Using calmagite as the compleximetric agent in spectro-photometric measurements of magnesium in serum involves a nonspecific matrix effect, which may bias results by as much as 25 to 30% if aqueous standards are used in serum assays. We have overcome this effect by simply adding 5 pL of the amphoteric detergent Empigen BB (300 g/L; Albright and Wilson Ltd., Whitehaven, U.K.) to each reaction cu...

Magnesium in plasma is determined by diluting a 50-microL sample with 5.0 mL of stable calmagite reagent containing the amphoteric detergent Empigen BB, and buffered with 2-amino-2-methyl-1-propanol at pH 11.5. The calcium response is masked with strontium-buffered [ethylene-bis(oxyethylenenitrilo)]tetraacetate (EGTA), while iron is masked with triethanolamine. The detergent causes an increased...

We show how serum magnesium can be determined with a centrifugal analyzer. The method is based upon a manual procedure involving magnesium/calmagite complex formation in an alkaline reagent mixture. The assay, performed at 30 degrees C, requires 5 mul of serum in a final reaction volume of 405 mul, including 350 mul of reagent mixture. The stable color produced at 1 min is measured at 520 nm. L...

Titration of a trichloracetic acid filtrate of serum with EDTA is carried out at pH 9.8 using an excess of Calmagite indicator. Successive photometric readings of percentage transmission, made with an EEL titrator, are plotted against the volume of EDTA added. There is very little change at first while calcium is being complexed; the reading then decreases rapidly while magnesium is being titra...

A simple and sensitive extraction-spectrophotometric method for rapid and accurate determination of benzocaine in pure and dosage forms was developed. Benzocaine was effectively extracted as a 1:1 ion pair complex with dicyclohexyl18-crown-6 and calmagite in acidic media into chloroform, followed by spectrophotometric determination at 486 nm. Molar absorptivity of the ternary complex at this wa...

A method for the preconcentration and determination of Cr(III), Co(II), Cu(II), Fe(III) and Pb(II) ions by atomic absorption spectrometry has been described. The method was based the collection of metal-calmagite complexes on a soluble cellulose nitrate membrane filter. The detection of the solution was obtained by flame atomic absorption spectrometry (FAAS) after completely dissolving the memb...

We describe the application to the Technicon SMAC system of a micellar-improved calmagite method for the measurement of magnesium. In this continuous-flow method a dialyzer is not needed, because protein interference is negligible. Sample interaction was estimated to be 3%. The increased sensitivity of the method allows for a small sample volume (37 microL/min). Results obtained agreed well wit...

An extraction-spectrophotometric method for the determination of trace amounts of ammonium ion is described. Ammonium ion is effectively extracted as a neutral ternary complex NH . DB 18C6. calmagite at pH 3.0 into chloroform, followed by spectrophotometric determination at =48 5 nm. Molar absorptivity of the ternary complex at this wavelength is 1.08 10 mol cm . Beer's law is obeyed over...

A simple and sensitive extraction-spectrophotometric method for rapid and accurate determination of benzocaine in pure and dosage forms was developed. Benzocaine was effectively extracted as a 1:1 ion pair complex with dicyclohexyl-18-crown-6 and calmagite in acidic media into chloroform, followed by spectrophotometric determination at 486 nm. Molar absorptivity of the ternary complex at this w...