SCCHM2001 Analytical Techniques

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Question:

The importance of accurate sample preparation is crucial for reliability of results

* ICP-AES analyses the mineral content in various beverages.

* recognizes that standard techniques evolve over time and are still applicable today

* Use correct standards of preparation, especially when ICP-AES analysis is being performed

* Use tables to effectively present data

* Provide data in an oral format for peers

Answer:

To determine the caffeine concentration in beverages by HPLC or UV-Vis spectroscopy

Gas Chroma Trophy and distillation techniques can be used to determine the alcohol concentration in beverages and then compare it with the manufacturer’s alcohol concentration.

ICP/AES is used to measure the mineral content in beverages

Materials and Methods

All Experiments were performed according to the Laboratory manual.

Results

The Absorbance of Caffeine measured at 270nm using the UV-Vis spectrumrophotometer. The calibration curve is shown in Figure 1.

The caffeine concentrations in the samples were determined using the UV-Vis calibration curves as well as HPLC chromatograms, taking into account the dilution factors. Table 1 summarizes these results.

Table 1: Comparison of Caffeine in beverages using UV-Vis and HPLC, with the Label and Literature values

UV-Vis Spectroscopy – mg/100ml

Australian Tables

Cocake

Coffee

* The online searchable database NUTTAB 2010 contains a reference to Australian tables

With UV-Vis, the Caffeine content of Coke and Pepsi, Red Bull and Coffee were determined to be 22.760 and 23.665 and 48.505 respectively. The 11.479mg/100ml, 8.885, 35.505 and 48.505 mg/100ml respective values using HPLC.

Pepsi, coke and red bull had label data of 9.6, 10.7, 30mg/100ml and respectively, 17.630 mg/100ml. However, the NUTTAB recommended values were 10, 10, 24mg/100ml and 10, respectively.

The label data for coffee was not available, while the recommended value was 31mg/100ml.

HPLC yielded results that were more in line with the Label and NUTTAB values for Pepsi and coke.

It was clear that there were significant errors in the experiment when UV-Vis spectroscopy results were obtained.

One possible explanation for high concentrations could be improper dilutions during the sample preparation.

Red bull had HPLC results slightly higher than the Label data.

Both the Label data and Experimental values were higher than NUTTAB, which indicates that Red bull’s caffeine content was not in accordance with Australian standards.

The UV-Vis results were twice the height of experimental HPLC results. This indicates that there may have been errors in the dilution factors calculations.

HPLC could not detect caffeine in coffee.

The UV-Vis spectrum results for coffee were lower than that of decaffeinated coffee, which suggests that the coffee conformed to Australian standards.

The label data for caffeine in coffee was not available.

All samples showed lower HPLC values than the UV spectroscopy method.

The presence of other compounds than caffeine in samples that absorb at the wavelength being studied (270nm) could cause errors in the UVVIS data.

Uv-Vis measures absorbance at all sample components that absorb at the wavelength of analysis. HPLC measures absorbance as each component leaves the column.

Therefore, HPLC measures the absorbance only for caffeine.

HPLC was able to obtain experimental values that were more similar than the literature values for the majority of the samples. HPLC is therefore the most appropriate method for determining caffeine in beverages.

Results

Table 2 lists the results of ethanol distillation using both the GC method and the GC.

The table 2 lists the quantitative results from GC using both the standard curve (Standard Curve) and relative response factor (RRF).

This table also includes the Ethanol contents calculated from Label data and the recommended values from the Australian Tables.

Table 2: Comparison of Ethanol content in beverages with the Literature Values And Label Data

Units

Gas Chromatography

Label

Australian Tables*

Standard Curve

g/100ml

g/100ml

* The online searchable database NUTTAB 2010 contains a reference to Australian tables

Gas Chromatography revealed that beer’s ethanol content was 5.9% when using the standard curve method and 6.4% when using the Relative response factor technique.

The distillation method produced 3.83% while label data and NUTTAB values were 4.9% & 4.0%, respectively.

