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# Why Wobb for 19F is so much dependant on the kind of sample while 1H not?!!

Normally for 1H, it doesn't matter so much to tune the probe with or without a sample inside. And during the measurement, when I change the sample, tuning (usually) doesn't change much. But for 19F: I have two samples, let's call them A and B. Tuning the probe without any sample in. Then I put sample A, and wobb => the minimum moves 0.86MHz to the right of the tune-line. Then I put sample B, and wobb => it moves 2.2MHz to the left of the tune-line. A and B are rather complex molecules/solvents I am using the Bruker Topspin 300MHz. Am I doing something wrong? If not, what is the explanation?

# Why Wobb for 19F is so much dependant on the kind of sample while 1H not?!!

Normally for 1H, it doesn't matter so much to tune the probe with or without a sample inside. And during the measurement, when I change the sample, tuning (usually) doesn't change much. But for 19F: I have two samples, let's call them A and B. Tuning the probe without any sample in. Then I put sample A, and wobb => the minimum moves 0.86MHz to the right of the tune-line. Then I put sample B, and wobb => it moves 2.2MHz to the left of the tune-line. A and B are rather complex molecules/solvents I am using the Bruker Topspin 300MHz. Am I doing something wrong? If not, what is the explanation?

# Why Wobb for 19F is so much dependant on the kind of sample while 1H not?!!

Normally for 1H, it doesn't matter so much to tune the probe with or without a sample inside. And during the measurement, when I change the sample, tuning (usually) doesn't change much. But for 19F: I have two samples, let's call them A and B. Tuning the probe without any sample in. Then I put sample A, and wobb => the minimum moves 0.86MHz to the right of the tune-line. Then I put sample B, and wobb => it moves 2.2MHz to the left of the tune-line. A and B are rather complex molecules/solvents I am using the Bruker Topspin 300MHz. Am I doing something wrong? If not, what is the explanation?

# Why Wobb for 19F is so much dependant on the kind of sample while 1H not?!!

Normally for 1H, it doesn't matter so much to tune the probe with or without a sample inside. And during the measurement, when I change the sample, tuning (usually) doesn't change much. But for 19F: I have two samples, let's call them A and B. Tuning the probe without any sample in. Then I put sample A, and wobb => the minimum moves 0.86MHz to the right of the tune-line. Then I put sample B, and wobb => it moves 2.2MHz to the left of the tune-line. A and B are rather complex molecules/solvents I am using the Bruker Topspin 300MHz. Am I doing something wrong? If not, what is the explanation?