Variability of matrix effects in liquid and gas chromatography-mass spectrometry analysis of pesticide residues after QuEChERS sample preparation of different food crops

Kwon, H.,Lehotay, S.J.,Geis-Asteggiante, L. Elsevier 2012 Journal of Chromatography A Vol.1270 No.-

Gas and liquid chromatography (GC and LC) coupled to mass spectrometry (MS) serve as the most powerful analytical tools commonly used to monitor pesticide residues in food, among other applications. However, both GC-MS and LC-MS are susceptible to matrix effects which can adversely affect quantification depending on the analyte, matrix, sample preparation, instrumentation, and operating conditions. Among the approaches that reduce matrix effects, the most common in pesticide residue applications is matrix-matched calibration because it is relatively inexpensive and simple. Also, it has been shown to work well during method validation when fortified samples are exactly matched with samples used for calibration. However, the quality of matrix-matched results in real-world analyses depends on the consistency of matrix effects among diverse samples. In this study, the variability of matrix effects was measured for 38 representative pesticides in 20 samples each (including different varieties) of rice, orange, apple, and spinach extracted using the ''quick, easy, cheap, effective, rugged, and safe'' (QuEChERS) method for analysis by LC-MS/MS and low-pressure GC-MS. Using LC-MS/MS, only oranges gave >20% matrix effects for a few pesticides. GC-MS exhibited larger matrix effects, but as in LC-MS/MS, the differences were reasonably consistent among the 20 samples tested. Main conclusions of this study are that for the conditions utilized: (1) matrix-matching was not needed for most pesticides in the simpler food matrices; and (2) for the more complex orange matrix, acceptably accurate quantitative results were achieved by using matrix-matching even with a different sample of the same type. However, full confidence cannot be extended to matrix-matched results, and for consequential applications such as regulatory enforcement, confirmatory analyses using alternate quantitative determinations should also be conducted.

Matrix Enhancement Effect: A Blessing or a Curse for Gas Chromatography?

심재한 ( Jae Han Shim ) 한국환경농학회 2013 한국환경농학회 학술대회집 Vol.2013 No.-

The matrix enhancement effect in gas chromatography (GC) has been a problem for the last decade as it results in unexpected high recovery. Most of the efforts, including the use of different types of injectors/matrix simplification procedure, and further clean-up associated with removing this effect was focused on equalizing the response of the standard in the solvent and matrix. However, after eliminating the matrix enhancement effect, the sensitivity of GC remained unchanged. But, GC sensitivity can be increased by utilizing this matrix effect originating from a matrix matched standard. Very few studies have highlighted utilizing the matrix effect but have rather advocated eliminating it. Analyte protectants (3-ethoxy-1, 2-propanediol, gulonolactone and sorbitol) have been introduced as an alternative for GC-mass spectroscopy (GC-MS) (not examined for other GC detectors), as they equalize the response without removing the matrix effect, and, hence, increase sensitivity. Versatile applications of analyte protectants are not observed in practice. The European guidelines recommend use of matrix matched standard calibration for residue measurements. As a result, numerous applications are available for matrix matched standards that compensate for the matrix effect. Moreover, the matrices (among them pepper leaf matrix) can act as a protectant for thermolabileanalytes in some cases. A lower detection limit should be achieved from the GC detector to comply with the maximum residue limits. Therefore, the matrix enhancement effect, which is considered a problem, can play an important role in lowering the detection limit by increasing the transfer of analyte from the injection port to the detector.

Matrices uniquely determined by their lonesums

Kim, H.K.,Krotov, D.S.,Lee, J.Y. North Holland [etc.] 2013 Linear algebra and its applications Vol.438 No.7

A matrix is lonesum if it can be uniquely reconstructed from its row and column sums. Brewbaker computed the number of mxn binary lonesum matrices. Kaneko defined the poly-Bernoulli numbers of an integer index, and showed that the number of mxn binary lonesum matrices is equal to the mth poly-Bernoulli number of index -n. In this paper, we are interested in q-ary lonesum matrices. There are two types of lonesumness for q-ary matrices, namely strongly and weakly lonesum. We first study strongly lonesum matrices: We compute the number of mxnq-ary strongly lonesum matrices, and provide a generalization of Kaneko's formulas by deriving the generating function for the number of mxnq-ary strongly lonesum matrices. Next, we study weakly lonesum matrices: We show that the number of forbidden patterns for q-ary weakly lonesum matrices is infinite if q≥5, and construct some forbidden patterns for q=3,4. We also suggest an open problem related to ternary and quaternary weakly lonesum matrices.

