• IMSS

THE FRAGMENT - 2016

On behalf of the committee of the IMSS I am very pleased to bring you the second issue of our newsletter ‘The Fragment’. The objective of the IMSS is to provide a forum for practitioners of Mass Spectrometry. To do this, a meeting of the IMSS is held each year. This year’s meeting will be held on 18th of May in the Moran Red Cow Hotel, Dublin.


On behalf of the committee of the IMSS I am very pleased to bring you the second issue of our newsletter ‘The Fragment’. The objective of the IMSS is to provide a forum for practitioners of Mass Spectrometry. To do this, a meeting of the IMSS is held each year. This year’s meeting will be held on 18th of May in the Moran Red Cow Hotel, Dublin.


We had an excellent meeting in May 2015 with a wide variety of Mass Spectrometry related presentations. In particular special mention goes to Caomhin Logue for his presentation on ’Sweetener Analysis using LC-MS-MS’. Caomhin is currently completing his Post Graduate Studies in UU Coleraine and was judged to have given the best student presentation by the IMSS judging panel. I hope you enjoy the newsletter and if you would like

to contribute please contact us at contact@imss.ie . We look forward to seeing you all at the next IMSS meeting.


Richie Maguire - IMSS Chairperson


DATES FOR THE DIARY 2016

  • IMSS annual meeting 18th of May, 2016, Red Cow Moran’s hotel, Dublin

  • Metabolomics 2016, 27th-30th June, 2016, Convention Centre, Dublin

  • ASMS annual conference, 5th-9th June 2016, San Antonio, TX

  • BSPR 2016 Meeting, 25th - 27th July 2016, University of Glasgow, UK

  • BMSS Annual meeting, 13th - 15th Sept 2016, Eastbourne Winter Gardens, UK


IMSS COMMITTEE 2016

  • Chairperson: Richie Maguire

  • Secretary: Edel Mullen

  • Treasurer: Julie Tierney

  • Communications: Brian Flatley and Philip White

  • IMSF Rep.: Peter Kenny

  • Committee Members: Stephen McClean, Steve Pennington, Gwen Manning, Patrick Ward, Mike Kinsella, Claire Tonry and Lorraine Brennan

  • Newsletter Editors: Brian Flatley, Philip White and Richie Maguire


PUBLICATION FOCUS: DETECTION OF PYRROLIZIDINE ALKALOIDS IN HONEY

Dr. Caroline T. Griffin


Pyrrolizidine alkaloids (PAs) are a large group of natural toxins produced by plants, several of which are known to be highly hepatotoxic and also have been shown to be carcinogenic. PAs have been associated with a number of livestock diseases and cases of human poisoning following contamination of staple foods, generally grain crops, or upon consumption of some herbal remedies. Other possible food sources of exposure include honey, milk and eggs. The European Food Safety Authority (EFSA) carried out a safety assessment of PAs in honey in 2011 and summarised that a health concern exists for high consumers of honey. A maximum daily PA intake limit of 0.007 μg per kilogram of body weight per day was recommended. However, there are no regulations for PAs in honey and as the European Union relies on imports for the majority of its honey, it is important that a testing protocol be implemented for PAs.


Research has been conducted at Cork Institute of Technology (CIT) under the ‘Safe and Healthy Foods’ project to investigate the presence of PAs in food using LC-MS.The focus of a recent publication in Food Additives and Contaminants: Part A was the development of a rapid protocol for the screening of honey involving minimal sample preparation via strong cation exchange (SCX) solid phase extraction (SPE) followed by an isocratic chromatographic method coupled to a triple quadrupole mass spectrometer. The significance of this protocol is that it allows for shorter analysis times facilitating a high-throughput, having a 50% improvement over previously published methodologies, which is particularly advantageous for regulatory testing laboratories.


This research group has determined, from a large scale survey of honeys over a three year period, that approximately 24% of retail honeys contain one or more PAs. Thus, high consumers of honey in Ireland are at risk of exceeding the maximum daily PA intake limit as proposed by EFSA. Of the indigenous honeys tested no PA toxins were detected. However, Ireland is heavily reliant on imported honey to meet consumer demand and although measures exist within the food supply chain to improve both food safety and traceability, there is still a distinct lack of same with regards to honey and PA toxins.


References:

  • Griffin CT, Mitrovic SM, Danaher M, Fur ey A. (2015). Development of a fast isocratic LC-MS/MS method for the high-throughput analysis of pyrrolizidine alkaloids in Australian honey. Food Additives and Contaminants: Part A, 32(2), 214-228.

  • Griffin CT, O’Mahony J, Danaher M, Furey A. (2015). Liquid chromatography tandem mass spectrometry detection of targeted pyrrolizidine alkaloids in honeys purchased within Ireland. Food Analytical Methods, 8(1), 18-31.

  • Griffin CT, Gosetto F, Danaher M, Sabatini S, Furey A. (2014). Investigation of targeted pyrrolizidine alkaloids in traditional Chinese medicines and selected herbal teas sourced in Ireland using LC-ESI-MS/MS. Food Additives and Contaminants: Part A, 31(5), 940-961.

