Flow accuracy

Pump Flow accuracy Run pump at 0.3 and 1.5 mL/min (65% acetonitrile/water) and collect 5 mL from detector into a volumetric flask. Measure time. < 5%... 

Flow accuracy is checked at 0.3 and 1.5mL/min with the column in place by measnring the time required to fill a 5-mL volumetric flask from... 

FIGURE 8 Example of HPCL pump power up, flow accuracy, and pressure pulsation verification document, as part of either an OQ or PQ protocol. Courtesy of PerkinElmer LAS, Shelton, CT. 

Pump Flow Accuracy and Pressure Pulsation Tests 7... 

Typically, the flow accuracy test is similar to the procedure used for OQ validation (described earlier in this chapter). The only thing that may differ is that the user may have specific flow requirements. 

This test could conceivably be performed holistically, as part of the injection reproducibility test (defined later). Using retention time as an indicator, such an approach would work provided the retention time for a test component was very stable from week to week. However, this is often not that easy to control consistently, since one often encounters column/mobile phase variations and other variables. Therefore, flow accuracy is typically not tested in this manner. 

It is recommended that OQ test the following on an HPLC system flow accuracy, pump compositional accuracy, pressure pulsations, column oven temperature accuracy/stability, detector noise/drift and wavelength accuracy, autosampler injection precision and carryover. 

Pressure loops are used to control the pump delivery rate, by the placement of a sensitive and highly responsive pressure transducer downstream of the pump heads. Once a normalized baseline is established, the sensing circuitry regulates motor speed to keep the pressure constant. A momentary decrease in pressure will cause the control loop to accelerate the motor in order to increase the pressure. Although the pressure loop is effective at maintaining a smooth pressure delivery, it is done at the expense of flow accuracy. 

The criteria used to judge the performance of a low-pressure pump include compositional accuracy, ripple, flow accuracy, and pressure accuracy. Compositional accuracy is tested by following the American Society for Testing and Materials (ASTM) procedure E-19.09.07.5 In this procedure, two bottles of eluent are used, one containing 100% methanol (eluent A) and the other containing methanol with a low concentration of acetone... 

Flow accuracy across a range of backpressures and solvent compositions can be evaluated by collecting and weighing timed aliquots of solvent. Pressure readings are plotted on a strip-chart recorder from a transducer signal output point. The recorded values should be within the manufacturer s specifications and as consistent and close to the programmed values as possible. 

If a mechanical system is chosen for drug administration, the appropriate infusion device must be selected based on its operating mechanism, flow accuracy, flow continuity,... 

Pressure Accuracy, Flow Accuracy, Flow Precision... 

Check the flow accuracy with measuring flask and stop-watch. It may be necessary... 

Control over product quality can best be aehieved by manipulating the material balance, free from disturbances in the heat balanee. This means that the composition co roller should set the flow of one of the product streams. Whether distillate or bottoms flow is chosen to be manipulated depends on their relative flow rates. The greater absolute flow accuracy will be obtained by mauipulatiag the smaller flow. So before a decision is made, a complete material balance should be drawn and the flows of the various streams eompared. 

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