Ball and disc integrator

Precision of the TWO methods The electronic integrator is almost 3 times more accurate and precise than the ball and disc integrator ... 

The mechanical ball and disc integrator is rapid, precise, and accurate. Reproducibility between instruments, individuals, and laboratories is really quite good. The integrator itself is quite economical (less than 1000) but it does require a recorder compatible with the integrator. The limitation in the accuracy appears to be in the recorder itself since it is the recorder pen drive itself that actuates the integrator. Thus any dead band or damping in the response of the recorder will be reflected in the performance of the integrator. 

A final point of consideration is the measurement time required. Certainly electronic integration is by far the fastest and the ball and disc integrator would also be considered fast. The manual methods in increasing slowness would be peak height, height and width, triangulation, planimeter, and finally cut and weigh technique. 

The ball and disc integrator is capable of excellent results on all but the most exacting analyses. The recorder used with it should be of top quality and in excellent working order to obtain full capability of the integrator. 

Figure 6.34. Ball and disc integrator. (A) Block diagram. (B) Tracing (no. of counts are manually calculated ). ...

Typical Response Peaks. Figure 2 shows some typical response peaks for the HPLC separation of the saturates and aromatics in a typical vacuum gas oil. The curve in the upper portion of the figure is the response for the sample using the RI detector. After the saturates peak appeared, the backflush valve was switched and the attenuation changed as indicated in the figure. The peaks were very sharp and symmetrical and appeared in less than 10-min lapsed time from the point of injection. Base line drift was minimal and the areas of the response peaks were obtained with a ball and disc integrator on the strip chart recorder. 

Recorder—A recording potentiometer with a full-scale response time of 2 s or less must be used. If a manual method of area measurement, such as a planimeter, is employed, the chart speed must be at least 152 cm/h (60 in./h) to minimize errors in peak area measurements. This requirement is waived if a ball-and-disc integrator or an electronic integrator is employed. 

---