GENEQ > Biotechnology > Magnetic Susceptibility Balances

Magnetic Susceptibility Balances
 

BASIC PRINCIPLES OF MAGNETIC BEHAVIOR
Based on their magnetic properties, all substances can be classified into one of three groups, those attracted by a strong magnetic field, known as paramagnetic, those repelled, designated diamagnetic, and , finally, the most recognised class, ferromagnetic, unique in their ability to retain their own magnetic field. Ferromagnets are able to retain a permanent magnetic field since their free electrons are in close proximity and remain aligned even after the external magnetic field is removed. Unlike the ferromagnets, the magnetic properties of the diamagnetic or paramagnetic materials could only be observed and measured when these samples are held within a magnetic field applied externally.

THE MAGNETIC SUSCEPTIBLITY IS DEFINED AS
"The ratio of the intensity of magnetism induced in a substance to the magnetising force or intensity of field to which it is subject.

CALCULATION OF MAGNETIC SUSCEPTIBILITY
The volume susceptibility (v) is defined by
v = I ÷ H
Where:
I = Intensity of magnetism produced in a substance
H = Intensity of magnetic field applied externally
 
The Mass Susceptibility (g) is defined by
g = v ÷ d
Where:
d = density of substance
 
The calculation of g from the readings on the MSB is simple
Where:
C = Calibration constant of the balance
L = Length of sample in cm. (L > 1.5 cm)
m = Mass of sample in grams
R = Reading on MSB of sample in tube
Ro = Reading of empty tube

MAGNETIC SUSCEPTIBILITY AT THE MOLECULAR LEVEL
The nature of the electrons within a sample determine the magnetic properties. The magnetic forces that are generated are more less neutralised when two electrons become paired. Free unpaired electrons give rise to magnetic forces which are attracted to a strong magnetic field, and the strength of these attractive forces are in direct proportion to the number of free electrons. The presence of free electrons results in materials being classified as paramagnetic and the lack of them results in a compounds being diamagnetic. Crystallinity, chemical reactions, oxidation states, and virtually anything that can alter the electronic configuration of a compound, may also change the magnetic properties. Analogous to spectral measurements, magnetic susceptibility measurements are both qualitative and quantitative in nature.

BASIC DESIGN PRINCIPLE
The Traditional Gouy Balance
The Traditional Technique, developed by Gouy, employs a conventional laboratory balance and a large permanent magnet. The magnet remains stationary while the sample is caused to move, giving apparent gain or loss in sample weight.
 
The Evans Design
Both the MSB - MK1 and the AUTO work on the basis of stationary sample and moving magnets. Two pairs of magnets are placed at opposite ends of a beam making a balanced system having a magnetic field at each end. Introduction of the sample into the magnetic field attempts to deflect the beam and the movement is optically detected. A compensating force is applied by introducing a current through a coil between the other pair of magnets. The current required to maintain the original position of the balance beam is proportional to the force created by the sample; and the direction that the beam (magnetic field) moves indicates whether the sample is paramagnetic or diamagnetic which is shown by a plus or minus indication on the display.

TWO MODELS
The Mark 1 MSB
The AUTO MSB

APPLICATIONS OF MAGNETIC SUSCEPTIBILITY MEASUREMENTS

As all substances exhibit magnetic properties it is possible to use magnetic phenomena to identify, differentiate and quantitatively measure components and contaminants in mixtures non destructively. Occasionally the magnetic suscepibility measurement offers a unique solution to a difficult analytical problem. We are happy to consider any new applications for the MSB.
  • Wear particulate analysis directly on lubricating oils
  • Pesticide and pharmaceutical analysis by generation of free radicals
  • Examination of chemical reactions on a microscale
  • Characterisation of Ion exchange adsorption and desorptlon processes
  • Measurement of concentration and size of magnetic beads
  • Analysis of rare earth elements and their oxidation states
  • Qualitative analysis of metal complexes
  • QC of catalysts in the petrochemical and plastics industries
  • QC of Industrial diamonds for trace metal contaminants
  • Measurement of synthetic diamonds
  • Archaeological studies of soil samples to indicate human occupation
  • Measurement of the oxidation state of haernoglobin
  • Quality control in the fabrication of superconductors
  • A redox detector in flow injection analysis

RESULTS
The following table shows measured mass susceptibility values versus literature values (C = 1.000). Values Lit Value

SPECIFICATIONS
 
Detector Unit
Control Unit
Complete in Case
Size (HxWxD)
70 x 180 x 235 mm
45 x 100 x 180 mm
250 x 550 x 400 mm
Weight
2.2 kg
0.4 kg
4.0 kg
Battery 4 x AA cells - Rechargeable only. Full charge gives > 8 hours operation
External Supply 6-9 V d.c. (a.c. input adapter, 110V or 240V, supplied also serves as battery charger)

INCLUDED
Mark 1 MSB
  • Main unit
  • Calibration standard tube
  • 2 normal sample tubes
  • Operating manual
AUTO MSB
  • Main unit
  • Display/keyboard unit
  • Cable
  • Software
  • 2 normal sample tubes
  • 1 large sample tube
  • 1 liquid sample tube (stoppered)
  • 1 stoppered gas tube
  • Metal Carrying Case
  • Operating manual
  • Guide magnetic susceptibility

CAT. NO. DESCRIPTION
710 00 001 Mark 1 MSB, 220V, 50Hz
710 00 000 Mark 1 MSB, 110V, 60Hz
700 00 109 AUTO MSB, 220V, 50Hz
700 00 110 AUTO MSB, 220V, 50Hz
Accessories for use with AUTO and Mark 1 models
M9TUB002 Sample tube, normal bore (0.400 cm OD, 0.324 cm ID)
M9TUB007 Sample tube, narrowl bore (0.400 cm OD, 0.200 cm ID)
M9TUB003 Flow cell
M9TUB005 Sample tube, gas tight top
M9TUB008 Sample tube, gas stopcock
PD-126 sample tube holder
Accessories for use with model AUTO only
M9TUB006 Sample tube, narrowl bore (0.400 cm OD, 0.100 cm ID)
M9TUB004 Sample tube, wide bore (0.500 cm OD, 0.420 cm ID)
PD-104 Adaptor sleeve, wide to normal
M-AUTO Manual for AUTO
Accessories for use with model Mark 1 only
AGTSTP02 Torsion wire
CLAMP Transport clamp
M-MK1 Manual for Mark 1