Determination of Nitrate in Vegetables by Continuous Flow: Interlaboratory Study

1994 ◽  
Vol 77 (6) ◽  
pp. 1522-1529 ◽  
Author(s):  
Paul R Beljaars ◽  
Remmelt Van Duk ◽  
Geertrutoa M Van Der Horst
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Continuous Flow ◽  
Collaborative Study ◽  
Leafy Vegetables ◽  
Collaborative Studies ◽  
Relative Standard ◽  
Metallic Cadmium ◽  
Inspection Service

Abstract A collaborative study for the determination of nitrate in leafy vegetables, such as endive, lettuce, spinach, and beetroot, by continuous flow (CF) was conducted by the Project Group on Collaborative Studies of the Inspectorate for Health Protection, Food Inspection Service, in The Netherlands. After extraction with water and filtration, samples were cleaned up by dialysis in the CF system. Extracted nitrates were reduced to nitrite in the system by metallic cadmium, and then the nitrite was reacted with sulfanilamide and N-naphthylethylenediamine to form a reddish-purple azo dye. This dye was measured colorimetrically at 530 nm. Fourteen vegetable samples (including 7 blind duplicates) containing nitrate at ca 900 to 5200 mg/kg were analyzed singly by the proposed procedure by 13 laboratories. The data were analyzed by the International Union for Pure and Applied Chemistry (IUPAC)–International Organization for Standardization (ISO)–AOAC protocol for statistics. One collaborator was identified as an outlier for all results. For all samples analyzed, the repeatability relative standard deviation values varied from 1.7 to 5.5%, whereas the reproducibility relative standard deviation values ranged from 3.3 to 5.9%.

Determination of p-Toluenesulfonamide in Ice Cream by Combination of Continuous Flow and Liquid Chromatography: Summary of Collaborative Study

1994 ◽  
Vol 77 (3) ◽  
pp. 672-674 ◽  
Author(s):  
Paul R Beuaars ◽  
Remmelt Van Dijk ◽  
Arie Brands
Keyword(s):  
Liquid Chromatography ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Continuous Flow ◽  
Collaborative Study ◽  
Ice Cream ◽  
Relative Standard ◽  
On Line ◽  
Positive Results

Abstract A collaborative study of the determination of p-tolu-enesulfonamide (p-TSA) in ice cream by a combination of continuous flow and on-line liquid chromatography was conducted. Seven ice cream samples containing 0-6.35 mg p-TSA/kg at 4 levels (1 blank and 3 pairs of split level samples) were analyzed by 11 laboratories. For all samples analyzed, the repeatability relative standard deviation varied from 2.08 to 3.67%, whereas the reproducibility relative standard deviation ranged from 7.79 to 11.68%. The average p-TSA values for the split levels 1,2, and 3 were 0.55,1.02, and 4.44 mg p-TSA/kg, respectively, with mean recoveries ranging from 76 to 79% (overall recovery range for all levels, 63-101 %). No false positive results were reported for the blank sample, and no interference was encountered by the presence of vanillin in samples. The method has been adopted first action by AOAC INTERNATIONAL.

scholarly journals Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study

1998 ◽  
Vol 81 (4) ◽  
pp. 763-774 ◽  
Author(s):  
Joanna M Lynch ◽  
David M Barbano ◽  
J Richard Fleming
Keyword(s):  
Standard Deviation ◽  
Nitrogen Content ◽  
Relative Standard Deviation ◽  
Collaborative Study ◽  
Direct Determination ◽  
Raw Milk ◽  
Method Performance ◽  
Relative Standard ◽  
Milk Casein

Abstract The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

scholarly journals Liquid Chromatographic Determination of Ampicillin Residues in Porcine Muscle Tissue by a Multipenicillin Analytical Method: European Collaborative Study

