Two different digestion methods were followed, and both confirmed the presence of Baa and Fee, although the concentrations obtained by each teeth differed: higher values m/m% was obtained for all samples digested by HCI than for samples digested by acetic acid. Trace amounts of many natural occurring chemical elements such as sodium, magnesium and iron are needed for the proper functioning of the human body . However, there are also elements which are toxic to the human body such as mercury, lead, thallium, arsenic, cadmium, nickel, selenium and barium.
These metals are part of a loosely defined group known as “heavy metals”. The toxicity of most heavy metals are caused by the fact that they accumulate In the body over time, and interfere with biological castles, for example mercury, which Irreversibly Inhibits enzyme activity, and lead, which also inhibits enzyme activity and interferes with neurotransmitters, causing a wide range of side effects, some of which are life threatening.
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These heavy metals are used in many industrial manufacturing applications which include the manufacturing of pesticides, batteries, alloys, electroplated metal parts, textile dyes, and of particular importance for this study, plants. According to studies In the USA, It appears that paints are the leading cause of lead poisoning amongst children, and in particular, the paint found on toys. In an attempt to ensure the safety of toys, certain international regulations have been formulated. ASTM F-963 is a set of regulations that cover many different safety aspects related to toys, including their heavy metal content.
ASTM F-963 prescribes deferent digestion methods for different toys, all of them aimed at imitating the human digestive system, to determine how much of a certain element For paints the ASTM F-963 does not recommend total digestions of the toy, but rather crapping off the paint, as the surface of a toy is the part most likely to be digested by the human stomach. 5 Various techniques and instruments can be used to analyses the digested and prepared samples, the different choices mostly dependent on the concentration range, and the elements being tested for.
For this study the analysis method of choice was ICP-GOES, inductively coupled plasma optical emission spectroscopy. This type of spectroscopy uses an inductively coupled plasma to excite atoms and ions to emit electromagnetic radiation at wavelengths unique to reticular elements. The intensity of the emission can be correlated to the concentration of the specific element within a sample. One of the advantages of ICP- GOES is that it is not only able to detect specific elements quantitatively, but it is also capable of performing multi-elemental qualitative scans.
This is extremely convenient when determining in advance whether it will be worthwhile to analyses quantitatively for a specific element. ICP-GOES can also detect more than 70 elements, making it very versatile. 7 However, it does have a few disadvantages. It doesn’t have ere low detection limits, with its dynamic range being a high pimp range. This Instrument is also very expensive, and the argon used for the plasma, is also a rather expensive inert gas. Furthermore this instrument does not allow the detection of Isotopes, but fortunately this is of very little importance for this specific study. EXPERIMENTAL 1.
Preparation of standards Standards were prepared for calibration curves for detection of Baa and Fee. Baa(NON)2 Nas used to prepare a 5 pimp Baa stock solution, from which 2 pimp, 1 pimp, 0. 5 pimp, J. Pimp, 0. 1 pimp and 0. 005 pimp solutions were made up by dilution. Fesses. OH Nas used to prepare a 5 pimp Fee stock solution, from which 2 pimp, 1 pimp, 0. 5 pimp, 3. 1 pimp, 0. 05 pimp and 0. 02 pimp solutions were made up by dilution. The solutions Newer measured by ICP-GOES. 2. Sample preparation Paint was scraped down from yellow and from black toy cars. The yellow batch was mixed to homogeneities it, as was the black batch. 3.
Sample digestion according to method 1 5 paint sample of yellow paint (z 100 MGM) and 5 samples of black paint (z 100 MGM) Newer weighed out. To each sample was added acetic acid (10 ml, 4%). The samples Newer left to stand for 24 hours in darkness. The samples were then filtered, and the extractions diluted to 50 ml. All the samples were measured by ICP-GOES. 4. Sample digestion according to method 2 Newer weighed out. To each sample was added HCI (5 ml, 0. 1 M). The HCI containing samples were heated in a water bath at 37 co in darkness for 1 hour, with agitation. Irish was followed by 1 hour in the water bath in darkness without agitation.
The samples were the filtered and the extractions diluted to 50 ml. All the samples were measured by ICP-GOES. All analysis was done on a SIPS-7510 Shimmied instrument. 1. Qualitative broad scan Before starting quantitative analysis, a qualitative elemental broad scan was performed to see what metals were present in sufficient quantities to merit analysis. AAA was the only discovered heavy metal, along with Fee and Ca. The decision was made not to analyses for Ca, as it is present in all water sources, and the ICP-GOES almost always gives false concentration values for Ca.
It was then decided to analyses only for Baa and Fee. 2. Barium A calibration curve was drawn from the intensities measured for the series of prepared standard solutions, giving a linear trend line y = 8. Xx – 0. 4183, RE = 3. 995, where y = intensity, and x = concentration. After measuring the standards, all the prepared samples were measured and from the calibration curve the concentration of Baa in both the yellow and black paint, prepared by different digestion methods, could be determined. Table 1 gives the summarized data obtained from the measurements.