The detection of boron and the response of some boronate derivatives of carbohydrates with an alkali flame ionization detector

Abstract

The use of boronic acids for the derivatization of compounds containing a diol moiety has been reported by Brooks and MacLean’. Preliminary reports2v3 suggested a potential for butylboronates as derivatives for some carbohydrates and alditols. These esters can be chromatographed by gas chromatography (GC) and detected by flame ionization (FID) or specifically by flame photometric detectors (FPD)“. In addition, it has now been found that they can be detected by an alkali flame ionization detector (AFID). Although the AFID is considered to be a specific detector for phosphorus and nitrogen, it is known to respond to other elements such as bromine, chlorine and iodine5, sulphurG and lead, silicon and tin ‘. For each element, the detector parameters, such as the jet diameter, electrode spacing, alkali salt and flame conditions required for optimum response are different. This paper describes the flame conditions most suitable for the detection of boron. The GC analyses were performed on a Pye 104 Model 154 gas chromatograph fitted with a three-electrode AFID and a CsBr annulus. The compounds were chromatographed on a 3 ft. X ‘/* in. glass column, packed with 100-120 mesh Gas-Chrom Q coated with 3% OV-17, which was conditioned after the manner of Bowman and Berosa’. A column flow of 40 ml/min was used throughout. The decaborane was purchased from ICN Research Prods., and the phenylboronic acid anhydride (triphenylboroxole) was synthesized by dehydration of phenylboronic acid (Alfa Inorganics Inc.) and crystallised from isopropyl ether/petroleum ether. The boronate derivatives of fucose, xylose and arabinose were prepared by the method of Wood and Siddiquig. The purity and elemental composition were established by carbon and hydrogen analysis and by mass spectrometry. In the AFID, the temperature of the flame and the stability of the detector are dependent on a very precise hydrogen flow-rate. Variation of this flow is the