Baseline shift, reducing

Curved surfaces, debossing, and scoring affect the spectrum of a tablet as positioning is varied, but the effect of such factors can be reduced by the methods just discussed. Natural variations in tablet mass and hardness also affect a tablet s spectrum through baseline shifting. Work by Baxter involved a method of normalizing weight variations [96]. 

Case Study 1 Reducing Baseline Shift and Noise for Gradient Analysis... 

The common gradient for peptide separation consists of a binary solvent system containing in solvent A 0.1% formic acid and in solvent B 0.1% formic acid and 84% acetonitrile. If no high-sensitive MS detection is required, formic acid can be replaced by TFA. For solvent B, the amount of TFA has to be reduced to 0.08% to prevent baseline shift during the gradient run time. 

A 2° order polynomial Savitzky-Golay smoothing followed by standard normal variate [59] was applied to MIR spectra to reduce baseline shift and instrumental noise (Figure 7). 

Column Preparation— Any satisfactory method used in the practice of the gas chromatography that will produce a column meeting the requirements of 5.3 may be used. The column must be conditioned at the maximum operating temperature until baseline shift due to column bleedng has been reduced to a minimum. 

Column Conditioning—The column must be conditioned at the operating temperature to reduce baseline shift due to bleeding of column substrate. 

Column Conditioning—The column must be conditioned at the maximum operating temperature to reduce baseline shifts due to bleeding of the column substrate. The column can be conditioned rapidly and effectively using the following procedure ... 

If the x-data of an object are time-series or digitized data from a continuous spectrum (infrared, IR near infrared, NIR) then smoothing and/or transformation to first or second derivative may be appropriate preprocessing techniques. Smoothing tries to reduce random noise and thus removes narrow spikes in a spectrum. Differentiation extracts relevant information (but increases noise). In the first derivative an additive baseline is removed and therefore spectra that are shifted in parallel to other... 

Sampling mode effects The goal was to be able to measure at-line, with no sample preparation at all, using a fiber-optic probe or a remote sampling head. However, the area sampled by the hber-optic probe is much smaller than for the sample transport module. It was found that the remote (probe) spectra were very similar to the static (sample transport) spectra, but the baselines were shifted significantly higher and the absorbance peaks consequently reduced in intensity as before, the characteristic peak positions were not affected. Calibration models developed using spectra obtained with the hber-optic probe performed equivalently to those developed with the sample transport module. 

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