Calibration Curves For Limit Of Detection

Published Date: 02 Nov 2017

The calibration curve obtained from the FAAS analysis of the series of low concentration standard solution with 0.5M nitric acid as the blank solution for Cu as follows:

Figure 10: Cu Calibration Curve of Standard Solutions from Range of 0.1 – 2.0 ppm.

The limit of detection (LOD) calculated from the calibration graph above is 0.384ppm. The calculation is as follows:

Limit of detection (LOD) = [3 x (standard error of estimate)] / slope of graph

= [3 x (0.123346119)] / 0.177

= 2.0906 (absorbance)

= 0.383694434 ppm (concentration)

4.1.2 Cadmium

The calibration curve obtained from the FAAS analysis of the series of low concentration standard solution with 0.5M nitric acid as the blank solution for Cd as follows:

Figure 11: Cd Calibration Curve of Standard Solutions from Range of 0.1 – 2.0 ppm.

The limit of detection (LOD) calculated from the calibration graph above is 0.487ppm. The calculation is as follows:

Limit of detection (LOD) = [3 x (standard error of estimate)] / slope of graph

= [3 x (0.15826414)] / 0.2311

= 2.0544 (absorbance)

= 0.487117741 ppm (concentration)

4.1.3 Chromium

The calibration curve obtained from the FAAS analysis of the series of low concentration standard solution with 0.5M nitric acid as the blank solution for Cr as follows:

Figure 12: Cr Calibration Curve of Standard Solutions from Range of 0.1 – 2.0 ppm.

The limit of detection (LOD) calculated from the calibration graph above is 0.018ppm. The calculation is as follows:

Limit of detection (LOD) = [3 x (standard error of estimate)] / slope of graph

= [3 x (0.00603776)] / 0.0088

= 2.0583 (absorbance)

= 0.018494196 ppm (concentration)

4.1.4 Lead

The calibration curve obtained from the FAAS analysis of the series of low concentration standard solution with 0.5M nitric acid as the blank solution for Pb as follows:

Figure 13: Pb Calibration Curve of Standard Solutions from Range of 0.1 – 2.0 ppm.

The limit of detection (LOD) calculated from the calibration graph above is 0.068ppm. The calculation is as follows:

Limit of detection (LOD) = [3 x (standard error of estimate)] / slope of graph

= [3 x (0.02137171)] / 0.0311

= 2.0615 (absorbance)

= 0.06761887 ppm (concentration)

4.1.5 Nickel

The calibration curve obtained from the FAAS analysis of the series of low concentration standard solution with 0.5M nitric acid as the blank solution for Ni as follows:

Figure 14: Ni Calibration Curve of Standard Solutions from Range of 0.1 – 2.0 ppm.

The limit of detection (LOD) calculated from the calibration graph above is 0.136ppm. The calculation is as follows:

Limit of detection (LOD) = [3 x (standard error of estimate)] / slope of graph

= [3 x (0.044815785)] / 0.0019

= 2.0526 (absorbance)

= 0.136363328 ppm (concentration)

4.2 Calibration Curves

4.2.1 Copper

The calibration curve obtained from the F-AAS analysis of the series of standard solutions with the range of concentration from 0.1 to 0.5 ppm, 0.5M nitric acid as the blank solution for Cu is as follows:

Figure 15: Cu Calibration Curve of Standard Solutions from Range of 1.0 – 5.0 ppm.

The working range calculated from the calibration graph above using the RSQ function in Microsoft Excel is up to 4.5ppm with the RSQ value of approximately 0.9968.

4.2.2 Cadmium

The calibration curve obtained from the F-AAS analysis of the series of standard solutions with the range of concentration from 0.1 to 0.5 ppm, 0.5M nitric acid as the blank solution for Cd is as follows:

Figure 16: Cd Calibration Curve of Standard Solutions from Range of 1.0 – 5.0 ppm.

