MTS Recommends... Water Purification Guide

Water Purification Guide
This buyer's guide from SelectScience provides a straightforward overview of the different methods of water purification used to produce the water used in laboratories.
From an HPLC perspective, water is a very common mobile phase component and effective troubleshooting requires an understanding of what could be present in the water being used. I think this guide may be helpful for this purpose.

Early Booking Deadlines Coming Up Soon!

MTS offer very generous discounts for early booking on our training courses. The deadline is coming up very soon for our London courses in April and Berlin courses in May. Submit a booking form, or just contact us, to secure our early booking rate by the 22nd March for London, and by the 10th April for Berlin.

The courses are:

Validation ofAnalytical Methods for Pharmaceutical Analysis
London (@ Jurys Inn Heathrow) on 10^th & 11^th April 2013
Berlin (@ Steigenberger Hotel Berlin) on 6^th & 7^th May 2013

Transfer of Analytical Methods for PharmaceuticalAnalysis
London (@ Jurys Inn Heathrow) on 12^th April 2013
Berlin (@ Steigenberger Hotel Berlin) on 8^th May 2013

How to Develop Stability Indicating HPLC Methods
London (@ Jurys Inn Heathrow) on 15^th & 16^th April 2013

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HPLC Troubleshooting Tip: Preventing Mobile Phase Problems When Using TFA

Trifluoroacetic acid (TFA) is a very common additive in reversed phase HPLC mobile phase. It is used extensively as an ion pairing reagent for peptide analysis but also as an acid modifier in a wide range of applications. Generally, TFA provides good peak shapes and reproducible chromatography and is compatible with a range of detectors, being volatile and of low UV absorbance.  However, if you are using TFA then there are a few things to be aware of which will ensure that you get the best results.

Impurities in TFA may cause noise, high background and spiking in your chromatography. These impurities may come from using low grade reagent or old bottles of TFA. I recommend that a suitable reagent grade is used (preferably HPLC grade) and also, to prevent stability problems, use small bottles so that an opened bottle of TFA is not sitting on your laboratory shelf for a long time. Be careful that a single bottle is opened at a time, especially if there are multiple users. Depending on your requirements, you may find it more convenient to use ampoules of TFA but, as you might expect, these are more costly.

TFA is a strong acid; amounts in mobile phase are typically ~ 0.1%v/v or lower. Concentrated TFA is quite dense (1.53 g/mL). This means that the difference between %w/v and %v/v is significant and may be enough to affect your chromatography. Therefore I recommend that you specify the units rather than just write ‘0.1%’ in your analytical procedure.

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HPLC Training Courses in Dublin – May 2013

Join us in Dublin this May to learn about how to get the most out of HPLC. We are offering four HPLC training courses from our 'How to...' series which are designed to provide both theoretical and practical advice, enabling straight to lab application. Whether you are a complete beginner or are already using HPLC we can help to develop your expertise.

The courses are as follows:

How to Run HPLC Methods: Monday 20^th May 2013
Ideal for anyone new to HPLC, this course will demystify all the parameters required to run a HPLC method.

How to Troubleshoot HPLC: Tuesday 21^st May 2013
Will suit HPLC users who want to be able to keep their HPLC system up and running, by sorting out problems as they occur.

How to Develop HPLCMethods – Part 1: Wednesday 22^nd May 2013 & How to Develop HPLC Methods– Part 2: Thursday 23^rd May 2013
These two courses can be taken together or separately and will describe a strategy for selecting the best HPLC method conditions for your separation.

We are offering the following discounts until 25th April 2013:

€350 per person per day, 2 days for €650, 3 days for €950 
or 4 days for €1250

Academic discounts and group discounts also available up to 25th April, contact us for a quote.

After 25th April all courses are charged at full price of €425 per person per day.

Note: All prices are quoted exclusive of VAT

Includes:

• Comprehensive handouts for each course containing useful reference data.
• Free tools to help you use HPLC efficiently.
• A Certificate of Attendance. There is an optional post training assessment to obtain a Certificate of Training.
• Expert Advice from the MTS trainer on your HPLC problems, both on the day of the training and after the event.

Click here for a printer friendly summary of these courses.

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Help on: Validation Shows that Method is Not Linear Through Zero

MTS HELPDESK
Do you have any problems relating to analytical chemistry for pharmaceuticals or training? Send your questions to the MTS helpdesk using our contact form.

Question:
"I am currently validating an assay method as per ICH guidance. I have a problem with the linearity determination. The method has a single concentration of calibration standard and therefore I believe that I have to show that the line goes through the origin but when I run the linearity standards at the range in ICH, i.e. 80% to 120% of the assay concentration, the intercept of the resulting line is not close to zero. Can you suggest what I should do?" 

Answer: 
"If an analytical method involves the use of calibration standards which are prepared at a single concentration (more than one standard solution is commonly prepared) then the actual calibration line generated for the analysis is drawn between the calibration standard concentration response and zero. This method of calibration will only work if the line does go through zero and therefore an important part of method validation is to confirm that this is the case.

A typical assay method will be designed such that the typical response of the analyte is at a concentration level where the response is not subject to random errors, such as injection repeatability and integration in the case of an HPLC method, and therefore is significantly greater than zero.

When validating an assay method the range to be considered is usually ± 20% of the expected sample concentration, expressed as 80 to 120% in the ICH validation guidance Q2(R1). This means that it seems sensible to investigate linearity using standards prepared over this range. However, when running the method in routine analysis the linear range of the method is from 0 to 120%. To assess whether the calibration line goes through the origin involves an extrapolation of the line from 80% down to zero. With this approach it is quite likely that the line derived from the linearity study does not go through zero but the method actually is linear through zero. 

I recommend that an extra linearity standard is included in the linearity study at a concentration equivalent to 40%. This represents the actual linear range of the method and reduces the extent of the extrapolation required.”

 

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