According to the results, wine contains almost three times as many ethanol as beer.

The GC results were higher that the NUTTAB and label values, while the distillation methods results were lower than either of these reference values.

However, the NUTTAB values were closer to what the distillation method produced than the GC methods.

For the determination of ethanol, the distillation method provides better results than GC.

The ethanol content in red wine was determined by GC using the standard curve method and 20.3% using RRF.

The Australian Tables value was 9.6% and the label data value 13.5%.

The standard curve technique gave results that were closer than those obtained by the RRF technique.

Based on these results, it is clear that the standard curve technique yielded better results then the RRF technique.

The GC method yielded higher values for both the Label as well as the Australian Table samples.

The chromatograms could have responded differently if the samples weren’t properly diluted.

Gas chromatography can be used with very diluted samples.

Concentrated samples will result in thick tailing peaks that can be difficult to replicate.

The best way to increase the resolution of your chromatogram is to use dilute samples and a standard of very low concentration.

Temperatures used incorrectly could lead to errors in the distillation procedure.

Although the density conversion tables are set at 20 0C for experimental densities, they were actually measured at room temperatures.

According to the label data, both samples contained higher levels of ethanol than recommended by the Australian Tables.

However, the experimental value of the beer produced by distillation was within the recommended limits.

After taking into account the dilution factor, the concentrations of calcium, sodium, and potassium were calculated. The results are summarized in tables 3 through 6.

Table 3: Comparisons Between The Minerals Content of Coke and Literature Values

Mineral

Units

This study

Australian Tables***

mg/100 ml

mg/100ml

* Calculated from the container label data

** Not found

NUTTAB 2010, an online searchable database that provides a reference to Australian tables, is the *** reference

Table 4: Comparison of The Red Bull’s Minerals Content With Literature and Label Values

Mineral

Units

This study

Australian Tables**

mg/100ml

mg/100ml

* Calculated from the label data of the container

** The online searchable database NUTTAB 2010 is the reference for Australian tables

Table 5: Comparisons Between The Minerals Content of Red Wine and Label Values

Mineral

Units

This study

Australian Tables**

mg/100ml

mg/100 ml

* Not found

NUTTAB 2010, an online searchable database that provides a reference to Australian tables, is the *** reference

Table 6: Comparisons Between The Minerals Content of Coffee and Label and Literature Values

Mineral

Units

This study

Australian Tables***

mg/100ml

mg/100 ml

* Not found

NUTTAB 2010 online searchable database is the reference for Australian table information

Coke did not contain any sodium or potassium.

The label data showed that the concentration was 4 and 3 mg/100ml. The NUTTAB recommended values were 11 or 1 mg/100ml.

Coke is compliant with the Australian standards of Sodium and Potassium based on experimental data.

Coke’s calcium content was 11.29mg/100ml. This was higher than the label value and the NUTTAB values.

Red-bull had a sodium, calcium and potassium concentration of 7.8, 238.24, and 3.32 mg/100ml.

The Na and Ca values of red-bull were lower than the Label and NUTTAB value and red-bull is therefore compliant with Australian standards.

The Potassium value was extremely high, which indicates major non-compliance.

For energy drinks, the recommended K value is 0mg.

The levels of Sodium, Calcium and Potassium in red wine were 8.7 mg/100ml and 9.69mg/100ml respectively. Potassium however was not detected.

The wine meets Australian standards as Potassium (and Sodium) were within the NUTTAB recommendations.

However, the recommended NUTTAB value was for Ca.

None of the three minerals had label data.

Coffee’s sodium and calcium levels were 3.35mg/100ml and 12.87mg/100ml, respectively.

The coffee did not contain potassium.

All minerals were in compliance with the NUTTAB recommendations, so the coffee meets Australian standards.

Conclusion

All objectives were met.

The HPLC method was found to be the most effective for measuring caffeine levels. Its results were comparable to those obtained by NUTTAB and Label.

The caffeine content of the analyzed samples increased according to the order Pepsi

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