The working range calculated from the calibration graph above using the RSQ function in Microsoft Excel is up to 8.7ppm with the RSQ value of approximately 0.971

4.2.3 Chromium

The calibration curve obtained from the F-AAS analysis of the series of standard solutions with the range of concentration from 0.1 to 0.5 ppm, 0.5M nitric acid as the blank solution for Cr is as follows:

Figure 17: Cr Calibration Curve of Standard Solutions from Range of 1.0 – 5.0 ppm.

The working range calculated from the calibration graph above using the RSQ function in Microsoft Excel is up to 34.5ppm with the RSQ value of approximately 0.9953.

4.2.4 Lead

The calibration curve obtained from the F-AAS analysis of the series of standard solutions with the range of concentration from 0.1 to 0.5 ppm, 0.5M nitric acid as the blank solution for Pb is as follows:

Figure 18: Pb Calibration Curve of Standard Solutions from Range of 1.0 – 5.0 ppm.

The working range calculated from the calibration graph above using the RSQ function in Microsoft Excel is up to 12.7ppm with the RSQ value of approximately 0.9921.

4.2.5 Nickel

The calibration curve obtained from the F-AAS analysis of the series of standard solutions with the range of concentration from 0.1 to 0.5 ppm, 0.5M nitric acid as the blank solution for Ni is as follows:

Figure 19: Ni Calibration Curve of Standard Solutions from Range of 1.0 – 5.0 ppm.

The working range calculated from the calibration graph above using the RSQ function in Microsoft Excel is up to 24.0ppm with the RSQ value of approximately 0.9886.

4.3 Effect of coagulant

4.3.1 Copper

The effect of aluminium sulfate which was acted as a coagulant in this experiment had been studied in order to determine the recovery percentage of Cu. Two sets of experiments were carried out, one set was with the presence of coagulant and another set was without the presence of coagulant. The recovery percentages of the both experiments were plotted as the following:

Figure 20: The effect of coagulant on Cu recovery analysis (n = 3)

The graph above showed that the recovery percentage of the experiment with the presence of coagulant was higher than the recovery percentage of experiment without the presence of coagulant.

4.3.2 Cadmium

The effect of aluminium sulfate which was acted as a coagulant in this experiment had been studied in order to determine the recovery percentage of Cd. Two sets of experiments were carried out, one set was with the presence of coagulant and another set was without the presence of coagulant. The recovery percentages of the both experiments were plotted as the following:

Figure 21: The effect of coagulant on Cd recovery analysis (n = 3)

The graph above showed that the recovery percentage of the experiment with the presence of coagulant was higher than the recovery percentage of experiment without the presence of coagulant.

4.3.3 Chromium

The effect of aluminium sulfate which was acted as a coagulant in this experiment had been studied in order to determine the recovery percentage of Cr. Two sets of experiments were carried out, one set was with the presence of coagulant and another set was without the presence of coagulant. The recovery percentages of the both experiments were plotted as the following:

Figure 22: The effect of coagulant on Cr recovery analysis (n = 3)

The graph above showed that the recovery percentage of the experiment with the presence of coagulant was higher than the recovery percentage of experiment without the presence of coagulant.

4.3.4 Lead

The effect of aluminium sulfate which was acted as a coagulant in this experiment had been studied in order to determine the recovery percentage of Cr. Two sets of experiments were carried out, one set was with the presence of coagulant and another set was without the presence of coagulant. The recovery percentages of the both experiments were plotted as the following:

Figure 23: The effect of coagulant on Pb recovery analysis (n = 3)

The graph above showed that the recovery percentage of the experiment with the presence of coagulant was higher than the recovery percentage of experiment without the presence of coagulant.

4.3.5 Nickel

The effect of aluminium sulfate which was acted as a coagulant in this experiment had been studied in order to determine the recovery percentage of Cr. Two sets of experiments were carried out, one set was with the presence of coagulant and another set was without the presence of coagulant. The recovery percentages of the both experiments were plotted as the following:

Figure 24: The effect of coagulant on Ni recovery analysis (n = 3)

The graph above showed that the recovery percentage of the experiment with the presence of coagulant was higher than the recovery percentage of experiment without the presence of coagulant.

