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Tin is considered to be a priority contaminant by the Codex Alimentarius Commission. Tin can enter foods either from natural sources, environmental pollution, packaging material or pesticides. Higher concentrations are found in processed food and canned foods. Dissolution of the tinplate depends on the of food matrix, acidity, presence of oxidising reagents (anthocyanin, nitrate, iron and copper) presence of air (oxygen) in the headspace, time and storage temperature. To reduce corrosion and dissolution of tin, nowadays cans are usually lacquered, which gives a marked reduction of tin migration into the food product. Due to the lack of modern validated published methods for food products, an ICP-AES (Inductively coupled plasma-atomic emission spectroscopy) method has been developed and evaluated. This technique is available in many laboratories in the food industry and is more sensitive than atomic absorption. Conditions of sample preparation and spectroscopic parameters for tin measurement by axial ICP-AES were investigated for their ruggedness. Two methods of preparation involving high-pressure ashing or microwave digestion in volumetric flasks were evaluated. They gave complete recovery of tin with similar accuracy and precision. Recoveries of tin from spiked products with two levels of tin were in the range 99+/-5%. Robust relative repeatabilities and intermediate reproducibilities were <5% for different food matrices containing >30 mg/kg of tin. Internal standard correction (indium or strontium) did not improve the method performance. Three emission lines for tin were tested (189.927, 283.998 and 235.485 nm) but only 189.927 nm was found to be robust enough with respect to interferences, especially at low tin concentrations. The LOQ (limit of quantification) was around 0.8 mg/kg at 189.927 nm. A survey of tin content in a range of canned foods is given.
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PMID:Determination of total tin in canned food using inductively coupled plasma atomic emission spectroscopy. 1232 43

Among the "traditional" hydride-forming elements, lead is probably the most difficult, and its determination in this form has rarely been reported in the literature. In this paper a simple and rapid method, axial-view inductively-coupled plasma optical-emission spectrometry using on-line hydride generation (HG-ICP-OES) from samples prepared as slurry, is proposed for determination of lead in environmental samples. The samples (20-50 mg, particle size <or=120 microm) were treated with 1 mL aqua regia in a 40-kHz ultrasonic bath for 60 min. The slurry was diluted to a final volume of 50 mL with a 10% m/v solution of (NH(4))(2)S(2)O(8). The concentrations of NaBH(4), tartaric acid, and (NH(4))(2)S(2)O(8), used for on-line plumbane generation were optimized by means of a complete factorial analysis applied to an aqueous standard solution and to the slurry of a sediment certified reference material (CRM). External calibration against aqueous standards in the concentration range 10-100 microg L(-1) was used for analysis of six CRM--three marine sediments, one river sediment, and two sewage sludges. Analysis of the filtered slurry showed that Pb was only partially extracted into the liquid phase. Several major concomitants tested did not affect the Pb signal. The detection limit (3s, n = 10) for 20 mg sample in a final volume of 50 mL was 5.0 microg g(-1). Tin was the only other hydride-forming analyte that could be determined satisfactorily with Pb; for tin the detection limit was 1.0 microg g(-1). The values obtained for Pb and Sn were not significantly different from the certified concentrations, according to the t-test at the 95% confidence level. Nine river sediments collected locally were also analyzed and the concentrations were in agreement with results obtained after total digestion.
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PMID:Determination of lead in sediments and sewage sludge by on-line hydride-generation axial-view inductively-coupled plasma optical-emission spectrometry using slurry sampling. 1724 88

Due to their widespread use in domestic and commercial premises, polyurethane foams, as either fragmented or bulk foam, are types of evidence commonly found at crime scenes. The traditional approach to determining the evidential value of polyurethane foam (PF) involves comparing recovered and control fragments under low and high magnification, under various lighting conditions, as well as the comparison of their respective dye spectra. As with most forms of trace evidence, chemical comparison is also desirable. In this work, two approaches to chemically comparing foam fragments were investigated, i.e. inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis of the Tin (Sn) content in different foam types; and gas chromatography-flame ionization detection (GC-FID) analysis of soluble components in PFs mobilized by dichloromethane. Seven different foam types were studied and their Sn content was found to be different. They also produced characteristic GC-FID chromatographic profiles whose compounds were identified with gas chromatography-mass spectrometry (GC-MS) analysis. This study suggests that incorporating chemical data obtained from GC-FID/GC-MS and ICP-OES into a case involving PF could be advantageous, as this will enable the forensic scientist to broaden the comparison between control and recovered fragments, and further assess the strength of the evidence. However, ICP-OES analysis is a destructive technique with a relatively short sample turnaround time, whilst GC-FID analysis is more time-consuming and non-destructive, requiring corroboration with GC-MS data. The values of these two analytical techniques in the forensic chemical characterization of PFs are discussed.
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PMID:A preliminary investigation into the comparison of dissolution/digestion techniques for the chemical characterization of polyurethane foam. 2107 94