Diatomaceous Earth Column Research Articles

Determination of Carcinogenic Primary Aromatic Amines Contained as Impurities in Synthetic Organic Colorants.

Several primary aromatic amines (PAAs) have been designated carcinogenic or suspected of carcinogenicity. Several kinds of PAAs may occur either via the reduction of azo compounds or as impurities in azo colorants or other agents. An analytical method was developed and applied to determine whether certain PAAs are present as impurities in synthetic organic colorants. Target chemicals were analyzed by the ultrasound extraction of the synthetic organic colorant with a hydrochloric acid solution containing 20% methanol, followed by conversion from an acidic to alkaline solution, and then extraction using a diatomaceous earth column. We analyzed certain PAAs in 38 synthetic organic colorants, resulting in the detection of 2,4-dimethylaniline in four samples at 1.2 to 19 μg/g, o-toluidine in three samples at 1.0 to 3.4 μg/g, p-phenylazoaniline in two samples at 74 to 305 μg/g, and, in one sample each, 2,4,5-trimethylaniline (13 μg/g), 5-nitro-o-toluidine (12 μg/g), and 2-methyl-4-(2-tolylazo)aniline (13 μg/g). Nearly all PAAs were determined to be starting materials for colorant synthesis, although p-phenylazoaniline in Yellow No. 407 was apparently a byproduct formed during synthesis. For Red No. 225, in which high concentrations of p-phenylazoaniline were detected, additional samples were purchased from five companies, and p-phenylazoaniline was detected at concentrations of 88 to 370 μg/g in all samples. A method to analyze certain PAAs contained as impurities in synthetic organic colorants was developed, and the actual status of them in colorants was clarified. The analytical method developed in this study for the determination of certain PAAs contained as impurities in synthetic organic colorants may be used to improve the safety of colorants.

Analysis of 81 pesticides and metabolite residues in fruits and vegetables by diatomaceous earth column extraction and LC/MS/MS determination

A multi-residue method for determining 81 pesticides and metabolite residues in vegetables and fruits by liquid chromatography/tandem mass spectrometry (LC/MS/MS) with electrospray ionization was developed. Pesticide residues were extracted from samples with acetone. Macroporous diatomaceous earth column was used instead of the separatory funnel for liquid/liquid extraction. Ethyl acetate was used as eluting solvent for diatomaceous earth column. This sample preparation technique by diatomaceous earth column was easy, fast and environment-friendly. It can reduce the sample preparation time and solvent consumption as well as eliminate the emulsion problem. Eighty-one analytes of different chemical families of insecticides, acaricides, fungicides, herbicides, plant growth regulators and 4 pesticide metabolites were determined in a single 25 min LC/MS/MS run. The pesticides were separated on an Atlantis T3 column using a gradient elution. Data acquisition under MS/MS for every pesticide or metabolite was achieved by applying multiple reaction monitoring (MRM) of two fragment ion transitions to provide high sensitivity and selectivity for both quantification and confirmation. A total of 162 MRM transitions were monitored. The standard addition was employed to compensate for the matrix effects to achieve the maximum accuracy of the LC/MS/MS method. Vegetable (bok choy) and fruit samples (grape or orange) were fortified with pesticides of low (0.05 or 0.1 ppm) and high (0.5 ppm) levels, and the triplicate results showed satisfactory recoveries and repeatability. The recoveries for most pesticides ranged from 70 to 120% and the coefficients of variation of all pesticides were below 25% in all matrices. The developed method, compared with traditional GC or LC method, showed less time-consumption and higher sensitivity. The proposed method is considered satisfactory for routine monitoring of pesticide residues in fruits and vegetables.