4.4 Effect of Centrifugation Time

4.4.1 Copper

The effect of centrifugation time for the separation of interested heavy metal elements was studied in this experiment. Centrifugation time is an important factor in order to ensure the interested heavy metals can be settled down at the bottom of centrifuge tube, separating from the unwanted supernatant. The experiment was carried out with centrifugation time in the range of 2 minutes to 25 minutes.

Figure 25: The effect of centrifugation time on Cu recovery analysis (n = 3)

Figure 25 showed the recovery percentages of Cu with the effect of centrifugation time in the range of 2 to 25 minutes. The longer the time of centrifugation, the better the recovery percentage of Cu. There was a constant of graph occurred start from period of 20 minutes. Therefore, centrifugation time of 20 minutes was specified for the further works.

4.4.2 Cadmium

The effect of centrifugation time for the separation of interested heavy metal elements was studied in this experiment. Centrifugation time is an important factor in order to ensure the interested heavy metals can be settled down at the bottom of centrifuge tube, separating from the unwanted supernatant. The experiment was carried out with centrifugation time in the range of 2 minutes to 25 minutes.

Figure 26: The effect of centrifugation time on Cd recovery analysis (n = 3)

Figure 26 showed the recovery percentages of Cu with the effect of centrifugation time in the range of 2 to 25 minutes. The longer the time of centrifugation, the better the recovery percentage of Cd. There was a constant of graph occurred start from period of 20 minutes. Therefore, centrifugation time of 20 minutes was specified for the further works.

4.4.3 Chromium

The effect of centrifugation time for the separation of interested heavy metal elements was studied in this experiment. Centrifugation time is an important factor in order to ensure the interested heavy metals can be settled down at the bottom of centrifuge tube, separating from the unwanted supernatant. The experiment was carried out with centrifugation time in the range of 2 minutes to 25 minutes.

Figure 27: The effect of centrifugation time on Cr recovery analysis (n = 3)

Figure 27 showed the recovery percentages of Cu with the effect of centrifugation time in the range of 2 to 25 minutes. The longer the time of centrifugation, the better the recovery percentage of Cr. There was a constant of graph occurred start from period of 20 minutes. Therefore, centrifugation time of 20 minutes was specified for the further works.

4.4.4 Lead

The effect of centrifugation time for the separation of interested heavy metal elements was studied in this experiment. Centrifugation time is an important factor in order to ensure the interested heavy metals can be settled down at the bottom of centrifuge tube, separating from the unwanted supernatant. The experiment was carried out with centrifugation time in the range of 2 minutes to 25 minutes.

Figure 28: The effect of centrifugation time on Pb recovery analysis (n = 3)

Figure 28 showed the recovery percentages of Cu with the effect of centrifugation time in the range of 2 to 25 minutes. The longer the time of centrifugation, the better the recovery percentage of Pb. There was a constant of graph occurred start from period of 20 minutes. Therefore, centrifugation time of 20 minutes was specified for the further works.

4.4.5 Nickel

The effect of centrifugation time for the separation of interested heavy metal elements was studied in this experiment. Centrifugation time is an important factor in order to ensure the interested heavy metals can be settled down at the bottom of centrifuge tube, separating from the unwanted supernatant. The experiment was carried out with centrifugation time in the range of 2 minutes to 25 minutes.

Figure 29: The effect of centrifugation time on Ni recovery analysis (n = 3)

Figure 29 showed the recovery percentages of Cu with the effect of centrifugation time in the range of 2 to 25 minutes. The longer the time of centrifugation, the better the recovery percentage of Ni. There was a constant of graph occurred start from period of 20 minutes. Therefore, centrifugation time of 20 minutes was specified for the further works.

4.5 Recovery Analysis

Recovery analysis was performed in the prepared spiked solutions to ensure the accuracy of the proposed procedures to be applied in the analysis of real samples. Three sets of samples by applying the proposed method were performed with five different concentration of spiked solution with heavy metals were prepared and subsequently subjected to F-AAS analysis. The result obtained n table forms as follows.