2002 ◽  
Vol 85 (4) ◽  
pp. 889-900 ◽  
Author(s):  
Eric Verdon ◽  
Pierric Couëdor ◽  
Pierre Maris ◽  
Michel Laurentie ◽  
P Batjoens ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Muscle Tissue ◽  
Phosphate Buffer ◽  
Collaborative Study ◽  
Porcine Muscle ◽  
Relative Standard ◽  
Liquid Chromatographic

Abstract A collaborative study involving 14 laboratories was conducted to determine residues of ampicillin in porcine muscle tissue by using a liquid chromatographic method developed for multipenicillin analysis that can quantitate 8 penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, amoxicillin, nafcillin, oxacillin, cloxacillin, and dicloxacillin) at trace levels in muscle tissue. This method involves extraction of the penicillins with phosphate buffer, pH 9, followed cleanup and concentration on a C18 solid-phase extraction column and reaction with benzoic anhydride at 50°C and with 1,2,4-triazole and mercury(II) chloride solution, pH 9.0, at 65°C. The derivatized compounds are eluted isocratically on a C8 column with a mobile phase of acetonitrile and phosphate buffer (pH 6; 0.1M) containing sodium thiosulfate and the ion-pair reagent tetrabutylammonium hydrogen sulfate. The penicillins are detected by UV absorption at 325 nm. The limit of detection and the limit of determination (quantitation) of the method were calculated to be approximately 3–5 and 25 μg/kg, respectively, in accordance with the criteria of European Union (EU) Decision No. 93/256/EEC. In this first interlaboratory study, collaborators were instructed to monitor 4 different penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, and amoxicillin) by analyzing 8 blind samples of muscle tissue in triplicate. These samples were prepared from 2 materials containing different concentrations of incurred ampicillin (63.5 μg/kg for material No. 1 and 358.1 μg/kg for material No. 2) and 1 blank material. The repeatability relative standard deviation and the reproducibility relative standard deviation were 10.2 and 17.4%, respectively, for material No. 1 and 7.0 and 16.0%, respectively, for material No. 2. These results demonstrate that the method is suitable for the determination of ampicillin residues in muscle tissue at the EU maximum residue limit (50 μg/kg) and above. However, the identification of positives by this procedure may need additional confirmation by techniques with greater specificity, such as liquid chromatography combined with mass spectrometry, or tandem mass spectrometry. Investigations regarding the basis of interlaboratory testing studies will further demonstrate the suitability of multiresidue methodology for detecting and quantitating other compounds in the family of penicillin antibiotics.

scholarly journals Determination of Clopidol Residues in Chicken Tissues by Liquid Chromatography: Collaborative Study

2003 ◽  
Vol 86 (4) ◽  
pp. 685-693 ◽  
Author(s):  
Guo-Fang Pang ◽  
Yan-Zhong Cao ◽  
Chun-Lin Fan ◽  
Jin-Jie Zhang ◽  
Xue-Min Li ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Solid Phase ◽  
Collaborative Study ◽  
Reversed Phase ◽  
Method Performance ◽  
Chicken Muscle ◽  
Relative Standard

Abstract Eighteen laboratories participated in a collaborative study on the determination of clopidol residues in chicken muscle tissues by liquid chromatography. Of these, results from 16 laboratories which rigorously followed the method were subjected to statistical analysis. The method performance was assessed by all participants using 14 samples of chicken muscle fortified at concentrations ranging from 0.1 to 5.0 mg/kg. In addition, 9 participants each reported results for 6 clopidol-incurred samples in chicken muscle. Test portions were extracted with acetonitrile, and the extracts were purified with alumina and anion exchange resin solid-phase extraction cartridges in sequence. Clopidol was separated by reversed-phase liquid chromatography and quantified at 270 nm. Average recoveries ranged from 81.8 to 85.4%, reproducibility relative standard deviation (RSDR) ranged from 11.9 to 22.6%, and repeatability relative standard deviation (RSDr) ranged from 9.9 to 15.1%. For clopidol-incurred samples at concentrations of 0.100–0.687 mg/kg, the mean determination value range was 0.099–0.659 mg/kg; RSDR was 12.6–19.8%, RSDr was 3.1–8.5%; and HORRAT values were 0.7–1.1. The accuracy and precision of the method are in conformity with the requirements specified by AOAC INTERNATIONAL. The method was adopted Official First Action in April 2003.