A New Explanation of Relation between Matrices

Li Fengxia 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.11

It is known that if two matrices are of same size, there may be the equivalent, similar or congruent relations between matrices. This paper has mainly launches the research about relations between matrices of the same size, different size by matrix operations. Such as there is an association between matrix and its adjoint matrix, adjoint matrix is linear combination of power of A. Using a mathematical formula to unify the three equivalence relations.

한국인 태아 조기질의 미세구조에 관한 연구

손형선,최재권,정윤영,배춘상,Sohn, Hyung-Sun,Choi, Jae-Kwon,Chung, Yun-Young,Bae, Choon-Sang 한국현미경학회 1996 Applied microscopy Vol.26 No.1

The differentiation of nail matrix and fine structure of matrix cells were studied with light and electron microscope using specimens from nails of thumb finger in Korean fetuses 14 to 24 weeks old. Fetal nail matrix consisted of two horizontal layers, thicker ventral and thinner dorsal matrices, originating from invagination of epidermis in proximal nail field. Matrix being generally thicker in its distal region than the apex became gradually thickened with increase of the fetal age. Each matrix consisted of single layer of basal cells and multiple layers of squamous cells which are arranged close to and parallel to the central axis of the nail mairix. The process of keratinization of fetal nail matrix was noted to be occured concurrently in the ventral and dorsal matrices along the central axis of matrix toward distal and dorsal direction. Squamous cells became matured with accumulation of tonofilaments, increase of keratohyalin granules, discharge of membrane coating granules, and narrowing of intercellular spaces, thickening of plasma membrane and finally being transformed into horny cells of nail plate. Horny cells of nail plate filled with fibrous elements in the electron dense amorphous substance. These findings of keratinization process of fetal nail matrix appeared to be similar to those of keratinization in epidermis and inner root sheath of the hair. In the nail matrix, however, corresponding region to the keratogenous zone of growing hair follicle was not observed. Vacuolated squamous cells of nail matrix seen on light microscopy was considered to be artefactual product, but squamous cells with condensed small nuclei rarely found adjacent nail plate was considered to be one of the squamous cells with unknown function. Proximal end of nail plate was observed on dorsal surface of nail field distal to the proximal nail fold at 14 and 16 weeks old human embryos. Proximal prolongation of the proximal end of nail plate was occured with advancing fetal age and afterward 21 weeks nail plate invaded into nail matrix. Melanin granule containing cells and Merkel cells were present only on the basal layer of dorsal nail matirx.

Fibroblasts in three dimensional matrices: cell migration and matrix remodeling

Sangmyung Rhee 생화학분자생물학회 2009 Experimental and molecular medicine Vol.41 No.12

Fibroblast-collagen matrix culture has facilitated the analysis of cell physiology under conditions that more closely resemble an in vivo-like environment compared to conventional 2-dimensional (2D) cell culture. Furthermore, it has led to significant progress in understanding reciprocal and adaptive interactions between fibroblasts and the collagen matrix, which occur in tissue. Recent studies on fibroblasts in 3-dimensional (3D) collagen matrices have revealed the importance of biomechanical conditions in addition to biochemical cues for cell signaling and migration. Depending on the surrounding mechanical conditions, cells utilize specific cytoskeletal proteins to adapt to their environment. More specifically, cells utilize microtubule dependent dendritic extensions to provide mechanical structure for matrix contraction under a low cell-matrix tension state, whereas cells in a high cell-matrix tension state utilize conventional acto-myosin activity for matrix remodeling. Results of collagen matrix contraction and cell migration in a 3D collagen matrix revealed that the use of appropriate growth factors led to promigratory and procontractile activity for cultured fibroblasts. Finally, the relationship between cell migration and tractional force for matrix remodeling was discussed. Fibroblast-collagen matrix culture has facilitated the analysis of cell physiology under conditions that more closely resemble an in vivo-like environment compared to conventional 2-dimensional (2D) cell culture. Furthermore, it has led to significant progress in understanding reciprocal and adaptive interactions between fibroblasts and the collagen matrix, which occur in tissue. Recent studies on fibroblasts in 3-dimensional (3D) collagen matrices have revealed the importance of biomechanical conditions in addition to biochemical cues for cell signaling and migration. Depending on the surrounding mechanical conditions, cells utilize specific cytoskeletal proteins to adapt to their environment. More specifically, cells utilize microtubule dependent dendritic extensions to provide mechanical structure for matrix contraction under a low cell-matrix tension state, whereas cells in a high cell-matrix tension state utilize conventional acto-myosin activity for matrix remodeling. Results of collagen matrix contraction and cell migration in a 3D collagen matrix revealed that the use of appropriate growth factors led to promigratory and procontractile activity for cultured fibroblasts. Finally, the relationship between cell migration and tractional force for matrix remodeling was discussed.