4.5.1 Copper

For recovery analysis of copper that carried out by using a series of standard solution in the range of concentration of 0.1 to 0.5 ppm with the proposed methods. The final concentrations of spiked solutions after preconcentration had a factor of 100 compare to the initial concentrations of spiked solutions. A set of reading was obtained by F-AAS analysis as tabulated in Table 6.

Table 6 : Recovery percentage analysis of Cu by F-AAS analysis (n=3)

Concentration(ppm)

1

2

3

4

5

Recovery Percentage (%)

94.20

95.15

90.70

95.01

96.42

98.10

99.15

96.93

98.00

99.10

93.00

99.80

96.40

97.35

99.86

Average

95.10

98.03

94.68

96.79

98.46

Standard Deviation

2.67

2.52

3.45

1.57

1.81

Relative Standard Deviation %

2.81

2.57

3.64

1.62

1.84

Average Recovery(%)

96.1

RSDp (%)

3.35

Table 6 shows the recovery percentage analysis of Cu in the prepared spiked solution by F-AAS analysis. Three sets of samples with the same concentration of heavy metals were analysed with F-AAS for recovery determination to increase the accuracy and precision of data obtained whereby an average was calculated based on the three readings obtained. The average recovery percentage obtained for 1 ppm Cu spiked solution is 95.10% which considered as a good recovery value. The recovery percentage for 2 ppm, 3 ppm, 4 ppm and 5 ppm are 98.03%, 94.68%, 96.79% and 98.46% respectively which are good recovery values and above the expected value of at least 75 %. Relative standard deviations of Cu recovery analysis are fallen in the range of 1.62% to 3.64%.

4.5.2 Cadmium

For recovery analysis of cadmium that carried out by using a series of standard solution in the range of concentration of 0.1 to 0.5 ppm with the proposed methods. The final concentrations of spiked solutions after preconcentration had a factor of 100 compare to the initial concentrations of spiked solutions. A set of reading was obtained by F-AAS analysis as tabulated in Table 7.

Table 7: Recovery percentage analysis of Cd by F-AAS analysis (n=3)

Concentration

1

2

3

4

5

Recovery Percentage (%)

64.90

95.00

98.13

99.73

93.20

73.20

98.40

87.1

98.90

89.90

65.80

98.35

95.5

99.08

93.42

Average

67.97

97.25

93.58

99.24

92.17

Standard Deviation

4.55

1.95

5.76

0.47

1.97

Relative Standard Deviation %

6.69

2.01

6.15

0.47

2.14

Average Recovery (%)

90.0

RSDp (%)

5.52

Table 7shows the recovery percentage analysis of Cd in the prepared spiked solution by F-AAS analysis. Three sets of samples with the same concentration of heavy metals were analysed with F-AAS for recovery determination to increase the accuracy and precision of data obtained whereby an average was calculated based on the three readings obtained. The average recovery percentage obtained for 1 ppm Cd spiked solution is 67.97% which is slightly lower than the expected recovery value of 75%. The loss of sample may be due to errors in sample preparation and spiking technique performed. The recovery percentage for 2 ppm, 3 ppm, 4 ppm and 5 ppm are 97.25%, 93.58%, 99.24%, and 92.17% respectively which are good recovery values and above the expected value of at least 75 %. Relative standard deviations of Cd recovery analysis are fallen in the range of 0.47% to 6.69%.

4.5.3 Chromium

For recovery analysis of chromium that carried out by using a series of standard solution in the range of concentration of 0.1 to 0.5 ppm with the proposed methods. The final concentrations of spiked solutions after preconcentration had a factor of 100 compare to the initial concentrations of spiked solutions. A set of reading was obtained by F-AAS analysis as tabulated in Table 8.

