. Dwell time is calculated for each cycle within an sMRM retention time window using a generic equation that accounts for pause time and system overhead (Fudge Factor = 1.2).

Average Dwell Time:
The average dwell time for each cycle is calculated and displayed in the Mass Table. This value remains constant throughout the acquisition and is sent to the firmware at the start of the acquisition.

Efficiency:
SCIEX OS is generally more efficient than Analyst, resulting in more scan cycles and better data acquisition.

---

Examples:

Compound elutes in an area with few overlapping RT windows:
The average dwell time calculated by SCIEX OS software and Analyst® software is similar, leading to comparable peak intensity and "Points Across Peak." In this case, actual cycle time may be shorter than target cycle time.

Compound elutes in an area with many overlapping RT windows:
SCIEX OS software calculates a higher average dwell time than Analyst® software, resulting in higher peak intensity but fewer "Points Across Peak." In this case, actual cycle time may be longer than target cycle time.

---

Conclusion:
The differences in "Points Across Peak" between SCIEX OS software and Analyst® software are due to the improved dwell time calculation algorithm in SCIEX OS software. These enhancements ensure more efficient data acquisition and better alignment with the target cycle time, making SCIEX OS software behavior more reasonable and accurate.