Preparation of Milk Samples for Immunoassay and Liquid Chromatographic Screening Using Matrix Solid-Phase Dispersion

1994 ◽  
Vol 77 (4) ◽  
pp. 848-854 ◽  
Author(s):  
Steven A Barker ◽  
Austin R Long
Keyword(s):  
Solid Phase ◽  
Screening Tests ◽  
Dairy Production ◽  
Milk Samples ◽  
Matrix Solid Phase Dispersion ◽  
Phase Dispersion ◽  
Negative Results ◽  
Microbial Inhibition ◽  
Receptor Assays ◽  
Liquid Chromatographic

Abstract The use of drugs to maintain the health and maximize the output of dairy cattle has made the monitoring of milk for such agents essential. Screening tests based on immunological, microbial inhibition, and bacterial receptor assays have been developed for the detection of violative levels of therapeutic substances. However, such assays are not infallible, and false positive or negative results can occur when contaminants bind receptors or compete for the binding of the target residues. Such effects may arise from dietary sources, diseases, or other variables. Thus, a violation by such a test is not definitive until further confirmation is obtained. Our laboratory has developed extraction procedures for several drugs used in dairy production. Our method uses matrix solid-phase dispersion (MSPD) to isolate drugs away from contaminants and to eliminate many possible interferences. MSPD can also be used to enhance the specificity of such assays by fractionating various classes of drugs that may cross-react. Similarly, such methods may be used for liquid chromatographic screening and confirmation of a suspect sample.

scholarly journals Liquid Chromatographic Analysis of Vitamin K1 in Milk-Based Infant Formula with Matrix Solid-Phase Dispersion

1999 ◽  
Vol 82 (5) ◽  
pp. 1140-1145 ◽  
Author(s):  
G William Chase ◽  
Ronald R Eitenmiller ◽  
Austin R Long
Keyword(s):  
Infant Formula ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Reversed Phase ◽  
Vitamin K1 ◽  
Matrix Solid Phase Dispersion ◽  
Phase Dispersion ◽  
Limit Of Quantitation ◽  
Liquid Chromatographic Analysis ◽  
Liquid Chromatographic

Abstract A liquid chromatographic method for vitamin K1 in milk-based infant formula is described. The vitamins are extracted from infant formula by matrix solid-phase dispersion and quantitated by reversed-phase chromatography with fluorescence detection. Vitamin K1 is converted to the fluorescent hydroquinone with a postcolumn zinc reductive reactor. The limit of detection is 12 pg, and the limit of quantitation is 38 pg on-column. Linear responses were obtained in the range 0.55-22.1 ng/mL (r2 = 0.9998). Recoveries of vitamin K1 from an analyte-fortified blank material for milk-based infant formula averaged 91.7% (n = 25). The method provides a rapid, specific, and easily controlled assay for vitamin K1 in fortified infant formula.

scholarly journals Liquid Chromatographic Method for Analysis of All-rac-α-Tocopheryl Acetate and Retinyl Palmitate in Milk-Based Infant Formula Using Matrix Solid-Phase Dispersion

1998 ◽  
Vol 81 (3) ◽  
pp. 582-586 ◽  
Author(s):  
G William Chase ◽  
Austin R Long
Keyword(s):  
Reference Material ◽  
Infant Formula ◽  
Chromatographic Method ◽  
Solid Phase ◽  
Retinyl Palmitate ◽  
Tocopheryl Acetate ◽  
Matrix Solid Phase Dispersion ◽  
Phase Dispersion ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic

abstract A liquid chromatographic method is described for analysis of all-rac-α-tocopheryl acetate, tocopherols, and retinyl palmitate in milk-based infant formula. The vitamins are extracted from infant formula without saponification by matrix solid-phase dispersion and quantitated by normal-phase chromatography with fluorescence detection. Retinyl palmitate and vitamin E are quantitated isocratically with mobile phases of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results were similar to the certified and non-certified ranges for all-rac-α-tocopheryl acetate, retinyl palmitate, and tocopherols in the infant formula standard reference material (SRM) 1846. Results also compared favorably with the label declaration on a retail infant formula. Recoveries were determined on an analyte-fortified zero control reference material for milk-based infant formula and averaged 96.8% (n = 30) for retinyl palmitate and 91.5% (n = 25) for all-rac-α-tocopheryl acetate. Examination of 5 concentrations for each analyte gave results that were linear (r = 0.999) over the concentration examined, with coefficients of variation ranging from 1.02 to 5.86%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and vitamin E in fortified infant formula. Additionally, the method minimizes solvent use by using only 14 ml_ solvent per extraction.