Table 8: Recovery percentage analysis of Cr by F-AAS analysis (n=3)

Concentration

1

2

3

4

5

Recovery Percentage (%)

95.39

93.10

90.82

94.87

95.95

81.90

82.50

94.70

91.80

95.82

85.60

84.15

95.70

96.95

96.98

Average

87.63

86.58

93.74

94.54

96.25

Standard Deviation

6.97

5.70

2.578

2.59

0.64

Relative Standard Deviation (%)

7.95

6.59

2.75

2.74

0.66

Average Recovery (%)

91.8

RSDp (%)

6.38

Table 8 shows the recovery percentage analysis of Cr in the prepared spiked solution by F-AAS analysis. Three sets of samples with the same concentration of heavy metals were analysed with F-AAS for recovery determination to increase the accuracy and precision of data obtained whereby an average was calculated based on the three readings obtained. The average recovery percentage obtained for 1 ppm Cr spiked solution is 87.63% which is higher than the expected recovery value of 75%. The recovery percentage for 2 ppm, 3 ppm, 4 ppm and 5 ppm are 86.58%, 93.74%, 94.54% and 96.25% respectively which are good recovery values and above the expected value of at least 75 %. Relative standard deviations of Cr recovery analysis are fallen in the range of 0.66% to 7.95%.

4.5.4 Lead

For recovery analysis of lead that carried out by using a series of standard solution in the range of concentration of 0.1 to 0.5 ppm with the proposed methods. The final concentrations of spiked solutions after preconcentration had a factor of 100 compare to the initial concentrations of spiked solutions. A set of reading was obtained by F-AAS analysis as tabulated in Table 9.

Table 9: Recovery percentage analysis of Cr by F-AAS analysis (n=3)

Concentration

1

2

3

4

5

Recovery Percentage (%)

95.40

86.55

91.80

97.5

88.90

99.20

87.25

97.57

97.2

95.68

96.20

91.45

94.13

97.08

95.76

Average

96.93

88.42

94.50

97.26

93.45

Standard Deviation

2.00

2.60

2.90

0.047

3.94

Relative Standard Deviation %

2.06

2.94

3.07

0.048

4.22

Average Recovery (%)

94.1

RSDp (%)

3.66

Table 9 shows the recovery percentage analysis of Pb in the prepared spiked solution by F-AAS analysis. Three sets of samples with the same concentration of heavy metals were analysed with F-AAS for recovery determination to increase the accuracy and precision of data obtained whereby an average was calculated based on the three readings obtained. The average recovery percentage obtained for 1 ppm Pb spiked solution is 87.63% which is higher than the expected recovery value of 75%. The recovery percentage for 2 ppm, 3 ppm, 4 ppm and 5 ppm are 86.58%, 93.74%, 94.54% and 96.25% respectively which are good recovery values and above the expected value of at least 75 %. Relative standard deviations of Pb recovery analysis are fallen in the range of 0.66% to 7.95%.

4.5.5 Nickel

For recovery analysis of nickel that carried out by using a series of standard solution in the range of concentration of 0.1 to 0.5 ppm with the proposed methods. The final concentrations of spiked solutions after preconcentration had a factor of 100 compare to the initial concentrations of spiked solutions. A set of reading was obtained by F-AAS analysis as tabulated in Table 10.

Table 10: Recovery percentage analysis of Cr by F-AAS analysis (n=3)

Concentration

1

2

3

4

5

Recovery Percentage (%)

95.40

86.55

91.80

97.50

88.90

79.60

95.80

97.80

97.50

90.24

75.60

92.35

97.13

98.85

91.28

Average

83.53

91.57

95.58

97.95

90.14

Standard Deviation

10.47

4.68

3.29

0.78

1.19

Relative Standard Deviation %

12.53

5.11

3.44

0.80

1.32

Average Recovery (%)

91.8

RSDp (%)

8.11

Table 10 shows the recovery percentage analysis of Ni in the prepared spiked solution by F-AAS analysis. Three sets of samples with the same concentration of heavy metals were analysed with F-AAS for recovery determination to increase the accuracy and precision of data obtained whereby an average was calculated based on the three readings obtained. The average recovery percentage obtained for 1 ppm Ni spiked solution is 83.53% which is higher than the expected recovery value of 75%. The recovery percentage for 2 ppm, 3 ppm, 4 ppm and 5 ppm are 91.57%, 95.58%, 97.95%, 90.14% respectively which are good recovery values and above the expected value of at least 75 %. Relative standard deviations of Ni recovery analysis are fallen in the range of 0.80% to 12.53%.