A matrix sequence {Γ(A^m)}_m=1^~ might converge even if the matrix A is not primitive

Park, W.,Park, B.,Kim, S.R. North Holland [etc.] 2013 Linear algebra and its applications Vol.438 No.5

It is well-known that, for an irreducible Boolean (0,1)-matrix A, the matrix sequence {A<SUP>m</SUP>}<SUB>m=1</SUB><SUP>~</SUP> converges if and only if A is primitive. In this paper, we introduce an operation Γ on the set of Boolean (0,1)-matrices such that a matrix sequence {Γ(A<SUP>m</SUP>)}<SUB>m=1</SUB><SUP>~</SUP> might converge even if the matrix A is not primitive. Given a Boolean (0,1)-matrix A, we define a matrix Γ(A) so that the (i,j)-entry of Γ(A) equals 0 if for i≠j, the inner product of the ith row and jth row of A is 0 and equals 1 otherwise. The aim of this paper is to study the convergence of {Γ(A<SUP>m</SUP>)}<SUB>m=1</SUB><SUP>~</SUP> for a Boolean (0,1)-matrix A whose digraph has at most two strong components. We show that {Γ(A<SUP>m</SUP>)}<SUB>m=1</SUB><SUP>~</SUP> converges to a very special type of matrix as m increases if A is an irreducible Boolean matrix. Furthermore, we completely characterize a Boolean (0,1)-matrix A whose digraph has exactly two strongly connected components and for which {Γ(A<SUP>m</SUP>)}<SUB>m=1</SUB><SUP>~</SUP> converges, and find the limit of {Γ(A<SUP>m</SUP>)}<SUB>m=1</SUB><SUP>~</SUP> in terms of its digraph when it converges. We derive these results in terms of the competition graph of the digraph of A.

On Jacket Matrices Based on Weighted Hadamard Matrices

Moon Ho Lee,Subash Shree Pokhrel,Chang-Hui Choe,Chang Joo Kim 한국전자파학회JEES 2007 Journal of Electromagnetic Engineering and Science Vol.7 No.1

Jacket matrices which are defined to be n×n matrices A=(ajk) over a field F with the property AA<SUP>†</SUP>=nIn where A<SUP>†</SUP> is the transpose matrix of elements inverse of A, i. e., A<SUP>†</SUP> = (a?jk), was introduced by Lee in 1984 and are used for signal processing and coding theory, which generalized the Hadamard matrices and Center Weighted Hadamard matrices. In this paper, some properties and constructions of Jacket matrices are extensively investigated and small orders of Jacket matrices are characterized, also present the full rate and the 1/2 code rate complex orthogonal space time code with full diversity.

