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A novel method for quantitative total protein determinations is presented. Total protein content is determined by particle beam/hollow cathode optical emission spectroscopy (PB/HC-OES) through monitoring of carbon atomic emission. The PB/HC-OES offers such advantages as ease of operation, exclusion of labor-intensive sample pretreatment processes, rapid analysis, high sensitivity, and low detection limit. The method could also be adapted to be integrated to current microfluidics devices. Parametric optimization for sample introduction, nebulization, desolvation, and hollow cathode source conditions is performed for the analysis of aqueous bovine serum albumin solutions. Response curves of C (I) 193.0-nm emission were obtained under the optimized conditions with both 10% HCl and 100 micromL KCl added to the sample matrix as potential carriers. The detection limit for triplicate injections of bovine serum albumin standards was found to be on the single-nanogram level with 200-microL injections. The addition of KCl significantly improved the sensitivity, supporting the proposed "carrier effect" of chloride salts in the particle transport process. Results obtained here suggest a range of applications for the use of the PB/HC-OES source for total protein determinations; emphasis here is future use in assessing protein quantification in microfluidic systems.

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4,6-Dimethyl-o-quinone methide (4) was produced by FVP of alcohol 3 or of the trimer 6 and matrix isolated in Ar at 7.6 K. Photolysis of 4 with long wavelength light (>345 nm) at this temperature afforded 4,6-dimethylbenzoxete (5), which was observable up to room temperature in the solid state in the absence of water. 5 can be converted back to 4 by UV irradiation at 254/190 nm. Quantum chemical calculations on the thermal interconversion of 4 and 5 indicate activation barriers of the order of 40 kcal/mol for 4 → 5, and 30 kcal/mol for 5 → 4. The dimer, trimer, and tetramer (8, 6, and 7) of 4 are characterized.

Particle beam hollow cathode optical emission spectroscopy (PB/HC-OES) is evaluated as a generic tool for total protein determinations by monitoring the carbon atomic emission (C (I) 193.0 nm) resultant from dissociated analyte species. Previous studies demonstrated the capability of the PB/HC-OES system for total protein determinations with limits of detection for bovine serum albumin (BSA) samples being at the single-nanogram level for 200 microl injections. Non-linear behavior across the concentration range in the calibration curve was observed due to the poor transport of small particles (owing to low analyte concentrations) through the PB interface. The potential use of non-volatile salts as carrier agents is investigated in the determination of protein samples by PB/HC-OES. A range of chloride salts (different cations), potassium salts (different anions), and an organic modifier (ammonium acetate) is investigated here for possible use as carriers upon addition as sample injection matrices for protein samples. The analyte response curves of BSA samples with KCl added as the sample injection matrix show higher sensitivity, better linearity (R2) and subsequently lower detection limits in comparison to those obtained with water, HCl, KNO3 or ammonium acetate as carrier matrices.