Flame Atomic Absorption / Emission Spectrometry

Analytes currently available include: sodium, potassium, calcium, magnesium and lithium. Future plans exist to transfer these methods onto an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) platform.

Traceability

Analyte	Standard (certfied purity)	Control Material
Sodium	Na CL, Sigma >99.999%	SRM 909al, 909all, 909b1, 909bll
Potassium	K Cl, Sigma >99.999%	SRM 909al, 909all, 909b1, 909bll
Calcium	CaCO, Sigma >99.995%	SRM 909al, 909all, 909b1, 909bll
Magnesium	Mg Gluconate, Sigma >98%	SRM 909al, 909all, 909b1, 909bll
Lithium	LiCO2, Sigma >99.997%	SRM 909al, 909all, 909b1, 909bll

Analytical Method Details

Cation	Sample pre-treatment	Technique	Wavelength (nm)
Sodium	1/2025 dilution Ionisation suppressant (CsCl)* Surfactant (0.1% Triton)	Emission	589.6
Potassium	1/450 dilution Ionisation suppressant (CsCl)* Surfactant (0.1% Triton)	Emission	766.5
Calcium	1/25 dilution Releasing agent (LaCl)** Surfactant (0.1% Triton)	Absorption	422.7
Magnesium	1/150 dilution Releasing agent (LaCl)** Surfactant (0.1% Triton)	Absorption	285.2
Lithium	1/15 dilution Releasing agent (NaCl & KNO3) Surfactant (0.1% Triton)	Absorption	670.8

*2000 PPM, **1000 PPM

Sample Handling

All samples are diluted using an automated robotic workstation directly from the primary sample.

Reference Method Proposed Limits

Analyte	Proposed AEmax(%)	Actual AEmax(%)	Proposed Biasmax(%)	Actual Biasmax(%)
Sodium	1.3	0.8	0.5	0.2
Potassium	2.0	1.7	0.8	0.7
Calcium	1.7	1.1	0.5	0.4
Magnesium	1.7	1.5	0.5	0.5
Lithium	2.4	1.9	1.2	1.9

Theinpoint et al: Specifications for Reference Methods and Networks of Reference Laboratories from Members of the External Quality Assessment (EQA) Working Group B on target Values in EQAS. Eur J Clin Chem Clin Biochem 1995, 33:949-957.

Resources

• Performance of electrolyte assays in the UK - comparison with reference method 142k