Determination of butachlor and pencycuron residues in vegetables and rice: Application of the Macroporous Diatomaceous Earth Column

Butachlor and pencycuron are commonly used pesticides in Taiwan, but still lack official methods for determining butachlor and pencycuron residues in agricultural products. An analytical method using a macroporous diatomaceous earth (MDE) column and florisil cartridge for cleanup procedure was developed for determination of butachlor and pencycuron in vegetables and rice. Butachlor and pencycuron were extracted from crops with acetone and the concentrated extract was transferred into the MDE column, eluted with n-hexane. The eluate was concentrated and applied on a florisil cartridge. The cartridge was washed with 5% diethyl ether in n-hexane (E/H), and then eluted with 15% E/H (fraction I) and 15% ethyl acetate in n-hexane (EA/H) (fraction II). Butachlor residue in fraction I was determined by GC-ECD. Pencycuron residue in fraction II was determined by HPLC-UV at 248 nm. Chinese mustard and rice samples were fortified with butachlor and pencycuron at levels of 0.25∼0.75 ppm and analyzed. The recoveries of butachlor and pencycuron were between 84.9∼94.9% and 88.3∼94.8%, respectively. The detection limits of both pesticides in Chinese mustard and rice were 0.05 ppm. MDE liquid/liquid extraction cartridges provide a means of simplifying and speeding up multiple liquid/liquid extractions.

A multiresidue method for determining 136 pesticides and metabolites in fruits and vegetables: Application of macroporous diatomaceous earth column

A fast and easy multiresidue method using the macroporous diatomaceous earth (MDE) column for determining 136 pesticide an metabolite residues in fruits and vegetables was developed. The MDE column was used instead of the separation funnel for liquid/liquid partition in sample preparation. Through MDF columns, the preparation of test solution became easier and faster than traditional funnel liquid/liquid partition. The emulsion problem can also be avoided. Fifty one pesticides including acephate were determined by gas chromatography (GC) with a pulsed flame photometric detector (GC/PFPD) and 63 pesticides including aldrin were detected by GC with electron capture detection (GC/ ECD). Twenty carbamate peticides and metabolites including aldicarb were determined by high performance liquid chromatography with a post-column derivaization system and a fluorescence detector (HPLC/FLD) and two benzimidazole pesticides including carbendazim and thiabendazole were detected by HPLC with an ultraviolet detector (HPLC/UV). Recovery studies were performed by spiking pesticides (0.05-2.0 ppm) in fruit and vegetable samples, and the triplicate results showed satisfactory recoveries and repeatability. The detection limits ranged from 0.003 to 0.2 ppm. The developed multireside method can be employed to other pesticides or matrices with an easier and less solvent consumption way to prepare sample solution. It is an environment-friendly and useful method for routine pesticide analysis.

Survey of pyrrolizidine alkaloids in seven varieties of Lappula squarrosa: An alternative source of heart-healthy vegetable oil.

Growing demand for heart-healthy omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), is putting stress on wild fish stocks. There is now a compelling need for new and novel sources of non-traditional seed oils containing high stearidonic acid (SDA), a precursor of EPA and DHA, to reduce this demand. The seed oil of Lappula squarrosa is one of the richest sources of SDA, however, the plant has been found to contain toxic pyrrolizidine alkaloids (PAs). In this study, the PA concentrations of seven varieties (A-G) of Lappula squarrosa were analysed to determine the most suitable varieties for commercial seed oil production. Whilst the clean-up procedure for the PAs in the roots, flowers and leaves was on diatomaceous earth columns and finally analysed with GC-EI-MS, that of the seeds was through SCX-SPE and a more sensitive HPLC-ESI-MS/MS sum parameter method was used in the analysis. Altogether six PAs (supinine, amabiline, intermedine, lycopsamine and 3'-acetylintermedine) including one unknown retronecine-type PA were identified with variety C recording the lowest total PA concentration (4.64 mg seneciphylline equivalents (SE)/g dry weight (d.w.)). Besides, the total PA concentrations in the seeds of Lappula squarrosa varieties ranged between 2.88 μg PA/g and 10.36 μg PA/g d.w. Based solely on overall PA concentrations and PA distribution, variety D (5.95 mg SE/g d.w.) was found to be a potential candidate for commercial seed oil cultivation.