쌍곡선에서의 재킷 행렬

양재승,박주용,이문호 한국인터넷방송통신학회 2015 한국인터넷방송통신학회 논문지 Vol.15 No.3

Jacket 행렬[2][8]은 1984년 이문호 교수에 의해 소개되어 신호처리 및 코딩이론에 사용되는† 1 TJ = ⎡⎣Ji−k ⎤⎦ 인 행렬로서, Galois field F 에서 J † 가 J 의 원소별 역행렬일 때†m JJ =mI 의 특성을 갖는 [ ] ik J = j 인 m×m 정방행렬이다. 본 논문에서는 Jacket 행렬에 의해 고유 값으로 분해될 수 있는 정방행렬 2 n A 을 제안하였다. 특히 2 A와 그의 확장인 3 A 행렬을 가지고 쌍곡선과 쌍곡면의 성질을 수정하는데 각각 적용할 수 있음을 보였다. 특히 쌍곡선이 배의 정보량을 갖게 되면 2 A 행렬의 EVD[7]를 이용하여 최종 행렬 2A n 을 쉽게 계산할 수 있다. 또한 여기서제안한 알고리즘을 가지고 컴퓨터 그래픽에서의 응용 프로그램과 수치해석에서도 이용될 수 있음을 보였다. Jacket matrices[2][8] which are defined to be m ×m matrices † 1 Tik J = ⎡⎣J− ⎤⎦ over a Galois field F with theproperty †m JJ =mI , J † is the transpose matrix of element-wise inverse of J , i.e., † 1 Tik J = ⎡⎣J− ⎤⎦ , were introducedby Lee in 1984 and are used for Digital Signal Processing and Coding theory. This paper presents some squarematrices 2 n A which can be eigenvalue decomposed by Jacket matrices. Specially, 2 A and its extension 3 A canbe used for modifying the properties of hyperbola and hyperboloid, respectively. Specially, when the hyperbola has times transformation, the final matrices 2A n can be easily calculated by employing the EVD[7] of matrices2 A . The ideas that we will develop here have applications in computer graphics and used in many importantnumerical algorithms.

THE INFLUENCE OF OBTURATION TIMING AND THICKNESS OF MINERAL TRIOXIDE AGGREAGATE ON SEALING ABILITY OF CANAL WITH OPEN APEX

곽경인,박동성,유현미,오태석 대한치과보존학회 2000 Restorative Dentistry & Endodontics Vol.25 No.4

임상에서 점차 Mineral Trioxide Aggregate (MTA) 에 대한 우수성이 소개되면서, apical matrix로의 사용은 주목할 만하다 할 수 있다. 본 연구의 목적은 개방형근관에서 MTA가 apical matrix로 사용될 때의 치근단 밀폐효과를 알아보고, 근관충전의 시기와 matrix의 두께가 치근단 밀폐에 미치는 영향을 치근단 미세누출의 측면과 matrix탈락빈도의 측면에서 관찰하고자 하는 것이다. 개방형 근관을 재현하고자 45개의 발거된 단근치에 #90크기로 근단공을 형성하였고, 투명레진등을 이용하여 치근단병소를 갖는 치조골을 재현한 후, 4개의 실험 군과 1개의 대조 군으로 분류하였다. A군: 2mm두께의 MTA matrix 형성후, 열연화된 Gutta-percha와AH26 sealer를 이용하여 즉시 근관충전. B군: 2mm두께의 MTA matrix 형성후, A군과 같은 방법으로 24시간 후 근관충전. C군: 4mm 두께의 MTA matrix 형성후, A군과 같은 방법으로 즉시 근관충전. D군: 4mm두께의 MTA matrix 형성후, A군과 같은 방법으로 24시간 후 근관충전. 대조군: matrix를 사용하지 않고 열연화된 Gutta-percha와 AH26 sealer를 이용하여 근관충전하였다. Matrix의 탈락이 있는 경우 기록하고 완전수세 후 다시 시행하였다. 색소침투정도의 평가를 위해 methylene blue 에 치아를 48시간 침수시킨 후 협설로 양분하였다. 각 시편들을 고배율 현미경 관찰 후 비디오촬영 하였고, digitalized image analysing program 을 이용하여 두명의 관찰자가 누출의 정도를 평가한 후, One-way ANOVA로 통계적 유의성을 검증하여 다음과 같은 결과를 얻었다. 1. Matrix를 사용한 실험 군이 matrix를 사용하지 않은 대조 군에 비해 유의성 있게 낮은 누출을 보였다(p<0.05) . 그러나 근관충전시기와 matrix의 두께를 달리한 실험군 내에서는 누출에 유의성 있는 차이가 나타나지 않았다. 2 모든 실험군에서 gutta-percha를 이용한 근관충전의 시기에 matrix탈락 및 gutta-percha 의 압출은 발생하지 않았다.