  • Griffin CT, Danaher M, Elliott CT, Kennedy DG, Furey A. (2013). Detection of pyrrolizidine alkaloids in commercial honey using liquid chromatography-ion trap mass spectrometry. Food Chemistry, 136(3-4), 1577-1583.

METHOD DEVELOPMENT: THE USE OF LARGE VOLUME INJECTION (LVI) TO IMPROVE SENSITIVITY IN THE ANALYSIS OF ULTRA TRACE COMPOUNDS USING GC-MS/MS

Dr. Philip White.


With the increased need for improved sensitivity the analytical chemist is constantly challenged to provide robust, fit for purpose analysis in a variety of different matrices. Coupled with the inherent difficulties encountered in the analysis of ultra trace compounds found in food safety testing samples, concurrent legislation seems to require lower and lower LOQs.


LARGE VOLUME INJECTIONS (LVI) AND GCMS

Many of these issues can be overcome by increasing sensitivity of the instrument through different technical setups. Large volume injection (LVI) is one of the methods available to the analytical chemist. LVI techniques in GC mass spectrometry have received much attention in the last 10 years because of the reduced LOQs and with the improvements in HRGC-MS/MS SIM and MRM methods in relation to baseline noise levels means that the amount of analyte reaching the detector can vastly increase sensitivity. The figure below shows the instrumental set up, including the inlet temperature ramp, used on an Agilent 7000A GC-MS/MS instrument.

Typical GC-MS inlet and Injector parameters used in LVI (left) 2 µl (green) vs 20 µl (Red) Injection of the same polychlorinated biphenyl (PCB) sample (40 ppb) using LVI

The chromatogram above shows an injection of a 40 ppb PCB standard, first using a regular 2µL injection analysed in a splitless GC-MS/MS set up (in green) overlaid with a 20 µL LVI injection (Red). It is clearly obvious that the LVI injection offers far better sensitivity in relation to the regular splitless set up. This indicates that, once a sample is clean in relation to matrix interference, LVI can offer the analytical chemist the opportunity to increase sensitivity and accuracy of analysis at a level far below what is currently possible using regular splitless GC injections.


One of the factors affecting sensitivity of a GC-MS/MS instrument is the amount of solvent that can be injected before poor chromatography (i.e. band broadening, peak tailing etc) can compromise your analysis. Typical splitless GC-MS/MS trace analysis entails 1–2µl of your standards and samples being injected into an inlet (Figure 3) where the temperature (typically 250–300oC) vaporises the semi-volatile analytes facilitating transfer to the GC column under the influence of the mobile fluid. LVI injections typically transfer anything up to 100µl of the sample into the inlet.

Typical GC-MS inlet

Typically, the temperature in the inlet during the injection cycle is kept low, approximately 20oC below the lowest vaporisation point of the analytes in question. The split valve (shown left) of the inlet is open to waste removing the evaporated solvent from the sample analytes. Once the solvent is removed, the split valve is closed and the inlet temperature is ramped quickly to a temperature of 250–350oC vaporising the analytes and allowing them to enter the column. The analytes are now free of the affects of the solvent meaning that they can be easily separated on the column with little of the adverse affects found when injecting excess solvent.


IS LVI FOR ME?

LVI, if used correctly can dramatically increase the sensitivity of the instrument. The potential of LVI to increase confidence in structural identification and sensitivity/specificity means that if trace analysis (sub PPB) is a requirement in your laboratory then you should consider using LVI.


WHAT DO I NEED TO PERFORM LVI ?

LVI can be performed on any GC instrument with pretty much any detector as long as you have an inlet capable of changing between split and splitless modes. Many of the more modern instruments have multi-mode inlets capable of performing a variety of injection types (cold on column, pulsed split/splitless) so solvent vent modes are also quiet common. The graphite/vespel types of ferrules may also require changing to a different type e.g graphite/stainless steel) because of the increased pressure placed on them during the inlet temperature ramp. You will need to change the regular 1–10µl syringe for a larger one (e.g. 50µl).


Consider also changing the liner from the typical straight type to the internally dimpled/baffled type. These liner types work by spreading the larger volume injected, over more surface area enhancing the solvent vent and analyte transfer portions of the inlet cycle. The larger injection volume may also mean more matrix being sent onto your column which can cause blockades and hence a reduction in sensitivity. With LVI therefore, it may be prudent to ensure good sample clean up in your extraction methodology or perhaps invest in a back-flush type system to prevent this from occurring.


Lastly, with the acceptance of this method, many of the major manufacturers provide LVI software in their instrument operating systems which can make the method development of such techniques very easy and also reduce the reluctance involved in attempting to try something different. With a little method development the powerful LVI technique can rightly take its place amongst the arsenal of the analytical chemist.

O'Brien Science Centre

University College Dublin, Belfield

 Dublin 4, Ireland

  • LinkedIn Social Icon
  • Facebook Social Icon
  • Twitter Social Icon

© 2020 by IMSS. Proudly created with Wix.com