Determination of Manganese in Tri Calcium Phosphate (TCP) by Atomic Absorption Spectrometry

Tricalcium phosphate Anhydrous Powder typically contains less than 10 ppm (mg/Kg) (w/w) manganese. This level can be determined utilizing Flame Atomic Absorption Spectrometer (AAS) and standard based on known standards. A number of analytical methods are presently used for the analysis of metals in the biochemical. The instrumental techniques available are Inductively Coupled Plasma (ICP/MS), X-Ray Fluorescence, UV-VIS Spectrophotometry, and Atomic Absorption Spectrometry. Flame AA has gained widespread acceptance as an analytical technique and is used for many applications. In this study, we have determined the amount of manganese metal present in Tricalcium Phosphate (TCP) using Flame Atomic Absorption Spectrophotometer. The method has high precision and accuracy. The percent recovery was found to be 99.8% for spiked sample. The results meet the requirement.


Introduction
Manganese (Mn) is associated with iron in many minerals. It is a common ingredient of alloy as well as iron and steel. It is present in small amounts in many biological samples [1]. Eating a small amount of manganese each day is important in maintaining your health. Too much manganese, however, can cause se-How to cite this paper: Yildiz, Y., Karadag, R., Cordera, M. and Gensinger, B. rious illness. Studies in animals have shown that very high levels of manganese in food or water can cause changes in the brain [2].
Tri-calcium phosphate (TCP) is a calcium salt of phosphoric acid with the chemical formula Ca 3 (PO 4 ) 2 . It is known as tri-basic calcium phosphate, calcium orthophosphate, tert-calcium phosphate and bone phosphate of lime. Tri-calcium phosphate salt occurs naturally in several forms, including as a rock, in milk, in skeletons and teeth of animals and found in many nutritional supplements. Calcium phosphate rocks have a content of 30% to 40% P 2 O 5 in weight. The human body needs phosphorus as well as calcium, and tri-calcium phosphate supplies both [2]. However, tricalcium phosphate is a concentrated source of calcium and taking too much can cause high calcium levels of hypercalcemia. High levels of calcium can cause; constipation, nausea, vomiting, stomach pain, muscle pain, weakness, excessive urination. It may also cause loss of appetite, thirst, dehydration, fatigue, and mental confusion. Tricalcium is commonly used in dental powders, household items, including baby powder, toothpaste, and medically as an antacid or calcium supplement.

Equipment/Instruments
• Perkin Elmer 5100 PC Atomic Absorption Spectrometer with Manganese lamp and 2 inches Nitrous Oxide/Acetylene burner head.
• Glassware: All glassware is washed in the following sequence: Alconox detergent solution, tap water, 1:1 nitric acid, tap water, 1:1 hydrochloric acid, tap water, and final rince with deionized water.

Instrument/Operating Parameters
Blank: 100 mL of D.I. water is taken through the digestion process. Duplicate: A separate aliquot of random sample is digested or analysis (approximately (10%). Spike: Using the formula C 1 V 1 = C 2 V 2 an appropriate volume and concentration of standards is brought through spiked into a sample and the digestion procedure.
Instruments HCl dropwise to affect dissolution. Allow the CO 2 escape before subsequent additions of HCl to prevent the solution from bubbling out of the flask. When the calcium carbonate completely dissolves and the solution clears, dilute to volume with deionized water and mix well [4].

4) Sample Preparation/Acid Digestion:
Analytically weigh 1.0 g grams of tri-calcium phosphate and transfer to a 100 mL volumetric flask. Add approximately 25 mL of DI water and swirl to form a slurry. Then add 10 mL of concentrated HCl and swirl to dissolve. Adding acid to dry product can cause coagulation of the product and impede dissolution. Dilute to volume with DI water and mix well. The sample prep for determination of Mn by AA is based on the USP monograph for tricalcium phosphate, sample prep for heavy metals test [5].

Procedure
1) In a 50 mL beaker with glass bead weigh 2.5 g sample to the nearest 0.1 mg.
add 18 mL 3N HCl and heat to boiling. Cool to room temperature, quantitatively transfer to 25 mL volumetric flask, and dilute to mark with water.

Contamination Control
All reagent were of a high purity grade. Eppendorf pipettes with plastic tips were used for all pipetting. All sample handling operations were conduct under a laminar flow hood to reduce atmospheric contamination.

Calibration Standards
The aqueous calibration standards were prepared in pre-cleaned 100-mL volumetric flasks using glass pipettes and fixed-volume Effendorf pipette for volume transfers (Table 1 and Table 2). These standards represent the stock calibration standards were prepared.

Background
The technique of atomic absorption spectrometry (AAS) depends on generating a cloud of free atoms in the ground or unexcited state. The first AA spectrometers used a flame to generate atoms of the element to be determined [5]. The most common method of background correction in atomic absorption (AA) spectrophotometry uses a continuum source such as a deuterium lamp to measure the background. Background is electronically subtracted from total absorbance to give background corrected atomic absorbance [6].

Calibration and Operation
Before operation the calibration of the instrument is necessary. Rinse aspirator tube with D.I. water. Aspirate sample, ensure within range (between blank and highest standard). Dilute sample if necessary, and repeat for each sample. Protocol: Blank (purpose of this second blank measurement is to "zero" the reading)

Result and Discussion
Historically, we have matched the standard matrix to the sample's matrix. When determining Mn in tricalcium phosphate, our Mn standards have calcium at concentrations calculated to equal those in the prepared sample solution. This may require some investigation for this reason: 1) if the reagent used for modifying the standard matrix contains, as a contaminant, traces of the element to be determined, this will artificially lower the result for the sample. 2) Therefore, use reagent of utmost purity for matrix matching standards to samples. Spike and recovery can be used to confirm that Mn can be determined accurately despite the fact that tricalcium phosphate sample contain 3 4 PO − .    (2) and (3).

Conclusions
Perkin-Elmer 5100PC Atomic Absorption Spectrophotometer was used with a short part burner and nitrous oxide/acetylene flame optimized with hollow cathode lamp and a single element was measured. The background correction was selectable on an element by element basis. Water had been run between each reading; AA measurements were thus performed [7] [8].
The results of a single method for the detection of manganese in the tricalcium phosphate were obtained and are shown in Figure 1 and Tables 2-4.  Atomic Absorption Spectrophotometric determination of manganese in tricalcium phosphate (TCP) was found to be adequately sensitive in terms of linearity, repeatability, and accuracy. The determination of correlation coefficient (R 2 ) was found to be 0.99992. Concentration of spiking solution: 100 mg/L, spiking solution: 0.5 mL, sample volume: 10 mL, spiked amount: 5.0 mg/L. Average percent matrix spike recovery (%R) was 99.8%, and relative percentage difference (%RPD) was 0.00%. The percent recovery was found to be 99.8% for spiked sample, and 99.8% for the duplicate spiked sample. The results were within the specification of 10 mg/Kg maximum, with the average concentration of Mn in sample found to be 4.31 mg/Kg. The results meet the requirement.