The Australian perspective

This presentation deals with issues of comparability and traceability in food analysis in Australia from several perspectives. This includes the current national (Australian) and increasingly international (Codex) performance-based approach to food analysis. The Australian food regulatory process will be described, particularly those aspects that impact on the analysis of food in a regulatory sense. This section will also describe two areas where specific methods have been mandated in legislation and discuss two case studies where the analytical method has impacted on the elaboration of standards. Other areas to be covered include regulation/requirements relating to supply/availability of reference materials, the use of proficiency testing as a means of ensuring comparability, and, finally, some thoughts on what role BIPM/CCQM may play in the analysis of food.Electronic Supplementary Material  Supplementary material is available for this article at

Extraction of phenolic compounds and organic acids by liquid membranes

Liquid membrane emulsions were used to extract phenolic compounds and organic acids from their aqueous solutions. The emulsions contained caustic as the reactive agent. When the phenolic compounds and organic acids permeated through the liquid membranes into the emulsion droplets, they reacted with caustic and became ionized. The ionized species could not permeate through the liquid membranes and therefore were held in the emulsion droplets.

The conclusions of this recent investigation are:

(1) More than 99% of phenol and cresols can be extracted in less than 1 minute.

(2) Acetic and propionic acids can also be extracted but at much slower rates. However, if the amount of caustic is not sufficient to react with all the permeating compounds, the acids will be extracted preferentially to the phenols.

(3) The acids can only be extracted at low pH (acidic) whereas the phenolic compounds can be extracted at pH of 7.

(4) The extraction rates for phenol and acetic acid are the same in individual-compound and binary-mixture permeations.

(5) The extraction can be described by a mass transfer model.     

Measurement of PCDDs, PCDFs, and non-ortho-PCBs by comprehensive two-dimensional gas chromatography-isotope dilution time-of-flight mass spectrometry (GC x GC-IDTOFMS)

Comprehensive two-dimensional gas chromatography with isotope-dilution time-of-flight mass spectrometry (GC × GC-IDTOFMS) was used to measure polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar polychlorinated biphenyl (cPCB) concentrations in ash, sediment, vegetation, and fish samples. The GC × GC capability was achieved by using a quad jet, dual stage, thermal modulator. Zone compression of the GC peaks from modulation resulted in a significant increase of the signal intensity over classical GC-IDTOFMS. The GC × GC column set used an Rtx-Dioxin 2 phase as the first dimension (¹D) and an Rtx-500 as the second dimension (²D). The chromatographic separation of the 17 PCDD/Fs and the 4 cPCBs was attained in ¹D except for 2,3,7,8-TCDD and CB126 for which deconvoluted ion currents (DIC) were required to be reported separately. The Rtx-500 phase separated the bulk matrix interfering compounds from the target analytes in ²D. The instrumental limit of detection (iLODs) was 0.5 pg for 2,3,7,8-TCDD. The calibration curves showed good correlation coefficients for all the compounds investigated in the concentration range of 0.5–200 pg. GC × GC-IDTOFMS results compared favorably to those from conventional isotope-dilution one-dimensional gas chromatography-high resolution mass spectrometry (GC-IDHRMS). The comprehensive mass analysis of the TOFMS further permitted the identification of other contaminants of concern in the samples.     

Sensitivity-enhanced quantitative 13C NMR spectroscopy via cancellation of 1J(CH) dependence in DEPT polarization transfers

A scheme has been developed to eliminate virtually all signal intensity dependence on 1JCH in polarization transfers between 1H and 13C nuclei, reducing differences in signal intensity to only 1.5% over the entire natural 1JCH range. The scheme relies on the summation of time-domain data acquired with four suitably selected Delta delays so that the J dependence is essentially canceled in the final, signal-averaged free-induction decay. These Delta delays have been incorporated into the DEPT pulse sequence to create sensitivity-enhanced experiments for collecting quantitative 13C{1H} spectra. Four experiments, each with unique read pulse angles, give quantitative spectra with 200-300% more sensitivity than conventional 13C spectra acquired with inverse-gated 1H decoupling. The experiments are ideal for recording spectra with improved quantitative information or for substantially reducing the long acquisition times indicative of quantitative 13C experiments. The ability of the experiments to provide quantitative spectra was demonstrated with a simple ethylbenzene solution, however, they can easily be adapted to various applications for analysis of complex mixtures.     

Microdetermination of fluorine in organo-metallic compounds

Summary A simple and fast method for the determination of fluorine in organic compounds is given. After closed-flask combustion, fluoride is measured by a solid state electrode. The procedure is applicable to organo-metallic compounds, but boron interferes.

