Measurement of Mineral Oil Content in Crystal Polystyrene Using NMR by Oxford Instruments

Topics Covered

Introduction
Advantages of Nuclear Magnetic Resonance (NMR) over Other Techniques
Measurement of Mineral Oils in Crystal Polystyrene
Calibration and Mineral Oil Content
The MQC-23 NMR Instrument

Introduction

Mineral Oil is added to Crystal Polystyrene to increase its flexibility. This process requires a high degree of regulation, as the addition of too much mineral oil would dissolve the polystyrene polymer. Nuclear Magnetic Resonance or NMR can provide a rapid and effective means of monitoring the mineral oil content in crystal polystyrene.

Advantages of Nuclear Magnetic Resonance (NMR) over Other Techniques

  • NMR has a number of advantages over other techniques:
  • It can be calibrated to cover a range from 0 to 100%.
  • The measurement time is short (typically two seconds), allowing rapid sample throughput.
  • The NMR technique is non-destructive, so polystyrene analysed is still usable.
  • NMR is insensitive to air voids between polystyrene granules.
  • NMR is very stable over the long-term, so calibrations will rarely require adjustment.
  • NMR does not require the use of hazardous solvents.
  • Both weighing and non-weighing methods are available for this application

Measurement of Mineral Oils in Crystal Polystyrene

Five samples of crystal polystyrene were selected for the analysis of mineral oil content. Each sample was weighed into a tared 26mm glass tube and preconditioned for an hour at 105ºC, before being placed in an MQC-23 for analysis.

Figure 1. The MQC-23 NMR instrument from Oxford Instruments.

Calibration and Mineral Oil Content

The graph in Figure 2 illustrates the calibration of the NMR measurements against mineral oil contents determined by an alternative method for these samples.

Figure 2. Calibration of NMR data and reference values for oil content. Correlation: r = 1; SD = 0.07.

The quality of the calibration exhibited in Figure 1 is excellent, as indicated by the correlation coefficient of 1 and the standard deviation of 0.07.

The MQC-23 NMR Instrument

The MQC-23 NMR system is fitted with a 26mm diameter probe is a suitable instrument for this application. The Oil in Crystal Polystyrene package comprises:

  • MQC-23 with a built-in computer operating the latest version of Microsoft® Windows® (no separate PC is required).
  • MultiQuant software including RI Calibration, RI Analysis, and the EasyCal ‘Oil in Crystal Polystyrene’ application.
  • 26mm glass tubes.
  • Installation Manual.
  • ‘Oil in Crystal Polystyrene’ method sheet. In addition to this package you will also require:
  • A dry heater and aluminium block with 26mm holes for sample conditioning at 105ºC.
  • A precision balance. The instrument offers multiple advantages over others on the market:
  • High signal sensitivity.
  • Small benchtop footprint.
  • Low maintenance.
  • Recyclable sample tubes, lowering consumable costs.
  • Minimal sample preparation.

Source: Oxford Instruments

For more information on this source, please visit Oxford Instruments Magnetic Resonance

Date Added: May 6, 2010 | Updated: Jun 11, 2013
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