Research in the Chemical Metrology Area
This page contains more information for the following projects:
- End of Life Vehicles Directive
- Persistent Organic Pollutants
- GC-FID as a primary method
- Laser spectroscopy
- Trace element speciation
- GC for Africa
End of Life Vehicles Directive
This project is a continuation of the End-of-Life Vehicle (ELV) project that started in 2006/7 and aimed to address the requirements raised in the EU Directive 2000/53/EC on End-of-Life Vehicles. This directive requires automotive manufacturers to confirm that the levels of the toxic elements Cr(VI), Cd, Hg and Pb (collective termed Substances of Concern – SOCs) do not exceed the maximum levels specified, in any part of the vehicle, and includes a wide range of materials such as metal (various grades of steel, aluminium, etc.), plastics, rubber, glass, paint, etc.
2006/7 focussed on creating increased awareness among the various OEMs in the automotive industry. This was attained through extensive road shows and three popular articles published in automotive magazines. The analytical capabilities available in the automotive metrology laboratories as well as commercial laboratories supporting the automotive industry were assessed and while most laboratories are capable of conducting wet chemistry analyses by measurement with either AAS or ICP-OES, a definite need for laboratories providing more reliable results was identified. Subsequently, a laboratory database was compiled and is hosted by NLA.
2007/8 will target the electrical and electronic equipment (EEE) industry and the SOCs will include the two brominated flame retardants (BFRs) targeted by the Restrictions on the use of Hazardous Substances (RoHS) Directive 2002/95/EC.
For details, contact Ms. Retha Rossouw
Persistent Organic Pollutants
Persistent Organic Pollutants (POPs) are organic compounds of natural or anthropogenic origin that resist photolytic, chemical and biological degradation. They are characterised by low water solubility, and high lipid solubility, resulting in bioaccumulation in fatty tissues of living organisms. POPs are transported in the environment in low concentrations by movement of fresh and marine waters and they are semi-volatile, enabling them to move long distances in the atmosphere, resulting in wide spread distribution across the earth, including regions where they have never been used. Thus both humans and environmental organisms are exposed to POPs around the world and in many cases, for an extended period of time.
With evidence of long-range transport of these substances to regions where they have never been used or produced and the consequent threats they pose to the global environment, the international community has called for urgent global actions to reduce and eliminate releases of these chemicals. Initially, twelve POPs chemicals have been earmarked for phase out and elimination.
Exposure to POPs comes mainly from the consumption of food, especially meat, fish and dairy products. However, due to POPs ability to travel long-range, the POPs found in food do not always come from industries located near the farms where the food was produced, or from the pesticides used on these farms. Instead, POPs cross international borders, moving thousands of miles in the air or water before entering a source point. POPs are considered among the most dangerous of all the pollutants released yearly into the environment. Animal and human studies link a wide variety of health problems to exposure to persistent organic pollutants, such as reproductive abnormalities, birth defects, immune system dysfunction, neurological defects and cancer in humans and wildlife.
The NMISA has acquired novel analytical equipment to be used for the separation, detection and quantification of POPs compounds by comprehensive gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS). During 2006/7, initial work has started for the quantification of polycyclic aromatic hydrocarbons and pesticides using GC-TOFMS. The results submitted for CCQM-P31a.1: PAHs in solution were analysed and quantified using GC-TOFMS (LECO Pegasus III GC-TOFMS). These were the first results ever reported by an NMI for measurement equivalence capability using TOFMS. The results for CCQM-P31.c.1: Pesticides in solution were analysed and quantified using a classic quadrupole system (Agilent GC-MSD). The pesticide work has been duplicated using the GC-TOFMS and these results were discussed at the Analytica 2006 conference held at Kwa Martiane, Pilanesburg, SA. The work continues in 2007/8.
For more details contact Ms. Betty-Jayne De Vos.
GC-FID as a primary method
Flame ionisation detection for gas chromatography (GC) was invented in the 1950s, and by the early 1960s had been widely adopted as a robust universal detector for GC. It responds to all organic compounds but has a very weak response to highly halogenated and oxidised molecules. It does not respond to permanent gasses, or to water. Its main field of application is as a GC detector, but more recently, it has also been used to monitor organic volatiles in free-flowing gasses.
