Objective : To determine Cadmium (Cd) and Chromiun (Cr) in plant tissue using absorption spectroscopy Introductions : Cadmium is well known to be one of the most toxic heavy elements for animals. It has recently become a serious problem that rice grains contain cadmium in some area of Japan. On the other hand, some types of plants can grow in contaminated soils and absorb a large amount of cadmium in their bodies. Such hyperaccumulator plants are expected to be used for remediation of environments. However, the accumulation mechanism has not yet been revealed, with the elemental distribution of cadmium and transportation during uptake remaining unclear. Cadmium appear to play a very pivotal role in thyroid disease, it is a very unique mineral. It is extremely toxic and has toxic biological effects at concentrations smaller than almost any commonly found mineral. An environmental poison found in water, on our food and in the air. It's found in processed grains, dairy products, meats, fish, fertilizers, auto exhaust, cigarette smoke, batteries, solder and dentures. It disrupts the absorption of other minerals and tends to settle in the heart and right kidney and affects proper functioning of several enzymes. Whereas for Chromium, taken in the right quantity, chromium has immense health benefits. It is available in extremely low quantities in animal and plant tissues which is why it is called a trace metal. Some of the sources of chromium are brewer’s yeast, coffee, tea, cereals, potatoes, potatoes, peas, oysters, rye, thyme, processed meats, whole grains, and beer. Chromium helps metabolize carbohydrates. It monitors blood sugar levels, and helps stabilize blood sugar. It can also prevent hypertension or high blood pressure. Although trials are still being conducted, chromium compounds are considered helpful in preventing memory loss and in treating Alzheimer’s disease. Procedure :
Day 1
1. Plant tissue was prepared ( mustard and spinach). 2. The vegetable was dried in and oven of 110’C Day 2 1. The dried vegetables was cut into pieces 2. About 3 grams of vegetable was weighed and placed in 250 ml beaker 3. 10 ml of nitric acid (HNO 3) was added into the beaker and was allowed to stand Overnight
Day 3 A) Sample preparation 1. The sample was heated until red fume came out 2. Then it was cooled 3. 1 ml of peroxide (H 2O2) was added into the cooled sample 4.The sample was reheated till concentrate 5. It was then filtered into 250ml volumetric flask 6. The sample was diluted with distilled water till marked B) Standard preparation Cr 1 ppm 2 ppm 3 ppm 4 ppm 5 ppm
Volume 0.5 ml 1.0 ml 1.5 ml 2.0 ml 2.5 ml
Cd 0.2 ppm 0.4 ppm 0.6 ppm 0.8 ppm 1.0 ppm
Volume 1 ml 2 ml 3 ml 4 ml 5 ml
1. The standard was prepared as in table given above in 100 ml volumetric flask 2. The stock solution given was in 1000 ppm for each sample 3. 5 ml of the stock solution was pipette into a 100 ml volumetric flask and diluted with distilled water till marked 4. For each concentration, the volume was pipette into a 50 volumetric flask as stated in the table above respectively 5. 7 ml of the sample was pipette into each volumetric flask and was diluted with distiiled water till mark 6. The sample was then analyzed using atomic absorption spectroscopy
Results : CONCENTRATION CHROMIUM CADMIUM Blank 1 ppm 2 ppm 3 ppm 4 ppm 5 ppm
ABSORBANCE CHROMIUM CHROMIUM CADMIUM
Blank 0.2 ppm 0.4 ppm 0.6 ppm 0.8 ppm 1.0 ppm
0.036 0.045 0.058 0.071 0.082 0.093
VOLUME CHROMIUM CHROMIUM CADMIUM
0.264 0.290 0.311 0.330 0.352 0.369
