On-line determination of cyanide in the presence of sulfide by flow injection with pervaporation

Quantitative proteomic analysis of Pseudomonas pseudoalcaligenes CECT5344 in response to industrial cyanide-containing wastewaters using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS)

Biological treatments to degrade cyanide are a powerful technology for cyanide removal from industrial wastewaters. It has been previously demonstrated that the alkaliphilic bacterium Pseudomonas pseudoalcaligenes CECT5344 is able to use free cyanide and several metal−cyanide complexes as the sole nitrogen source. In this work, the strain CECT5344 has been used for detoxification of the different chemical forms of cyanide that are present in alkaline wastewaters from the jewelry industry. This liquid residue also contains large concentrations of metals like iron, copper and zinc, making this wastewater even more toxic. To elucidate the molecular mechanisms involved in the bioremediation process, a quantitative proteomic analysis by LC-MS/MS has been carried out in P. pseudoalcaligenes CECT5344 cells grown with the jewelry residue as sole nitrogen source. Different proteins related to cyanide and cyanate assimilation, as well as other proteins involved in transport and resistance to metals were induced by the cyanide-containing jewelry residue. GntR-like regulatory proteins were also induced by this industrial residue and mutational analysis revealed that GntR-like regulatory proteins may play a role in the regulation of cyanide assimilation in P. pseudoalcaligenes CECT5344. The strain CECT5344 has been used in a batch reactor to remove at pH 9 the different forms of cyanide present in industrial wastewaters from the jewelry industry (0.3 g/L, ca. 12 mM total cyanide, including both free cyanide and metal−cyanide complexes). This is the first report describing the biological removal at alkaline pH of such as elevated concentration of cyanide present in a heterogeneous mixture from an industrial source.

Sensitivity enhancement in membrane separation flow injection analysis by ultrasound

The effect of ultrasound on gas-diffusion and pervaporation flow injection separation was investigated. Ammonia and three aliphatic amines (propylamine, tri-ethylamine and di-n-butylamine) with different volatility and surface activity were used as model analytes. Under the experimental conditions used, sonication did not enhance gas-diffusion separation efficiency and resulted in up to 62% improvement in pervaporation mass transfer. Based on these findings and taking into account the surface activity of the analytes studied which decreased with their molecular mass it was postulated that ultrasound-induced surface rippling was primarily responsible for the enhanced evaporation in the donor chamber of the pervaporation cell. The results reported in this paper suggest that ultrasonic pervaporation separation could extend the applicability of this on-line flow injection separation technique to the direct determination of higher molecular mass volatile and semi-volatile analytes in 'dirty' samples.

Application of hydrocyanic acid vapor generation via focused microwave radiation to the preparation of industrial effluent samples prior to free and total cyanide determinations by spectrophotometric flow injection analysis

A sample preparation procedure for the quantitative determination of free and total cyanides in industrial effluents has been developed that involves hydrocyanic acid vapor generation via focused microwave radiation. Hydrocyanic acid vapor was generated from free cyanides using only 5 min of irradiation time (90 W power) and a purge time of 5 min. The HCN generated was absorbed into an accepting NaOH solution using very simple glassware apparatus that was appropriate for the microwave oven cavity. After that, the cyanide concentration was determined within 90 s using a well-known spectrophotometric flow injection analysis system. Total cyanide analysis required 15 min irradiation time (90 W power), as well as chemical conditions such as the presence of EDTA-acetate buffer solution or ascorbic acid, depending on the effluent to be analyzed (petroleum refinery or electroplating effluents, respectively). The detection limit was 0.018 mg CN l(-1) (quantification limit of 0.05 mg CN l(-1)), and the measured RSD was better than 8% for ten independent analyses of effluent samples (1.4 mg l(-1) cyanide). The accuracy of the procedure was assessed via analyte spiking (with free and complex cyanides) and by performing an independent sample analysis based on the standard methodology recommended by the APHA for comparison. The sample preparation procedure takes only 10 min for free and 20 min for total cyanide, making this procedure much faster than traditional methodologies (conventional heating and distillation), which are time-consuming (they require at least 1 h). Samples from oil (sour and stripping tower bottom waters) and electroplating effluents were analyzed successfully.

Ultra-sensitive trace analysis of cyanide water pollutant in a PDMS microfluidic channel using surface-enhanced Raman spectroscopy

Rapid and highly sensitive trace analysis of cyanide water pollutant in an alligator teeth-shaped PDMS microfluidic channel was investigated using surface-enhanced Raman spectroscopy. Compared with previously reported analytical methods, the detection sensitivity was enhanced by several orders of magnitude.

Semi-quantitative "spot-test" of cyanide

A selective, sensitive, rapid and simple-handling analytical method for the determination of cyanide at low detection limits in surface and underground water, soil and industrial waste samples was developed. The method is based on a reaction, proposed by Guilbault and Kramer, where free cyanide reacts with p-nitrobenzaldehyde to form an intermediate cyanohydrin, which reacts with o-dinitrobenzene to give a highly colored purple compound. The original procedure was modified for application in a small device containing a gas-permeable membrane. The cyanide is converted in the volatile hydrogen cyanide, which permeates through a PTFE membrane, reaching colorimetric reagents. In order to obtain semi-quantitative results, printed color scales were built. The method allows rapid, accurate, selective, low-cost and simple-handling determinations of free cyanide, even in complex samples. About 150 real samples were analyzed. Less than 10 ng of free cyanide per ml (10 microg l(-1)) can be easily detected. For more concentrated solutions, the results had been compared to those obtained using differential pulse polarography. The standard addition method was used for more diluted solutions.

Determination of Henry's law constants of phenols by pervaporation-flow injection analysis

A novel dynamic nonequilibrium technique for the determination of Henry's law constant (HLC) of phenols based on pervaporation-flow injection (PFI) is described. A linear relationship between HLC and the amount of phenol measured by a detector in the acceptor line of a PFI system was demonstrated. This relationship was constructed using five frequently encountered phenols (phenol, 2,4-dimethylphenol, 2,4-dichlorophenol, 2-chlorophenol, and 2,3-dimethylphenol) and used for the determination of the HLC of three other phenols (2,4,6-trichlorophenol, 2-methylphenol, and 3-methylphenol). The HLC of all eight phenols were also determined by the single equilibrium static technique (SEST). Fairly good agreementwas observed between both techniques regarding the HLC of 2,4,6-trichlorophenol, 2-methylphenol, and 3-methylphenol. On the basis of the results obtained, it was concluded that the PFI technique offers considerable advantages over SEST in terms of precision, speed, labor intensity, and possibilities for automation.