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A method for the rapid determination of 4-hexylresorcinol (4-HR) residue in shrimp by solid phase extraction (SPE) ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. 4-HR was extracted twice with methanol, and the extract was formulated into methanol-water solution (1:1). After being cleaned up and concentrated by a PRIME HLB solid phase extraction column, the sample was analyzed by UPLC-MS/MS and quantitatively determined by an external standard method. The separation was performed with a gradient system consisting of water and acetonitrile as the mobile phase. Monitoring was performed by electrospray ionization (ESI) in negative ion mode using multiple ion reaction monitoring (MRM). Good linearity was obtained in the concentration range of 1.0⁻100.0 µg/L, with correlation coefficients larger than 0.999. The limit of detection (LOD) was 0.25 µg/kg and the limit of quantification (LOQ) was 0.80 µg/kg. The average recoveries of 4-HR at spiked concentrations of 2.40, 6.40 and 16 µg/kg ranged from 81.35% to 94.68% with the relative standard deviations (n = 6) from 3.57% to 6.86%. The results showed that the method is simple, fast, sensitive, reliable, and reproducible; thus, it could be used as a rapid confirmation and quantitative analysis method of 4-HR residue in aquatic products.

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A method for the determination of 4-hexylresorcinol residues in prawn and crab meat by HPLC was developed. 4-Hexylresorcinol in prawn and crab meats was extracted with methanol using a homogenizer. The extract was diluted 4 times with water, and the diluted solution was passed through a C18 cartridge. The cartridge was washed with water and methanol-water (4 : 6), and then 4-hexylresorcinol was eluted with acetonitrile-0.1% phosphoric acid (55 : 45). The eluate was separated on a Capcell Pak C18 MG column with a mobile phase of acetonitrile-0.1% phosphoric acid (6 : 4) and 4-hexylresorcinol was determined with a UV detector (210 nm). Recoveries of 4-hexylresorcinol from commercial prawn and crab meats spiked at 1.0 and 10 microg/g were 82.4-92.2 and 88.9-91.8%, respectively. The determination limit of 4-hexylresorcinol was 1.0 microg/g in the samples.

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A method was developed to determine 4-hexylresorcinol in shrimp meat. The procedure is based on extraction of test portions with methanol followed by liquid chromatographic analysis of the extracts, using a reversed-phase column and fluorimetric detection (excitation: 280 nm, and emission: 310 nm). The confidence interval of the recovery in working range of 1.5-2.5 mg/kg was 81.6 +/- 0.8%. The relative standard deviation in the working range was 2.1%. Limits of quantitation and detection were 6.59 and 1.98 ng/mL extract, respectively, corresponding to 0.26 and 0.08 mg/kg in shrimp.

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A method is described for determining 4-hexylresorcinol in crab meat. 4-Hexylresorcinol is used to prevent melanosis in shrimp, and the same use has been proposed for crab meat. Because 4-hexylresorcinol may be added illegally to crab meat as a preservative, consumer protection requires that residues of the compound be monitored in crab meat. 4-Hexylresorcinol is extracted from crab meat with acetonitrile. After dilution with water, the extract is passed through a C18 solid-phase extraction column and 4-hexylresorcinol is eluted from the column with ethanol. The compound is determined by reversed-phase liquid chromatography with diode array detection at 206 nm. Limit of quantitation is 1.0 microgram/g. Mean recovery in the range 1-20 micrograms/g is 89%, with a relative standard deviation of 6.3.

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A liquid chromatographic method was developed for the simultaneous separation and determination of noscapine hydrochloride, hexylresorcinol and anethole in cough lozenges. Analysis was performed on a phenyl column with phosphate buffer- acetonitrile as mobile phase and the separated components were detected at 282 mm. Recoveries obtained for the analytes were of 94.6% for noscapine hydrochloride, 99.1% for hexylresorcinol and 96.3% for anethole. The values of the relative standard deviation were 0.8% for noscapine hydrochloride, 1.5% for hexylresorcinol and 1.1% for anethole. The analytical method was validated and a system suitability test was accomplished for the chromatographic method.

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A rapid, sensitive, liquid chromatographic (LC) method has been developed for determination of residuals of the processing aid, 4-hexylresorcinol, on shrimp meat. An aqueous homogenate of shrimp meat is extracted with ethyl acetate followed by precolumn preparation on a silica Sep-Pak cartridge. LC determination is preformed with a Nova-Pak C18 column, with UV detection at 214 nm. Sensitivity was 0.006 micrograms, and recovery from shrimp meat samples of known 4-hexylresorcinol addition was 94%. Shrimp treated with 4-hexylresorcinol under the recommended dip protocol had mean residuals of 1.18 ppm, with a standard deviation of 0.13 ppm.

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High-pressure liquid chromatography was used with a 5-micron silica gel column to quantitate hexylresorcinol in a commercial antiseptic solution following extraction with methylene chloride. This method shows linearity to at least 0.025% hexylresorcinol. A mobile phase consisting of 63% heptane, 34% chloroform, and 5% methanol was used with a UV detector (254 nm) and a flow of 3 ml/min. No interfering substances were observed.

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