Determination of Tyramine in Hair Samples by GC–MS

A simple and sensitive method for the determination of tyramine in hair as N-heptafluorobutyryl derivative by gas chromatography–mass spectrometry has been developed. After digestion of the hair with aqueous NaOH, the aimed the analytes were extracted with solid-phase extraction on diatomaceous earth columns, followed by derivatization with heptafluorobutyryl chloride and elution with n-hexane: propyl acetate (30:1, v/v) simultaneously. The method was linear (r 2 = 0.9982) in the concentration range of 0.5–200 pmol mL−1, reproducible (intra-day precision = 4.4–5.5 %, inter-day precision = 3.3–6.5 %), accurate (recoveries = 96.0–97.9 %) and sensitive (LOD = 0.1 pmol mL−1). The method was successfully applied for analyzing the hair tyramine from the control group, the patients with schizophrenia group and the drug abuse group. Compared with the control group, there is a significant difference to the patients with schizophrenia group, while there is no significant difference to the drug abuse group. Additionally, there is no significant difference between the drug abuse group and the patients with schizophrenia group. It is a clue that tyramine could be a biological marker for schizophrenia.

Determination of Fluopicolide in Livestock Products and Seafood by LC-MS/MS.

An analytical method for the determination of fluopicolide in livestock products and seafood was developed using LC-MS/MS. Sodium chloride was added to livestock products and seafood samples and fluopicolide was extracted twice with acetone after acidification with formic acid. The fat from the crude extract was removed using a macroporous diatomaceous earth column, followed by purification with a combination of mini-columns of GC (graphite carbon) and PSA (ethylenediamine-N-propyl silylation silica gel). The average recovery (n=5) of fluopicolide from 10 types of livestock products and seafood (cattle fat, cattle liver, cattle muscle, chicken, eel, egg, freshwater clam, honey, milk and salmon) spiked at the MRLs or at the uniform limit (0.01 ppm) was 96-100%, with a relative standard deviation of 2.3-6.2%. The limit of quantitation of the developed method was calculated to be 0.01 mg/kg.

Effects of lipids on analysis of residue pesticides in herbal medicines

Serious problems in residue analysis of acetamipirid, chlorpyrifos, and bifenthrin caused by lipids present in herbal medicines, platycodon root, safflower, and persicae semen have been found during the pesticide residue analysis using a currently used analytical method. Particularly, recovery tests for artificially spiked pesticides showed poor recoveries for bifenthrin in persicae semen, which may be due to the low polarity of the pesticide and high lipid content in the matrix. An unclear layer separation between water and organic solvent, methylene chloride, has been also observed during the liquid-liquid partitioning process, which favors modification of the liquid-liquid partitioning by replacement with acetonitrile and a macroporous diatomaceous earth column, respectively. The effectiveness of newly modified methods was evaluated based on the recoveries of three pesticides in the herbal medicines at two fortification levels (1.0 and 4.0 mg/kg). The modified methods increased recoveries to 81.8–98.9%, suggesting those methods could be effective and feasible alternatives to determine acetamiprid, bifenthrin, and chlorpyrifos in lipidic samples.

A Rapid Method To Determine Sterol, Erythrodiol, and Uvaol Concentrations in Olive Oil

A rapid, accurate, and efficient method for determining the sterol, uvaol, and erythrodiol concentrations was developed to meet International Olive Council (IOC) certification criteria for extra virgin olive oil (EVOO). The unsaponifiable fraction of the sample (0.2 g) was separated with a diatomaceous earth column, and the sterol and triterpenic dialcohols were isolated with a novel base-activated silica solid-phase extraction (SPE) cartridge cleanup protocol. The improved method and the IOC method provided identical pass/fail results (n = 34) for each of the six sterol and erythrodiol/uvaol IOC criteria used to assess olive oil. This method was validated, and recoveries of stigmasterol (88%) and β-sitosterol (84%) were greater than previously published values obtained using the IOC method. This method requires approximately one-third the time required to complete the IOC method and has great utility for the rapid screening of EVOO to detect adulteration, false labeling, and an inferior product.

