Simple techniques can save many hours of troubleshooting and downtime. Sample filtration should also be considered when there is a risk of insoluble material entering the system. The problem of blocked frits is highlighted in: ACE Ultra Low Dispersion, High Quality UHPLC and HPLC Pre-column Filters. Using in-line filters and column guards can reduce the incidence of blockages in a chromatography system, so preventing peak problems. If so, change the solvent and whenever possible, inject samples in the mobile phase. If the problem persists, the inlet is likely to be pluggedĪnother possibility is that the sample solvent may be incompatible with the mobile phase.If problem persists, the column may be fouled with strongly retained contaminants.If the analytical column is obstructed, reverse and flush it.Remove the guard column and attempt analysis.If there is contamination on the guard or analytical column inlet In modern columns it can be simpler to replace the column unless it is a specialized column. Does flushing or back-flushing the column help?.Is the method set up correctly with the right column? Is the mobile phase ok?.Fixing ProblemsĪs with all analytical instrumentation problem solving, it pays to approach the issues in a systematic way. The sample is spread out before it enters the column and all of the peaks in the chromatogram are split. Diffraction peak positions can be used to calculated unit cell dimensions. The effect is the same as with a blocked frit. The X-ray diffraction pattern is a sum of the diffraction patterns produced by. The analyzed material is finely ground, homogenized, and average bulk composition is determined. If there is a void in the packing material, some of the sample travels faster to the column. X-ray powder diffraction (XRD) is a rapid analytical technique primarily used for phase identification of a crystalline material and can provide information on unit cell dimensions. Hence the peaks for each component are split, and all peaks in the chromatogram are split. Since the delivery of the sample to the column is spread out, the separation of the sample is spread out. But if there is a blockage in the frit, then part of the sample is delayed and enters the column later. Normally the sample flows through the frit in a parallel band. A void in the packing at the head of the columnĪ blocked frit causes a spreading out of the sample as it enters the column.There are two common causes for splitting of all the peaks namely: If all of the peaks are split in an HPLC run, it is an indication of a problem happening before separation has taken place. This can be achieved by revisiting the method parameters such as mobile phase, temperature, flow rate or even column type. In this case the separation resolution needs to be improved. If this results in two discernible peaks, the problem could be two components eluting close together. One way of checking this is to inject a smaller sample volume. For instance, a distortion from cubic symmetry to tetragonal or orthorhombic (hexagonal or trigonal) symmetries should result in splitting of some peaks. If only one peak in a chromatogram is splitting or has a shoulder, the problem is likely to be something related to the separation. Samples and sample preparation are also contributory factors as determinants of the degree of peak splitting. It is not always an instrument problem that causes peak splitting. The splitting can affect all peaks or just one, and different effects can be attributed to different causes. They have the same base, are unexpected and can be caused by a number of factors. Theoretical development of the new approach is described in detail, which includes two linear regressions, \(\frac\), seeing details of the expressions in Eq. ( 10).Peak splitting is when a Gaussian peak gets a shoulder or a twin. In this paper, we propose a new approach to make simultaneous measurement of both residual normal and shear stresses. The total broadening of the diffraction peak is due to sample and the instrument. The observed line broadening will be used to estimate the average size of the particles. Diffraction pattern will show broadening because of particle size and strain. In particular, the conventional method can only be applied to measure the residual normal stress while leaving the residual shear stress unknown. When particle size is less than 100 nm, appreciable broadening in x-ray diffraction lines will occur. A drawback of the conventional d ~ sin 2 ψ method is the increased uncertainty arising from sin 2 ψ splitting when a significant residual shear stress co-exists with a residual normal stress. X-ray diffraction has been widely used in measuring surface residual stresses.
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