---
title: "Control Chart for Standard Blanks"
canonical: "https://servicedesk.maxgeo.com/space/MAXGEO/1083211877/Control%20Chart%20for%20Standard%20Blanks"
format: markdown
---
### Control Charts: Blanks


Blanks are standards which have no detectable amount of the elements of interest in them.  They are used to detect contamination either in the sampling or analytical process depending on what stage they are inserted.  As all results will be on or near the detection limit it is difficult to view the results in the same way as other standards.  


The following configuration is suggested so that blanks can be plotted against the detection limit rather than the expected value.  In this example 10x the detection limit is used as the upper warning value. 


**Blank Reference tblSYSQCReference:**

![image](media://3c6ac2eb-7f91-4201-8739-217052c7a876)

**Blank Reference Values: tblSYSQCReferenceValues**

To achieve plotting the analysed blank results, the standard id assigned to the samples must be consistent with the detection limits of the element and technique.  In the example below.  blanks are assigned to each lab.  If different analytical techniques are used, multiple records recording the different detection limits should be stored in the reference value table. 

To alter the definition of a bad result then the ExpectedMax should be altered.  

![image](media://3772d837-fb6b-4ced-ab31-50bd75a87fce)

**Plotting the Control Chart**

In the example below, the Expected Max value in the reference value table has been set to 10x the detection limit, and a filter applied to set all the BDL values to the detection limit. (0.01ppm).  

![image](media://3b38c65b-c08b-4291-8262-a3e3279572dc)

The method selected must match the method in the reference value table so that the correct min and max values are selected. 

![image](media://423e831f-153d-4772-b039-7fd1784e7f5b)

Select *Use Lib Values* for the Warning Limits.  Selecting the *High/.Low* in the Warning Limits will utilise the minimum and maximum values from the QC reference value table. 

The chart produced will therefore flag any result greater than 10x detection (ExpectedMax) as a Bad results.  

![image](media://3b08228e-a44b-41fc-a01e-7ba089f55e24)

![image](media://855f4f72-67e3-4b30-b62c-9e6bb7cff72c)

To ensure that the Outlier functionality is not used, set the expected outlier value in the ReferenceValue table to 100.