scholarly journals A Liquid Chromatographic Method for Analysis of AU-Rac-α-Tocopheryl Acetate and Retinyl Palmitate in Medical Food Using Matrix Solid-Phase Dispersion in Conjunction with a Zero Reference Material as a Method Development Tool

1999 ◽  
Vol 82 (1) ◽  
pp. 107-111 ◽  
Author(s):  
G William Chase ◽  
Ronald R Eitenmiller ◽  
Austin R Long
Keyword(s):  
Solid Phase ◽  
Retinyl Palmitate ◽  
Tocopheryl Acetate ◽  
Medical Food ◽  
Matrix Solid Phase Dispersion ◽  
Phase Dispersion ◽  
Liquid Chromatographic Method ◽  
Zero Reference ◽  
Medical Foods ◽  
Liquid Chromatographic

Abstract A liquid chromatographic method is described for analysis of all-rac-α-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted from medical food without saponification by matrix solid-phase dispersion and chromatographed by normal-phase chromatography with fluorescence detection. Retinyl palmitate and all-rac-α-tocopheryl acetate are quantitated isocratically with a mobile phase of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results compared favorably with label declarations on retail medical foods. Recoveries determined on an analyte-fortified zero reference material for a milk-based medical food averaged 98.3% (n = 25) for retinyl palmitate spikes and 95.7% (n = 25) for all-rac-α-tocopheryl acetate spikes. Five concentrations were examined for each analyte, and results were linear (r2 = 0.995 for retinyl palmitate and 0.9998 for all-rac-α-tocopheryl acetate) over the concentration range examined, with coefficients of variation in the range 0.81-4.22%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and all-rac-α-toco-pheryl acetate in fortified medical foods.

Extraction and Liquid Chromatographic Analysis of Sulfadimethoxine and 4-N-Acetylsulfadimethoxine Residues in Channel Catfish (Ictalurus punctatus) Muscle and Plasma

1994 ◽  
Vol 77 (6) ◽  
pp. 1460-1466 ◽  
Author(s):  
Calvin C Walker ◽  
Steven A Barker
Keyword(s):  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Chromatographic Analysis ◽  
Solid Phase ◽  
Matrix Solid Phase Dispersion ◽  
Phase Dispersion ◽  
Liquid Chromatographic Analysis ◽  
Liquid Chromatographic ◽  
Inter Assay Variation

Abstract A simple and rapid method was developed for the simultaneous extraction and liquid chromatographic (LC) determination of sulfadimethoxine (SDM) and 4-N-acetylsulfadimethoxine (N-acetyl SDM) in channel catfish muscle and plasma. Tissues fortified at 0, 50,100,200,400, and 1000 ppb were examined. Matrix solid phase dispersion (MSPD) was used for muscle extraction. Plasma was extracted with a modified MSPD procedure in which 100 μL plasma and 400 mg C18 were blended by Vortex mixing in a disposable chromatographic column. Recovery of SDM based on radioactivity was 79% for muscle and 67% for plasma. Standard curves based on extracted fortified samples were used for quantitation of /V-acetyl SDM. LC run times of 12 min were obtained using a microbore analytical column and an isocratic mobile phase of aqueous 0.017M phosphoric acid–acetonitrile at ratios of 71:29 for muscle and 73:27 for plasma extracts. Method detection limits were 26 ng SDM and 26 ng N-acetyl SDM/g muscle, and 33 ng SDM and 11 ng N-acetyl SDM/mL plasma. Intra-assay variation was <10% for both compounds at all concentrations examined. Inter-assay variation for SDM was 13% for muscle and 14% for plasma, and for N-acetyl SDM was 11% for muscle and 10% for plasma.

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