Determination of malachite green residues in fish using a highly sensitive electrochemiluminescence method combined with molecularly imprinted solid phase extraction

An electrochemiluminescence (ECL) inhibition method combined with molecularly imprinted solid phase extraction (MISPE) was developed for quantitative determination of malachite green (MG) residues in fish. It was found that MG could strongly inhibit the ECL signal of luminol. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of MG was in good linear relationship over a concentration range from 20 to 5000 ppt. The method detection limit was found to be about 6 ppt. Molecularly imprinted polymers (MIPs) were synthesized as solid phase extraction (SPE) sorbents, and MISPE was used for the selective extraction and purification of MG. By carrying out the oxidation reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), which could convert leucomalachite green (LMG) into MG, this method was successfully applied to determine MG residues in fish. A possible mechanism for the quenching effects of MG on luminol was also proposed.     

Production of antibodies for selective detection of malachite green and the related triphenylmethane dyes in fish and fishpond water

This study provides a practical method for production of the antibodies against malachite green (MG) and its primary metabolite leucomalachite green (LMG). Two ELISA kits are constructed with the MG and LMG antibodies for detection of the residual MG and LMG in fish muscle and fishpond water. The detection limit is established at the level of 0.05 microg/L for both MG and LMG. Our ELISA kits show the advantages of good specificity, high sensitivity, and convenience in rapid screening of MG and LMG residues. The sample of fishpond water, without extraction or prior preparation, is directly assayed by the ELISA kit. More then 80 fish samples can be simultaneously tested in a kit. The toxic crystal violet and its metabolite leucocrystal violet of illegal use in aquaculture are detected by our prepared MG and LMG antibodies, whereas the antibodies do not cross-react with common antibiotics, sulfonamides, and benzene derivatives.     

Determination of phosphate in solution at different ionic composition using malachite green

Abstract

The malachite green method was sometimes used to determine low concentrations of inorganic phosphate due to its high sensitivity. The aim of this work was to test the suitability of this method for the determination of phosphorus (P) extracted by various reagents, e.g., KCl 0.01–1.20M, CaCl₂ 0.01–0.1M, Na₂SO₄ 0.01–0.40M, NaHCO₃ 0.1M at pH 8.5, and NaOH 0.1M+NaCl 1M. The malachite green method was also compared with the traditional molybdenum blue method on 35 soil extracts. Color development reached stability within 2 hrs and was stable for up to 24 hrs for dilute solutions. For concentrated solutions the stability was inversely proportional to the concentration of the reagent. Salt concentration appeared to have no effect on absorbance in KCl extracts of up to 1.2M and in Na₂SO₄ extracts of up to 0.05M. Higher concentrations of sodium sulfate induced flocculation and precipitation of the dye complex, as did CaCl₂ above 0.04 M. A strong correlation was found between the malachite green and the molybdenum blue method. The malachite green method can be used for P determination in soil extracts when appropriate time of color development is provided and salt concentration is taken into account.     

Automated determination of trace amounts of phosphate in soil extracts using malachite green

Abstract

A sensitive and simple automatic continuous‐flow determination of orthophosphate at trace levels has been worked out. The detection limit was lower than 2 μg/L. The interferences due to silicate and dissolved organic matter in soil extracts have been eliminated.     

Identification of O,O-dialkyl-S-methylphosphorodithioate residues in fish

O,O-Dialkyl-S-methylphosphorodithioates were found in Mississippi River buffalo fish caught near several chemical plants and oil refineries in Hartford and Wood River, IL. These chemicals, which have not been previously recognized as environmental or food contaminants, were identified and quantitated by a procedure similar to the AOAC multiresidue method for organochlorine and organophosphorus pesticides, using gas chromatography (GC) with flame photometric detection (FPD). The key to their identification was a GC/FPD retention time pattern that was virtually the same as that for the diazomethane reaction products of a commercial zinc dialkyl dithiophosphate motor oil additive. GC/mass spectrometry (MS) showed that the compound producing the largest GC/FPD peak contained butoxy groups. The identification of this compound as O,O-di(2-methylpropyl)-S-methyl-phosphorodithioate (Compound C) was confirmed by GC/MS analysis by comparison with the authentic material. The buffalo fish contained 0.15 ppm Compound C and 0.5 ppm total O,O-dialkyl-S-methylphosphorodithioates. Subsequent analyses of fish from other areas showed that these contaminants were not limited to the Hartford-Wood River area. Lower residue levels of Compound C, ranging from 0.01 to 0.05 ppm, were found in fish from the Mississippi River at Sauget, IL, and from the Delaware River and Newark Bay in NJ.     

Re-evaluation of selectivity of malachite green test for presence of sulfite in mechanically deboned poultry

A study was undertaken to determine whether free chlorine or sulfide anions could yield positive results for the malachite green test in meat samples when sulfite was not present. Malachite green solution was added to a mechanically deboned poultry (MDP) sample spiked with either chlorine or sulfide ions. The presence of chlorine in MDP samples at any concentration tested did not yield a positive reaction for the malachite green test. When sulfide ions were introduced into MDP samples, positive results were observed at 40 micrograms sulfide ion/g MDP and above. Because aqueous solutions of sulfide at the levels mentioned have a relatively high pH, it was necessary to determine whether the pH or the presence of the sulfide ions had caused this positive reaction to the malachite green test. After a comparison of a solution of sulfide, and a solution of a matching pH, it was observed that the sulfide present caused the positive reaction to the malachite green test.     

