Method and 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 coiled tube comprising a coiled tube outlet,
wherein the coiled tube outlet is connected only to an inlet of a flow through cell configured to be viewed by detector elements,
wherein a bend radius to bore radius ratio of the coiled tube is less than 50,
wherein the coiled tube is configured to allow a liquid sample to flow into the inlet of the flow through cell; and
a flow distributor housed within the inlet of the flow through cell,
wherein the flow distributor is configured to allow the liquid sample to flow from the coiled tube, through the flow distributor, and into the flow through cell,
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 through cell is transparent.
3. The apparatus of claim 1 wherein the coiled tube is a helix.
4. The apparatus of claim 1 wherein the flow distributor is a mesh screen.
5. The apparatus of claim 1 wherein the flow distributor is a frit.
6. The apparatus of claim 4 wherein the mesh screen is comprises stainless steel.
7. The apparatus of claim 4 wherein the mesh screen has a pore size of 25 μm.
8. The apparatus of claim 1 wherein the coiled tube comprises stainless steel.
9. The apparatus of claim 1 wherein the coiled tube has a nominal inner diameter of 127 microns.
10. A method comprising:
flowing a particle bearing liquid sample through
a coiled tube comprising a coiled tube outlet,
wherein the coiled tube outlet is connected only to an inlet of a flow through cell configured to be viewed by detector elements,
wherein a bend radius to bore radius ratio of the coiled tube is less than 50; and
flowing the liquid sample from the coiled tube outlet through a flow distributor housed within the inlet of the flow through cell,
resulting in a flow entering the flow through cell,
wherein the flow approximates plug flow as the flow enters the flow through cell.
11. An apparatus comprising:
a coiled tube comprising a coiled tube outlet,
wherein the coiled tube outlet is connected only to an inlet of a flow through cell configured to be viewed by detector elements,
wherein a bend radius to bore radius ratio of the coiled tube is less than 50,
wherein the coiled tube is configured to allow a liquid mixture to flow into the inlet of the flow through cell; and
a flow distributor housed within the inlet of the flow through cell,
wherein the flow distributor is configured to allow the liquid mixture to flow from the coiled tube, through the flow distributor, and into the flow through cell,
resulting in a flow entering the flow through cell,
wherein the flow approximates plug flow as the flow enters the flow through cell.
12. The apparatus of claim 11 wherein the flow distributor comprises a mesh screen.