4.6 Analysis of Real Sample

Real water sample collected from five different industrial areas were subjected to nitric acid digestion and subsequently analysed using F-AAS method to determine the presence of copper, cadmium, chromium, lead and nickel. Standard solutions of concentration ranging between 1.00ppm to 5.00ppm were used as the calibration standards and 1.0M nitric acid was used as blank. The concentration of heavy metals present in the real sample was calculated based on the calibration curves plotted and absorbance value obtained.

4.6.1 Copper

The calibration curve obtained from the F-AAS analysis of the series of standard solutions of concentration ranging between 1.00ppm to 5.00ppm is as follows:

Figure 30: Cu Calibration Curve of Series of Standard Solutions (1.00- 5.00ppm)

The absorbance of Cu detected in all of the five real water samples are tabulated in Table 11 below:

Table 11: The concentration of Cu in five water samples

Sample(s)

Absorbance

Concentration (ppm)

Batu Caves Pewter KL Company

Not detected

-

BZ Chemical Company

Not detected

-

Excellent Chemical Industrial Company

Not detected

-

Kian Joo Can Factory

Not detected

-

Selangor Rubber Factory

Not detected

-

4.6.2 Cadmium

The calibration curve obtained from the F-AAS analysis of the series of standard solutions of concentration ranging between 1.00ppm to 5.00ppm is as follows:

Figure 31: Cd Calibration Curve of Series of Standard Solutions (1.00- 5.00ppm)

The absorbance of Cd detected in all of the five real water samples are tabulated as following:

Table 12: The concentration of Cd in five water samples

Sample(s)

Absorbance

Concentration (ppm)

Batu Caves Pewter KL Company

0.034

0.009

BZ Chemical Company

0.033

0.007

Excellent Chemical Industrial Company

0.034

0.009

Kian Joo Can Factory

0.032

0.005

Selangor Rubber Factory

0.032

0.005

4.6.3 Chromium

The calibration curve obtained from the F-AAS analysis of the series of standard solutions of concentration ranging between 1.00ppm to 5.00ppm is as follows:

Figure 32: Cr Calibration Curve of Series of Standard Solutions (1.00- 5.00ppm)

The absorbance of Cr detected in all of the five real water samples are tabulated in Table 13 below:

Table 13: The concentration of Cr in five water samples

Sample(s)

Absorbance

Concentration (ppm)

Batu Caves Pewter KL Company

Not detected

-

BZ Chemical Company

Not detected

-

Excellent Chemical Industrial Company

Not detected

-

Kian Joo Can Factory

0.007

0.036

Selangor Rubber Factory

0.007

0.036

4.6.4 Lead

The calibration curve obtained from the F-AAS analysis of the series of standard solutions of concentration ranging between 1.00ppm to 5.00ppm is as follows:

Figure 33: Pb Calibration Curve of Series of Standard Solutions (1.00- 5.00ppm)

The absorbance of Pb detected in all of the five real water samples are tabulated in the table below:

Table 14: The concentration of Pb in five water samples

Sample(s)

Absorbance

Concentration (ppm)

Batu Caves Pewter KL Company

0.005

0.036

BZ Chemical Company

0.008

0.075

Excellent Chemical Industrial Company

0.006

0.049

Kian Joo Can Factory

0.011

0.113

Selangor Rubber Factory

0.012

0.126

4.6.5 Nickel

The calibration curve obtained from the F-AAS analysis of the series of standard solutions of concentration ranging between 1.00ppm to 5.00ppm is as follows:

Figure 34: Ni Calibration Curve of Series of Standard Solutions (1.00- 5.00ppm)

The absorbance of Ni detected in all of the five real water samples are tabulated in the table below:

Table 15: The concentration of Ni in five water samples

Sample(s)

Absorbance

Concentration (ppm)

Batu Caves Pewter KL Company

0.006

0.049

BZ Chemical Company

0.014

0.200

Excellent Chemical Industrial Company

0.008

0.054

Kian Joo Can Factory

0.010

0.102

Selangor Rubber Factory

0.009

0.078

4.6.6 Comparison of heavy metals present in real water samples

The concentration of the five heavy metals in five waste water samples analysed by F-AAS analysis with the standard solutions of concentration ranging from 1.00ppm to 5ppm as the standards for calibration curve were determined and a comparison was made and tabulated in Table 16.