Determination of ampicillin residues in fish tissues by liquid chromatography

A liquid chromatographic (LC) method is described for determination of ampicillin residues in fish tissues. The drug is extracted from tissues with methanol, and the extract is evaporated to dryness. This residue is cleaned up by Florisil cartridge chromatography. LC analysis is carried out on a Nucleosil C18 column, and ampicillin is quantitated by ultraviolet detection at 222 nm. Recoveries of ampicillin added to tissues at levels of 0.2 and 0.1 ppm were 73.2 and 61.5%, respectively. The detection limit was 3 ng for ampicillin standard, and 0.03 ppm in tissues.     

Pesticide residues in milk and fish samples collected from upper Egypt

In Egypt, buffalo milk is much preferred by consumers over cow's milk, while small catfish and bolti fish are common in the diet of farmers. Samples of buffalo milk, catfish, and bolti fish collected from Beni-Suef Governorate (Upper Egypt) were analyzed for organochlorines and polychlorinated biphenyls. The results obtained by gas chromatography and confirmed by thin-layer chromatographic techniques revealed high amounts of organochlorines in milk; residues were lower but occurred more frequently in fish samples. Pesticide contaminants found most often were HCH isomers including lindane, DDT complex, aldrin and dieldrin, heptachlor and heptachlor epoxide, hexachlorobenzene, and oxychlordane. Polychlorinated biphenyls were not detected in any of the analyzed samples.     

Survey of residues of organochlorine pesticides in some marketable Egyptian fish

One hundred random samples representing 34 species of marketable fish were collected from 8 Egyptian governorates during the period March 1986 to March 1988 and were analyzed for the presence of some organochlorine pesticides. The results showed the predominance of beta-BHC and lindane at maximum levels of 435.30 and 59.00 micrograms/kg, respectively, for fish samples obtained from Damietta governorate. The corresponding levels of aldrin, and o,p'-DDT were 34.27 and 734.10 micrograms/kg, respectively, for fish from the Red Sea governorate. gamma-Chlordane, p,p'-DDE, and p,p'-DDT were found in fish from Ismailia governorate at respective maximum levels of 36.17, 234.40, and 57.19 microgram/kg. Heptachlor was identified at 8.50 micrograms/kg in Port Said governorate fish and o,p'-DDE at 10.59 micrograms/kg in Suez governorate fish. Mirex, on the other hand, could not be detected in any of the samples investigated.     

Pesticide residues in milk and fish samples collected from two Egyptian Governorates

Because of the intensive use of pesticides for the control of certain pests in Egypt, country-wide residue monitoring programs must be established that can cover all the Egyptian Governorates exposed to pesticide treatments. To do so, limited programs must be adopted first, so that current situations and future needs for improved programs are identified. The present paper reports results from a limited monitoring program, which started in 1985 in one governorate and then expanded to include another in 1986. Fish and milk samples were the commodities selected for residue analysis. The results showed that milk samples collected from Beni-Suef Governorate in 1986 had lower levels of organochlorine residues compared to those collected in 1985. Residues in boltifish and catfish samples in 1986 were much higher than those detected in 1985. In comparison with Beni-Suef Governorate, and contrary to expectations, milk derived from Fayoum Governorate in 1986 was more contaminated with pesticides. While the amount of residues in boltifish was comparatively higher, catfish samples were less contaminated.     

Liquid chromatography-tandem mass spectrometry for the determination of protein-bound residues in shrimp dosed with nitrofurans

An analytical method was developed for the determination of bound residues of the nitrofuran drugs furazolidone, nitrofurazone, furaltadone, and nitrofurantoin with a sensitivity of 1 ppb in shrimp. In this procedure, shrimp tissue is prewashed with solvents followed by overnight acid hydrolysis, during which the side chains of the bound residues are released and simultaneously derivatized with 2-nitrobenzaldehyde. After liquid-liquid extraction cleanup, the derivatives are detected and quantitated using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) with an atmospheric pressure chemical ionization interface. The method was validated using control shrimp fortified with each side-chain analyte at 1, 2, and 4 ppb. Method accuracies were >80% with coefficients of variation of <20% for all four analytes. Tissues from dosed shrimp were assayed to demonstrate the effectiveness of the method for recovering bound residues of nitrofurans. In shrimp dosed with nitrofurans, nitrofurantoin exhibited the lowest level of bound residues.     

Effect of protein on the detection of fluoroquinolone residues in fish meat

Using fish serum albumin (FSA) as the model protein, molecular fluorescence spectrometry and high-performance liquid chromatography (HPLC) were applied to study the effect of protein on the extraction of fluoroquinolone (FQ) residues in fish meat. There was a strong interaction between FQs and protein through hydrogen bonds, which could be broken as protein degenerated with 60-100% (v/v) acetonitrile acid solution, and FQs bound with protein were released in various degrees. On the basis of the results, a novel sample preparation procedure loosely based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) methodology was developed for the determination of FQ residues in fish muscle samples, using 90% (v/v) acetonitrile acid solution as the extractant, combined with a dispersive solid-phase extraction (DSPE) cleanup step. Mean recoveries of four FQs from spiked samples at a concentration range of 50-200 ng g(-1) were 73.3-95.9% with relative standard deviations (RSD) lower than 10.7%.