Multifunctional Column Coupled with Liquid Chromatography for Determination of Aflatoxins B1, B2, G1, and G2 in Corn, Almonds, Brazil Nuts, Peanuts, and Pistachio Nuts: Collaborative Study

1994 ◽  
Vol 77 (6) ◽  
pp. 1512-1521 ◽  
Author(s):  
Mary W Trucksess ◽  
Michael E Stack ◽  
Stanley Nesheim ◽  
Richard H Albert ◽  
Thomas R Romer
Keyword(s):  
Liquid Chromatography ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Collaborative Study ◽  
The United States ◽  
Test Portion ◽  
Brazil Nuts ◽  
Pistachio Nuts ◽  
Relative Standard

Abstract An AOAC/IUPAC collaborative study was conducted to evaluate the effectiveness of a multifunctional column for the determination of aflatoxins. The test portion is extracted with acetonitrile–water (9 + 1), the extract is filtered, and the filtrate is passed through the column. The aflatoxins in the eluate are determined by reversed-phase liquid chromatography after derivatization with trifluoroacetic acid. Naturally contaminated corn, almonds, Brazil nuts, peanuts, and pistachio nuts spiked with total aflatoxins at 5,10,20, and 30 ng/g were sent to 12 collaborators in the United States, Denmark, France, Japan, and Switzerland. Eleven collaborators completed the study. Average recoveries of total aflatoxins for each spike level for the various commodities (excluding Brazil nuts at 5 ng/g) were 93,97,95, and 95%, respectively; the repeatability relative standard deviation (RSDr) ranged from 6.0 to 23.2% and the reproducibility relative standard deviation (RSDR) ranged from 12.0 to 69.4%. The multifunctional column coupled with a liquid chromatographic method for determination of aflatoxins in corn, almonds, Brazil nuts, peanuts, and pistachio nuts has been adopted first action by AOAC INTERNATIONAL.

scholarly journals Determination of Aflatoxin B1 in Baby Food (Infant Formula) by Immunoaffinity Column Cleanup Liquid Chromatography with Postcolumn Bromination: Collaborative Study

2001 ◽  
Vol 84 (4) ◽  
pp. 1116-1124 ◽  
Author(s):  
Joerg Stroka ◽  
Elke Anklam ◽  
Urban Joerissen ◽  
John Gilbert ◽  
A Barmark ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Infant Formula ◽  
Aflatoxin B1 ◽  
Collaborative Study ◽  
Baby Food ◽  
Immunoaffinity Column ◽  
Relative Standard

Abstract A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for determination of aflatoxin B1 in a milk powder based infant formula at a possible future European regulatory limit (0.1 ng/g). The test portion was extracted with methanol–water (8 + 2 [v + v]), filtered, diluted with water, and applied to an immunoaffinity column. The column was washed with water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. The separation and determination of the aflatoxin B1 was performed by reversed-phase LC and detected by fluorescence after postcolumn derivatization (PCD) involving bromination. PCD was achieved with either pyridinum hydrobromide perbromide (PBPB) or an electrochemical (Kobra) cell by addition of bromide to the mobile phase. The baby food (infant formula) test samples, both spiked and naturally contaminated with aflatoxin B1, were sent to 14 laboratories in 13 different European countries. Test portions were spiked at levels of 0.1 and 0.2 ng/g for aflatoxin B1. Recoveries ranged from 101 to 92%. Based on results for spiked test samples (blind pairs at 2 levels) and naturally contaminated test samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 3.5 to 14%. The relative standard deviation for reproducibility (RSDR) ranged from 9 to 23%. Nine participants used PBPB derivatization, and 5 particpants used the Kobra cell. There was no evidence of method performance depending on the derivatization method used. The method showed acceptable within- and between-laboratory precision for baby food matrix, as evidenced by HORRAT values, at the target levels of determination for aflatoxin B1.

