Applications

Determination of Iron in Graphite Powder (Flame Atomic Absorption Spectrometry)

October 10, 2025

1. Method Overview

After the sample is digested with aqua regia, the determination is carried out using an air-acetylene flame at an instrument wavelength of 248.3 nm.

2. Instruments and Reagents

2.1 Instruments and Equipment

2.1.1 Testing Instruments

Serial No.	Name	Quantity	Technical Requirements	Accessories
1	Flame Atomic Absorption Spectrophotometer	1 set	–	Iron Hollow Cathode Lamp
2	Acetylene Gas	1 cylinder	Purity ≥ 99.99%	–
3	Air Compressor	1 set	Rated discharge pressure: 0.3 MPa	–

2.1.2 Sample Pretreatment Equipment

Serial No.	Name	Quantity	Technical Requirements	Accessories
1	Temperature-Controlled Hot Plate	1 set	Rated temperature range: Room temperature ~ 300 ℃	–
2	Electronic Balance	1 set	Sensitivity: 0.1 mg	–
3	Ultrapure Water System	1 set	–	–
4	Micropipette	1 each	Ranges: 20 μL ~ 200 μL, 100 μL ~ 1000 μL	–
5	Volumetric Flask	Several	Volume: 100 mL	–
6	Test Tube	Several	Volume: 25 mL	–

2.2 Reagents

2.2.1 Raw Reagents

Serial No.	Name	Technical Requirements	Remarks
1	Nitric Acid	MOS Grade	–
2	Hydrochloric Acid	Guaranteed Reagent (GR)	–

2.2.2 Prepared Reagents

Serial No.	Name	Preparation Method	Remarks
1	(1+99) Nitric Acid Solution	Measure 10 mL of nitric acid, slowly add it to 990 mL of deionized water, and mix well.	–

2.3 Reference Standards

2.3.1 Stock Solution

Serial No.	No.	Name	Technical Requirements	Remarks
1	GBW08616	Iron Single-Element Standard Substance Solution	Concentration: 1000 μg/mL	Provided by National Institute of Metrology, China

3. Operational Procedures

3.1 Sample Preparation

3.1.1 Preparation of Test Solution

Weigh 0.25 g of the sample (accurate to 0.00001 g) into a digestion tank. Add 3 mL of concentrated nitric acid and 9 mL of concentrated hydrochloric acid, cover and tighten the digestion tank, then place it in a microwave digestion system for digestion. Prepare a blank sample using the same method. After cooling, filter the solution and dilute it to the marked volume in a 25 mL volumetric flask. The solution is ready for on-machine testing.

Microwave Heating Program

Step	Temperature (℃)	Holding Time (min)
1	100	3
2	120	3
3	140	3
4	160	3
5	180	30

3.1.2 Preparation of Standard Solutions

Preparation of Iron Standard Series

Accurately pipette 0.0, 0.05, 0.1, 0.2, and 0.3 mL of the iron standard solution (1000 μg/mL) into separate 100 mL volumetric flasks respectively. Add 5 mL of strontium chloride solution to each flask, then dilute to the marked volume with (1+99) nitric acid solution and mix well. The concentrations of this standard series are 0.0, 0.5, 1.0, 2.0, and 3.0 μg/mL.

3.2 Sample Testing

Testing Conditions

Reference Conditions for Flame Atomic Absorption Spectrophotometer

Parameter	Specification
Element	Iron
Wavelength (nm)	(To be specified based on instrument calibration)
Spectral Bandwidth (nm)	(To be specified based on instrument calibration)
Element Lamp Current (mA)	3.0
Fuel Height (mm)	6
Fuel Flow Rate (mL/min)	1400
Air Compressor Pressure (MPa)	0.22
Background Correction Method	None

Sample Testing

Adjust the instrument to its optimal working state, ignite the flame and adjust the fuel flow rate. Test the standard solutions and sample solutions in sequence, read the data, input the sample weight, then check and record the results.