The aim of the project is to establish whether or not a flame ionisation detector (FID) (used commonly in gas chromatography) can be used to make primary ratio measurements of amount of substance of organic compounds. In chemical metrology, a primary method of measurement is a method having the highest metrological qualities , and whose operation can be completely described and understood, and for which a complete uncertainty statement can be written down in terms of SI units. The requirement for primary methods in organic chemical metrology is driven by the practical impossibility of preparing pure certified standards for every individual analyte.
This study proposes to eliminate the uncertainties in analyte mass contributed by the GC, by introducing gravimetrically measured quantities of organic compounds in the vapour phase direct to into the FID, and measuring its response under steady state conditions. The work is novel in that all published work on the FID’s response behavior has used the FID as a gas chromatography (GC) detector, so that the quantity of compound that actually entered the detector was always subject to large uncertainties due to injection errors, inlet discrimination, column effects and operating conditions.
For more details, contact Dr. Peter Apps.
Laser spectroscopy
The aim of the project is to develop a method or to purchase a commercial instrument to measure trace amounts of gas (first water and then other gases as analysis capability is expanded) in nitrogen using cavity ringdown spectroscopy (CRDS). This would further the NMISA gas metrology laboratory’s maintenance of the national measurement standard by improving the purity analysis capabilities of the laboratory.
Cavity ringdown spectroscopy (CRD) is a sensitive absorption technique in which the rate of absorption confined in an optical cavity is measured. The sample is placed inside an optical cavity consisting of two high reflectivity mirrors. A short laser pulse is coupled into the cavity; the light is reflected back and forth inside the cavity and with each reflection, a small fraction of the light leaks out of the cavity. The decay time is measured, i.e. the time dependence of the light exiting the cavity.
In an empty cavity, the decay time is determined by the mirror reflectivity and this provides a measure for the zero absorption baseline. The more a sample absorbs, the shorter the decay time.
The technique of CRDS may be considered as a primary method, being directly traceable to the SI unit of time, where a complete uncertainty statement can be written in terms of SI units.
For more details, contact Ms. Mellisa Janse van Rensburg.
Trace element speciation
The overall objective of this project is to establish an internationally recognised national analytical facility at the NMISA to do metal speciation analysis. There is a need to expand the analytical abilities and expertise of the NMISA’s analytical inorganic chemistry laboratory (IPS) to include speciation analysis.
Speciation analysis has been one of most prominent developments in analytical inorganic chemistry over the last few years. It relates to the analysis of metals in their different oxidation states, as the toxicity, bioavailability, bioactivity, transport in the organism, bio-geological distribution and transportation, will often be dictated by the particular species or form present in the sample.
Generally, identification and quantification of these species, requires a combination of current instrumental techniques (hyphenated techniques) such as HPLC-ICP-MS and GC-ICP-MS. Not only does coupling of these instruments require dedicated interfaces (matching of flows, organic eluent introduced into ICP, derivatization of non-volatile analytes, etc.), but preparation of samples becomes critical; while ensuring that species integrity are maintained during extraction and separation, analyte recoveries are often very low. Validation of methods therefore becomes crucial, but complicated, whilst only a limited number of CRMs are available. In establishing a speciation facility at NMISA, all these aspects would have to be addressed.
The project will address skills development through a series of collaborations, firstly focussing on more established methodology such as the speciation of Cr in automotive and electronic applications (RoHS and ELV Directives-requirements). Once this has been successfully completed, the focus will shift towards organo-metallic species such as is often encountered in environmental, health and pharmaceutical applications.
Ultimately, it is anticipated that this project would result in participation in IAWG intercomparisons where speciation would be required.
For more details, contact Ms. Sara Prins.
GC for Africa
The project consists of the presentation of two basic training courses:
- Capillary gas chromatography
- Calibration in chromatography and spectroscopy.
This course is the precursor to a longer-term preparation, where the aim is to include SADC laboratories in a planned GC intercomparison/pilot study planned for South African laboratories.
The courses will be presented in a SADC country (non South African) in order to make them accessible to larger numbers of trainees. Partial sponsorship or a minimum course fee to cover at least the venue costs will also be investigated.
For more details, contact Dr. Peter Apps.