Table 16: Comparison of heavy metals present in five waste water samples.

Metals

Concentration of Metals (ppm)

Maximum Contaminant Level (ppm)

Pewter KL

BZ Chemical

Excellent Chemical

Kian Joo Can Factory

Selangor Rubber Factory

Cu

0.036

-

0.018

0.022

-

0.200

Cd

0.009

0.007

0.009

0.005

0.005

0.010

Cr

-

-

-

0.036

0.036

0.050

Pb

0.036

0.075

0.049

0.113

0.126

0.200

Ni

0.049

0.200

0.054

0.102

0.078

0.200

Based on the results on Table 16, water sample collected from Batu Caves Pewter KL Company has the highest copper concentration of 0.036ppm compared to others water samples. This could be due to copper which acts as a hardener, involved in the making of pewter. There is no detection of copper in the water sample collected from BZ Chemical Company and Selangor Rubber Factory. This could be due to there is no involvement of copper ion in the making in cleaning product and plastic product. For cadmium detection, water sample colleted from Batu Caves Pewter KL Company and Excellent Chemical Industrial Company have the highest concentration of cadmium which is 0.009ppm. Excellent Chemical Industrial Company is a manufacturer of contact and sprayable adhesive for furniture, shoes and sofa. Adhesive is mainly made by polymer which involved heavy metals as stabilizer. In the other hands, there is no cadmium ion needed for manufacturing pewter product. Thus, the presence of cadmium in waste water collected from pewter factory is due to the mixing of waste water discharged from other factory which use cadmium ion in their product. The detection of chromium showed only in water samples from Kian Joo Can Factory and Selangor Rubber Factory is due to the involvement of chromium as pigment in plastic product. Water samples from Kian Joo Can Factory and Selangor Rubber Factory have the highest concentration of lead. This is due to lead is the main ingredient in the manufacturing of plastic product. The highest concentration of nickel is showed in the water sample collected from BZ Chemical Company which is due to the use of nickel as the ingredient in laundry detergent which is the main product produced by BZ Chemical Company. The contents of all the five heavy metals in the samples are lower than the maximum contaminant level regulated by Environmental Quality Act 1974. These results showed that the five factories had practiced waste water treatment before the water is being discharged to environment.

5.0 CONCLUSION

In conclusion, the F-AAS procedures used in this work are suitable to be applied in the analysis of waste water samples for efficient, effective and simple determination of trace amount of heavy metals as the detection limits of the interested heavy metals are achieved and overall high recovery percentages can be obtained from the recovery analysis. Among the five waste water samples, sample collected from Batu Caves Pewter KL Company has the highest copper concentration of 0.036ppm. There is no detection of copper in the water sample collected from BZ Chemical Company and Selangor Rubber Factory. For cadmium detection, water sample colleted from Batu Caves Pewter KL Company and Excellent Chemical Industrial Company have the highest concentration of cadmium which is 0.009ppm. The detection of chromium showed only in water samples from Kian Joo Can Factory and Selangor Rubber Factory. Water samples from Selangor Rubber Factory also have the highest concentration of lead which is 0.126ppm. The highest concentration of nickel, 0.200ppm is showed in the water sample collected from BZ Chemical Company which is due to the use of nickel as the ingredient in laundry detergent which is the main product produced by BZ Chemical Company. The contents of all the five heavy metals in the samples are lower than the maximum contaminant level regulated by Environmental Quality Act 1974. These results showed that the five factories had practiced waste water treatment before the water is being discharged to environment.