Apparatus to measure multiple signals from a liquid sample
One or more homogenizing elements are employed in a flow through, multi-detector optical measurement system. The homogenizing elements correct for problems common to multi-detector flow-through systems such as peak tailing and non-uniform sample profile within the measurement cell. The homogenizing elements include coiled inlet tubing, a flow distributor near the inlet of the cell, and a flow distributor at the outlet of the cell. This homogenization of the sample mimics plug flow within the measurement cell and enables each detector to view the same sample composition in each individual corresponding viewed sample volume. This system is particularly beneficial when performing multiangle light scattering (MALS) measurements of narrow chromatographic peaks such as those produced by ultra-high pressure liquid chromatography (UHPLC).
1. An apparatus comprising:
an inlet entry volume configured to be connected to inlet tubing and configured to allow a liquid sample to flow from the inlet tubing, through the inlet entry volume, and into an inlet of a flow through cell configured to be viewed by detector elements;
a flow distributor configured to allow the liquid sample to flow from the inlet entry volume, through the flow distributor, and into the inlet of the flow through cell; and
a cell entry volume directly adjacent to the inlet of the flow through cell and configured to allow the liquid sample to flow from the flow distributor, through the cell entry volume, and into the inlet of the flow through cell,
wherein a diameter of the flow distributor is approximately equal to a diameter of the cell entry volume and said inlet entry volume,
resulting in a flow entering the flow through cell,
wherein the flow approximates plug flow as the flow enters the flow through cell.
2. The apparatus of claim 1 wherein the flow distributor is a mesh screen.
3. The apparatus of claim 1 wherein the flow distributor is a frit.
4. The apparatus of claim 2 wherein the mesh screen comprises stainless steel.
5. The apparatus of claim 2 wherein the mesh screen has a pore size of 25 μm.