DETERMINATION OF IMIDOCARB IN BOVINE TISSUES AND MILK SAMPLES BY LC-MS/MS

We present a sensitive and selective method for detecting imidocarb in bovine tissues and milk samples using a solid-phase extraction (SPE) with diatomaceous earth column and liquid chromatography with electrospray tandem mass spectrometry (LC-ESI-MS/MS) on positive mode. Chromatographic separation was performed on a TSK-GEL ODS 100 V column using 0.1% formic acid in water/methanol. Limit of detection (LOD) was 0.5 ng/mL for standard solution. Limit of quantitation (LOQ) was ranged from 1.0 to 10 µg/kg for bovine tissue and milk samples. The linearity of the calibration curve was excellent in matrix matched standards, and yielded the coefficients (r2 = 0.997–0.999, range from LOQ to 250, 750, or 5000 µg/kg) of imidocarb. Recoveries were in the range of 73.3–98.6% with associated precision values (within-day: 1.0–6.7%, n = 6, and between-day: 2.0–7.7% for 3 days) for repeatability and reproducibility. This developed method is well adapted for residue analysis of imidocarb in bovine tissues and milk based on maximum tolerated residue levels.

한약재 중 살충제 Endosulfan의 잔류분석을 위한 Macroporous Diatomaceous Earth 컬럼 적용

Application of Macroporous Diatomaceous Earth Column for Residue Analysis of Insecticide Endosulfan in Herbal Medicines Jeong-In Hwang, Young-Hwan Jeon, Hyo-Young Kim, Ji-Hwan Kim, Yoon-Jeong Lee, Ju-Young Park, Do-Hoon Kim and Jang-Eok Kim (School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Korea, Division of Herbal Medicine Research, Korea Food and Drug Administration, Osong 363-951, Korea)

Application of macroporous diatomaceous earth column chromatography for pesticide residues analysis in foods

Application of macroporous diatomaceous earth column chromatography for pesticide residues analysis in foods

Rapid determination of cyanide in human plasma and urine by gas chromatography–mass spectrometry with two-step derivatization

Cyanide (CN) is a powerful poison and rapidly toxic agent. Because of its wide availability and high toxicity, quantification of CN in blood and urine is frequently required in clinical and forensic practice. We present a sensitive and less time consuming method based on solid-supported liquid–liquid extraction (SLE) and gas chromatography–mass spectrometry (GC–MS) with two-step derivatization for determination of CN in plasma and urine. Buffer solution, 1,3,5-tribromobenzene (internal standard) and benzaidehyde were added to sample to complete the first-step derivatization. Then the analytes were poured onto the column of diatomaceous earth, eluted with n-hexane containing 0.4% of heptafluorobutyryl chloride (HFB-Cl) to complete the second-step derivatization forming the final analyte, heptafluoro-butyric acid-alpha-cyanobenzyl ester. This method was linear ( r 2 = 0.9988, 0.9993), reproducible (intra-day RSD = 4.37–7.24%, 3.19–5.74%; inter-day RSD = 5.13–7.63%, 4.31–6.69%), accurate (recoveries = 90.58–115.56%, 93.01–114.6%) and sensitive (LOD = 0.04, 0.01 μg/mL) for plasma and urine, respectively. The total time was about 25 min. This method was successfully applied to the analysis of blood sample and urine sample collected from a victim who died as a result of ingestion of potassium cyanide.

Rapid and simultaneous determination of hair polyamines as N-heptafluorobutyryl derivatives by gas chromatography–mass spectrometry

We have developed a simple and sensitive method for the simultaneous determination of putrescine, spermidine and spermine in hair as their N-heptafluorobutyryl derivatives by gas chromatography–mass spectrometry (GC–MS) in selected ion-monitoring (SIM) mode. After base hydrolysis, hair samples were extracted with solid-phase extraction (SPE) with diatomaceous earth columns, followed by derivatization with heptafluorobutyryl chloride (HFB-Cl) and elution with n-hexane simultaneously. This method was linear ( r ≥ 0.9989), reproducible (intra-day R.S.D. = 3.4–15.5%, inter-day R.S.D. = 2.6–14.6%), accurate (recoveries = 67.8–94.6%) and sensitive (LOD = 0.05–1.0 ng). The method was successfully applied to the analysis of 36 hair samples from 14 healthy men and 22 healthy women. Results showed that the levels of hair polyamines were 4.39–12.15 μg/g for putrescine, 3.89–27.91 μg/g for spermidine, and 0.81–15.15 μg/g for spermine. Either in the male or female group, the most abundant hair polyamine was spermidine, followed by putrescine and spermine, while the mean levels of the three polyamines in hair samples were all found to be higher in men than in women.

