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Entwisle John
Research analyst
LGC Ltd, Queens Road, Teddington, Middlesex, TW11 OLY, United Kingdom
+44(0)20 8943 7306
+ 44(0) 20 8943 2767
Entwisle John
Development of methodologies for the determination of species/total elements in food/environmental sample types at a metrological level in order to improve measurement capabilities. Where, possible using isotope dilution techniques including species-specific IDMS to provide primary reference values for the certification of reference materials and CCQM studies. Some examples of method development:
  • Enzymatic extraction and chromatography for mercury and methyl-mercury using HPLC-ICP-MS species specific isotope dilution  to provide primary reference values.
  • Procedure for the determination of total arsenic in food matrices (fish, bovine liver, herbal medicine) using high accuracy standard addition technique.
  • LC separation which enables the rapid determination of ultra trace levels of plutonium and uranium isotopes in food and environmental samples.
  • Microwave assisted acid hydrolysis for the accurate determination of methionine and selenomethionine in animal feed and selenium yeast supplements. Using HPLC-ICP-MS with Xe collision gas enabling species specific isotope dilution analysis.
  • A method for the simultaneous determination of total P, S, Se and As in food samples  employing  methane addition to the plasma gas and Xe/hydrogen mix in the collision cell.
  • A novel ion pair liquid chromatography separation of strontium from rubidium (wine digests).  Enabling accurate isotopic Strontium measurements to be made using a multi-collector ICP-MS.
  • A procedure for the determination of  PBDE and PBB (brominated flame retardants) in polymer using ASE extraction and HPLC-ICP-MS detection.
  •  Chromatography and extraction for the simultaneous determination of Cr(VI) and Cr(III) in Cr enriched yeast using isotope pattern de-convolution with double spiking species-specific isotope dilution mass spectrometry (IDMS).
  • GC, HPLC, nano-LC hyphenated    
  • Collision cell ICP-MS (Agilent 7500, Agilent 7700)
  • High resolution ICP-MS (Thermo Element 2)
  • Electrospray ion trap MS (Agilent 6300)

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