Amperometric techniques in flow-injection analysis: determination of magnesium in sera and natural waters

✍ Scribed by Alison J. Downard; Joanne B. Hart; H.Kipton J. Powell; Shuanghua Xu

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 712 KB
• Volume: 269
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(92)85131-o

✦ Synopsis

Magnesmm was determined m a flow-mqectlon system by formatlon of the magnesmm-Enochrome Black T (EBT) complex at pH 115 (5% 1,Zdlammoethane m 0 1 M KCl) and amperometrlc measurement of the excess of EBT at +0 175 V on a glassy carbon electrode From modelhng calculations, pH and concentrations of EBT (3 75 x 10e5 M) and maskmg agent EGTA (1 12 X 10m4 M) were chosen so as to mmlmlze Interference from calcmm Electrode fouhng from EBT oxldatlon products was countered by use of 0 2% surfactant (Hostapur SA 93) m the tamer stream Iron(III) was masked with trlethanolamme For analysis of natural waters the hnear workmg range was 0 027-l 8 mg kg-' Mg and the R S D was 0 7% at 16 mg kg-' Mg (n = ll), the detectlon hmlt was 5 5 LLg kg-' Analysis of human blood serum samples was effected by two methods direct mlectlon of serum after a 20-fold ddutlon (Hostapur SA 93 countered the assoclatlon of EBT with serum albumm) and after dlalysls (2 5 mm) to separate Mg from acldlfled serum m the flow system The hnear workmg range for direct mlectlon was as above andtheRSD wasO4%(n=9)atlOmgkg -* Mg For each method the results were compared with those from flame atomic absorption spectrometry