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An improved capillary zone electrophoresis (CZE)/ mass spectrometer interface comprises a liquid junction adapted to makeup the volume/flow rate of the CZE column eluent stream to be more compatible with the ion spray LC/MS interface flow rates required by mass spectrometer detectors in on-line separation/detection systems for variouscompositions and mixtures including biological fluids and environmental samples. Analytes eluting from the CZE capillary column are diluted with a suitable buffer thereby adjusting the volume and flow rates to prevent flow and pressure discrepanies which would otherwise result in peak broadening. The new liquid junction system for CZE/MS and CZE/MS/MS is useful in separating, detecting and analyzing compositions and mixtures such as amino acids, pesticides, peptides, mucleotides, sulfonated azo dyes and enzymatic digests such as tryptic digest of recombinant bovine somatotropan. Detection can be carried out in both positive and negative ion modes. High separation efficiencies ranging from 50,000 to 1,000,000 theoretical plates and peak asymmetries of 1.2 to 1.8 for tryptic digest are achieved.

A liquid–solid extraction method suitable for rapid screening of sulfonated azo dyes in municipal wastewater has been developed. The dyes (Color Index Acid Yellow 23, Red 14 and Yellow 49) were separated on a short, reversedphase liquid chromatographic column with a water-methanol gradient containing 2 mM sulfuric acid. The column effluent was directed via a split-valve to an ion spray liquid chromatography/mass spectrometry (LC/MS) interface to an atmospheric pressure ionization mass spectrometer. The ion spray LC/MS system produced abundant [M – Na]− and [M – 2Na]2− ions according to the number of sulfonic acid substituents. Collision-induced dissociation of the parent ions for the dyes studied gave the SO3−. fragment common to sulfonated compounds plus additional daughter ion fragments characteristic of each dye. The dyes were quantified by monitoring from four to six different daughter ions of each dye. The relative abundances and the sum of the daughter ion current counts were used for confirmation and quantification with external standards. Recoveries of the dyes were in the range of 70–122%, and the relative standard deviation of replicate determinations was 5.4–12%. The method detection limit was three times higher for Acid Yellow 23 compared with the other two dyes, which could be detected down to 50 ppb in municipal wastewater.

Full-scan capillary zone electrophoresis/mass spectrometry and capillary zone electrophoresis/tandem mass spectrometry (CZE/MS/MS) are demonstrated for the determination of monosulfonated and polysulfonated azo dyes at the low picomole levels. Under selected ion monitoring conditions femtomole levels of the dyes are detectable. Ion evaporation via the ion spray liquid chromatography/mass spectrometry interface is a mild form of ionization exhibiting only deprotonated singly charged or poly-deprotonated multiply charged negative molecular ions for sulfonated azo dyes. CZE/MS/MS daughter ion scanning after collision-induced dissociation of the molecular species for all sulfonated azo dyes contained the sulfonate ion (m/z 80). The presence of three sulfonated azo dyes in a wastewater extract was confirmed by parent ion scanning for the sulfonate daughter ion (m/z 80).

Sulfoconjugated anabolic steroids were separated by micro-bore high-performance liquid chromatography. The eluent was introduced into the atmospheric pressure ion source of the triple-quadrupole mass spectrometer via an ion spray liquid chromatograph/mass spectrometer interface operated in the negative ion mode. The limit of detection was 10 pg on-column by selected ion monitoring of the molecular ion and the response increased linearly over a concentration range of 2.4 orders of magnitude. Following work-up by a liquid-solid extraction procedure of equine urine samples, full-scan daughter ion spectra of boldenone sulfate could be obtained up to 17 days after a therapeutic dose of boldenone undecylenate to a horse.