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Zusammenfassung Eine einfache Methode zur raschen Fluorbestimmung in organischen Verbindungen wurde angegeben. Nach Verbrennung im verschlossenen Kolben wird das Fluorid mit einer ionenspezifischen Elektrode gemessen. Das Verfahren ist für metallorganische Verbindungen anwendbar, aber Bor stört die Bestimmung.

     

Identification and quantitative analysis of nitrogen-containing polycyclic aromatic hydrocarbons in sediments

An integrated analytical methodology has been developed for determining nitrogen-containing polycyclic aromatic hydrocarbons, which enables quantitation of individual contaminants as low as 1 μg/kg in sediment samples. A cross-sectional profile from the Hamilton Harbour sediment samples was analyzed for azaarenes. These contaminants were separated by Soxhlet extraction, and pH adjustment allowed their isolation from different classes of neutral and acidic components. Separation and identification of the organic bases in each sample were achieved by using open tubular column gas chromatography with thermionic detection and HRGC-mass spectrometry. Organic bases present in the samples included mostly azaarenes such as acridines, benzacridines, azafluorene, benzoquinolines, azapyrenes, etc. Quantitation and environmental significance of these compounds are discussed. Recoveries of individual azaarenes at two different levels were evaluated. Data presented indicate that detection limits of this method are between 1 and 10 μg/kg. Recovery azaarenes from bottom sediment samples at concentration levels between 1 to 100 μg/kg is 81 ± 17%.     

Separation of Natural Food Pigments in Saponified and Un-Saponified Paprika Oleoresin by Ultra High Performance Supercritical Fluid Chromatography (UHPSFC)

The natural pigments in paprika were rapidly and efficiently separated by ultra high performance supercritical fluid chromatography. The separation of both un-saponified and saponified mixtures of paprika oleoresin were optimized, with run times of 10.6 min. Three different C18 columns, a cyano, silica and diol column, all 3 × 100 mm, with 1.8 μm particles were compared. The best separation for the un-saponified sample was found with an SB-C18 column, while the saponified samples were best separated on a bare silica, RX-Sil column. A SB-CN column allowed near optimum separation of both the unsaponified, and saponified samples, with similar run times. The best mobile phase was carbon dioxide (CO₂) modified with isopropyl alcohol (IPA), with a composition gradient. Fingerprints of several commercial pepper products indicated that one appeared to be colored with artificial dyes, while the color of a chili powder may have been enhanced with a paprika extract. Spectra, using CO₂ with IPA as modifier, produced a single maximum at 453 nm, which appears to represent up to a 30 nm solvatochromic shift from the maxima in most organic solvents. Acetonitrile (ACN) as modifier produced spectra with two maxima and a similar solvatochromic shift. These results appear to be the first on saponified paprika oleoresin samples using SFC. It is also the first detailed report on the separation of un-saponified samples. The results are up to six times faster than comparable results by HPLC. It appears that SFC is a viable, superior alternative to HPLC for the analysis of this important commercial product, without using ACN, or chlorinated solvents.

     

Rapid, Direct Quantitation of the Preservatives Benzoic and Sorbic Acid (and Salts) Plus Caffeine in Foods and Aqueous Beverages Using Supercritical Fluid Chromatography

The preservatives benzoate and sorbate, plus caffeine were rapidly separated and quantified, in just over 2 min, in a wide range of beverages and foods, using supercritical fluid chromatography (SFC). Fifteen beverages and 10 semi-liquid foods were evaluated. The benzoate and sorbate were originally present in the samples as the acid, or the sodium, or potassium salt. The aqueous samples were diluted 3:1 with acidified methanol, to insure the acids were protonated, then directly injected. The solutes were isocratically eluted from a 4 × 250 mm, 5 μm Diol column with 3.5 mL min^?1 of 8.5 % methanol containing 0.3 % acetic acid at 50 °C and a column outlet pressure of 150 bar. The real samples exhibited remarkably little interference. All the beverages were accurately labeled. However, many of the foods, such as salad dressings, mustard, etc., were mislabeled. The method was linear over a wide range with correlation coefficients for all three solutes >0.999. RSD’s were generally less than 1 %. The results agreed with the caffeine content on the labels within a few percent. Surprisingly, this appears to be the first published separation of benzoic and sorbic acid preservatives in food, and beverages using SFC, and one of a very few SFC applications where aqueous samples were simply diluted and injected. Compared to published references, the SFC method was found to be up to 7 times faster than HPLC, and eliminated the use of acetonitrile.