Macroporous Diatomaceous Earth Column for the Separation and Simultaneous Determination of Pesticides in the Soil of Golf Courses

A macroporous diatomaceous earth column was applied to the separation and simultaneous determination of pesticides in soil on a golf course. Two analytical procedures were used for this technique. One was GC/MS determination of cyproconazole, propiconazole, tetraconazole and triflumizole, and the other was HPLC/UV determination of azoxystrobin, flazasulfuron, halosulfuron-methyl and siduron. One enormous advantage of this column technique was the fact that surfactants sprayed together with pesticides produced no emulsion formation. It also made the separation process very simple and rapid in comparison with liquid-liquid extraction technique with a separating funnel. The recoveries of the pesticides spiked to the soil of a golf course were 84.4∼93.5 %, and the relative standard deviations were 0.7∼5.8 % by the proposed methods.

A Simple Method for Extraction of High Molecular Weight DNA fromPorphyra Tenera (Rhodophyta) Using Diatomaceous Earth

The innate soluble polysaccharides and phenolic compounds of marine macroalgae are serious contaminants which interfere with experimental procedures such as restriction enzyme digestion, polymerase chain reaction (PCR) and other enzymatic reactions using extracted DNA samples. The viscous polysaccharides are co-precipitated with DNA samples by isopropanol or ethanol precipitation in conventional experiment. To overcome the problem, a method for the isolation of high molecular weight DNA from Porphyra tenera is developed with the application of diatomaceous earth column. The isolated DNAs by this method were about 50-100 kb in size and could be digested well with restriction enzymes. The nuclease activity seemed to be minimal, and high reproducibility in the arbitrary primed PCR for RAPD analyses was a distinctive feature. These results suggest that this method is very efficient in isolating nucleic acid from macroalgae including Porphyra.

Automated determination of ethyl carbamate in stone-fruit spirits using headspace solid-phase microextraction and gas chromatography–tandem mass spectrometry

A fully automated procedure using headspace solid-phase microextraction (HS-SPME) followed by gas chromatographic/tandem mass spectrometric (GC/MS/MS) detection was developed for the determination of the toxic contaminant ethyl carbamate (EC) in stone-fruit spirits. After addition of deuterated internal standard, the optimised HS-SPME extraction with carbowax/divinylbenzene fibres (30 min at 70 °C) was done applying salting out with sodium chloride in the presence of pH 7 buffer solution. For quantitative analysis the characteristic fragmentations of m/ z 74 > 44 and m/ z 62 > 44 for ethyl carbamate as well as m/ z 64 > 44 for ethyl carbamate-d 5 were monitored in the multiple reaction monitoring (MRM) mode using a triple quadrupole instrument. In the validation studies, ethyl carbamate exhibited good linearity with a regression coefficient of 0.998. The limits of detection and quantitation were 0.03 and 0.11 mg/l. The precision never exceeded 4.3% (intraday) and 8.2% (interday) at any of the concentrations examined. A good agreement of analysis results in comparison to conventional sample clean-up over diatomaceous earth columns was found ( R = 0.956, Bias = 0.08 mg/l). The new HS-SPME/GC/MS/MS procedure is suitable for the fast, reliable and inexpensive determination of ethyl carbamate in alcoholic beverages in an automated, and therefore, convenient procedure.

