Page:NIOSH Manual of Analytical Methods - 3601.pdf/4

 MA NEB, Hand W ash: ME TH OD 3601, Issue 1, dated 1 5 Ma rch 2003 - page 4 of 5 CONFIRMATION: No confirm ation me thod has be en tested. The re are several poss ible alternatives, such as ion-pairing chrom atog raph y with a C -18 c olum n [5], or ana lysis of m ethylated de rivatives on a C-1 8 co lum n [3,4].

EVALUATION OF METHOD: This method has been evaluated in the laboratory only. No field samples have been analyzed to date. LOD/LOQ A series of liquid standards from 0.1 to 100 µg/mL was prepared in duplicate, analyzed, and fitted with a linear curve. The Limit of Detection (LOD), 0.2 µg/mL, and L im i t o f Q uantitation (LOQ), 0.66 µg/mL, were es timated with the NIO SH SO P 01 8 m etho d [10]. PRECISION AND ACCURACY Twenty-four liquid standards were prepared, six at each of four levels: 3xLOQ, 10xLOQ, 30xLOQ, and 100xLOQ. The relative standard deviation of the 100xLOQ level was considerably lower than that of the other three levels and, there fore, was not used to com pute the pooled relative standa rd de viation. The pooled rela tive sta ndard deviation fo r the first th ree levels was 0.015. Since all samples w ere spike d liquid standards, accuracy and bias were not determined. Since no samples were generated, overall precision was not calculated. STABILITY Stab ility studies were performed on solutions at 6.6 µg/mL Maneb concentration. It was determined that it is necessary to store the samples at 4 / C in a solution of 1% L-cysteine, 3% Na 4EDTA•2H 2O. Samples stored at 4 / C were stable to 30 days with greater than 90% recovery with or without headspace. At 24 / C, however, samples with headspace deteriorated more rapidly. Therefore, as a precaution against the pos sibility of elevated temperatures during shipping, samples should be stored and shipped with no headspace.

COM MEN TS: Most ethylene-bis-dithioc arba m ates (EB DC ) con taining divalen t (or higher) m etals, (e.g., Maneb, Mancozeb, and Zineb) dissolve with difficulty in alm ost every so lvent. If the m etal ion is rem oved by co m plexation w ith EDTA (at high pH), the EBDC will dissolve but will begin to deg rade rapidly, presu m ably by ox idation, to disulfides or other products. Adding an an tioxidant such as L-cysteine greatly inhibits this oxidative degradation. Excluding headspace air has bee n sh own to assist in reduc ing ox idation; how ever, coo ling to 4 / C is one of the most important factors in sample preservation.

REFERENCES: [1] [2]

[3] [4] [5]

[6] [7]

DataChem Laboratories [1995]. Backup Data Report for Maneb, dermal patch and hand wash. Unpublished report, DataChem Laboratories, Salt Lake City, UT. Bardarov V,. Zaikov Chr, Mitewa M [1989]. Application of High-Performanc e Liquid Chromatography with Spectrophotom etric and Electrochem ical De tec tion to th e Analysis of A lkyle nebis(dithiocarbamates) and their M etab olites. Journ al of C hrom atog raph y, 479: 97. Gustafsson KH, Thompson R A [1981]. High-Pressure Liquid Chrom ato grap hic Determination of Fungicidal Dithiocarbam ates. J. Agric. Fo od C hem. 29: 729. Gustafsson, KH, Fah lgren CH [1983]. Determination of Dithiocarbamate Fungicides in Vegeta ble Foods tuffs by High -Perform anc e Liqu id Ch rom atog raph y. J. Agric. Foo d Chem. 31: 461. Irth H, De Jong GJ, Frei RW, Brinkm an UATh [1990]. Determination of Dithiocarbamates in Residues by Liquid Chromatography with Selective Precolumn or Reaction-Detection Systems. Intern J Environ Anal Ch em. 39: 129. Seiler J.F [1 974 ]. Mutat. Re s. 26: 189. Vogeler K, D reze P, Rapp A , Steffan S H, U llem eyer H [1977]. Pflanzen sch utz-N ach r, 30: 72.

NIOSH Manual of Analytical Methods, Fourth Edition