CSols Instrument Interfacing — Configurable Calculations and Corrections
CSols Instrument Interfacing
Configurable Calculations and Corrections
Introduction
Today instrument interfaces are deployed in numerous laboratories and application areas. They are capable of operating with any instrument, CDS or LIMS. A primary focus of such products should be to automate what is currently done manually in the laboratory (and not just act as a simple data transfer mechanism to LIMS).
As data is transferred between instruments and LIMS, there is often a requirement for results to be modified in some manner. At first sight this might seem strange as most LIMS and many instruments have effective calculation packages. The reality is, however, that often these systems do not have either all the information to perform a calculation or they lack the precise calculation functionality necessary.
This article gives an overview of what calculation and correction facilities are included as standard within CSols’ Links for LIMS (L4L) product. It is aimed at the end user with analytical knowledge and points out many of the subtleties that have to be addressed to ensure that results are processed correctly.
Where Should Calculations be Performed?
Some calculations may be addressed in the instrument (or chromatography data system), the LIMS or the Integration software. In this case, customer preference may be applied easily. However, pragmatism often has to prevail because certain calculations may only be available in one application. .Normally it is more useful if the calculations are performed at the earliest opportunity.
Some Concepts
Methods
L4L uses configurable methods to handle what happens to data as it is transferred to and from Instruments and LIMS. There can be any number of methods configured on a system. Calculations and corrections are configurable as part of the method.
Cells
Within Links for LIMS, result or calculation data is placed in cells for a particular sample. So for example, a Tablet sample that LIMS wants sample results on (eg Sample 12345) might have a cell labelled Ashed Weight on the screen. The contents of the cell might be used in a calculation or may be produced by a calculation (or both). Cells might be visible to the operator or may be hidden to handle individual calculation steps.
In the rest of the document, these cells will be shown in square brackets eg [WEIGHT1] and [WEIGHT2]. So a simple calculation might be [ASHED WEIGHT] = [WEIGHT1] – [WEIGHT2].
Sample Types
L4L can use strong sample type based behavior. There can be any number of sample types defined in a method. An application needs to distinguish behaviors between LIMS samples, Blanks, Standards and Quality Control Standards for example. Consequently, all configurable behaviors that can be configured in a method (including calculations and corrections) can be different if necessary for each sample type.
So for example our Tablet sample 12345 might have its Ashed weight calculated entirely differently from sample Standard 1 even though both have a cell labeled Ashed Weight on the screen.
Sample type differences might also occur with LIMS samples. One product might require calculations to be performed differently from another.
Our experience of an extremely wide range of analytical situations has led us to the conclusion that generalized and configurable software calculation functionality (as opposed to programming scripting) can only operate effectively if strong sample typing is an integral part of the application.
Within Sample Calculations
L4L supports the following calculation operands:
^ Exponentiation
* Multiplication
/ Division
Integer Division
+ Addition
– Subtraction (or unary minus such as -15)
ABS Absolute value
CLG Log to base 10
EXP Exponentiation
LOG Natural Log
SQR Square Root
When configuring a method, cells are defined and given names for each sample type. Calculated cells are given formulae based on certain operators (see table) and named cells.
L4L then performs the calculations when results are available to do the calculation. So with [ASHED WEIGHT] = [WEIGHT1] – [WEIGHT2], the ASHED WEIGHT cell would get a value as soon as WEIGHT1 and WEIGHT2 were entered.
Conditional calculations can also be included:
§ an IF block
§ followed by a THEN block
§ and an optional ELSE block
ELSE blocks may hold further blocks, which must also conform to the above rules,e.g.:
§ IF cond1 THEN calc1
§ IF cond1 THEN calc1 ELSE calc2
§ IF cond1 THEN calc1 ELSE IF cond2 THEN calc2 ELSE calc3
Where:
§ cond n – comparison condition
§ calc n – calculation to be performed, to produce required result
Null values can be the result of conditional calculations. This enables a result not to be calculated in certain situations.
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In this example the three calculated results have been configured to generate Null values because the Room Temperature was outside fixed limits.
Across Sample Calculations
In some situations it is necessary to perform calculations across samples. In the example below, the single sample on LIMS might need to have the same operation performed 10 times and various cross sample calculations performed.
Within Links for LIMS, each of these twenty would be given a sample “qualifier”. These might be 01, 02 … maximum etc. Calculations can then be performed by referencing the qualifier name as well as the cell name.
Certain calculations e.g. Average, Maximum and Minimum work across all qualifiers with the same sample name.
In this figure, the grayed out cells are for results not required by LIMS. Bright Blue results cells are where the result was out of specification.
Drilling down on a result shows various details including the calculations and the actual values used in the calculations.
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In this case the Pass 1 indicates an order in which calculations were forced. L4L can explicitly define the order of calculations
Corrections
Certain common analytical corrections may be configured in the method. These are
§ Drift
§ Blank
§ Recovery
§ Dilution , weight, volume
These corrections are normally switched on or off for particular components in a run. For any given sample type it is possible to configure what corrections occur and even what order they are applied. It often matters whether dilution was applied before blank correction or vice versa for example.
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In the example above, wear metals in oil are being determined by ICP Optical Emission. Because of the viscosity of the oil and build up of carbon deposits, drift is unavoidable. L4L is used here not only to perform drift correction of the results but also to check that the drift is not too severe. Color coding of the check standard results indicates whether drift had been too large to allow for correction. This is the case with B(oron) where a yellow cell indicates a warning and red cell indicates a failure.
Drilling down into a cell shows (amongst other things) details of the corrections that have been applied
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The ability of L4L to be able to generate the “right” answer for an instrument through the combination of its corrections and calculations ensures that it is often used to process results from an instrument even when transfer to LIMS is not required. Indeed the software has been shipped directly for this purpose by instrument vendors such as PerkinElmer.
Specialist Functionality
L4L also contains advanced functionality for particular methodology. In the very common
example, shown below, for Pharmaceutical analysis for Impurities or Assay and Impurities, the requirement is to report the mean values for several replicate analyses back to LIMS for each impurity. Reporting mean values is normally a simple issue. However in this case the replicate unknown peaks appear at different relative retention times. Specific software functionality must be in place to allow the correct matching of unknowns between replicate samples as it is here:
Configuration and Security
Creating and modifying L4L calculations is normally a job performed by a suitably trained user – typically a senior analyst. All such configuration is performed through the L4L Configuration editor. This only allows authorized password controlled access. All changes to configurations are stored in an audit trail and electronic signatures are required when the system is used in regulated environments.
Summary
The calculation functionality within L4L has been developed to address specific requirements in real world analytical laboratories over a period of 15 years utilizing more than 200 man-years of applied experience. We believe that the existing configurable calculation capabilities are unmatched by other applications. However, we also recognize that new requirements appear from time to time and accordingly we provide a mechanism for such calculations to be incorporated in the standard product at no cost to the customer.
Calculations and corrections may be configured as part of the L4L method in a secure and compliant manner. Actual configuration of L4L is a straightforward task for a trained user with the appropriate analytical background and requires absolutely no programming or scripting.
Further Information
For further information please contact one of the CSols offices listed below. Alternatively visit our website at http://www.csols.com and complete the on-line enquiry form at http://www.csols.com/response.html
CSols Inc. CSols plc CSols plc
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Suite 405 Runcorn 6045 ET Roermond
Newark, DE 19713 Cheshire, WA7 4QX
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Tel: +1 302 731 5290 Tel: +44 (0) 1928 513535 Tel: +31 (0) 475 375170
Fax: +1 302 731 4820 Fax: +44 (0) 1928 572145 Fax: +31 (0) 475 375171