Liquid Chromatographic Method for Determination of Explosives Residues in Soil: Collaborative Study

1990 ◽  
Vol 73 (4) ◽  
pp. 541-552 ◽  
Author(s):  
Christopher F Bauer ◽  
Stephan M Koza ◽  
Thomas F Jenkins
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Contaminated Soils ◽  
Chromatographic Method ◽  
Collaborative Study ◽  
Liquid Chromatographic Method ◽  
Relative Standard ◽  
Explosives Residues ◽  
Liquid Chromatographic

Abstract A collaborative study of a sonic extraction/liquid chromatographic method for determining nitroaromatic and nitramlne explosives In soil was conducted at 8 participating laboratories. Analytes HMX, RDX, TNB, DNB, tetryl, TNT, and 2,4-DNT were measured In duplicate for 4 field-contaminated soils and 4 spiked standard-matrix soils. Concentrations ranged from detection limits of about 1 μg/g to nearly 1000 μg/g. Results were evaluated with and without data Identified as outliers, which were often caused by electronic integrator miscalculation of chromatographic peak response. When outliers are excluded, method repeatability (within-laboratory relative standard deviation) for all analytes except tetryl Is less than 5% for spiked soils and less than 18% for fieldcontaminated soils. Relative standard deviation generally decreases as analyte concentration Increases. Reproducibility (between-laboratory relative standard deviation), except for tetryl and DNT, Is less than 7% for spiked soils and 26% for fleld-contamlnated soils. Thus, collaborators have nearly equivalent performance on spiked samples. For fleld-contamlnated soils, some additional Imprecision seems to result from the variability of extraction recoveries. Analyte recoveries from spiked soils are 95-97% for HMX, RDX, TNT, and DNT (similar to recoveries from aqueous samples); 92-93% for DNB and TNB; and 70% for tetryl. Poor results for tetryl (due to thermal degradation) are correctable If sonic bath temperatures are maintained near ambient. The method has been approved Interim official first action by AOAC.

scholarly journals Determination of Methylcellulose and Hydroxypropyl Methylcellulose Food Gums in Food and Food Products: Collaborative Study

2007 ◽  
Vol 90 (3) ◽  
pp. 786-793 ◽  
Author(s):  
Robert G Harfmann ◽  
Balasaheb K Deshmukh ◽  
Jerry Conklin ◽  
Maciej Turowski ◽  
Stephanie Lynch ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Hydroxypropyl Methylcellulose ◽  
Collaborative Study ◽  
Food Samples ◽  
Size Exclusion ◽  
Official Method ◽  
Relative Standard ◽  
Aoac Official

Abstract A collaborative study was performed to determine the reproducibility of a method for the determination of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) in food. These widely used food gums possess unusual solubility characteristics and cannot accurately be determined by existing dietary fiber methods. The new method uses the enzyme-digestion procedure of AOAC Official Method 991.43. Digestate solutions must be refrigerated to fully hydrate MC or HPMC. The chilled solutions are filtered and analyzed by size-exclusion liquid chromatography. Collaborating laboratories received 28 samples containing MC or HPMC in the range of 0100%. The sample set included blind duplicates of 5 food matrixes (bread, milk, fish, potato, and powdered juice drink). Cochran and Grubbs tests were used to eliminate outliers. For food samples containing MC, values for within-laboratory precision, repeatability relative standard deviation (RSDr), ranged from 4.2 to 16%, and values for among-laboratories precision, reproducibility relative standard deviation (RSDR), ranged from 11 to 20%. For HPMC samples, RSDr values ranged from 6.4 to 27%, and RSDR values ranged from 17 to 39%. Recoveries of MC and HPMC from the food matrixes ranged from 78 to 101%. These results show acceptable precision and reproducibility for the determination of MC and HPMC, for which no Official AOAC Methods exist. It is recommended that this method be adopted as AOAC Official First Action.