0 0.5 ml 1.0 ml 1.5 ml 2.0 ml 2.5 ml
0 1 ml 2 ml 3 ml 4 ml 5 ml
Calculation : Least square method : CONCENTRATI ON Cr Cd
ABSORBANCE (y1) Cr Cd
VOLUME (x1) Cr
Cd
Cr
Cd
Cr
Cd
Blank 1 ppm 2 ppm 3 ppm 4 ppm 5 ppm
0.036 0.045 0.058 0.071 0.082 0.093 ∑y= 0.385
0 0.5 ml 1.0 ml 1.5 ml 2.0 ml 2.5 ml
0 1 ml 2 ml 3 ml 4 ml 5 ml
∑ = 7.5
∑ = 15
0 0.25 1.00 2.25 4.00 6.25 ∑xx= 13.75
0 1 4 9 16 25 ∑xx= 55
0 0.0225 0.0580 0.1065 0.1640 0.2325 ∑xy= 0.5835
0 0.290 0.622 0.990 1.408 1.845 ∑xy= 5.155
Blank 0.2 ppm 0.4 ppm 0.6 ppm 0.8 ppm 1.0 ppm
0.264 0.290 0.311 0.330 0.352 0.369 ∑y= 1.916
X1X1
X1Y1
CHROMIUM
chromium 0.1 y = 0.0234x + 0.035 R² = 0.9979
0.09 0.08 0.07 0.06 0.05
chromium
0.04
Linear (chromium)
0.03 0.02 0.01 0 0
1
∑xy = ((∑xy) -
=0.5835
=
=
13.75 – 13.75 –
= 4.375
=
-
0.10225
∑xx = (∑xx) –
m=
= 0.0234
2
3
= 0.035 Concentration of Chromium in plant tissue : C=
=
= 2.137 ppm
CADMIUM
cadmium 0.4 y = 0.0209x + 0.2672 R² = 0.9965
0.35 0.3 0.25
cadmium
0.2
Linear (cadmium)
0.15 0.1 0.05 0 0
1
∑xy = ((∑xy) -
=5.155
=
-
2
0.365
∑xx = (∑xx) –
3
4
5
6
=
55 – 55 –
= 17.5 m=
=
= 0.0209
= 0.2671 Concentration of cadmium in plant tissue C=
=
=12.78 ppm
Discussions : In this experiment, we used wet digestion methods for sample preparation. It is for elemental analysis that involves the chemical degradation of sample matrices in solution, usually with a combination of acids to increase solubility as it has been done on day 2 and allow to stand overnight. The various acid and flux treatments are carry out at high temperatures in specially designed vessels that help to minimize contamination of the sample with substances in the air, the local environment, and from the vessel walls. Sample may be loss due to adsorption onto the vessel walls, volatilization, and coextraction, but these can be reduced by procedural modifications. The use of closed systems, where the digestion reaction is completely isolated
from the surroundings, may help to reduce both contamination and sample loss. For this experiment, the sample was covered with aluminium foil. Standard addition method are particularly useful for analyzing complex samples in which the likelihood of matrix effects is substantial. A standard addition method can take several form. One of the most common form is spiking method as we had use it in preparing standard. Each solution was diluted to marked point before measuring or analyzing it. The least square method, is a typical calibration graph where I have plotted in calculation area for both sample chromium and cadmium respectively. The sample was injected into the atomic absorption spectroscopy and the result was obtained. Absorbance versus volume graph was 2 plotted and the linear equation and R was calculated in Microsoft excel and as well as manually which had been shown. Conclusion : in this experiment, I had used mustard in determination of Chromium while for determination of Cadmium, I had used spinanch. I had achieved my objective to determine Cadmium and Chromium in plant tissue. The concentration of Cadmium in spinach is 12.78 ppm. The concentration of Chromium in mustard is 2.137 ppm.
References :
1. http://www.writescience.com/RMT%20PDFs/Elsevier/eans%20wetdig.pdf 2. http://www.newsmax.com/FastFeatures/chromium-health-benefitsnutrition/2011/01/21/id/369681 3. http://www.ipap.jp/proc/cs7/pdf/cs7_323.pdf 4. http://www.best-home-remedies.com/minerals/cadmium.htm th
5. Principle of instrumental analysis 6 analysis, Douglas.A.Skoog.F.James Holler, Stanley R.Crouch
