Development of non-aqueous single stage derivatisation method for the determination of putrescine and cadaverine using GC-MS

A single step derivatisation for the determination of putrescine and cadaverine by gas chromatography using trifluoroacetylacetone (TFAA) in methanol or ethanol was studied and optimised. The derivatives were analysed by an iontrap gas chromatograph-mass spectrometer (GC-MS) operating with electron impact ionisation with selective ion storage (EI-SIS) mode. The optimised mole ratios for TFAA/putrescine and TFAA/cadaverine reactions were 5/1 and 5.8/1 respectively with a reaction time of 15 minutes at 95oC. The retention times for the derivatised putrescine and cadaverine were 11.3 and 12.2 minutes respectively using the capillary column, CP-Sil 8CB; 30 m length x 0.25 mm i.d. x 0.25 mm film. The correlation coefficients (R²) of calibration curves for putrescine and cadaverine were 0.991 and 0.990 respectively over a concentration range of 100 ng cm⁻³ to 1500 ng cm⁻³. The method developed was found to be simple (single-stage derivatisation), rapid (15 minutes derivatisation & 14 minutes GC/MS run) and accurate (putrescine and cadaverine recoveries 94.8%–97.7%).      

离子色谱法测定水中的腐胺、尸胺和组胺

建立了离子色谱法快速测定水中腐胺、尸胺和组胺的方法, 考察了淋洗液条件、干扰离子对实验的影响, 优化了分离条件, 进行了方法学评估. 实验结果表明: 3种物质可以在9 min内达到基线分离, 腐胺和尸胺在1.0～20.0 mg/L、组胺在1.0～100.0 mg/L的浓度范围内, 峰面积和浓度之间线性关系良好, 保留时间的RSD＜0.01%, 峰高的RSD＜2.32%, 峰面积的RSD＜2.08%, 回收率在92.0%～107.4%之间. 本方法适用于水中腐胺、尸胺和组胺的测定.     

Gas chromatographic method for determining free fatty acids in cheese

Summary A rapid gas chromatographic method for the analysis of individual free fatty acids (FFA) in cheese has been developed. Lipds were extract from a cheese paste acidified with diethyl ether and tetramethylammonium hydroxide (TMAM) was used for converting the FFA to TMA-soaps, which are transformed to methyl esters in the chromatographic injector. The effect of lactic acid was determined. The reproducibility of the method was studied and the coefficient of variation for the total FFA was found to be 2.2%. Recovery of individual FFA was in the range 87 to 106%.     

离子色谱-抑制型电导检测牛肝菌中胆碱、腐胺和尸胺

建立离子色谱-抑制型电导检测牛肝菌中胆碱、腐胺和尸胺的方法。牛肝菌干片样品经7 mmol/L甲烷磺酸溶液提取,过滤膜,经反相固相萃取柱净化后进样分析。胆碱、腐胺、尸胺与样品中共存离子在IonPac CS17（250 mm×4 mm）阳离子交换色谱柱上可实现较好分离。以7 mmol/L甲烷磺酸为淋洗液等度淋洗,25 min可完成一次样品测定。胆碱、腐胺和尸胺的检出限（S/N=3）分别为0.002、0.002和0.003 mg/L,具有较宽的线性范围（0.01~10 mg/L）,样品加标回收率为91.6%~100.2%。该方法简便、选择性好、灵敏度高,适用于牛肝菌中胆碱、腐胺和尸胺的检测分析。     

Gas chromatographic method for the analysis of nitrochlorobenzene isomers

Summary An efficient, reproducible and rapid gas chromatographic method for the analysis of nitrochlorobenzenes has been described in this paper. The method uses FFAP as stationary phase and 3,4-dichloronitrobenzene as internal standard. The total analysis time of the method is less than 15 minutes with a coefficient of variation ranging from 0.41% to 1.19% for different levels of three isomers.     

Optimising cell temperature and dispersion field strength for the screening for putrescine and cadaverine with thermal desorption-gas chromatography-differential mobility spectrometry

Biogenic amines, and putrescine and cadaverine in particular, have significant importance in the area of food quality monitoring, and are also potentially important markers of infection, for cancer, diabetes, arthritis and cystic fibrosis. A thermal desorption-gas chromatograph-heated differential mobility spectrometer was constructed and the significant effect of interactions between cell temperature and dispersion field strength on the observed responses studied. The experiment design was a Box-Wilson central composite design (CCD) over the levels of 10-24 kV cm⁻¹ for dispersion field strength and 100-130 °C for cell temperature. The optimum values were estimated to be 16.22 kV cm⁻¹ and 116 °C for putrescine and 14.78 kV cm⁻¹ and 112 °C for cadaverine, respectively with an ammonia dopant at 19 mg m⁻³.An amine test atmosphere generator was constructed and produced stable concentrations of putrescine (7 mg m⁻³) and cadaverine (4 mg m⁻³) vapours at 50 ± 0.5 °C. Tenax TA-Carbotrap adsorbent tubes were used to sample putrescine and cadaverine vapour standards and a linear response function over the range of sample masses 5-20 ng was obtained at 15.0 kV cm⁻¹ 115 °C, with a R² of 0.99 for both putrescine and cadaverine. The sample mass at the limit of detection was estimated to be 3 ng for putrescine and cadaverine. Preliminary data from sampling the headspace of chicken meat revealed a 62% increase in the recovered masses of putrescine from 0.84 to 1.36 ng in the sampled air.     