scholarly journals Immunoaffinity Column Cleanup with Liquid Chromatography for Determination of Aflatoxin M1 in Liquid Milk: Collaborative Study

2001 ◽  
Vol 84 (2) ◽  
pp. 437-443 ◽  
Author(s):  
Sylviane Dragacci ◽  
Frederic Grosso ◽  
John Gilbert ◽  
M Agnedal ◽  
L Hyndrick ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Collaborative Study ◽  
Aflatoxin M1 ◽  
Immunoaffinity Column ◽  
Precision Data ◽  
Relative Standard ◽  
Liquid Milk

Abstract A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatographic method for determination of aflatoxin M1 in milk at proposed European regulatory limits. The test portion of liquid milk was centrifuged, filtered, and applied to an immunoaffinity column. The column was washed with water, and aflatoxin was eluted with pure acetonitrile. Aflatoxin M1 was separated by reversed-phase liquid chromatography (LC) with fluorescence detection. Frozen liquid milk samples both naturally contaminated with aflatoxin M1 and blank samples for spiking, were sent to 12 collaborators in 12 different European countries. Test portions of samples were spiked at 0.05 ng aflatoxin M1 per mL. After removal of 2 noncompliant sets of results, the mean recovery of aflatoxin M1 was 74%. Based on results for spiked samples (blind pairs at 1 level) and naturally contaminated samples (blind pairs at 3 levels) the relative standard deviation for repeatability (RSDr) ranged from 8 to 18%. The relative standard deviation for reproducibility (RSDR) ranged from 21 to 31%. The method showed acceptable within- and between-laboratory precision data for liquid milk, as evidenced by HORRAT values at the low level of aflatoxin M1 contamination.

scholarly journals Immunoaffinity Column Cleanup with Liquid Chromatography Using Post-Column Bromination for Determination of Aflatoxin B1 in Cattle Feed: Collaborative Study

2003 ◽  
Vol 86 (6) ◽  
pp. 1179-1186 ◽  
Author(s):  
Joerg Stroka ◽  
Christoph von Holst ◽  
Elke Anklam ◽  
Matthias Reutter ◽  
A Barmark ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Aflatoxin B1 ◽  
Collaborative Study ◽  
Immunoaffinity Column ◽  
Test Portion ◽  
Cattle Feed ◽  
Relative Standard

Abstract A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for determination of aflatoxin B1 in cattle feed at a possible future European regulatory limit (1 ng/g). The test portion was extracted with acetone–water (85 + 15), filtered, diluted with water, and applied to an immunoaffinity column. The column was washed with water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. Aflatoxin B1 was separated and determined by reversed-phase liquid chromatography (RP–LC) and detected by fluorescence after post column derivatization (PCD) involving bromination. PCD was achieved with either pyridinium hydrobromide perbromide (PBPB), used by 14 laboratories, or an electrochemical cell and addition of bromide to the mobile phase, used by 7 laboratories. Both derivatization techniques were not significantly different when compared by the t-test; the method was statistically evaluated for all laboratories together (bromination and PBPB). The cattle feed samples, both spiked and naturally contaminatedwithaflatoxinB1, were sent to 21 laboratories in 14 different countries (United States, Japan, and Europe). Test portions were spiked at levels of 1.2 and 3.6 ng/g for aflatoxin B1. Recoveries ranged from 74 to 157%. Based on results for spiked samples (blind pairs at 2 levels) as well as naturally con-taminated samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 5.9 to 8.7%. The relative standard deviation for reproducibility (RSDR) ranged from 17.5 to 19.6%. The method showed acceptable within-and between-laboratory precision for this matrix, as evidenced by HORRAT values, at the target levels of determination for aflatoxin B1. No major differences in RSD were observed, showing that the composition of the feeds was not a factor for the samples tested and that the method was applicable for all materials used.

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