Application of combination column of macroporous diatomaceous earth and graphitized carbon black for pesticide residue analysis

An analytical method for pesticide residue for agricultural products was developed using combination column of macroporous diatomaceous earth (MDE) and graphitized carbon black (GCB). The on-column liquid–liquid partition was performed by the following procedure. The concentrated sample extract was diluted with an equal volume of acetonitrile and transferred into the MDE column, and the residue pesticides were eluted with hexane. It was possible to elute the non-polar pesticides (log POW>4.3) from the MDE column by using a smaller volume of organic solvent. One hundred-seventy-three of 238 pesticides were recovered at more than 70% with hexane from the MDE columns when applied in acetonitrile–water (1 : 1, v/v) solution. After eluting from the MDE column, the elution profiles with the GCB cartridge indicated that the majority of pesticides could be eluted with common organic solvents such as hexane, ethyl acetate and acetone. The applicability of this method was evaluated by the recovery from 5 fortified agricultural products (cucumber, spinach, tomato, carrot and chinese cabbage) at 0.02 and 2.0 μg/g. The recovery of 2 synthetic pyrethroid insecticides and 7 organic chlorine pesticides ranged from 81% to 113%, and the limit of detection was 0.005 μg/g.

Determination of Pesticides and PCBs in Virgin Olive Oil by Multicolumn Solid-Phase Extraction Cleanup Followed by GC-NPD/ECD and Confirmation by Ion-Trap GC−MS

A multicolumn solid-phase extraction cleanup for the determination of organophosphorus (OP) and organochlorine (OC) pesticides plus PCB congeners in virgin olive oil is presented. The method involves dissolution of the olive oil in hexane, followed by a cleanup system using a diatomaceous earth column (Extrelut-QE) with reversed (C(18)) and normal (alumina) phase SPE columns. Determination of OPs was by GC-NPD, while the OCs and PCBs were analyzed using GC-ECD. Recovery assays for OPs varied from 81.7% to 105.3%, for OCs ranged between 74.3% and 99.4%, while for PCBs were from 60.1% to 119.2%. Quantitation limits ranged from 10 to 25 microg/kg olive oil for OPs, and from 1 to 6 microg/kg olive oil for OCs and PCBs. In the case of positive samples, the confirmation of pesticide identity was performed by ion-trap GC-MS/MS. The applicability of the method was assayed with 19 virgin olive oil samples collected from different olive mills of Aragón (Spain). Only one OP pesticide (acephate) was detected in one sample at a concentration of 10 microg/kg. Organochlorine pesticides were found in 5-47% of samples at very low levels ranging from 1.5 to 5.2 microg/kg. PCBs were found in 20-90% of samples, showing concentrations between 2.3 and 17.3 microg/kg.

Application of tandem mass spectrometry combined with gas chromatography to the routine analysis of ethyl carbamate in stone‐fruit spirits

Gas chromatography (GC) coupled to mass spectrometry (MS) operated in selected ion monitoring (SIM) mode is currently the method of choice for the determination of the toxic contaminant ethyl carbamate in alcoholic beverages. However, even after extensive sample cleanup over diatomaceous earth columns, the identity of ethyl carbamate often cannot be ascertained with confidence, due to inconsistent ratios of the SIM ions m/z 62, 74 and 44 because the qualifier ions are highly susceptible to interferences. Therefore, a new method combining GC and tandem MS using a triple-quadrupole instrument is introduced to determine ethyl carbamate in stone-fruit spirits. For quantitative analysis the characteristic transitions of m/z 74 --> 44 and m/z 62 --> 44 for ethyl carbamate as well as m/z 64 --> 44 for the deuterated internal standard ethyl carbamate-d5 were monitored in the multiple reaction monitoring (MRM) mode. In the validation studies, ethyl carbamate exhibited good linearity with a regression coefficient of 1.000. The limits of detection and quantitation were 0.01 and 0.04 mg/L. The recovery of the method was 100.4 +/- 9.4%. The precision never exceeded 7.8% (intraday) and 10.1% (interday) and the trueness never exceeded 11.3% (intraday) and 12.2% (interday) at any of the concentrations examined, indicating good assay accuracy. A good agreement of analytical results between a previously developed GC/MS SIM method and the GC/MS/MS MRM procedure was found (R=0.987). Regarding the validation data, the procedure is sensitive, selective and reproducible. The applicability of the developed method was demonstrated by the investigation of 70 stone-fruit spirits from commercial trade. The ethyl carbamate concentration of the samples ranged between 0.07 and 7.70 mg/L (mean 1.21 mg/L). The main advantage of the developed GC/MS/MS method is the reliability of the results without the need for time-consuming confirmatory analyses.