ADC library sampling rate on Teensy 3.2

[pmartinet]

Hi,
I'm working on Teensy 3.2, and using ADC lib to sample A2 pin input (ADC1).
I read the samples and pass them (collected in array of 2048 samples) to arm_cfft_radix4_f32 function in order to perform fft.
I need to know the frequency step of the 1024 samples of FFT and the frequency of the 1024-th fft element.

My ADC setup code is:
adc->setReference(ADC_REFERENCE::REF_1V2, ADC_1); adc->setAveraging(16); adc->setResolution(16); adc->setConversionSpeed(ADC_CONVERSION_SPEED::VERY_HIGH_SPEED); adc->setSamplingSpeed(ADC_SAMPLING_SPEED::VERY_LOW_SPEED);

Thanks in advance.
Best Regards