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:
a retaining inlet manifold configured to be connected to inlet tubing and configured to allow a liquid sample to flow from the inlet tubing, through the retaining inlet manifold, and into an inlet of a flow cell configured to be viewed by detector elements; and
an annular distributor comprising a channel extending around a circumference of the distributor, an inner surface, and an empty region,
wherein the inner surface is porous,
wherein the distributor is configured to allow the liquid sample to flow from the retaining inlet manifold, through the inner surface radially into the empty region, and from the empty region into the inlet of the flow cell,
resulting in a flow entering the flow cell,
wherein the flow is well mixed as the flow enters the flow cell.
2. The apparatus of claim 1 wherein the inner surface comprises an annular frit.
3. The apparatus of claim 1 wherein the inner surface comprises a screen.
4. The apparatus of claim 1 wherein the distributor comprises a series of radial holes.
5. The apparatus of claim 1 further comprising:
a first seal proximate to a surface of the flow cell and proximate to a first side of the distributor,
a second seal proximate to a second side of the distributor and proximate to a first side of a window within the manifold,
wherein the first seal and the second seal are configured to contain the distributor in the manifold; and
a retaining ring proximate to a second side of the window and configured to hold the window in the manifold.