Determination of putrescine and cadaverine in seafood (finfish and shellfish) by liquid chromatography using pyrene excimer fluorescence

A liquid chromatography (LC) method is described for the easy determination of the biogenic diamines putrescine (PUT) and cadaverine (CAD) in canned tuna, frozen tuna loin, fresh mahimahi fillet, frozen raw shrimp, cooked lump crabmeat, and fresh and cold-smoked salmon. The method is also a useful screen for histamine (HTA). The method involves homogenization of fish tissue, extraction of biogenic amines into borate-trichloroacetic acid solution, centrifugation, and derivatization of supernatant with 1-pyrenebutanoic acid succinimidyl ester. The derivatized diamine species allow for the intramolecular excimer fluorescence of the pyrene moiety at a higher emission wavelength than is possible for the endogenous tissue monoamines, thus providing visual specificity of detection. All seafood species were fortified with 0.5, 1.0, 5.0, 10.0, and 15.0 microg/g (ppm) of PUT and CAD. Determination was based on standard graphs for PUT and CAD using peak areas with standard solutions equivalent to 0.375, 1.0, 5.0, 10.0, and 20.0 ppm in tissue. A set of five matrix controls (unfortified seafood tissue) were also analyzed; endogenous PUT was found in all samples except the canned tuna, and CAD found only in the shrimp, crab, and cold-smoked salmon. The background amines were thus subtracted prior to determining spike recovery. The intra-assay average recoveries ranged from 71 to 94% across species and spike levels.     

Gas chromatographic method for the determination of nomifensine in human plasma.

An analytical method based on solvent extraction, formation of a fluorinated derivative and quantitation by gas-liquid chromatography using an electron capture detector has been developed for the determination of nomifensine in biological fluids. The specificity (controlled by mass spectrometry) and the sensitivity appear to be satisfactory for drug level measurements in human body fluids. Its relative simplicity in fact permits its use in serial analysis.     

Impact of quality parameters on the recovery of putrescine and cadaverine in fish using methanol-hydrochloric acid solvent extraction

Methanol (MeOH) extraction by AOAC Official Method 996.07 has resulted in low amine recoveries in fresh fish tissue. Addition of 25% 0.4 M HCl to the 75% methanol-water extraction solvent resulted in higher recoveries of putrescine and cadaverine. Average putrescine recovery increased from 55 to 92% in flounder, scup, bluefish, and salmon; from 92 to 98% in mackerel; and from 83 to 107% in processed mackerel. Average cadaverine recovery increased from 57 to 95% in flounder, scup, bluefish, and salmon; from 91 to 97% in mackerel; and from 92 to 108% in processed mackerel. Fish stored on ice for 12 days also showed differences between background concentrations determined with the two solvents. However, the values decreased with storage time, indicating that degradation of the protein matrix may cause more comparable measurements between the two solvents. However, consistently higher putrescine and cadaverine measurements were determined using MeOH-HCl. Although significant differences in the extraction of amines from the high-fat fish tissue were not seen between MeOH and MeOH-HCl, it would be ideal to have one solvent for biogenic amine extraction. This study confirms that MeOH-HCl is a better solvent for complete extraction and recovery of putrescine and cadaverine in fresh and processed fish tissues.     

Gas chromatographic method for the determination of selenite and total selenium in sea water

A method is described for the determination of dissolved selenite and total selenium in natural waters. The detection limit is approximately 10 pmol l^-1 and the reproducibility ±2.4% (1σ) at 394 pmol l^-1. A 100-ml sample containing selenite is reacted with 4-nitro-o-phenylenediamine to form 5-nitropiazselenol which is extracted into toluene and then determined by gas chromatography with an electron-capture detector. Other forms of selenium can be determined after photo-oxidizing samples under controlled pH conditions. This leads to a reproducible proportionation of species between selenite and selenate. The method has been used successfully to analyze samples both at sea and in the laboratory.     

Aqueous sulfuric acid as the mobile phase in cation ion chromatography for determination of histamine, putrescine, and cadaverine in fish samples

Aqueous sulfuric acid can be used as the mobile phase in cation ion chromatography to separate the three biogenic amines, putrescine, cadaverine, and histamine, from fish. Various concentrations of aqueous sulfuric acid were investigated to optimize the separation of these three biogenic amines. Aqueous sulfuric acid (5.0 mM) was found to be optimum for the separation and was used to determine the three biogenic amines in fish. The LOQ, defined as the lowest level of the standard calibration curve, was 0.055 ppm (equivalent to 0.55 microg/g sample) for putrescine, 0.05 ppm (equivalent to 0.5 microg/g sample) for cadaverine, and 1.0 ppm (equivalent to 10 microg/g sample) for histamine. From statistical analysis of the LOQ, the method detection limit was 0.003 ppm for putrescine, 0.009 ppm for cadaverine, and 0.16 ppm for histamine. For sample preparation, the fish was composited, homogenized in methanol-water (75 + 25, v/v), incubated for 15 min at 60 degrees C, and centrifuged. The sample solution was micron-filtered before injection. The mobile phase flow rate was 0.8 mL/min under isocratic conditions at room temperature (15-25 degrees C). The three biogenic amines were separated in the order of increasing retention time, i.e., putrescine, cadaverine, and histamine, within 30 min. The chromatograms showed complete peak separation of the three amines regardless of the difference in fish matrixes.